如何从服务中检查应用程序是否在前台？

Question

只有当应用程序不在前台时，我才需要向用户显示通知。这是我的公共类 MyFirebaseMessagingService 扩展

FirebaseMessagingService {
    @Override
    public void onMessageReceived(RemoteMessage remoteMessage) {
        if(applicationInForeground()) {
            Map<String, String> data = remoteMessage.getData();
            sendNotification(data.get("title"), data.get("detail"));
        }

    }

需要实现applicationInForeground()方法

Answer 1

我只报告了@bompfanswer 的 Kotlin 版本

import androidx.lifecycle.Lifecycle
import androidx.lifecycle.LifecycleObserver
import androidx.lifecycle.OnLifecycleEvent
import androidx.lifecycle.ProcessLifecycleOwner
import com.google.firebase.messaging.FirebaseMessagingService
import com.google.firebase.messaging.RemoteMessage

class AppFirebaseMessagingService : FirebaseMessagingService(), LifecycleObserver {

    private var isAppInForeground = false

    override fun onCreate() {
        super.onCreate()
        ProcessLifecycleOwner.get().lifecycle.addObserver(this)
    }

    override fun onDestroy() {
        super.onDestroy()
        ProcessLifecycleOwner.get().lifecycle.removeObserver(this)
    }

    @OnLifecycleEvent(Lifecycle.Event.ON_START)
    fun onForegroundStart() {
        isAppInForeground = true
    }

    @OnLifecycleEvent(Lifecycle.Event.ON_STOP)
    fun onForegroundStop() {
        isAppInForeground = false
    }

    override fun onMessageReceived(remoteMessage: RemoteMessage) {
        if (isAppInForeground) {
            // do foreground stuff on your activities
        } else {
            // send a notification
        }
    }
}

Answer 2

您可以从 android 系统服务控制正在运行的应用程序进程。试试这个：

private boolean applicationInForeground() {
    ActivityManager activityManager = (ActivityManager) getSystemService(Context.ACTIVITY_SERVICE);
    List<ActivityManager.RunningAppProcessInfo> services = activityManager.getRunningAppProcesses();
    boolean isActivityFound = false;

    if (services.get(0).processName
            .equalsIgnoreCase(getPackageName()) && services.get(0).importance == RunningAppProcessInfo.IMPORTANCE_FOREGROUND) {
        isActivityFound = true;
    }

    return isActivityFound;
}

祝你好运。

Answer 3

您也可以尝试使用Android Jetpack lifecycle components。

public class AppFirebaseMessagingService extends FirebaseMessagingService implements LifecycleObserver {

    private boolean isAppInForeground;

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

        ProcessLifecycleOwner.get().getLifecycle().addObserver(this);
    }

    @Override
    public void onDestroy() {
        super.onDestroy();

        ProcessLifecycleOwner.get().getLifecycle().removeObserver(this);
    }

    @OnLifecycleEvent(Lifecycle.Event.ON_START)
    public void onForegroundStart() {
        isAppInForeground = true;
    }

    @OnLifecycleEvent(Lifecycle.Event.ON_STOP)
    public void onForegroundStop() {
        isAppInForeground = false;
    }

    @Override
    public void onMessageReceived(RemoteMessage remoteMessage) {
        if(isAppInForeground) {
            // do foreground stuff on your activities
        } else {
            // send a notification
        }
    }
}

请参阅 here 如何导入必要的依赖项，因为生命周期不是标准 Android SDK 的一部分。

Answer 4

在 2016 年 Google I/O 上，我发表了一次演讲，其中一个主题是 Firebase 如何检测您的应用是否在前台。您可以为此使用ActivityLifecycleCallbacks，方法是为应用程序中启动的每个活动增加一个计数器，然后为每个停止的活动减少它。如果计数器 > 1，则您的应用程序位于前台。演讲的相关部分可以在 YouTube here 上看到。