lifecycle的简单实用

古城微笑少年丶 2022-05-17 04:26 220阅读 0赞

MVP模式中，我们的presenter可能需要在activity销毁的时候释放一些资源

通常我们会这么写

override fun onDestroy() {
            super.onDestroy()
            presenter.destory():
        }

如果有很多个类或者自定义的view都需要在activity销毁的额时候释放，可能会造成onDestroy方法很臃肿。  
而使用lifecycle可以很方便的监听activity的生命周期，从而在presenter内部资源，而不需要外部调用presenter.destory():方法

使用非常简单：

presenter集成LifecycleObserver

public class MainPresenter implements LifecycleObserver { 
    
        public MainPresenter() {
        }
    
        @OnLifecycleEvent(Lifecycle.Event.ON_RESUME)
        private void onResume(){
            Log.i("LHD", "onResume onResume onResume");
        }
    
        @OnLifecycleEvent(Lifecycle.Event.ON_DESTROY)
        private void onDestroy() {
            Log.i("LHD", "onDestroy onDestroy onDestroy");
        }
    }

以下是activity代码，（kotlin）

override fun onCreate(savedInstanceState: Bundle?) {
            super.onCreate(savedInstanceState)
            setContentView(R.layout.activity_main)
            presenter = MainPresenter()
            //将实现了LifecycleObserver接口的presenter传递给lifecycle即可
            lifecycle.addObserver(presenter)
    }

只要这样，presenter就能监听到activity的生命周期啦。

如图：  
![lifecycle][]

还可以监听其它生命周期方法：

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
        }

以上就是lifecycle的简单使用。

[lifecycle]: /images/20220517/0ee9cfbf557b4884bcdd5c94570d1e40.png