这是我的解决方案。只需在您的主Application类中注册这个ActivityLifecycleCallbacks。在评论中，我提到了一个用户配置文件活动边缘情况。该活动只是一个具有透明边缘的活动。

/**
 * This class used Activity lifecycle callbacks to determine when the application goes to the
 * background as well as when it is brought to the foreground.
 */
public class Foreground implements Application.ActivityLifecycleCallbacks
{
    /**
     * How long to wait before checking onStart()/onStop() count to determine if the app has been
     * backgrounded.
     */
    public static final long BACKGROUND_CHECK_DELAY_MS = 500;

    private static Foreground sInstance;

    private final Handler mMainThreadHandler = new Handler(Looper.getMainLooper());
    private boolean mIsForeground = false;
    private int mCount;

    public static void init(final Application application)
    {
        if (sInstance == null)
        {
            sInstance = new Foreground();
            application.registerActivityLifecycleCallbacks(sInstance);
        }
    }

    public static Foreground getInstance()
    {
        return sInstance;
    }

    public boolean isForeground()
    {
        return mIsForeground;
    }

    public boolean isBackground()
    {
        return !mIsForeground;
    }

    @Override
    public void onActivityStarted(final Activity activity)
    {
        mCount++;

        // Remove posted Runnables so any Meteor disconnect is cancelled if the user comes back to
        // the app before it runs.
        mMainThreadHandler.removeCallbacksAndMessages(null);

        if (!mIsForeground)
        {
            mIsForeground = true;
        }
    }

    @Override
    public void onActivityStopped(final Activity activity)
    {
        mCount--;

        // A transparent Activity like community user profile won't stop the Activity that launched
        // it. If you launch another Activity from the user profile or hit the Android home button,
        // there are two onStops(). One for the user profile and one for its parent. Remove any
        // posted Runnables so we don't get two session ended events.
        mMainThreadHandler.removeCallbacksAndMessages(null);
        mMainThreadHandler.postDelayed(new Runnable()
        {
            @Override
            public void run()
            {
                if (mCount == 0)
                {
                    mIsForeground = false;
                }
            }
        }, BACKGROUND_CHECK_DELAY_MS);
    }

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

    }

    @Override
    public void onActivityResumed(final Activity activity)
    {

    }

    @Override
    public void onActivityPaused(final Activity activity)
    {

    }

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

    }

    @Override
    public void onActivityDestroyed(final Activity activity)
    {

    }
}

有三种方法可以实现这一点:

单一活动架构 ActivityLifecycleCallback 生命周期观察者和进程生命周期所有者

我在这里写了一篇关于这个的详细文章。希望能有所帮助。

考虑使用onUserLeaveHint。它只会在应用进入后台时被调用。onPause会有一些极端情况需要处理，因为它可以被用于其他原因;例如，如果用户在你的应用程序中打开另一个活动，比如你的设置页面，你的主活动的onPause方法将被调用，即使它们仍然在你的应用程序中;当你可以简单地使用onUserLeaveHint回调函数来做你所要求的事情时，跟踪正在进行的事情将导致错误。

当调用on UserLeaveHint时，你可以设置一个boolean inBackground标志为true。当onResume被调用时，如果inBackground标志被设置，只假设你回到前台。这是因为onResume也将被调用在你的主要活动，如果用户只是在你的设置菜单，从来没有离开应用程序。

Remember that if the user hits the home button while in your settings screen, onUserLeaveHint will be called in your settings activity, and when they return onResume will be called in your settings activity. If you only have this detection code in your main activity you will miss this use case. To have this code in all your activities without duplicating code, have an abstract activity class which extends Activity, and put your common code in it. Then each activity you have can extend this abstract activity.

例如:

public abstract AbstractActivity extends Activity {
    private static boolean inBackground = false;

    @Override
    public void onResume() {
        if (inBackground) {
            // You just came from the background
            inBackground = false;
        }
        else {
            // You just returned from another activity within your own app
        }
    }

    @Override
    public void onUserLeaveHint() {
        inBackground = true;
    }
}

public abstract MainActivity extends AbstractActivity {
    ...
}

public abstract SettingsActivity extends AbstractActivity {
    ...
}

onPause()和onResume()方法在应用程序被带到后台并再次进入前台时被调用。但是，在应用程序第一次启动时和关闭之前也会调用它们。你可以在活动中阅读更多。

没有任何直接的方法来获得应用程序的状态，而在后台或前台，但即使我已经面临这个问题，并找到解决方案与onWindowFocusChanged和onStop。

更多细节请查看这里Android:解决方案检测当一个Android应用程序去后台，回到前台没有getRunningTasks或getRunningAppProcesses。

这是我的解决方案https://github.com/doridori/AndroidUtils/blob/master/App/src/main/java/com/doridori/lib/app/ActivityCounter.java

基本上涉及到用计时器计算所有Activity的生命周期方法，以捕捉当前前台没有活动但应用程序(即在旋转)的情况

你可以使用:

onRestart ()

重新开始和重新开始的区别。