Android官方实现的层次状态机Hierarchical State Machine源代码

电玩女神 2022-12-05 15:22 194阅读 0赞

Android官方内部的源代码中实现了一套层次状态机(Hierarchical State Machine)，总共有三个代码文件：IState.java ， State.java， StateMachine.java，目录位置在：

[https://android.googlesource.com/platform/frameworks/base/+/refs/heads/master/core/java/com/android/internal/util/][https_android.googlesource.com_platform_frameworks_base_refs_heads_master_core_java_com_android_internal_util]

package com.android.internal.util;
    import android.compat.annotation.UnsupportedAppUsage;
    import android.os.Message;
    /**
     * {@hide}
     *
     * The interface for implementing states in a {@link StateMachine}
     */
    public interface IState {
        /**
         * Returned by processMessage to indicate the the message was processed.
         */
        static final boolean HANDLED = true;
        /**
         * Returned by processMessage to indicate the the message was NOT processed.
         */
        static final boolean NOT_HANDLED = false;
        /**
         * Called when a state is entered.
         */
        void enter();
        /**
         * Called when a state is exited.
         */
        void exit();
        /**
         * Called when a message is to be processed by the
         * state machine.
         *
         * This routine is never reentered thus no synchronization
         * is needed as only one processMessage method will ever be
         * executing within a state machine at any given time. This
         * does mean that processing by this routine must be completed
         * as expeditiously as possible as no subsequent messages will
         * be processed until this routine returns.
         *
         * @param msg to process
         * @return HANDLED if processing has completed and NOT_HANDLED
         *         if the message wasn't processed.
         */
        boolean processMessage(Message msg);
        /**
         * Name of State for debugging purposes.
         *
         * @return name of state.
         */
        @UnsupportedAppUsage
        String getName();
    }

package com.android.internal.util;
    import android.compat.annotation.UnsupportedAppUsage;
    import android.os.Message;
    /**
     * {@hide}
     *
     * The class for implementing states in a StateMachine
     */
    public class State implements IState {
        /**
         * Constructor
         */
        @UnsupportedAppUsage
        protected State() {
        }
        /* (non-Javadoc)
         * @see com.android.internal.util.IState#enter()
         */
        @UnsupportedAppUsage
        @Override
        public void enter() {
        }
        /* (non-Javadoc)
         * @see com.android.internal.util.IState#exit()
         */
        @UnsupportedAppUsage
        @Override
        public void exit() {
        }
        /* (non-Javadoc)
         * @see com.android.internal.util.IState#processMessage(android.os.Message)
         */
        @UnsupportedAppUsage
        @Override
        public boolean processMessage(Message msg) {
            return false;
        }
        /**
         * Name of State for debugging purposes.
         *
         * This default implementation returns the class name, returning
         * the instance name would better in cases where a State class
         * is used for multiple states. But normally there is one class per
         * state and the class name is sufficient and easy to get. You may
         * want to provide a setName or some other mechanism for setting
         * another name if the class name is not appropriate.
         *
         * @see com.android.internal.util.IState#processMessage(android.os.Message)
         */
        @UnsupportedAppUsage
        @Override
        public String getName() {
            String name = getClass().getName();
            int lastDollar = name.lastIndexOf('$');
            return name.substring(lastDollar + 1);
        }
    }

package com.android.internal.util;
 import android.compat.annotation.UnsupportedAppUsage;
 import android.os.Handler;
 import android.os.HandlerThread;
 import android.os.Looper;
 import android.os.Message;
 import android.text.TextUtils;
 import android.util.Log;
 import com.android.internal.annotations.VisibleForTesting;
 import java.io.FileDescriptor;
 import java.io.PrintWriter;
 import java.util.ArrayList;
 import java.util.Calendar;
 import java.util.Collection;
 import java.util.HashMap;
 import java.util.Iterator;
 import java.util.Vector;
 /**
 * {@hide}
 *
 * The state machine defined here is a hierarchical state machine which processes messages
 * and can have states arranged hierarchically.
 *
 * A state is a <code>State</code> object and must implement
 * <code>processMessage</code> and optionally <code>enter/exit/getName</code>.
 * The enter/exit methods are equivalent to the construction and destruction
 * in Object Oriented programming and are used to perform initialization and
 * cleanup of the state respectively. The <code>getName</code> method returns the
 * name of the state; the default implementation returns the class name. It may be
 * desirable to have <code>getName</code> return the the state instance name instead,
 * in particular if a particular state class has multiple instances.
 *
 * When a state machine is created, <code>addState</code> is used to build the
 * hierarchy and <code>setInitialState</code> is used to identify which of these
 * is the initial state. After construction the programmer calls <code>start</code>
 * which initializes and starts the state machine. The first action the StateMachine
 * is to the invoke <code>enter</code> for all of the initial state's hierarchy,
 * starting at its eldest parent. The calls to enter will be done in the context
 * of the StateMachine's Handler, not in the context of the call to start, and they
 * will be invoked before any messages are processed. For example, given the simple
 * state machine below, mP1.enter will be invoked and then mS1.enter. Finally,
 * messages sent to the state machine will be processed by the current state;
 * in our simple state machine below that would initially be mS1.processMessage.
 <pre>
 mP1
 / \
 mS2 mS1 ----> initial state
 </pre>
 * After the state machine is created and started, messages are sent to a state
 * machine using <code>sendMessage</code> and the messages are created using
 * <code>obtainMessage</code>. When the state machine receives a message the
 * current state's <code>processMessage</code> is invoked. In the above example
 * mS1.processMessage will be invoked first. The state may use <code>transitionTo</code>
 * to change the current state to a new state.
 *
 * Each state in the state machine may have a zero or one parent states. If
 * a child state is unable to handle a message it may have the message processed
 * by its parent by returning false or NOT_HANDLED. If a message is not handled by
 * a child state or any of its ancestors, <code>unhandledMessage</code> will be invoked
 * to give one last chance for the state machine to process the message.
 *
 * When all processing is completed a state machine may choose to call
 * <code>transitionToHaltingState</code>. When the current <code>processingMessage</code>
 * returns the state machine will transfer to an internal <code>HaltingState</code>
 * and invoke <code>halting</code>. Any message subsequently received by the state
 * machine will cause <code>haltedProcessMessage</code> to be invoked.
 *
 * If it is desirable to completely stop the state machine call <code>quit</code> or
 * <code>quitNow</code>. These will call <code>exit</code> of the current state and its parents,
 * call <code>onQuitting</code> and then exit Thread/Loopers.
 *
 * In addition to <code>processMessage</code> each <code>State</code> has
 * an <code>enter</code> method and <code>exit</code> method which may be overridden.
 *
 * Since the states are arranged in a hierarchy transitioning to a new state
 * causes current states to be exited and new states to be entered. To determine
 * the list of states to be entered/exited the common parent closest to
 * the current state is found. We then exit from the current state and its
 * parent's up to but not including the common parent state and then enter all
 * of the new states below the common parent down to the destination state.
 * If there is no common parent all states are exited and then the new states
 * are entered.
 *
 * Two other methods that states can use are <code>deferMessage</code> and
 * <code>sendMessageAtFrontOfQueue</code>. The <code>sendMessageAtFrontOfQueue</code> sends
 * a message but places it on the front of the queue rather than the back. The
 * <code>deferMessage</code> causes the message to be saved on a list until a
 * transition is made to a new state. At which time all of the deferred messages
 * will be put on the front of the state machine queue with the oldest message
 * at the front. These will then be processed by the new current state before
 * any other messages that are on the queue or might be added later. Both of
 * these are protected and may only be invoked from within a state machine.
 *
 * To illustrate some of these properties we'll use state machine with an 8
 * state hierarchy:
 <pre>
 mP0
 / \
 mP1 mS0
 / \
 mS2 mS1
 / \ \
 mS3 mS4 mS5 ---> initial state
 </pre>
 * After starting mS5 the list of active states is mP0, mP1, mS1 and mS5.
 * So the order of calling processMessage when a message is received is mS5,
 * mS1, mP1, mP0 assuming each processMessage indicates it can't handle this
 * message by returning false or NOT_HANDLED.
 *
 * Now assume mS5.processMessage receives a message it can handle, and during
 * the handling determines the machine should change states. It could call
 * transitionTo(mS4) and return true or HANDLED. Immediately after returning from
 * processMessage the state machine runtime will find the common parent,
 * which is mP1. It will then call mS5.exit, mS1.exit, mS2.enter and then
 * mS4.enter. The new list of active states is mP0, mP1, mS2 and mS4. So
 * when the next message is received mS4.processMessage will be invoked.
 *
 * Now for some concrete examples, here is the canonical HelloWorld as a state machine.
 * It responds with "Hello World" being printed to the log for every message.
 <pre>
 class HelloWorld extends StateMachine {
 HelloWorld(String name) {
 super(name);
 addState(mState1);
 setInitialState(mState1);
 }
 public static HelloWorld makeHelloWorld() {
 HelloWorld hw = new HelloWorld("hw");
 hw.start();
 return hw;
 }
 class State1 extends State {
 @Override public boolean processMessage(Message message) {
 log("Hello World");
 return HANDLED;
 }
 }
 State1 mState1 = new State1();
 }
 void testHelloWorld() {
 HelloWorld hw = makeHelloWorld();
 hw.sendMessage(hw.obtainMessage());
 }
 </pre>
 * A more interesting state machine is one with four states
 * with two independent parent states.
 <pre>
 mP1 mP2
 / \
 mS2 mS1
 </pre>
 * Here is a description of this state machine using pseudo code.
 <pre>
 state mP1 {
 enter { log("mP1.enter"); }
 exit { log("mP1.exit"); }
 on msg {
 CMD_2 {
 send(CMD_3);
 defer(msg);
 transitionTo(mS2);
 return HANDLED;
 }
 return NOT_HANDLED;
 }
 }
 INITIAL
 state mS1 parent mP1 {
 enter { log("mS1.enter"); }
 exit { log("mS1.exit"); }
 on msg {
 CMD_1 {
 transitionTo(mS1);
 return HANDLED;
 }
 return NOT_HANDLED;
 }
 }
 state mS2 parent mP1 {
 enter { log("mS2.enter"); }
 exit { log("mS2.exit"); }
 on msg {
 CMD_2 {
 send(CMD_4);
 return HANDLED;
 }
 CMD_3 {
 defer(msg);
 transitionTo(mP2);
 return HANDLED;
 }
 return NOT_HANDLED;
 }
 }
 state mP2 {
 enter {
 log("mP2.enter");
 send(CMD_5);
 }
 exit { log("mP2.exit"); }
 on msg {
 CMD_3, CMD_4 { return HANDLED; }
 CMD_5 {
 transitionTo(HaltingState);
 return HANDLED;
 }
 return NOT_HANDLED;
 }
 }
 </pre>
 * The implementation is below and also in StateMachineTest:
 <pre>
 class Hsm1 extends StateMachine {
 public static final int CMD_1 = 1;
 public static final int CMD_2 = 2;
 public static final int CMD_3 = 3;
 public static final int CMD_4 = 4;
 public static final int CMD_5 = 5;
 public static Hsm1 makeHsm1() {
 log("makeHsm1 E");
 Hsm1 sm = new Hsm1("hsm1");
 sm.start();
 log("makeHsm1 X");
 return sm;
 }
 Hsm1(String name) {
 super(name);
 log("ctor E");
 // Add states, use indentation to show hierarchy
 addState(mP1);
 addState(mS1, mP1);
 addState(mS2, mP1);
 addState(mP2);
 // Set the initial state
 setInitialState(mS1);
 log("ctor X");
 }
 class P1 extends State {
 @Override public void enter() {
 log("mP1.enter");
 }
 @Override public boolean processMessage(Message message) {
 boolean retVal;
 log("mP1.processMessage what=" + message.what);
 switch(message.what) {
 case CMD_2:
 // CMD_2 will arrive in mS2 before CMD_3
 sendMessage(obtainMessage(CMD_3));
 deferMessage(message);
 transitionTo(mS2);
 retVal = HANDLED;
 break;
 default:
 // Any message we don't understand in this state invokes unhandledMessage
 retVal = NOT_HANDLED;
 break;
 }
 return retVal;
 }
 @Override public void exit() {
 log("mP1.exit");
 }
 }
 class S1 extends State {
 @Override public void enter() {
 log("mS1.enter");
 }
 @Override public boolean processMessage(Message message) {
 log("S1.processMessage what=" + message.what);
 if (message.what == CMD_1) {
 // Transition to ourself to show that enter/exit is called
 transitionTo(mS1);
 return HANDLED;
 } else {
 // Let parent process all other messages
 return NOT_HANDLED;
 }
 }
 @Override public void exit() {
 log("mS1.exit");
 }
 }
 class S2 extends State {
 @Override public void enter() {
 log("mS2.enter");
 }
 @Override public boolean processMessage(Message message) {
 boolean retVal;
 log("mS2.processMessage what=" + message.what);
 switch(message.what) {
 case(CMD_2):
 sendMessage(obtainMessage(CMD_4));
 retVal = HANDLED;
 break;
 case(CMD_3):
 deferMessage(message);
 transitionTo(mP2);
 retVal = HANDLED;
 break;
 default:
 retVal = NOT_HANDLED;
 break;
 }
 return retVal;
 }
 @Override public void exit() {
 log("mS2.exit");
 }
 }
 class P2 extends State {
 @Override public void enter() {
 log("mP2.enter");
 sendMessage(obtainMessage(CMD_5));
 }
 @Override public boolean processMessage(Message message) {
 log("P2.processMessage what=" + message.what);
 switch(message.what) {
 case(CMD_3):
 break;
 case(CMD_4):
 break;
 case(CMD_5):
 transitionToHaltingState();
 break;
 }
 return HANDLED;
 }
 @Override public void exit() {
 log("mP2.exit");
 }
 }
 @Override
 void onHalting() {
 log("halting");
 synchronized (this) {
 this.notifyAll();
 }
 }
 P1 mP1 = new P1();
 S1 mS1 = new S1();
 S2 mS2 = new S2();
 P2 mP2 = new P2();
 }
 </pre>
 * If this is executed by sending two messages CMD_1 and CMD_2
 * (Note the synchronize is only needed because we use hsm.wait())
 <pre>
 Hsm1 hsm = makeHsm1();
 synchronize(hsm) {
 hsm.sendMessage(obtainMessage(hsm.CMD_1));
 hsm.sendMessage(obtainMessage(hsm.CMD_2));
 try {
 // wait for the messages to be handled
 hsm.wait();
 } catch (InterruptedException e) {
 loge("exception while waiting " + e.getMessage());
 }
 }
 </pre>
 * The output is:
 <pre>
 D/hsm1 ( 1999): makeHsm1 E
 D/hsm1 ( 1999): ctor E
 D/hsm1 ( 1999): ctor X
 D/hsm1 ( 1999): mP1.enter
 D/hsm1 ( 1999): mS1.enter
 D/hsm1 ( 1999): makeHsm1 X
 D/hsm1 ( 1999): mS1.processMessage what=1
 D/hsm1 ( 1999): mS1.exit
 D/hsm1 ( 1999): mS1.enter
 D/hsm1 ( 1999): mS1.processMessage what=2
 D/hsm1 ( 1999): mP1.processMessage what=2
 D/hsm1 ( 1999): mS1.exit
 D/hsm1 ( 1999): mS2.enter
 D/hsm1 ( 1999): mS2.processMessage what=2
 D/hsm1 ( 1999): mS2.processMessage what=3
 D/hsm1 ( 1999): mS2.exit
 D/hsm1 ( 1999): mP1.exit
 D/hsm1 ( 1999): mP2.enter
 D/hsm1 ( 1999): mP2.processMessage what=3
 D/hsm1 ( 1999): mP2.processMessage what=4
 D/hsm1 ( 1999): mP2.processMessage what=5
 D/hsm1 ( 1999): mP2.exit
 D/hsm1 ( 1999): halting
 </pre>
 */
 public class StateMachine {
 // Name of the state machine and used as logging tag
 private String mName;
 /** Message.what value when quitting */
 private static final int SM_QUIT_CMD = -1;
 /** Message.what value when initializing */
 private static final int SM_INIT_CMD = -2;
 /**
 * Convenience constant that maybe returned by processMessage
 * to indicate the the message was processed and is not to be
 * processed by parent states
 */
 public static final boolean HANDLED = true;
 /**
 * Convenience constant that maybe returned by processMessage
 * to indicate the the message was NOT processed and is to be
 * processed by parent states
 */
 public static final boolean NOT_HANDLED = false;
 /**
 * StateMachine logging record.
 * {@hide}
 */
 public static class LogRec {
 private StateMachine mSm;
 private long mTime;
 private int mWhat;
 private String mInfo;
 private IState mState;
 private IState mOrgState;
 private IState mDstState;
 /**
 * Constructor
 *
 * @param msg
 * @param state the state which handled the message
 * @param orgState is the first state the received the message but
 * did not processes the message.
 * @param transToState is the state that was transitioned to after the message was
 * processed.
 */
 LogRec(StateMachine sm, Message msg, String info, IState state, IState orgState,
 IState transToState) {
 update(sm, msg, info, state, orgState, transToState);
 }
 /**
 * Update the information in the record.
 * @param state that handled the message
 * @param orgState is the first state the received the message
 * @param dstState is the state that was the transition target when logging
 */
 public void update(StateMachine sm, Message msg, String info, IState state, IState orgState,
 IState dstState) {
 mSm = sm;
 mTime = System.currentTimeMillis();
 mWhat = (msg != null) ? msg.what : 0;
 mInfo = info;
 mState = state;
 mOrgState = orgState;
 mDstState = dstState;
 }
 /**
 * @return time stamp
 */
 public long getTime() {
 return mTime;
 }
 /**
 * @return msg.what
 */
 public long getWhat() {
 return mWhat;
 }
 /**
 * @return the command that was executing
 */
 public String getInfo() {
 return mInfo;
 }
 /**
 * @return the state that handled this message
 */
 public IState getState() {
 return mState;
 }
 /**
 * @return the state destination state if a transition is occurring or null if none.
 */
 public IState getDestState() {
 return mDstState;
 }
 /**
 * @return the original state that received the message.
 */
 public IState getOriginalState() {
 return mOrgState;
 }
 @Override
 public String toString() {
 StringBuilder sb = new StringBuilder();
 sb.append("time=");
 Calendar c = Calendar.getInstance();
 c.setTimeInMillis(mTime);
 sb.append(String.format("%tm-%td %tH:%tM:%tS.%tL", c, c, c, c, c, c));
 sb.append(" processed=");
 sb.append(mState == null ? "<null>" : mState.getName());
 sb.append(" org=");
 sb.append(mOrgState == null ? "<null>" : mOrgState.getName());
 sb.append(" dest=");
 sb.append(mDstState == null ? "<null>" : mDstState.getName());
 sb.append(" what=");
 String what = mSm != null ? mSm.getWhatToString(mWhat) : "";
 if (TextUtils.isEmpty(what)) {
 sb.append(mWhat);
 sb.append("(0x");
 sb.append(Integer.toHexString(mWhat));
 sb.append(")");
 } else {
 sb.append(what);
 }
 if (!TextUtils.isEmpty(mInfo)) {
 sb.append(" ");
 sb.append(mInfo);
 }
 return sb.toString();
 }
 }
 /**
 * A list of log records including messages recently processed by the state machine.
 *
 * The class maintains a list of log records including messages
 * recently processed. The list is finite and may be set in the
 * constructor or by calling setSize. The public interface also
 * includes size which returns the number of recent records,
 * count which is the number of records processed since the
 * the last setSize, get which returns a record and
 * add which adds a record.
 */
 private static class LogRecords {
 private static final int DEFAULT_SIZE = 20;
 private Vector<LogRec> mLogRecVector = new Vector<LogRec>();
 private int mMaxSize = DEFAULT_SIZE;
 private int mOldestIndex = 0;
 private int mCount = 0;
 private boolean mLogOnlyTransitions = false;
 /**
 * private constructor use add
 */
 private LogRecords() {
 }
 /**
 * Set size of messages to maintain and clears all current records.
 *
 * @param maxSize number of records to maintain at anyone time.
 */
 synchronized void setSize(int maxSize) {
 // TODO: once b/28217358 is fixed, add unit tests to verify that these variables are
 // cleared after calling this method, and that subsequent calls to get() function as
 // expected.
 mMaxSize = maxSize;
 mOldestIndex = 0;
 mCount = 0;
 mLogRecVector.clear();
 }
 synchronized void setLogOnlyTransitions(boolean enable) {
 mLogOnlyTransitions = enable;
 }
 synchronized boolean logOnlyTransitions() {
 return mLogOnlyTransitions;
 }
 /**
 * @return the number of recent records.
 */
 synchronized int size() {
 return mLogRecVector.size();
 }
 /**
 * @return the total number of records processed since size was set.
 */
 synchronized int count() {
 return mCount;
 }
 /**
 * Clear the list of records.
 */
 synchronized void cleanup() {
 mLogRecVector.clear();
 }
 /**
 * @return the information on a particular record. 0 is the oldest
 * record and size()-1 is the newest record. If the index is to
 * large null is returned.
 */
 synchronized LogRec get(int index) {
 int nextIndex = mOldestIndex + index;
 if (nextIndex >= mMaxSize) {
 nextIndex -= mMaxSize;
 }
 if (nextIndex >= size()) {
 return null;
 } else {
 return mLogRecVector.get(nextIndex);
 }
 }
 /**
 * Add a processed message.
 *
 * @param msg
 * @param messageInfo to be stored
 * @param state that handled the message
 * @param orgState is the first state the received the message but
 * did not processes the message.
 * @param transToState is the state that was transitioned to after the message was
 * processed.
 *
 */
 synchronized void add(StateMachine sm, Message msg, String messageInfo, IState state,
 IState orgState, IState transToState) {
 mCount += 1;
 if (mLogRecVector.size() < mMaxSize) {
 mLogRecVector.add(new LogRec(sm, msg, messageInfo, state, orgState, transToState));
 } else {
 LogRec pmi = mLogRecVector.get(mOldestIndex);
 mOldestIndex += 1;
 if (mOldestIndex >= mMaxSize) {
 mOldestIndex = 0;
 }
 pmi.update(sm, msg, messageInfo, state, orgState, transToState);
 }
 }
 }
 private static class SmHandler extends Handler {
 /** true if StateMachine has quit */
 private boolean mHasQuit = false;
 /** The debug flag */
 private boolean mDbg = false;
 /** The SmHandler object, identifies that message is internal */
 private static final Object mSmHandlerObj = new Object();
 /** The current message */
 private Message mMsg;
 /** A list of log records including messages this state machine has processed */
 private LogRecords mLogRecords = new LogRecords();
 /** true if construction of the state machine has not been completed */
 private boolean mIsConstructionCompleted;
 /** Stack used to manage the current hierarchy of states */
 private StateInfo mStateStack[];
 /** Top of mStateStack */
 private int mStateStackTopIndex = -1;
 /** A temporary stack used to manage the state stack */
 private StateInfo mTempStateStack[];
 /** The top of the mTempStateStack */
 private int mTempStateStackCount;
 /** State used when state machine is halted */
 private HaltingState mHaltingState = new HaltingState();
 /** State used when state machine is quitting */
 private QuittingState mQuittingState = new QuittingState();
 /** Reference to the StateMachine */
 private StateMachine mSm;
 /**
 * Information about a state.
 * Used to maintain the hierarchy.
 */
 private class StateInfo {
 /** The state */
 State state;
 /** The parent of this state, null if there is no parent */
 StateInfo parentStateInfo;
 /** True when the state has been entered and on the stack */
 boolean active;
 /**
 * Convert StateInfo to string
 */
 @Override
 public String toString() {
 return "state=" + state.getName() + ",active=" + active + ",parent="
 + ((parentStateInfo == null) ? "null" : parentStateInfo.state.getName());
 }
 }
 /** The map of all of the states in the state machine */
 private HashMap<State, StateInfo> mStateInfo = new HashMap<State, StateInfo>();
 /** The initial state that will process the first message */
 private State mInitialState;
 /** The destination state when transitionTo has been invoked */
 private State mDestState;
 /**
 * Indicates if a transition is in progress
 *
 * This will be true for all calls of State.exit and all calls of State.enter except for the
 * last enter call for the current destination state.
 */
 private boolean mTransitionInProgress = false;
 /** The list of deferred messages */
 private ArrayList<Message> mDeferredMessages = new ArrayList<Message>();
 /**
 * State entered when transitionToHaltingState is called.
 */
 private class HaltingState extends State {
 @Override
 public boolean processMessage(Message msg) {
 mSm.haltedProcessMessage(msg);
 return true;
 }
 }
 /**
 * State entered when a valid quit message is handled.
 */
 private class QuittingState extends State {
 @Override
 public boolean processMessage(Message msg) {
 return NOT_HANDLED;
 }
 }
 /**
 * Handle messages sent to the state machine by calling
 * the current state's processMessage. It also handles
 * the enter/exit calls and placing any deferred messages
 * back onto the queue when transitioning to a new state.
 */
 @Override
 public final void handleMessage(Message msg) {
 if (!mHasQuit) {
 if (mSm != null && msg.what != SM_INIT_CMD && msg.what != SM_QUIT_CMD) {
 mSm.onPreHandleMessage(msg);
 }
 if (mDbg) mSm.log("handleMessage: E msg.what=" + msg.what);
 /** Save the current message */
 mMsg = msg;
 /** State that processed the message */
 State msgProcessedState = null;
 if (mIsConstructionCompleted || (mMsg.what == SM_QUIT_CMD)) {
 /** Normal path */
 msgProcessedState = processMsg(msg);
 } else if (!mIsConstructionCompleted && (mMsg.what == SM_INIT_CMD)
 && (mMsg.obj == mSmHandlerObj)) {
 /** Initial one time path. */
 mIsConstructionCompleted = true;
 invokeEnterMethods(0);
 } else {
 throw new RuntimeException("StateMachine.handleMessage: "
 + "The start method not called, received msg: " + msg);
 }
 performTransitions(msgProcessedState, msg);
 // We need to check if mSm == null here as we could be quitting.
 if (mDbg && mSm != null) mSm.log("handleMessage: X");
 if (mSm != null && msg.what != SM_INIT_CMD && msg.what != SM_QUIT_CMD) {
 mSm.onPostHandleMessage(msg);
 }
 }
 }
 /**
 * Do any transitions
 * @param msgProcessedState is the state that processed the message
 */
 private void performTransitions(State msgProcessedState, Message msg) {
 /**
 * If transitionTo has been called, exit and then enter
 * the appropriate states. We loop on this to allow
 * enter and exit methods to use transitionTo.
 */
 State orgState = mStateStack[mStateStackTopIndex].state;
 /**
 * Record whether message needs to be logged before we transition and
 * and we won't log special messages SM_INIT_CMD or SM_QUIT_CMD which
 * always set msg.obj to the handler.
 */
 boolean recordLogMsg = mSm.recordLogRec(mMsg) && (msg.obj != mSmHandlerObj);
 if (mLogRecords.logOnlyTransitions()) {
 /** Record only if there is a transition */
 if (mDestState != null) {
 mLogRecords.add(mSm, mMsg, mSm.getLogRecString(mMsg), msgProcessedState,
 orgState, mDestState);
 }
 } else if (recordLogMsg) {
 /** Record message */
 mLogRecords.add(mSm, mMsg, mSm.getLogRecString(mMsg), msgProcessedState, orgState,
 mDestState);
 }
 State destState = mDestState;
 if (destState != null) {
 /**
 * Process the transitions including transitions in the enter/exit methods
 */
 while (true) {
 if (mDbg) mSm.log("handleMessage: new destination call exit/enter");
 /**
 * Determine the states to exit and enter and return the
 * common ancestor state of the enter/exit states. Then
 * invoke the exit methods then the enter methods.
 */
 StateInfo commonStateInfo = setupTempStateStackWithStatesToEnter(destState);
 // flag is cleared in invokeEnterMethods before entering the target state
 mTransitionInProgress = true;
 invokeExitMethods(commonStateInfo);
 int stateStackEnteringIndex = moveTempStateStackToStateStack();
 invokeEnterMethods(stateStackEnteringIndex);
 /**
 * Since we have transitioned to a new state we need to have
 * any deferred messages moved to the front of the message queue
 * so they will be processed before any other messages in the
 * message queue.
 */
 moveDeferredMessageAtFrontOfQueue();
 if (destState != mDestState) {
 // A new mDestState so continue looping
 destState = mDestState;
 } else {
 // No change in mDestState so we're done
 break;
 }
 }
 mDestState = null;
 }
 /**
 * After processing all transitions check and
 * see if the last transition was to quit or halt.
 */
 if (destState != null) {
 if (destState == mQuittingState) {
 /**
 * Call onQuitting to let subclasses cleanup.
 */
 mSm.onQuitting();
 cleanupAfterQuitting();
 } else if (destState == mHaltingState) {
 /**
 * Call onHalting() if we've transitioned to the halting
 * state. All subsequent messages will be processed in
 * in the halting state which invokes haltedProcessMessage(msg);
 */
 mSm.onHalting();
 }
 }
 }
 /**
 * Cleanup all the static variables and the looper after the SM has been quit.
 */
 private final void cleanupAfterQuitting() {
 if (mSm.mSmThread != null) {
 // If we made the thread then quit looper which stops the thread.
 getLooper().quit();
 mSm.mSmThread = null;
 }
 mSm.mSmHandler = null;
 mSm = null;
 mMsg = null;
 mLogRecords.cleanup();
 mStateStack = null;
 mTempStateStack = null;
 mStateInfo.clear();
 mInitialState = null;
 mDestState = null;
 mDeferredMessages.clear();
 mHasQuit = true;
 }
 /**
 * Complete the construction of the state machine.
 */
 private final void completeConstruction() {
 if (mDbg) mSm.log("completeConstruction: E");
 /**
 * Determine the maximum depth of the state hierarchy
 * so we can allocate the state stacks.
 */
 int maxDepth = 0;
 for (StateInfo si : mStateInfo.values()) {
 int depth = 0;
 for (StateInfo i = si; i != null; depth++) {
 i = i.parentStateInfo;
 }
 if (maxDepth < depth) {
 maxDepth = depth;
 }
 }
 if (mDbg) mSm.log("completeConstruction: maxDepth=" + maxDepth);
 mStateStack = new StateInfo[maxDepth];
 mTempStateStack = new StateInfo[maxDepth];
 setupInitialStateStack();
 /** Sending SM_INIT_CMD message to invoke enter methods asynchronously */
 sendMessageAtFrontOfQueue(obtainMessage(SM_INIT_CMD, mSmHandlerObj));
 if (mDbg) mSm.log("completeConstruction: X");
 }
 /**
 * Process the message. If the current state doesn't handle
 * it, call the states parent and so on. If it is never handled then
 * call the state machines unhandledMessage method.
 * @return the state that processed the message
 */
 private final State processMsg(Message msg) {
 StateInfo curStateInfo = mStateStack[mStateStackTopIndex];
 if (mDbg) {
 mSm.log("processMsg: " + curStateInfo.state.getName());
 }
 if (isQuit(msg)) {
 transitionTo(mQuittingState);
 } else {
 while (!curStateInfo.state.processMessage(msg)) {
 /**
 * Not processed
 */
 curStateInfo = curStateInfo.parentStateInfo;
 if (curStateInfo == null) {
 /**
 * No parents left so it's not handled
 */
 mSm.unhandledMessage(msg);
 break;
 }
 if (mDbg) {
 mSm.log("processMsg: " + curStateInfo.state.getName());
 }
 }
 }
 return (curStateInfo != null) ? curStateInfo.state : null;
 }
 /**
 * Call the exit method for each state from the top of stack
 * up to the common ancestor state.
 */
 private final void invokeExitMethods(StateInfo commonStateInfo) {
 while ((mStateStackTopIndex >= 0)
 && (mStateStack[mStateStackTopIndex] != commonStateInfo)) {
 State curState = mStateStack[mStateStackTopIndex].state;
 if (mDbg) mSm.log("invokeExitMethods: " + curState.getName());
 curState.exit();
 mStateStack[mStateStackTopIndex].active = false;
 mStateStackTopIndex -= 1;
 }
 }
 /**
 * Invoke the enter method starting at the entering index to top of state stack
 */
 private final void invokeEnterMethods(int stateStackEnteringIndex) {
 for (int i = stateStackEnteringIndex; i <= mStateStackTopIndex; i++) {
 if (stateStackEnteringIndex == mStateStackTopIndex) {
 // Last enter state for transition
 mTransitionInProgress = false;
 }
 if (mDbg) mSm.log("invokeEnterMethods: " + mStateStack[i].state.getName());
 mStateStack[i].state.enter();
 mStateStack[i].active = true;
 }
 mTransitionInProgress = false; // ensure flag set to false if no methods called
 }
 /**
 * Move the deferred message to the front of the message queue.
 */
 private final void moveDeferredMessageAtFrontOfQueue() {
 /**
 * The oldest messages on the deferred list must be at
 * the front of the queue so start at the back, which
 * as the most resent message and end with the oldest
 * messages at the front of the queue.
 */
 for (int i = mDeferredMessages.size() - 1; i >= 0; i--) {
 Message curMsg = mDeferredMessages.get(i);
 if (mDbg) mSm.log("moveDeferredMessageAtFrontOfQueue; what=" + curMsg.what);
 sendMessageAtFrontOfQueue(curMsg);
 }
 mDeferredMessages.clear();
 }
 /**
 * Move the contents of the temporary stack to the state stack
 * reversing the order of the items on the temporary stack as
 * they are moved.
 *
 * @return index into mStateStack where entering needs to start
 */
 private final int moveTempStateStackToStateStack() {
 int startingIndex = mStateStackTopIndex + 1;
 int i = mTempStateStackCount - 1;
 int j = startingIndex;
 while (i >= 0) {
 if (mDbg) mSm.log("moveTempStackToStateStack: i=" + i + ",j=" + j);
 mStateStack[j] = mTempStateStack[i];
 j += 1;
 i -= 1;
 }
 mStateStackTopIndex = j - 1;
 if (mDbg) {
 mSm.log("moveTempStackToStateStack: X mStateStackTop=" + mStateStackTopIndex
 + ",startingIndex=" + startingIndex + ",Top="
 + mStateStack[mStateStackTopIndex].state.getName());
 }
 return startingIndex;
 }
 /**
 * Setup the mTempStateStack with the states we are going to enter.
 *
 * This is found by searching up the destState's ancestors for a
 * state that is already active i.e. StateInfo.active == true.
 * The destStae and all of its inactive parents will be on the
 * TempStateStack as the list of states to enter.
 *
 * @return StateInfo of the common ancestor for the destState and
 * current state or null if there is no common parent.
 */
 private final StateInfo setupTempStateStackWithStatesToEnter(State destState) {
 /**
 * Search up the parent list of the destination state for an active
 * state. Use a do while() loop as the destState must always be entered
 * even if it is active. This can happen if we are exiting/entering
 * the current state.
 */
 mTempStateStackCount = 0;
 StateInfo curStateInfo = mStateInfo.get(destState);
 do {
 mTempStateStack[mTempStateStackCount++] = curStateInfo;
 curStateInfo = curStateInfo.parentStateInfo;
 } while ((curStateInfo != null) && !curStateInfo.active);
 if (mDbg) {
 mSm.log("setupTempStateStackWithStatesToEnter: X mTempStateStackCount="
 + mTempStateStackCount + ",curStateInfo: " + curStateInfo);
 }
 return curStateInfo;
 }
 /**
 * Initialize StateStack to mInitialState.
 */
 private final void setupInitialStateStack() {
 if (mDbg) {
 mSm.log("setupInitialStateStack: E mInitialState=" + mInitialState.getName());
 }
 StateInfo curStateInfo = mStateInfo.get(mInitialState);
 for (mTempStateStackCount = 0; curStateInfo != null; mTempStateStackCount++) {
 mTempStateStack[mTempStateStackCount] = curStateInfo;
 curStateInfo = curStateInfo.parentStateInfo;
 }
 // Empty the StateStack
 mStateStackTopIndex = -1;
 moveTempStateStackToStateStack();
 }
 /**
 * @return current message
 */
 private final Message getCurrentMessage() {
 return mMsg;
 }
 /**
 * @return current state
 */
 private final IState getCurrentState() {
 return mStateStack[mStateStackTopIndex].state;
 }
 /**
 * Add a new state to the state machine. Bottom up addition
 * of states is allowed but the same state may only exist
 * in one hierarchy.
 *
 * @param state the state to add
 * @param parent the parent of state
 * @return stateInfo for this state
 */
 private final StateInfo addState(State state, State parent) {
 if (mDbg) {
 mSm.log("addStateInternal: E state=" + state.getName() + ",parent="
 + ((parent == null) ? "" : parent.getName()));
 }
 StateInfo parentStateInfo = null;
 if (parent != null) {
 parentStateInfo = mStateInfo.get(parent);
 if (parentStateInfo == null) {
 // Recursively add our parent as it's not been added yet.
 parentStateInfo = addState(parent, null);
 }
 }
 StateInfo stateInfo = mStateInfo.get(state);
 if (stateInfo == null) {
 stateInfo = new StateInfo();
 mStateInfo.put(state, stateInfo);
 }
 // Validate that we aren't adding the same state in two different hierarchies.
 if ((stateInfo.parentStateInfo != null)
 && (stateInfo.parentStateInfo != parentStateInfo)) {
 throw new RuntimeException("state already added");
 }
 stateInfo.state = state;
 stateInfo.parentStateInfo = parentStateInfo;
 stateInfo.active = false;
 if (mDbg) mSm.log("addStateInternal: X stateInfo: " + stateInfo);
 return stateInfo;
 }
 /**
 * Remove a state from the state machine. Will not remove the state if it is currently
 * active or if it has any children in the hierarchy.
 * @param state the state to remove
 */
 private void removeState(State state) {
 StateInfo stateInfo = mStateInfo.get(state);
 if (stateInfo == null || stateInfo.active) {
 return;
 }
 boolean isParent = mStateInfo.values().stream()
 .filter(si -> si.parentStateInfo == stateInfo)
 .findAny()
 .isPresent();
 if (isParent) {
 return;
 }
 mStateInfo.remove(state);
 }
 /**
 * Constructor
 *
 * @param looper for dispatching messages
 * @param sm the hierarchical state machine
 */
 private SmHandler(Looper looper, StateMachine sm) {
 super(looper);
 mSm = sm;
 addState(mHaltingState, null);
 addState(mQuittingState, null);
 }
 /** @see StateMachine#setInitialState(State) */
 private final void setInitialState(State initialState) {
 if (mDbg) mSm.log("setInitialState: initialState=" + initialState.getName());
 mInitialState = initialState;
 }
 /** @see StateMachine#transitionTo(IState) */
 private final void transitionTo(IState destState) {
 if (mTransitionInProgress) {
 Log.wtf(mSm.mName, "transitionTo called while transition already in progress to " +
 mDestState + ", new target state=" + destState);
 }
 mDestState = (State) destState;
 if (mDbg) mSm.log("transitionTo: destState=" + mDestState.getName());
 }
 /** @see StateMachine#deferMessage(Message) */
 private final void deferMessage(Message msg) {
 if (mDbg) mSm.log("deferMessage: msg=" + msg.what);
 /* Copy the "msg" to "newMsg" as "msg" will be recycled */
 Message newMsg = obtainMessage();
 newMsg.copyFrom(msg);
 mDeferredMessages.add(newMsg);
 }
 /** @see StateMachine#quit() */
 private final void quit() {
 if (mDbg) mSm.log("quit:");
 sendMessage(obtainMessage(SM_QUIT_CMD, mSmHandlerObj));
 }
 /** @see StateMachine#quitNow() */
 private final void quitNow() {
 if (mDbg) mSm.log("quitNow:");
 sendMessageAtFrontOfQueue(obtainMessage(SM_QUIT_CMD, mSmHandlerObj));
 }
 /** Validate that the message was sent by quit or quitNow. */
 private final boolean isQuit(Message msg) {
 return (msg.what == SM_QUIT_CMD) && (msg.obj == mSmHandlerObj);
 }
 /** @see StateMachine#isDbg() */
 private final boolean isDbg() {
 return mDbg;
 }
 /** @see StateMachine#setDbg(boolean) */
 private final void setDbg(boolean dbg) {
 mDbg = dbg;
 }
 }
 private SmHandler mSmHandler;
 private HandlerThread mSmThread;
 /**
 * Initialize.
 *
 * @param looper for this state machine
 * @param name of the state machine
 */
 private void initStateMachine(String name, Looper looper) {
 mName = name;
 mSmHandler = new SmHandler(looper, this);
 }
 /**
 * Constructor creates a StateMachine with its own thread.
 *
 * @param name of the state machine
 */
 @UnsupportedAppUsage
 protected StateMachine(String name) {
 mSmThread = new HandlerThread(name);
 mSmThread.start();
 Looper looper = mSmThread.getLooper();
 initStateMachine(name, looper);
 }
 /**
 * Constructor creates a StateMachine using the looper.
 *
 * @param name of the state machine
 */
 @UnsupportedAppUsage
 protected StateMachine(String name, Looper looper) {
 initStateMachine(name, looper);
 }
 /**
 * Constructor creates a StateMachine using the handler.
 *
 * @param name of the state machine
 */
 @UnsupportedAppUsage
 protected StateMachine(String name, Handler handler) {
 initStateMachine(name, handler.getLooper());
 }
 /**
 * Notifies subclass that the StateMachine handler is about to process the Message msg
 * @param msg The message that is being handled
 */
 protected void onPreHandleMessage(Message msg) {
 }
 /**
 * Notifies subclass that the StateMachine handler has finished processing the Message msg and
 * has possibly transitioned to a new state.
 * @param msg The message that is being handled
 */
 protected void onPostHandleMessage(Message msg) {
 }
 /**
 * Add a new state to the state machine
 * @param state the state to add
 * @param parent the parent of state
 */
 public final void addState(State state, State parent) {
 mSmHandler.addState(state, parent);
 }
 /**
 * Add a new state to the state machine, parent will be null
 * @param state to add
 */
 @UnsupportedAppUsage
 public final void addState(State state) {
 mSmHandler.addState(state, null);
 }
 /**
 * Removes a state from the state machine, unless it is currently active or if it has children.
 * @param state state to remove
 */
 public final void removeState(State state) {
 mSmHandler.removeState(state);
 }
 /**
 * Set the initial state. This must be invoked before
 * and messages are sent to the state machine.
 *
 * @param initialState is the state which will receive the first message.
 */
 @UnsupportedAppUsage
 public final void setInitialState(State initialState) {
 mSmHandler.setInitialState(initialState);
 }
 /**
 * @return current message
 */
 public final Message getCurrentMessage() {
 // mSmHandler can be null if the state machine has quit.
 SmHandler smh = mSmHandler;
 if (smh == null) return null;
 return smh.getCurrentMessage();
 }
 /**
 * @return current state
 */
 public final IState getCurrentState() {
 // mSmHandler can be null if the state machine has quit.
 SmHandler smh = mSmHandler;
 if (smh == null) return null;
 return smh.getCurrentState();
 }
 /**
 * transition to destination state. Upon returning
 * from processMessage the current state's exit will
 * be executed and upon the next message arriving
 * destState.enter will be invoked.
 *
 * this function can also be called inside the enter function of the
 * previous transition target, but the behavior is undefined when it is
 * called mid-way through a previous transition (for example, calling this
 * in the enter() routine of a intermediate node when the current transition
 * target is one of the nodes descendants).
 *
 * @param destState will be the state that receives the next message.
 */
 @UnsupportedAppUsage
 public final void transitionTo(IState destState) {
 mSmHandler.transitionTo(destState);
 }
 /**
 * transition to halt state. Upon returning
 * from processMessage we will exit all current
 * states, execute the onHalting() method and then
 * for all subsequent messages haltedProcessMessage
 * will be called.
 */
 public final void transitionToHaltingState() {
 mSmHandler.transitionTo(mSmHandler.mHaltingState);
 }
 /**
 * Defer this message until next state transition.
 * Upon transitioning all deferred messages will be
 * placed on the queue and reprocessed in the original
 * order. (i.e. The next state the oldest messages will
 * be processed first)
 *
 * @param msg is deferred until the next transition.
 */
 public final void deferMessage(Message msg) {
 mSmHandler.deferMessage(msg);
 }
 /**
 * Called when message wasn't handled
 *
 * @param msg that couldn't be handled.
 */
 protected void unhandledMessage(Message msg) {
 if (mSmHandler.mDbg) loge(" - unhandledMessage: msg.what=" + msg.what);
 }
 /**
 * Called for any message that is received after
 * transitionToHalting is called.
 */
 protected void haltedProcessMessage(Message msg) {
 }
 /**
 * This will be called once after handling a message that called
 * transitionToHalting. All subsequent messages will invoke
 * {@link StateMachine#haltedProcessMessage(Message)}
 */
 protected void onHalting() {
 }
 /**
 * This will be called once after a quit message that was NOT handled by
 * the derived StateMachine. The StateMachine will stop and any subsequent messages will be
 * ignored. In addition, if this StateMachine created the thread, the thread will
 * be stopped after this method returns.
 */
 protected void onQuitting() {
 }
 /**
 * @return the name
 */
 public final String getName() {
 return mName;
 }
 /**
 * Set number of log records to maintain and clears all current records.
 *
 * @param maxSize number of messages to maintain at anyone time.
 */
 public final void setLogRecSize(int maxSize) {
 mSmHandler.mLogRecords.setSize(maxSize);
 }
 /**
 * Set to log only messages that cause a state transition
 *
 * @param enable {@code true} to enable, {@code false} to disable
 */
 public final void setLogOnlyTransitions(boolean enable) {
 mSmHandler.mLogRecords.setLogOnlyTransitions(enable);
 }
 /**
 * @return the number of log records currently readable
 */
 public final int getLogRecSize() {
 // mSmHandler can be null if the state machine has quit.
 SmHandler smh = mSmHandler;
 if (smh == null) return 0;
 return smh.mLogRecords.size();
 }
 /**
 * @return the number of log records we can store
 */
 @VisibleForTesting
 public final int getLogRecMaxSize() {
 // mSmHandler can be null if the state machine has quit.
 SmHandler smh = mSmHandler;
 if (smh == null) return 0;
 return smh.mLogRecords.mMaxSize;
 }
 /**
 * @return the total number of records processed
 */
 public final int getLogRecCount() {
 // mSmHandler can be null if the state machine has quit.
 SmHandler smh = mSmHandler;
 if (smh == null) return 0;
 return smh.mLogRecords.count();
 }
 /**
 * @return a log record, or null if index is out of range
 */
 public final LogRec getLogRec(int index) {
 // mSmHandler can be null if the state machine has quit.
 SmHandler smh = mSmHandler;
 if (smh == null) return null;
 return smh.mLogRecords.get(index);
 }
 /**
 * @return a copy of LogRecs as a collection
 */
 public final Collection<LogRec> copyLogRecs() {
 Vector<LogRec> vlr = new Vector<LogRec>();
 SmHandler smh = mSmHandler;
 if (smh != null) {
 for (LogRec lr : smh.mLogRecords.mLogRecVector) {
 vlr.add(lr);
 }
 }
 return vlr;
 }
 /**
 * Add the string to LogRecords.
 *
 * @param string
 */
 public void addLogRec(String string) {
 // mSmHandler can be null if the state machine has quit.
 SmHandler smh = mSmHandler;
 if (smh == null) return;
 smh.mLogRecords.add(this, smh.getCurrentMessage(), string, smh.getCurrentState(),
 smh.mStateStack[smh.mStateStackTopIndex].state, smh.mDestState);
 }
 /**
 * @return true if msg should be saved in the log, default is true.
 */
 protected boolean recordLogRec(Message msg) {
 return true;
 }
 /**
 * Return a string to be logged by LogRec, default
 * is an empty string. Override if additional information is desired.
 *
 * @param msg that was processed
 * @return information to be logged as a String
 */
 protected String getLogRecString(Message msg) {
 return "";
 }
 /**
 * @return the string for msg.what
 */
 protected String getWhatToString(int what) {
 return null;
 }
 /**
 * @return Handler, maybe null if state machine has quit.
 */
 public final Handler getHandler() {
 return mSmHandler;
 }
 /**
 * Get a message and set Message.target state machine handler.
 *
 * Note: The handler can be null if the state machine has quit,
 * which means target will be null and may cause a AndroidRuntimeException
 * in MessageQueue#enqueMessage if sent directly or if sent using
 * StateMachine#sendMessage the message will just be ignored.
 *
 * @return A Message object from the global pool
 */
 public final Message obtainMessage() {
 return Message.obtain(mSmHandler);
 }
 /**
 * Get a message and set Message.target state machine handler, what.
 *
 * Note: The handler can be null if the state machine has quit,
 * which means target will be null and may cause a AndroidRuntimeException
 * in MessageQueue#enqueMessage if sent directly or if sent using
 * StateMachine#sendMessage the message will just be ignored.
 *
 * @param what is the assigned to Message.what.
 * @return A Message object from the global pool
 */
 public final Message obtainMessage(int what) {
 return Message.obtain(mSmHandler, what);
 }
 /**
 * Get a message and set Message.target state machine handler,
 * what and obj.
 *
 * Note: The handler can be null if the state machine has quit,
 * which means target will be null and may cause a AndroidRuntimeException
 * in MessageQueue#enqueMessage if sent directly or if sent using
 * StateMachine#sendMessage the message will just be ignored.
 *
 * @param what is the assigned to Message.what.
 * @param obj is assigned to Message.obj.
 * @return A Message object from the global pool
 */
 public final Message obtainMessage(int what, Object obj) {
 return Message.obtain(mSmHandler, what, obj);
 }
 /**
 * Get a message and set Message.target state machine handler,
 * what, arg1 and arg2
 *
 * Note: The handler can be null if the state machine has quit,
 * which means target will be null and may cause a AndroidRuntimeException
 * in MessageQueue#enqueMessage if sent directly or if sent using
 * StateMachine#sendMessage the message will just be ignored.
 *
 * @param what is assigned to Message.what
 * @param arg1 is assigned to Message.arg1
 * @return A Message object from the global pool
 */
 public final Message obtainMessage(int what, int arg1) {
 // use this obtain so we don't match the obtain(h, what, Object) method
 return Message.obtain(mSmHandler, what, arg1, 0);
 }
 /**
 * Get a message and set Message.target state machine handler,
 * what, arg1 and arg2
 *
 * Note: The handler can be null if the state machine has quit,
 * which means target will be null and may cause a AndroidRuntimeException
 * in MessageQueue#enqueMessage if sent directly or if sent using
 * StateMachine#sendMessage the message will just be ignored.
 *
 * @param what is assigned to Message.what
 * @param arg1 is assigned to Message.arg1
 * @param arg2 is assigned to Message.arg2
 * @return A Message object from the global pool
 */
 @UnsupportedAppUsage
 public final Message obtainMessage(int what, int arg1, int arg2) {
 return Message.obtain(mSmHandler, what, arg1, arg2);
 }
 /**
 * Get a message and set Message.target state machine handler,
 * what, arg1, arg2 and obj
 *
 * Note: The handler can be null if the state machine has quit,
 * which means target will be null and may cause a AndroidRuntimeException
 * in MessageQueue#enqueMessage if sent directly or if sent using
 * StateMachine#sendMessage the message will just be ignored.
 *
 * @param what is assigned to Message.what
 * @param arg1 is assigned to Message.arg1
 * @param arg2 is assigned to Message.arg2
 * @param obj is assigned to Message.obj
 * @return A Message object from the global pool
 */
 @UnsupportedAppUsage
 public final Message obtainMessage(int what, int arg1, int arg2, Object obj) {
 return Message.obtain(mSmHandler, what, arg1, arg2, obj);
 }
 /**
 * Enqueue a message to this state machine.
 *
 * Message is ignored if state machine has quit.
 */
 @UnsupportedAppUsage
 public void sendMessage(int what) {
 // mSmHandler can be null if the state machine has quit.
 SmHandler smh = mSmHandler;
 if (smh == null) return;
 smh.sendMessage(obtainMessage(what));
 }
 /**
 * Enqueue a message to this state machine.
 *
 * Message is ignored if state machine has quit.
 */
 @UnsupportedAppUsage
 public void sendMessage(int what, Object obj) {
 // mSmHandler can be null if the state machine has quit.
 SmHandler smh = mSmHandler;
 if (smh == null) return;
 smh.sendMessage(obtainMessage(what, obj));
 }
 /**
 * Enqueue a message to this state machine.
 *
 * Message is ignored if state machine has quit.
 */
 @UnsupportedAppUsage
 public void sendMessage(int what, int arg1) {
 // mSmHandler can be null if the state machine has quit.
 SmHandler smh = mSmHandler;
 if (smh == null) return;
 smh.sendMessage(obtainMessage(what, arg1));
 }
 /**
 * Enqueue a message to this state machine.
 *
 * Message is ignored if state machine has quit.
 */
 public void sendMessage(int what, int arg1, int arg2) {
 // mSmHandler can be null if the state machine has quit.
 SmHandler smh = mSmHandler;
 if (smh == null) return;
 smh.sendMessage(obtainMessage(what, arg1, arg2));
 }
 /**
 * Enqueue a message to this state machine.
 *
 * Message is ignored if state machine has quit.
 */
 @UnsupportedAppUsage
 public void sendMessage(int what, int arg1, int arg2, Object obj) {
 // mSmHandler can be null if the state machine has quit.
 SmHandler smh = mSmHandler;
 if (smh == null) return;
 smh.sendMessage(obtainMessage(what, arg1, arg2, obj));
 }
 /**
 * Enqueue a message to this state machine.
 *
 * Message is ignored if state machine has quit.
 */
 @UnsupportedAppUsage
 public void sendMessage(Message msg) {
 // mSmHandler can be null if the state machine has quit.
 SmHandler smh = mSmHandler;
 if (smh == null) return;
 smh.sendMessage(msg);
 }
 /**
 * Enqueue a message to this state machine after a delay.
 *
 * Message is ignored if state machine has quit.
 */
 public void sendMessageDelayed(int what, long delayMillis) {
 // mSmHandler can be null if the state machine has quit.
 SmHandler smh = mSmHandler;
 if (smh == null) return;
 smh.sendMessageDelayed(obtainMessage(what), delayMillis);
 }
 /**
 * Enqueue a message to this state machine after a delay.
 *
 * Message is ignored if state machine has quit.
 */
 public void sendMessageDelayed(int what, Object obj, long delayMillis) {
 // mSmHandler can be null if the state machine has quit.
 SmHandler smh = mSmHandler;
 if (smh == null) return;
 smh.sendMessageDelayed(obtainMessage(what, obj), delayMillis);
 }
 /**
 * Enqueue a message to this state machine after a delay.
 *
 * Message is ignored if state machine has quit.
 */
 public void sendMessageDelayed(int what, int arg1, long delayMillis) {
 // mSmHandler can be null if the state machine has quit.
 SmHandler smh = mSmHandler;
 if (smh == null) return;
 smh.sendMessageDelayed(obtainMessage(what, arg1), delayMillis);
 }
 /**
 * Enqueue a message to this state machine after a delay.
 *
 * Message is ignored if state machine has quit.
 */
 public void sendMessageDelayed(int what, int arg1, int arg2, long delayMillis) {
 // mSmHandler can be null if the state machine has quit.
 SmHandler smh = mSmHandler;
 if (smh == null) return;
 smh.sendMessageDelayed(obtainMessage(what, arg1, arg2), delayMillis);
 }
 /**
 * Enqueue a message to this state machine after a delay.
 *
 * Message is ignored if state machine has quit.
 */
 public void sendMessageDelayed(int what, int arg1, int arg2, Object obj,
 long delayMillis) {
 // mSmHandler can be null if the state machine has quit.
 SmHandler smh = mSmHandler;
 if (smh == null) return;
 smh.sendMessageDelayed(obtainMessage(what, arg1, arg2, obj), delayMillis);
 }
 /**
 * Enqueue a message to this state machine after a delay.
 *
 * Message is ignored if state machine has quit.
 */
 public void sendMessageDelayed(Message msg, long delayMillis) {
 // mSmHandler can be null if the state machine has quit.
 SmHandler smh = mSmHandler;
 if (smh == null) return;
 smh.sendMessageDelayed(msg, delayMillis);
 }
 /**
 * Enqueue a message to the front of the queue for this state machine.
 * Protected, may only be called by instances of StateMachine.
 *
 * Message is ignored if state machine has quit.
 */
 protected final void sendMessageAtFrontOfQueue(int what) {
 // mSmHandler can be null if the state machine has quit.
 SmHandler smh = mSmHandler;
 if (smh == null) return;
 smh.sendMessageAtFrontOfQueue(obtainMessage(what));
 }
 /**
 * Enqueue a message to the front of the queue for this state machine.
 * Protected, may only be called by instances of StateMachine.
 *
 * Message is ignored if state machine has quit.
 */
 protected final void sendMessageAtFrontOfQueue(int what, Object obj) {
 // mSmHandler can be null if the state machine has quit.
 SmHandler smh = mSmHandler;
 if (smh == null) return;
 smh.sendMessageAtFrontOfQueue(obtainMessage(what, obj));
 }
 /**
 * Enqueue a message to the front of the queue for this state machine.
 * Protected, may only be called by instances of StateMachine.
 *
 * Message is ignored if state machine has quit.
 */
 protected final void sendMessageAtFrontOfQueue(int what, int arg1) {
 // mSmHandler can be null if the state machine has quit.
 SmHandler smh = mSmHandler;
 if (smh == null) return;
 smh.sendMessageAtFrontOfQueue(obtainMessage(what, arg1));
 }
 /**
 * Enqueue a message to the front of the queue for this state machine.
 * Protected, may only be called by instances of StateMachine.
 *
 * Message is ignored if state machine has quit.
 */
 protected final void sendMessageAtFrontOfQueue(int what, int arg1, int arg2) {
 // mSmHandler can be null if the state machine has quit.
 SmHandler smh = mSmHandler;
 if (smh == null) return;
 smh.sendMessageAtFrontOfQueue(obtainMessage(what, arg1, arg2));
 }
 /**
 * Enqueue a message to the front of the queue for this state machine.
 * Protected, may only be called by instances of StateMachine.
 *
 * Message is ignored if state machine has quit.
 */
 protected final void sendMessageAtFrontOfQueue(int what, int arg1, int arg2, Object obj) {
 // mSmHandler can be null if the state machine has quit.
 SmHandler smh = mSmHandler;
 if (smh == null) return;
 smh.sendMessageAtFrontOfQueue(obtainMessage(what, arg1, arg2, obj));
 }
 /**
 * Enqueue a message to the front of the queue for this state machine.
 * Protected, may only be called by instances of StateMachine.
 *
 * Message is ignored if state machine has quit.
 */
 protected final void sendMessageAtFrontOfQueue(Message msg) {
 // mSmHandler can be null if the state machine has quit.
 SmHandler smh = mSmHandler;
 if (smh == null) return;
 smh.sendMessageAtFrontOfQueue(msg);
 }
 /**
 * Removes a message from the message queue.
 * Protected, may only be called by instances of StateMachine.
 */
 protected final void removeMessages(int what) {
 // mSmHandler can be null if the state machine has quit.
 SmHandler smh = mSmHandler;
 if (smh == null) return;
 smh.removeMessages(what);
 }
 /**
 * Removes a message from the deferred messages queue.
 */
 protected final void removeDeferredMessages(int what) {
 SmHandler smh = mSmHandler;
 if (smh == null) return;
 Iterator<Message> iterator = smh.mDeferredMessages.iterator();
 while (iterator.hasNext()) {
 Message msg = iterator.next();
 if (msg.what == what) iterator.remove();
 }
 }
 /**
 * Check if there are any pending messages with code 'what' in deferred messages queue.
 */
 protected final boolean hasDeferredMessages(int what) {
 SmHandler smh = mSmHandler;
 if (smh == null) return false;
 Iterator<Message> iterator = smh.mDeferredMessages.iterator();
 while (iterator.hasNext()) {
 Message msg = iterator.next();
 if (msg.what == what) return true;
 }
 return false;
 }
 /**
 * Check if there are any pending posts of messages with code 'what' in
 * the message queue. This does NOT check messages in deferred message queue.
 */
 protected final boolean hasMessages(int what) {
 SmHandler smh = mSmHandler;
 if (smh == null) return false;
 return smh.hasMessages(what);
 }
 /**
 * Validate that the message was sent by
 * {@link StateMachine#quit} or {@link StateMachine#quitNow}.
 * */
 protected final boolean isQuit(Message msg) {
 // mSmHandler can be null if the state machine has quit.
 SmHandler smh = mSmHandler;
 if (smh == null) return msg.what == SM_QUIT_CMD;
 return smh.isQuit(msg);
 }
 /**
 * Quit the state machine after all currently queued up messages are processed.
 */
 public final void quit() {
 // mSmHandler can be null if the state machine is already stopped.
 SmHandler smh = mSmHandler;
 if (smh == null) return;
 smh.quit();
 }
 /**
 * Quit the state machine immediately all currently queued messages will be discarded.
 */
 public final void quitNow() {
 // mSmHandler can be null if the state machine is already stopped.
 SmHandler smh = mSmHandler;
 if (smh == null) return;
 smh.quitNow();
 }
 /**
 * @return if debugging is enabled
 */
 public boolean isDbg() {
 // mSmHandler can be null if the state machine has quit.
 SmHandler smh = mSmHandler;
 if (smh == null) return false;
 return smh.isDbg();
 }
 /**
 * Set debug enable/disabled.
 *
 * @param dbg is true to enable debugging.
 */
 public void setDbg(boolean dbg) {
 // mSmHandler can be null if the state machine has quit.
 SmHandler smh = mSmHandler;
 if (smh == null) return;
 smh.setDbg(dbg);
 }
 /**
 * Start the state machine.
 */
 @UnsupportedAppUsage
 public void start() {
 // mSmHandler can be null if the state machine has quit.
 SmHandler smh = mSmHandler;
 if (smh == null) return;
 /** Send the complete construction message */
 smh.completeConstruction();
 }
 /**
 * Dump the current state.
 *
 * @param fd
 * @param pw
 * @param args
 */
 @UnsupportedAppUsage
 public void dump(FileDescriptor fd, PrintWriter pw, String[] args) {
 pw.println(getName() + ":");
 pw.println(" total records=" + getLogRecCount());
 for (int i = 0; i < getLogRecSize(); i++) {
 pw.println(" rec[" + i + "]: " + getLogRec(i));
 pw.flush();
 }
 final IState curState = getCurrentState();
 pw.println("curState=" + (curState == null ? "<QUIT>" : curState.getName()));
 }
 @Override
 public String toString() {
 String name = "(null)";
 String state = "(null)";
 try {
 name = mName.toString();
 state = mSmHandler.getCurrentState().getName().toString();
 } catch (NullPointerException | ArrayIndexOutOfBoundsException e) {
 // Will use default(s) initialized above.
 }
 return "name=" + name + " state=" + state;
 }
 /**
 * Log with debug and add to the LogRecords.
 *
 * @param s is string log
 */
 protected void logAndAddLogRec(String s) {
 addLogRec(s);
 log(s);
 }
 /**
 * Log with debug
 *
 * @param s is string log
 */
 protected void log(String s) {
 Log.d(mName, s);
 }
 /**
 * Log with debug attribute
 *
 * @param s is string log
 */
 protected void logd(String s) {
 Log.d(mName, s);
 }
 /**
 * Log with verbose attribute
 *
 * @param s is string log
 */
 protected void logv(String s) {
 Log.v(mName, s);
 }
 /**
 * Log with info attribute
 *
 * @param s is string log
 */
 protected void logi(String s) {
 Log.i(mName, s);
 }
 /**
 * Log with warning attribute
 *
 * @param s is string log
 */
 protected void logw(String s) {
 Log.w(mName, s);
 }
 /**
 * Log with error attribute
 *
 * @param s is string log
 */
 protected void loge(String s) {
 Log.e(mName, s);
 }
 /**
 * Log with error attribute
 *
 * @param s is string log
 * @param e is a Throwable which logs additional information.
 */
 protected void loge(String s, Throwable e) {
 Log.e(mName, s, e);
 }
 }

如果在自己项目中使用HSM层次状态机,把上面三个文件直接复制到自己项目中去。去掉一些源代码中无关紧要的注解符即可。

[https_android.googlesource.com_platform_frameworks_base_refs_heads_master_core_java_com_android_internal_util]: https://android.googlesource.com/platform/frameworks/base/+/refs/heads/master/core/java/com/android/internal/util/