Lifecycle使用篇

骑猪看日落 2022-09-09 09:28 176阅读 0赞

> Lifecycle是Google提供的生命周期感知型组件，androidx.lifecycle 软件包提供了可用于构建生命周期感知型组件的类和接口，这些组件可以感知 Activity 和 Fragment 的生命周期状态，让我们在处理一些需要根据生命周期改变而改变的功能的时候显得更加的优雅，避免了在Actvity和Fragemnt中添加大量的处理逻辑和监听逻辑。

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## 1、Lifecycle的使用方式 ##

**LifeCycle 基于观察者模式实现，使用步骤一般如下：  
1.确定被观察者 ——继承实现了LifecycleOwner的父类，或者自己实现LifecycleOwner，创建LifecycleRegistry，并分发事件。  
2.创建观察者 ——实现LifecycleObserver接口  
3.建立监听关系。 ——lifecycleOwner.getLifecycle().addObserver(this)**

### 1.1、组件中已经实现了LifecycleOwner ###

ComponentActivity、androidx包中的Fragment已经实现了LifecycleOwner接口和创建了实现了Lifecycle接口的LifecycleRegistry类，下面我们用一个View实现LifecycleObserver的方式使View感知所在页面的生命周期变化。

**页面**

public class TestLifecycle extends AppCompatActivity { 
        LifecycleView lifecycleView;
        
        @Override
        protected void onCreate(@Nullable Bundle savedInstanceState) { 
            Log.e("czk", "onCreate: ————————> start"+"————state————>"+getLifecycle().getCurrentState());
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_lifecycle);
            init();
            Log.e("czk", "onCreate: ————————> end"+"————state————>"+getLifecycle().getCurrentState());
        }
    
        public void init(){ 
            lifecycleView = findViewById(R.id.view_tree_lifecycle_owner);
            lifecycleView.setLifecycleOwner(this);
        }
    
        @Override
        protected void onStart() { 
            Log.e("czk", "onStart: ————————> start"+"————state————>"+getLifecycle().getCurrentState());
            super.onStart();
            Log.e("czk", "onStart: ————————> end" +"————state————>"+getLifecycle().getCurrentState());
        }
    
        @Override
        protected void onResume() { 
            Log.e("czk", "onResume: ————————> start"+"————state————>"+getLifecycle().getCurrentState());
            super.onResume();
            Log.e("czk", "onResume: ————————> end"+"————state————>"+getLifecycle().getCurrentState());
        }
    
        @Override
        protected void onPause() { 
            Log.e("czk", "onPause: ————————> start"+"————state————>"+getLifecycle().getCurrentState());
            super.onPause();
            Log.e("czk", "onPause: ————————> end"+"————state————>"+getLifecycle().getCurrentState());
        }
    
        @Override
        protected void onStop() { 
            Log.e("czk", "onStop: ————————> start"+"————state————>"+getLifecycle().getCurrentState());
            super.onStop();
            Log.e("czk", "onStop: ————————> end"+"————state————>"+getLifecycle().getCurrentState());
        }
    
        @Override
        protected void onDestroy() { 
            Log.e("czk", "onDestroy: ————————> start"+"————state————>"+getLifecycle().getCurrentState());
            super.onDestroy();
            Log.e("czk", "onDestroy: ————————> end"+"————state————>"+getLifecycle().getCurrentState());
        }
    }

**View**

public class LifecycleView extends View implements LifecycleObserver { 
        private WeakReference<LifecycleOwner> mLifecycleOwner;
    
        public void setLifecycleOwner(LifecycleOwner lifecycleOwner){ 
            mLifecycleOwner = new WeakReference<LifecycleOwner(lifecycleOwner);
            LifecycleOwner owner = mLifecycleOwner.get();
            if(owner!=null){ 
                owner.getLifecycle().addObserver(this);
            }
        }
    
        @OnLifecycleEvent(Lifecycle.Event.ON_CREATE)
        public void onMyCreate(){ 
            Log.e("czk", "onMyCreate: ————————>" );
        }
    
        @OnLifecycleEvent(Lifecycle.Event.ON_START)
        public void onMyStart(){ 
            Log.e("czk", "onMyStart: ————————>" );
        }
    
        @OnLifecycleEvent(Lifecycle.Event.ON_RESUME)
        public void onMyResume(){ 
            Log.e("czk", "onMyResume: ————————>" );
        }
    
        @OnLifecycleEvent(Lifecycle.Event.ON_PAUSE)
        public void onMyPause(){ 
            Log.e("czk", "onMyPause: ————————>" );
        }
    
        @OnLifecycleEvent(Lifecycle.Event.ON_STOP)
        public void onMyStop(){ 
            Log.e("czk", "onMyStop: ————————>" );
        }
    
        @OnLifecycleEvent(Lifecycle.Event.ON_DESTROY)
        public void onMyDestroy(){ 
            Log.e("czk", "onMyDestroy: ————————>" );
        }
    }

**查看log，onMyCreate、onMyStart、onMyStop是在被观察者生命周期方法后执行  
onMyPause、onMyStop、onMyDestroy是在被观察者生命周期方法前执行**

E/czk: onCreate: ————————> start————state————>INITIALIZED
    E/czk: onCreate: ————————> end————state————>INITIALIZED
    E/czk: onMyCreate: ————————>
    E/czk: onStart: ————————> start————state————>CREATED
    E/czk: onStart: ————————> end————state————>CREATED
    E/czk: onMyStart: ————————>
    E/czk: onResume: ————————> start————state————>STARTED
    E/czk: onResume: ————————> end————state————>STARTED
    E/czk: onMyResume: ————————>
    E/czk: onMyPause: ————————>
    E/czk: onPause: ————————> start————state————>STARTED
    E/czk: onPause: ————————> end————state————>STARTED
    E/czk: onMyStop: ————————>
    E/czk: onStop: ————————> start————state————>CREATED
    E/czk: onStop: ————————> end————state————>CREATED
    E/czk: onMyDestroy: ————————>
    E/czk: onDestroy: ————————> start————state————>DESTROYED
    E/czk: onDestroy: ————————> end————state————>DESTROYED

--------------------

### 1.2、自己实现LifecycleOwner，可以自己决定分发事件的时机 ###

**页面**

public class TestLifecycle2 extends Activity implements LifecycleOwner { 
        private LifecycleRegistry mLifecycleRegistry = new LifecycleRegistry(this);
        private LifecycleView lifecycleView;
        
        @NonNull
        @Override
        public Lifecycle getLifecycle() { 
            return mLifecycleRegistry;
        }
    
        @SuppressLint("RestrictedApi")
        @Override
        protected void onCreate(@Nullable Bundle savedInstanceState) { 
            Log.e("czk", "onCreate: ————————> start"+"————state————>"+getLifecycle().getCurrentState());
            super.onCreate(savedInstanceState);
            //方式1
    // ReportFragment.injectIfNeededIn(this);
            setContentView(R.layout.activity_lifecycle);
            init();
            Log.e("czk", "onCreate: ————————> end"+"————state————>"+getLifecycle().getCurrentState());
            //方式2
            mLifecycleRegistry.handleLifecycleEvent(Lifecycle.Event.ON_CREATE);
        }
    
        public void init(){ 
            lifecycleView = findViewById(R.id.view_tree_lifecycle_owner);
            lifecycleView.setLifecycleOwner(this);
        }
    
        @Override
        protected void onStart() { 
            Log.e("czk", "onStart: ————————> start"+"————state————>"+getLifecycle().getCurrentState());
            super.onStart();
            Log.e("czk", "onStart: ————————> end" +"————state————>"+getLifecycle().getCurrentState());
            mLifecycleRegistry.handleLifecycleEvent(Lifecycle.Event.ON_START);
        }
    
        @Override
        protected void onResume() { 
            Log.e("czk", "onResume: ————————> start"+"————state————>"+getLifecycle().getCurrentState());
            super.onResume();
            Log.e("czk", "onResume: ————————> end"+"————state————>"+getLifecycle().getCurrentState());
            mLifecycleRegistry.handleLifecycleEvent(Lifecycle.Event.ON_RESUME);
        }
    
        @Override
        protected void onPause() { 
            mLifecycleRegistry.handleLifecycleEvent(Lifecycle.Event.ON_PAUSE);
            Log.e("czk", "onPause: ————————> start"+"————state————>"+getLifecycle().getCurrentState());
            super.onPause();
            Log.e("czk", "onPause: ————————> end"+"————state————>"+getLifecycle().getCurrentState());
        }
    
        @Override
        protected void onStop() { 
            mLifecycleRegistry.handleLifecycleEvent(Lifecycle.Event.ON_STOP);
            Log.e("czk", "onStop: ————————> start"+"————state————>"+getLifecycle().getCurrentState());
            super.onStop();
            Log.e("czk", "onStop: ————————> end"+"————state————>"+getLifecycle().getCurrentState());
        }
    
        @Override
        protected void onDestroy() { 
            mLifecycleRegistry.handleLifecycleEvent(Lifecycle.Event.ON_DESTROY);
            Log.e("czk", "onDestroy: ————————> start"+"————state————>"+getLifecycle().getCurrentState());
            super.onDestroy();
            Log.e("czk", "onDestroy: ————————> end"+"————state————>"+getLifecycle().getCurrentState());
        }
    }

**View还是方式1中的那个**

--------------------

**查看Log如下：**

### 1.3 Lifecycle 在任务控件组件中的使用 ###

mTaskFloat = new TaskFloatManager.Float()
                    .setLifecycleOwner(this)
                    .create(this)
                    .setTypeModel(new TaskFloatVideoDetailModel())
                    .setParentView(rootView);

public static class Float implements LifecycleObserver{ 
    
    public Float setLifecycleOwner(LifecycleOwner lifecycleOwner){ 
           this.lifecycleOwner = lifecycleOwner;
           if(lifecycleOwner != null){ 
               lifecycleOwner.getLifecycle().addObserver(this);
           }
           return this;
    }
     
    @OnLifecycleEvent(Lifecycle.Event.ON_START)
    public void onStart(){ 
    		...
    }
     
    @OnLifecycleEvent(Lifecycle.Event.ON_RESUME)
    public void onResume(){ 
    		...
    }
    
    @OnLifecycleEvent(Lifecycle.Event.ON_PAUSE)
    public void onPause(){ 
    		...
    }
    
    @OnLifecycleEvent(Lifecycle.Event.ON_STOP)
    public void onStop(){ 
    		...
    }
    
    @OnLifecycleEvent(Lifecycle.Event.ON_DESTROY)
    public void onDestory(){ 
    		...
    }
    
    }