原文链接

• 本质是观察者模式，LifecycleOwner作为被观察者，LifecycleObserver作为观察者

1、LifecycleObserver 观察者

• 观察者实现此接口
• 顶层接口，没有任何方法和属性

package androidx.lifecycle;


@SuppressWarnings("WeakerAccess")
public interface LifecycleObserver {

}

FullLifecycleObserver

• FullLifecycleObserver定义了全生命周期方法

interface FullLifecycleObserver extends LifecycleObserver {

    void onCreate(LifecycleOwner owner);

    void onStart(LifecycleOwner owner);

    void onResume(LifecycleOwner owner);

    void onPause(LifecycleOwner owner);

    void onStop(LifecycleOwner owner);

    void onDestroy(LifecycleOwner owner);
}

2、LifecycleOwner 被观察者

• LifecycleOwner接口只有一个方法，getLifecycle()

public interface LifecycleOwner {
    /**
     * Returns the Lifecycle of the provider.
     *
     * @return The lifecycle of the provider.
     */
    @NonNull
    Lifecycle getLifecycle();
}

Activity

• AppCompatActivity继承自FragmentActivity，FragmentActivity继承自ComponentActivity
• ComponentActivity实现了LifecycleOwner接口

public class ComponentActivity extends Activity
        implements LifecycleOwner, KeyEventDispatcher.Component {
        
		private final LifecycleRegistry mLifecycleRegistry = new LifecycleRegistry(this);
 
    @Override
    public Lifecycle getLifecycle() {
        return mLifecycleRegistry;
    }
}

Fragment

• Lifecycle在Fragment中的使用方法与Activity中的使用方法相同，因为Fragment也实现了LifecycleOwner接口

public class Fragment implements ComponentCallbacks, OnCreateContextMenuListener, 		    LifecycleOwner, ViewModelStoreOwner {
  
    @Override
    public Lifecycle getLifecycle() {
        return mLifecycleRegistry;
    }
}

service

• 创建Service时，继承LifecycleService，这个类也实现了LifecycleOwner接口

package androidx.lifecycle;
public class LifecycleService extends Service implements LifecycleOwner {

}