Android官方架构组件:Lifecycle详解&迪士尼彩乐园定制开发原理分析

Lifecycle 是一个类，它持有关于组件（如 Activity 或 Fragment）生命周期状态的信息，并且允许其他对象观察此状态。

我们只需要2步：

1、Prestener继承LifecycleObserver接口
public interface IPresenter extends LifecycleObserver {

@OnLifecycleEvent(Lifecycle.Event.ON_CREATE)
void onCreate(@NotNull LifecycleOwner owner);

@OnLifecycleEvent(Lifecycle.Event.ON_DESTROY)
void onDestroy(@NotNull LifecycleOwner owner);

@OnLifecycleEvent(Lifecycle.Event.ON_ANY)
void onLifecycleChanged(@NotNull LifecycleOwner owner,
                        @NotNull Lifecycle.Event event);

}
Android官方架构组件:Lifecycle详解&原理分析
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public class BasePresenter implements IPresenter {

private static final String TAG = "com.qingmei2.module.base.BasePresenter";    

@Override
public void onLifecycleChanged(@NotNull LifecycleOwner owner, @NotNull Lifecycle.Event event) {

}

@Override
public void onCreate(@NotNull LifecycleOwner owner) {
    Log.d("tag", "BasePresenter.onCreate" + this.getClass().toString());
}

@Override
public void onDestroy(@NotNull LifecycleOwner owner) {
    Log.d("tag", "BasePresenter.onDestroy" + this.getClass().toString());
}

}

这里我直接将我想要观察到Presenter的生命周期事件都列了出来，然后封装到BasePresenter 中，这样每一个BasePresenter 的子类都能感知到Activity容器对应的生命周期事件，并在子类重写的方法中，对应相应行为。

2、在Activity/Fragment容器中添加Observer：
public class MainActivity extends AppCompatActivity {
private IPresenter mPresenter;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    Log.d("tag", "onCreate" + this.getClass().toString());
    setContentView(R.layout.activity_main);
    mPresenter = new MainPresenter(this);
    getLifecycle().addObserver(mPresenter);//添加LifecycleObserver
}

@Override
protected void onDestroy() {
    Log.d("tag", "onDestroy" + this.getClass().toString());
    super.onDestroy();
}

}

如此，每当Activity发生了对应的生命周期改变，Presenter就会执行对应事件注解的方法：

除onCreate和onDestroy事件之外，Lifecycle一共提供了所有的生命周期事件，只要
通过注解进行声明，就能够使LifecycleObserver观察到对应的生命周期事件：

//以下为logcat日志
01-08 23:21:01.702 D/tag: onCreate class com.qingmei2.mvparchitecture.mvp.ui.MainActivity
01-08 23:21:01.778 D/tag: onCreate class com.qingmei2.mvparchitecture.mvp.presenter.MainPresenter

01-08 23:21:21.074 D/tag: onDestroy class com.qingmei2.mvparchitecture.mvp.presenter.MainPresenter
01-08 23:21:21.074 D/tag: onDestroy class com.qingmei2.mvparchitecture.mvp.ui.MainActivity

public enum Event {
/**

• Constant for onCreate event of the {@link LifecycleOwner}.
  */
  ON_CREATE,
  /**
• Constant for onStart event of the {@link LifecycleOwner}.
  */
  ON_START,
  /**
• Constant for onResume event of the {@link LifecycleOwner}.
  */
  ON_RESUME,
  /**
• Constant for onPause event of the {@link LifecycleOwner}.
  */
  ON_PAUSE,
  /**
• Constant for onStop event of the {@link LifecycleOwner}.
  */
  ON_STOP,
  /**
• Constant for onDestroy event of the {@link LifecycleOwner}.
  */
  ON_DESTROY,
  /**
• An {@link Event Event} constant that can be used to match all events.
  */
  ON_ANY
  }