前言

在API 14之后，在Application类中，提供了一个应用生命周期回调的注册方法，用来对应用的生命周期进行集中管理，这个接口叫registerActivityLifecycleCallbacks。可以通过它注册自己的ActivityLifeCycleCallback，每一个Activity的生命周期都会回调到这里的对应方法。

实现1

参考：Android应用前后台切换的判断

public class MyApplication extends Application{
    public int count = 0;
    @Override
    public void onCreate() {
        super.onCreate();

        registerActivityLifecycleCallbacks(new ActivityLifecycleCallbacks() {

            @Override
            public void onActivityStopped(Activity activity) {
                Log.v("viclee", activity + "onActivityStopped");
                count--;
                if (count == 0) {
                    Log.v("viclee", ">>>>>>>>>>>>>>>>>>>切到后台  lifecycle");
                }
            }

            @Override
            public void onActivityStarted(Activity activity) {
                Log.v("viclee", activity + "onActivityStarted");
                if (count == 0) {
                    Log.v("viclee", ">>>>>>>>>>>>>>>>>>>切到前台  lifecycle");
                }
                count++;
            }

            @Override
            public void onActivitySaveInstanceState(Activity activity, Bundle outState) {
                Log.v("viclee", activity + "onActivitySaveInstanceState");
            }

            @Override
            public void onActivityResumed(Activity activity) {
                Log.v("viclee", activity + "onActivityResumed");
            }

            @Override
            public void onActivityPaused(Activity activity) {
                Log.v("viclee", activity + "onActivityPaused");
            }

            @Override
            public void onActivityDestroyed(Activity activity) {
                Log.v("viclee", activity + "onActivityDestroyed");
            }

            @Override
            public void onActivityCreated(Activity activity, Bundle savedInstanceState) {
                Log.v("viclee", activity + "onActivityCreated");
            }
        });
    }
}

实现2-ActivityManager

ActivityManager