1.直接添加如下依赖就可以满足日常的工作,如果缺少哪个库,再去单独添加就好了
implementation "android.arch.lifecycle:extensions:1.1.1"
2.先不谈Activity和Fragment中如何使用,先举一个Lifecycle的简单例子。
1 ackage com.example.lifecycledemo1; 2 3 import android.arch.lifecycle.Lifecycle; 4 import android.arch.lifecycle.LifecycleObserver; 5 import android.arch.lifecycle.OnLifecycleEvent; 6 import android.support.v7.app.AppCompatActivity; 7 import android.os.Bundle; 8 import android.util.Log; 9 10 public class MainActivity extends AppCompatActivity {11 12 private static final String TAG = "MainActivity";13 14 @Override15 protected void onCreate(Bundle savedInstanceState) {16 super.onCreate(savedInstanceState);17 setContentView(R.layout.activity_main);18 getLifecycle().addObserver(new MyObserver());//119 }20 21 public class MyObserver implements LifecycleObserver{22 23 @OnLifecycleEvent(Lifecycle.Event.ON_RESUME)24 void onResume(){25 Log.d(TAG, "Lifecycle call onResume");26 }27 @OnLifecycleEvent(Lifecycle.Event.ON_PAUSE)28 void onPause(){29 Log.d(TAG, "Lifecycle call onPause");30 }31 }32 33 @Override34 protected void onResume() {35 super.onResume();36 Log.d(TAG, "onResume");37 }38 39 @Override40 protected void onPause() {41 super.onPause();42 Log.d(TAG, "onPause");43 44 }45 }
先实现MyObserver,对ON_CREATE和ON_RESUME事件进行监听。因为在Android Support Library 26.1.0 及其之后的版本,Activity和Fragment已经默认实现了LifecycleOwner接口,所以在注释1处可以直接使用getLifecycle方法获取Lifecycle对象,这样MyObserver就可以观察MainActivity的生命周期变化了,LifecycleOwner可以理解为被观察者,MainActivity默认实现了LifecycleOwner接口,也就是说MainActivity是被观察者。
运行程序,打印的log如下所示。
D/MainActivity: onResumeD/MainActivity: Lifecycle call onResumeD/MainActivity: Lifecycle call onPauseD/MainActivity: onPause
3.MVP的例子
1 public class MyPresenter implements IPresenter { 2 private static final String TAG = "test"; 3 4 @Override 5 public void onResume() { 6 Log.d(TAG, "Lifecycle call onResume"); 7 } 8 9 @Override10 public void onPause() {11 Log.d(TAG, "Lifecycle call onPause");12 }13 }14 15 interface IPresenter extends LifecycleObserver {16 17 @OnLifecycleEvent(Lifecycle.Event.ON_RESUME)18 void onResume();19 20 @OnLifecycleEvent(Lifecycle.Event.ON_PAUSE)21 void onPause();22 }
IPresenter接口继承自LifecycleObserver接口,MyPresenter又实现了IPresenter接口,这样MyPresenter成为了一个观察者。
接在在MainActivity中加入MyPresenter:
1 public class MainActivity extends AppCompatActivity { 2 3 private static final String TAG = "test"; 4 private IPresenter mPresenter; 5 @Override 6 protected void onCreate(Bundle savedInstanceState) { 7 super.onCreate(savedInstanceState); 8 setContentView(R.layout.activity_main); 9 mPresenter = new MyPresenter();10 getLifecycle().addObserver(mPresenter);11 }12 13 @Override14 protected void onResume() {15 super.onResume();16 Log.d(TAG, "onResume");17 }18 19 @Override20 protected void onPause() {21 super.onPause();22 Log.d(TAG, "onPause");23 24 }25 }
MainActivity成为了被观察者,当它的生命周期发生变化时,MyPresenter就可以观察到,这样就不需要在MainActivity的多个生命周期方法中调用MyPresenter的方法了。
打印的日志如下:
D/test: onResumeD/test: Lifecycle call onResumeD/test: Lifecycle call onPauseD/test: onPause
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