Android判断前台进程的有效方法

判断Android本应用是否在前台的最有效方法

Android SDK14也就是4.0中加入了ActivityLifecycleCallbacks,我们可以通过这个CallBack拿到所有Activity 里面的生命周期回调。

public interface ActivityLifecycleCallbacks {
        void onActivityCreated(Activity activity, Bundle savedInstanceState);
        void onActivityStarted(Activity activity);
        void onActivityResumed(Activity activity);
        void onActivityPaused(Activity activity);
        void onActivityStopped(Activity activity);
        void onActivitySaveInstanceState(Activity activity, Bundle outState);
        void onActivityDestroyed(Activity activity);
    }

了解了这个 我们就可以写一个实现类。

public class MyLifecycleHandler implements Application.ActivityLifecycleCallbacks {
    private static int resumed;
    private static int paused;
    private static int started;
    private static int stopped;

    @Override
    public void onActivityCreated(Activity activity, Bundle savedInstanceState) {
    }

    @Override
    public void onActivityStarted(Activity activity) {
        ++started;
    }

    @Override
    public void onActivityResumed(Activity activity) {
        ++resumed;
    }

    @Override
    public void onActivityPaused(Activity activity) {
        ++paused;
        android.util.Log.w("test", "application is in foreground: " + (resumed > paused));
    }

    @Override
    public void onActivityStopped(Activity activity) {
        ++stopped;
        android.util.Log.w("test", "application is visible: " + (started > stopped));
    }

    @Override
    public void onActivityDestroyed(Activity activity) {
    }

    @Override
    public void onActivitySaveInstanceState(Activity activity, Bundle outState) {
    }

    public static boolean isApplicationVisible() {
        return started > stopped;
    }

    public static boolean isApplicationInForeground() {
    // 当所有 Activity 的状态中处于 resumed 的大于 paused 状态的，即可认为有Activity处于前台状态中 
        return resumed > paused;
    }

然后在自己定义的全局Application中的onCreate()方法中注册

  registerActivityLifecycleCallbacks(new MyLifecycleHandler());

注册成功后，调用isApplicationInForeground()方法判断是否在前台

    /***
     * 判断应用是否在前台
     * @return
     */
    public boolean isAppOnForeground() {
      return  MyLifecycleHandler.isApplicationInForeground();
    }