一、简介

Lifecycle ：Lifecycle 包含有关Activity与Fragment生命周期状态的信息，并允许其他对象观察此状态，主要作用于避免内存泄漏和观察组件(Activtiy、Fragment)的生命周期状态。

二、基本使用

1、创建观察者

public class MyObserver implements LifecycleObserver {

    @OnLifecycleEvent(Lifecycle.Event.ON_START)
    public void onStart() {

    }

    @OnLifecycleEvent(Lifecycle.Event.ON_STOP)
    public void onStop() {

    }
}

// 使用java8，可以实现DefaultLifecycleObserver并添加 androidx.lifecycle:common-java8:<version>
class MyObserver implements DefaultLifecycleObserver {
     @Override
     public void onCreate(LifecycleOwner owner) {
     }
 }

2、使用
2.1 AppCompatActivity中

public class MainActivity extends AppCompatActivity {

    private static final String TAG = "MainActivity";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        getLifecycle().addObserver(new MyObserver());
    }
}

2.2 Activity中

ublic class MainActivity extends Activity implements LifecycleOwner {

    private static final String TAG = "MainActivity";
    private LifecycleRegistry mLifecycleRegistry;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        mLifecycleRegistry = new LifecycleRegistry(this);
        mLifecycleRegistry.markState(Lifecycle.State.CREATED);
        //添加观察者
        getLifecycle().addObserver(new MyObserver());
    }

    @Override
    protected void onStart() {
        super.onStart();
        mLifecycleRegistry.markState(Lifecycle.State.STARTED);
    }

    @Override
    @NonNull
    public Lifecycle getLifecycle() {
        return mLifecycleRegistry;
    }
}

Lifecycle的优势我们以及结合MVP使用，可以去看MVPArms框架怎么结合Lifecycle使用。