Android 触摸手势(来自官方文档)

女爷i 2022-07-18 00:09 258阅读 0赞

# Detecting Common Gestures(参考来自官方文档) #

本文翻译自安卓官方文档: [https://developer.android.com/training/gestures/detector.html\#detect][https_developer.android.com_training_gestures_detector.html_detect]

Detecting Common Gestures,一般分为两个阶段:

**一: Gathering data about touch events.(收集数据)**

**二: Interpreting the data to see if it meets the criteria for any of the gestures your app supports.(根据自己需要使用检测到的数据)**

本文主要涉及到 GestureDetectorCompat 和 MotionEventCompat 两个类,这两个类在 Support Library中,Support Library classes 可以支持在API 1.6版本 以上使用.

**另外,关于 MotionEvent 和MotionEventCompat:** 和MotionEventCompat不是MotionEvent的替代,它仅仅提供了一些静态方法,

> Note that MotionEventCompat is not a replacement for the MotionEvent class. Rather, it provides static utility methods to which you pass your MotionEvent object in order to receive the desired action associated with that event

## Gather Data ##

当手指触摸屏幕时,就会触发 onTouchEvent() 方法,作为一个 系统任务 接收触摸事件,  
当最后一个手指离开时,结束 gesture ,并把 MotionEvent 传递给onTouchEvent(),这样就可以  
根据需要使用MotionEvent提供的详细测量数据.

### 在Activity 或者View中获取触摸事件 ###

为了截获touch事件，你需要覆写Activity或View的onTouchEvent方法

下面是一个在Activity中,获取触摸事件的示例:

public class MainActivity extends AppCompatActivity { 
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);
        }
    
        // This example shows an Activity, but you would use the same approach if
        // you were subclassing a View.
        @Override
        public boolean onTouchEvent(MotionEvent event) {
              final String DEBUG_TAG = "Gestures";
    
            int action = MotionEventCompat.getActionMasked(event);
    
            switch (action) {
                case (MotionEvent.ACTION_DOWN):
                    Log.d(DEBUG_TAG, "Action was DOWN");
                    return true;
                case (MotionEvent.ACTION_MOVE):
                    Log.d(DEBUG_TAG, "Action was MOVE");
                    return true;
                case (MotionEvent.ACTION_UP):
                    Log.d(DEBUG_TAG, "Action was UP");
                    return true;
                case (MotionEvent.ACTION_CANCEL):
                    Log.d(DEBUG_TAG, "Action was CANCEL");
                    return true;
                case (MotionEvent.ACTION_OUTSIDE):
                    Log.d(DEBUG_TAG, "Movement occurred outside bounds " +
                            "of current screen element");
                    return true;
                default:
                    return super.onTouchEvent(event);
            }
    
    
        }
    }

如图:

![这里写图片描述][20160902113416386]

**接下来看看在View中如何获取触摸事件呢:**

在view中,你可以使用 setOnTouchListener() 方法依附于任何一个 实现了 View.OnTouchListener 接口的对象.这样就可以不继承View而处理点击事件

public class MainActivity extends AppCompatActivity implements View.OnTouchListener{ 
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);
    
            TextView textView = (TextView) findViewById(R.id.tv);
            textView.setOnTouchListener(this);
    
        }
    
        @Override
        public boolean onTouch(View v, MotionEvent event) {
    
            // ... Respond to touch events
            final String DEBUG_TAG = "Gestures";
    
            int action = MotionEventCompat.getActionMasked(event);
    
            switch (action) {
                case (MotionEvent.ACTION_DOWN):
                    Log.d(DEBUG_TAG, "Action was DOWN");
                    return true;
                case (MotionEvent.ACTION_MOVE):
                    Log.d(DEBUG_TAG, "Action was MOVE");
                    return true;
                case (MotionEvent.ACTION_UP):
                    Log.d(DEBUG_TAG, "Action was UP");
                    return true;
                case (MotionEvent.ACTION_CANCEL):
                    Log.d(DEBUG_TAG, "Action was CANCEL");
                    return true;
                case (MotionEvent.ACTION_OUTSIDE):
                    Log.d(DEBUG_TAG, "Movement occurred outside bounds " +
                            "of current screen element");
                    return true;
                default:
                    return super.onTouchEvent(event);
            }
        }
    }

运行后如图:

![这里写图片描述][20160902113644656]

可以看出,当点击TextView时,会相应不同的触摸事件.而点击TextView以外的部分则不会.

**注意:**创建Listener的时候,对于ACTION\_DOWN 如果返回的是 false,listener将不会调用 ACTION\_MOVE 和ACTION\_UP 等事件,这是因为ACTION\_DOWN 是所有触摸事件的开始

当然,如果你创建一个自定义的View,你可以重写 上面的 onTouchEvent() 方法.

## Detect Gestures(检测手势) ##

Android提供了GestureDetector 类来检测一般的手势。

### Detecting All Supported Gestures ###

1.生成GestureDetector 对象（或GestureDetectorCompat对象），构造时的参数传入监听器对象。

监听器对象实现GestureDetector.OnGestureListener 接口。当一个触摸事件发生的时候,接口 GestureDetector.OnGestureListener 就会通知用户.

**为了让 GestureDetector对象接收到事件，需要覆写View或Activity中的 onTouchEvent()方法，将事件传递给detector对象。**

public class MainActivity extends AppCompatActivity implements GestureDetector.OnGestureListener, GestureDetector.OnDoubleTapListener { 
        private static final String DEBUG_TAG = "Gestures";
        private GestureDetector mDetector;
    
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);
    
            // Instantiate the gesture detector with the
            // application context and an implementation of
            // GestureDetector.OnGestureListener
            mDetector = new GestureDetector(this, this);
            // Set the gesture detector as the double tap
            // listener.
            mDetector.setOnDoubleTapListener(this);
    
    
        }
    
    //为了让 GestureDetector对象接收到事件，需要覆写View或Activity中的 onTouchEvent()方法，将事件传递给detector对象
        @Override
        public boolean onTouchEvent(MotionEvent event) {
            this.mDetector.onTouchEvent(event);
            // Be sure to call the superclass implementation
            return super.onTouchEvent(event);
        }
    
        @Override
        public boolean onDown(MotionEvent event) {
            Log.d(DEBUG_TAG,"onDown:-------------- " + event.toString());
            return true;
        }
    
        @Override
        public void onShowPress(MotionEvent event) {
            Log.d(DEBUG_TAG, "onShowPress:-------------- " + event.toString());
        }
    
    
    
        @Override
        public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {
            Log.d(DEBUG_TAG, "onScroll:-------------- " + e1.toString()+e2.toString());
            return true;
        }
    
        @Override
        public void onLongPress(MotionEvent event) {
            Log.d(DEBUG_TAG, "onLongPress:-------------- " + event.toString());
        }
    
        @Override
        public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
            Log.d(DEBUG_TAG, "onFling: --------------" + e1.toString()+e2.toString());
            return true;
        }
    
        @Override
        public boolean onSingleTapConfirmed(MotionEvent event) {
            Log.d(DEBUG_TAG, "onSingleTapConfirmed:-------------- " + event.toString());
            return true;
        }
        @Override
        public boolean onSingleTapUp(MotionEvent event) {
            Log.d(DEBUG_TAG, "onSingleTapUp:-------------- " + event.toString());
            return true;
        }
    
        @Override
        public boolean onDoubleTap(MotionEvent event) {
            Log.d(DEBUG_TAG, "onDoubleTap:-------------- " + event.toString());
            return true;
        }
    
        @Override
        public boolean onDoubleTapEvent(MotionEvent event) {
            Log.d(DEBUG_TAG, "onDoubleTapEvent:-------------- " + event.toString());
            return true;
        }
    }

*  实现 GestureDetector.OnGestureListener 接口需要重写一下抽象方法

![这里写图片描述][20160902113558471]  
\* 实现 GestureDetector.OnDoubleTapListener 接口需要重写以下方法:

![这里写图片描述][20160902113519705]

上述方法,返回值为 ture 表明拦截该事件,反而言之,返回false表明不拦截,事件继续传递.

通过上面的实例,在实际操作之后,你就会明白 你的一次屏幕触摸竟会怎样引起一个相互作用的MotionEvent事件,你的一次简单的触摸会引起怎样的复杂的 事件交互.

### GestureDetector.SimpleOnGestureListener类 ###

如果你仅仅是想利用其中的一些手势而不是全部，那么你可以选择继承GestureDetector.SimpleOnGestureListener类，这是一个适配器模式，即这个类实现了GestureDetector.OnGestureListener 接口，为其中所有的方法提供了空实现（返回值都是false），当继承GestureDetector.SimpleOnGestureListener类时，子类只需要覆写感兴趣的方法，其他方法是空实现。

下面这个实例,创建了一个内部类继承了 GestureDetector.SimpleOnGestureListener ,并且选择性的重写了 GestureDetector.SimpleOnGestureListener 的 onDown() 和 onFling() 方法

public class MainActivity extends AppCompatActivity{ 
        private static final String DEBUG_TAG = "Gestures";
        private GestureDetectorCompat mGesture;
    
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);
    
            mGesture = new GestureDetectorCompat(this,new MyGestureListener());
    
        }
    
        @Override
        public boolean onTouchEvent(MotionEvent event) {
            this.mGesture.onTouchEvent(event);
            return super.onTouchEvent(event);
        }
    
        class MyGestureListener extends GestureDetector.SimpleOnGestureListener{
    
            //选择性的重写 GestureDetector.SimpleOnGestureListener 的方法
            @Override
            public boolean onDown(MotionEvent event) {
                Log.d(DEBUG_TAG,"onDown: " + event.toString());
                return true;
            }
    
            @Override
            public boolean onFling(MotionEvent event1, MotionEvent event2,
                                   float velocityX, float velocityY) {
                Log.d(DEBUG_TAG, "onFling: " + event1.toString()+event2.toString());
                return true;
            }
    
        }
    
    
    }

[https_developer.android.com_training_gestures_detector.html_detect]: https://developer.android.com/training/gestures/detector.html#detect
[20160902113416386]: /images/20220717/80172110a626468ebd72348243eeac3a.png
[20160902113644656]: /images/20220717/2820c072cbed4ffba5c670a9cc67f471.png
[20160902113558471]: /images/20220717/0c1652fa6b8c4479b6570c820ce6115e.png
[20160902113519705]: /images/20220717/43e787adfee04d678ea442b825da2de3.png