我在谷歌Analytics EasyTracker中使用了这个，它起作用了。可以将其扩展为使用简单整数来完成您想要的任务。

public class MainApplication extends Application {

    int isAppBackgrounded = 0;

    @Override
    public void onCreate() {
        super.onCreate();
        appBackgroundedDetector();
    }

    private void appBackgroundedDetector() {
        registerActivityLifecycleCallbacks(new ActivityLifecycleCallbacks() {
            @Override
            public void onActivityCreated(Activity activity, Bundle bundle) {

            }

            @Override
            public void onActivityStarted(Activity activity) {
                EasyTracker.getInstance(MainApplication.this).activityStart(activity);
            }

            @Override
            public void onActivityResumed(Activity activity) {
                isAppBackgrounded++;
                if (isAppBackgrounded > 0) {
                    // Do something here
                }
            }

            @Override
            public void onActivityPaused(Activity activity) {
                isAppBackgrounded--;
            }

            @Override
            public void onActivityStopped(Activity activity) {
                EasyTracker.getInstance(MainApplication.this).activityStop(activity);
            }

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

            }

            @Override
            public void onActivityDestroyed(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。

创建一个扩展Application的类。然后我们可以在其中使用它的重载方法onTrimMemory()。

为了检测应用程序是否进入了后台，我们将使用:

 @Override
    public void onTrimMemory(final int level) {
        if (level == ComponentCallbacks2.TRIM_MEMORY_UI_HIDDEN) { // Works for Activity
            // Get called every-time when application went to background.
        } 
        else if (level == ComponentCallbacks2.TRIM_MEMORY_COMPLETE) { // Works for FragmentActivty
        }
    }

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。

My app needs to "reboot" after return from background - show a series of activities, according to client solicitations. After extensive search on how to manage the background/foreground transitions (treated very differently between iOS and Android), I crossed this question. Found very useful help here, specially from the most voted answer and the one flagged as correct. However, simply reinstantiate the root activity EVERY TIME the app enters foreground looked too annoying, when you think about UX. The solution that worked for me, and the one I think's most adequated - based on the Youtube and Twitter apps functionality - was to combine the answers from @GirishNair and @d60402: Calling the timer when the app's trimming memory, as follows:

@Override
public void onTrimMemory(int level) {
    if (stateOfLifeCycle.equals("Stop")) {
        startActivityTransitionTimer();
    }

    super.onTrimMemory(level);
}

我的定时器限制设置为30秒-我正在考虑增加一点。

private final long MAX_ACTIVITY_TRANSITION_TIME = 30000;

当app进入前台，重新启动，或者app被销毁时，调用方法取消定时器。

在应用程序扩展:

@Override
public void onActivityCreated(Activity activity, Bundle arg1) {
    stopActivityTransitionTimer();
    stateOfLifeCycle = "Create";
}

@Override
public void onActivityDestroyed(Activity activity) {
    stopActivityTransitionTimer();
    stateOfLifeCycle = "Destroy";
}

在活动上(最好是在一个基础活动上，由其他活动继承):

@Override
protected void onStart() {
    super.onStart();
    if (App.wasInBackground) {
        stopActivityTransitionTimer();
    }
}

在我的情况下，当应用程序在最大时间后进入前台时，会创建一个新任务，因此stopActivityTransitionTimer()在onActivityCreated()或onActivityDestroyed()上被调用，在应用程序扩展类中-转向不必要调用活动中的方法。 希望能有所帮助。

您可以在ActivityLifecycleCallbacks和ComponentCallbacks2的帮助下轻松实现这一点。

创建一个实现上述接口的类AppLifeCycleHandler。

package com.sample.app;

import android.app.Activity;
import android.app.Application;
import android.content.ComponentCallbacks2;
import android.content.res.Configuration;
import android.os.Bundle;

/**
 * Created by Naveen on 17/04/18
 */
public class AppLifeCycleHandler
    implements Application.ActivityLifecycleCallbacks, ComponentCallbacks2 {

  AppLifeCycleCallback appLifeCycleCallback;

  boolean appInForeground;

  public AppLifeCycleHandler(AppLifeCycleCallback appLifeCycleCallback) {
    this.appLifeCycleCallback = appLifeCycleCallback;
  }

  @Override
  public void onActivityResumed(Activity activity) {
    if (!appInForeground) {
      appInForeground = true;
      appLifeCycleCallback.onAppForeground();
    }
  }

  @Override
  public void onTrimMemory(int i) {
    if (i == ComponentCallbacks2.TRIM_MEMORY_UI_HIDDEN) {
      appInForeground = false;
      appLifeCycleCallback.onAppBackground();
    }
  }

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

  }

  @Override
  public void onActivityStarted(Activity activity) {

  }

  @Override
  public void onActivityPaused(Activity activity) {

  }

  @Override
  public void onActivityStopped(Activity activity) {

  }

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

  }

  @Override
  public void onActivityDestroyed(Activity activity) {

  }

  @Override
  public void onConfigurationChanged(Configuration configuration) {

  }

  @Override
  public void onLowMemory() {

  }

  interface AppLifeCycleCallback {

    void onAppBackground();

    void onAppForeground();
  }
}

在你的类中，当应用程序在前台和后台之间切换时，应用程序实现AppLifeCycleCallback来获得回调。如下图所示。

public class BaseApplication extends Application implements AppLifeCycleHandler.AppLifeCycleCallback{

    @Override
    public void onCreate() {
        super.onCreate();
        AppLifeCycleHandler appLifeCycleHandler = new AppLifeCycleHandler(this);
        registerActivityLifecycleCallbacks(appLifeCycleHandler);
        registerComponentCallbacks(appLifeCycleHandler);
    }

    @Override
    public void onAppBackground() {
        Log.d("LifecycleEvent", "onAppBackground");
    }

    @Override
    public void onAppForeground() {
        Log.d("LifecycleEvent", "onAppForeground");
    }
}

希望这能有所帮助。

编辑 作为替代方案，您现在可以使用生命周期感知的体系结构组件。