Android开发

ActivityLifecycleCallbacks是什么？

• Application通过此接口提供了一套回调方法，用于让开发人员对Activity的生命周期事件进行集中处理。

为什么用ActivityLifecycleCallbacks？

• 以往若需监測Activity的生命周期事件代码，你可能是这样做的。重写每个Acivity的onResume()，然后作统计和处理：

  @Override
  protected void onResume() {
    super.onResume();
    //TODO 处理和统计代码
    Log.v(TAG, "onResume");
    Logger.v(TAG, "onResume");
    Logging.v(TAG, "onResume");
    ...
  }
  

• ActivityLifecycleCallbacks接口回调能够简化这一繁琐过程。在一个类中作统一处理

ActivityLifecycleCallbacks怎么用？

• android.app.Application.ActivityLifecycleCallbacks
• 要求API 14+ （Android 4.0+）
• 继承Application

  public class BaseApplication extends Application
  

• 在AndroidManifest里起用自己定义Application

  <application android:name=".global.BaseApplication"
  

• 重写Application的onCreate()方法，或在Application的无參构造方法内，调用Application.registerActivityLifecycleCallbacks()方法，并实现ActivityLifecycleCallbacks接口

  public void onCreate() {
    super.onCreate();
    this.registerActivityLifecycleCallbacks(new ActivityLifecycleCallbacks() {
   
      @Override
      public void onActivityStopped(Activity activity) {
          Logger.v(activity, "onActivityStopped");
      }
   
      @Override
      public void onActivityStarted(Activity activity) {
          Logger.v(activity, "onActivityStarted");
      }
   
      @Override
      public void onActivitySaveInstanceState(Activity activity, Bundle outState) {
          Logger.v(activity, "onActivitySaveInstanceState");
      }
   
      @Override
      public void onActivityResumed(Activity activity) {
          Logger.v(activity, "onActivityResumed");
      }
   
      @Override
      public void onActivityPaused(Activity activity) {
          Logger.v(activity, "onActivityPaused");
      }
   
      @Override
      public void onActivityDestroyed(Activity activity) {
          Logger.v(activity, "onActivityDestroyed");
      }
   
      @Override
      public void onActivityCreated(Activity activity, Bundle savedInstanceState) {
          Logger.v(activity, "onActivityCreated");
      }
    });
  };
  

• 执行结果(Logcat日志)

  10-21 14:32:57.722: V/WelcomeActivity(8085): onActivityCreated
  10-21 14:32:57.762: V/WelcomeActivity(8085): onActivityStarted
  10-21 14:32:57.762: V/WelcomeActivity(8085): onActivityResumed
  10-21 14:32:59.164: V/WelcomeActivity(8085): onActivityPaused
  10-21 14:32:59.194: V/MainActivity(8085): onActivityCreated
  10-21 14:32:59.224: V/MainActivity(8085): onActivityStarted
  10-21 14:32:59.224: V/MainActivity(8085): onActivityResumed
  10-21 14:32:59.735: V/WelcomeActivity(8085): onActivityStopped
  10-21 14:32:59.735: V/WelcomeActivity(8085): onActivityDestroyed
  10-21 14:33:06.502: V/MainActivity(8085): onActivityPaused
  10-21 14:33:06.612: V/MainActivity(8085): onActivityStopped
  10-21 14:33:06.612: V/MainActivity(8085): onActivityDestroyed
  

ActivityLifecycleCallbacks的拓展使用方法

• 本次初探仅尝试使用Log日志工具作简要測试。如需满足较复杂的统计或调试需求时。此法可能会大大降低插入代码量，提高效率

• API仅在14+版本号上提供此接口回调，Android 4.0下面系统怎样使用？

• API仅针对上述几个Activity的生命周期事件留出了接口回调，可能已无法满足日益过渡为使用Fragment的今日需求。 怎样在更大范围内应用LifecycleCallbacks？