Android lifecycle 实战及使用进阶
前言
github sample 地址： ArchiteComponentsSample
Android Architecture Components 的，前面我们已经讲解了 lifecycle， LiveData 的使用及原理，今天，让我们一起赖看看 lifecycle 在项目中的实战。主要讲解两点
- LifecycleHandler 的封装
- MVP 中引入 lifecycle，可以自行监听 activity 生命周期变化
LifecycleHandle 的封装
我们平时在使用 handler 的时候，在 activity onDestroy 的时候，需要手动取 removeMessage 或者 removeCallBack，不然的话，很容易发生内存泄漏。
@Override
protected void onDestroy() {
super.onDestroy();
mHandler.removeCallbacksAndMessages(null);
}这对我们开发者来说，很明显是一个重复的动作。我们一起通过 lifecycle 来减少这种重复性的动作，让其内部自己释放。
核心原理其实很简单，内部监听 activity 生命周期的变化，在 onDestroy 的时候移除 message 和 callback。
public class LifecycleHandler extends Handler implements FullLifecycleObserver {
private LifecycleOwner mLifecycleOwner;
public LifecycleHandler(LifecycleOwner lifecycleOwner) {
mLifecycleOwner = lifecycleOwner;
addObserver();
}
public LifecycleHandler(LifecycleOwner lifecycleOwner, Callback callback) {
super(callback);
mLifecycleOwner = lifecycleOwner;
addObserver();
}
public LifecycleHandler(LifecycleOwner lifecycleOwner, Looper looper) {
super(looper);
mLifecycleOwner = lifecycleOwner;
addObserver();
}
public LifecycleHandler(LifecycleOwner lifecycleOwner, Looper looper, Callback callback) {
super(looper, callback);
mLifecycleOwner = lifecycleOwner;
addObserver();
}
private void addObserver() {
if (mLifecycleOwner != null) {
mLifecycleOwner.getLifecycle().addObserver(new FullLifecycleObserverAstrong textdapter(mLifecycleOwner, this));
}
}
@Override
public void onCreate(LifecycleOwner owner) {
}
@Override
public void onStart(LifecycleOwner owner) {
}
@Override
public void onResume(LifecycleOwner owner) {
}
@Override
public void onPause(LifecycleOwner owner) {
}
@Override
public void onStop(LifecycleOwner owner) {
}
@Override
public void onDestroy(LifecycleOwner owner) {
removeCallbacksAndMessages(null);
}
}我们来看一下这一行代码
mLifecycleOwner.getLifecycle().addObserver(new FullLifecycleObserverAdapter(mLifecycleOwner, this));FullLifecycleObserverAdapter 是什么呢？
FullLifecycleObserverAdapter
public class FullLifecycleObserverAdapter implements LifecycleObserver {
private final FullLifecycleObserver mObserver;
private static final String TAG = "FullLifecycleObserverAd";
private final LifecycleOwner mLifecycleOwner;
FullLifecycleObserverAdapter(LifecycleOwner lifecycleOwner, FullLifecycleObserver observer) {
mLifecycleOwner = lifecycleOwner;
mObserver = observer;
}
@OnLifecycleEvent(Lifecycle.Event.ON_CREATE)
public void onCreate() {
Log.i(TAG, "onCreate: ");
mObserver.onCreate(mLifecycleOwner);
}
@OnLifecycleEvent(Lifecycle.Event.ON_START)
public void onStart() {
Log.i(TAG, "onStart: ");
mObserver.onStart(mLifecycleOwner);
}
@OnLifecycleEvent(Lifecycle.Event.ON_RESUME)
public void onResume() {
Log.i(TAG, "onResume: ");
mObserver.onResume(mLifecycleOwner);
}
@OnLifecycleEvent(Lifecycle.Event.ON_PAUSE)
public void onPause() {
Log.i(TAG, "onPause: ");
mObserver.onPause(mLifecycleOwner);
}
@OnLifecycleEvent(Lifecycle.Event.ON_STOP)
public void onStop() {
Log.i(TAG, "onStop: ");
mObserver.onStop(mLifecycleOwner);
}
@OnLifecycleEvent(Lifecycle.Event.ON_DESTROY)
public void onDestroy() {
Log.i(TAG, "onDestroy: ");
mObserver.onDestroy(mLifecycleOwner);
}
}FullLifecycleObserver
public 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);
}FullLifecycleObserver 是我们自己自定义的一个接口，继承 LifecycleObserver，各个方法一一对应 activity 的生命周期。
FullLifecycleObserverAdapter 实现了 LifecycleObserver，使用了 @OnLifecycleEvent 注解，在 activity 生命周期变化的时候会回调相应的方法，我们再在里面回调 observer 的 onCreate， onStart 等方法，这有点类似代理模式。调用关系总结如下：
以后想观察 lifecycle 生命周期变化的话，只需要 mLifecycleOwner.getLifecycle().addObserver(new FullLifecycleObserverAdapter(mLifecycleOwner, this)); 这一行代码即可
有人可能会这样问了，为什么要这样设计呢
加 FullLifecycleObserver 这个接口，主要是为了跟 activity 的生命周期一一对应。
LifecyclePresenter 的封装
public class LifecyclePresenter implements IPresenter, FullLifecycleObserver {
private static final String TAG = "BasePresenter";
private final LifecycleOwner mLifecycleOwner;
public LifecyclePresenter(LifecycleOwner lifecycleOwner) {
mLifecycleOwner = lifecycleOwner;
mLifecycleOwner.getLifecycle().addObserver(new FullLifecycleObserverAdapter(lifecycleOwner, this));
}
@Override
public void onCreate(LifecycleOwner owner) {
Log.i(TAG, "onCreate: owner = " + owner);
}
@Override
public void onStart(LifecycleOwner owner) {
Log.i(TAG, "onStart: owner = " + owner);
}
@Override
public void onResume(LifecycleOwner owner) {
Log.i(TAG, "onResume: owner = " + owner);
}
@Override
public void onPause(LifecycleOwner owner) {
Log.i(TAG, "onPause: owner = " + owner);
}
@Override
public void onStop(LifecycleOwner owner) {
Log.i(TAG, "onStop: owner = " + owner);
}
@Override
public void onDestroy(LifecycleOwner owner) {
Log.i(TAG, "onDestroy: owner = " + owner);
}
}
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