Android判断App前台运行还是后台运行(运行状态)

下面是详细讲解“Android判断App前台运行还是后台运行(运行状态)”的完整攻略。

问题描述

在Android开发中，有时需要判断App当前是前台运行还是后台运行，这个可以通过不同的逻辑实现。本文将给出两种常用的方法，并且结合示例说明。

方法一：使用ActivityLifecycleCallbacks

ActivityLifecycleCallbacks是一个回调接口，它可以在Activity的生命周期中监听变化，包括Activity的创建、销毁、暂停、恢复等状态。可以通过该接口监听到App的前台和后台状态。具体实现步骤如下：

1. 创建一个类实现ActivityLifecycleCallbacks接口，并在onActivityResumed和onActivityPaused方法中做出相应的逻辑处理

public class AppStatusTracker implements Application.ActivityLifecycleCallbacks {

    private int resumed;
    private int paused;
    private int started;
    private int stopped;

    private static AppStatusTracker instance;

    private AppStatusTracker() {
    }

    public static AppStatusTracker getInstance() {
        if (instance == null) {
            instance = new AppStatusTracker();
        }
        return instance;
    }

    @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++;
        if (resumed == paused) {
            Log.i("AppStatus", "App is in Background!");
        }
    }

    @Override
    public void onActivityStopped(Activity activity) {
        stopped++;
        if (started == stopped) {
            Log.i("AppStatus", "App is in Foreground!");
        }
    }

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

    }

    @Override
    public void onActivityDestroyed(Activity activity) {

    }
}

1. 在Application的onCreate()方法中注册ActivityLifecycleCallbacks回调

public class MyApp extends Application {
    @Override
    public void onCreate() {
        super.onCreate();
        registerActivityLifecycleCallbacks(AppStatusTracker.getInstance());
    }
}

1. 最后需要注意，在使用ActivityLifecycleCallbacks进行判断时，需要在onDestroy()方法取消回调。

方法二：使用ActivityManager

ActivityManager是一个可以获取系统中运行的任务和进程信息的服务，它提供了许多与任务和进程相关的方法，包括获取正在运行的任务、获取运行中的进程信息等。可以通过ActivityManager获取所有正在运行的进程，如果其中有当前App的进程，则说明App在前台运行，否则在后台运行。具体实现步骤如下：

1. 获取ActivityManager的实例

ActivityManager am = (ActivityManager) getSystemService(Context.ACTIVITY_SERVICE);

1. 获取当前系统所有正在运行的进程

List<ActivityManager.RunningAppProcessInfo> runningAppProcesses = am.getRunningAppProcesses();

1. 遍历所有正在运行的进程，如果其中有当前App的进程，则说明App在前台运行，否则在后台运行。

boolean isAppRunning = false;
for (ActivityManager.RunningAppProcessInfo process : runningAppProcesses) {
    if (process.processName.equals(getPackageName())) {
        if (process.importance == ActivityManager.RunningAppProcessInfo.IMPORTANCE_FOREGROUND) {
            isAppRunning = true;
        } else if (process.importance == ActivityManager.RunningAppProcessInfo.IMPORTANCE_BACKGROUND) {
            isAppRunning = false;
        }
    }
}
if (isAppRunning) {
    Log.i("AppStatus", "App is in Foreground!");
} else {
    Log.i("AppStatus", "App is in Background!");
}

示例说明

以下是两个简单的示例，分别使用上述两种方法进行App前后台判断。

示例一：使用ActivityLifecycleCallbacks

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        registerActivityLifecycleCallbacks(AppStatusTracker.getInstance());
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        unregisterActivityLifecycleCallbacks(AppStatusTracker.getInstance());
    }
}

示例二：使用ActivityManager

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        checkAppStatus();
    }

    private void checkAppStatus() {
        ActivityManager am = (ActivityManager) getSystemService(Context.ACTIVITY_SERVICE);
        List<ActivityManager.RunningAppProcessInfo> runningAppProcesses = am.getRunningAppProcesses();
        boolean isAppRunning = false;
        for (ActivityManager.RunningAppProcessInfo process : runningAppProcesses) {
            if (process.processName.equals(getPackageName())) {
                if (process.importance == ActivityManager.RunningAppProcessInfo.IMPORTANCE_FOREGROUND) {
                    isAppRunning = true;
                } else if (process.importance == ActivityManager.RunningAppProcessInfo.IMPORTANCE_BACKGROUND) {
                    isAppRunning = false;
                }
            }
        }
        if (isAppRunning) {
            Log.i("AppStatus", "App is in Foreground!");
        } else {
            Log.i("AppStatus", "App is in Background!");
        }
    }
}

以上是关于Android判断App前台运行还是后台运行(运行状态)的完整攻略，希望对你有所帮助。