当应用程序处于前台或后台时，如何用FCM处理通知

Answer 1

有比官方网站教程更好的方法

官网表示，通知将在app后台时由系统创建。所以您不能通过重写“onMessageReceived（）”来处理它。因为“onMessageReceived（）”只有在应用程序处于前台时才会触发。

但事实并非如此。实际上，通知（当应用程序在后台时）是由Firebase库创建的。

@Override
public void handleIntent(Intent intent) {
    Log.d( "FCM", "handleIntent ");
}

步骤2。解析来自FCM的消息
How:
如果您不知道所设置的消息格式。打印并尝试分析它。
下面是基本示例

Bundle bundle = intent.getExtras();
if (bundle != null) {
    for (String key : bundle.keySet()) {
        Object value = bundle.get(key);
        Log.d("FCM", "Key: " + key + " Value: " + value);
    }
}

private void removeFirebaseOrigianlNotificaitons() {

    //check notificationManager is available
    NotificationManager notificationManager = 
        (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);
    if (notificationManager == null )
        return;

    //check api level for getActiveNotifications()
    if (Build.VERSION.SDK_INT < Build.VERSION_CODES.M) {
        //if your Build version is less than android 6.0
        //we can remove all notifications instead. 
        //notificationManager.cancelAll();
        return;
    }


    //check there are notifications
    StatusBarNotification[] activeNotifications = 
        notificationManager.getActiveNotifications();
    if (activeNotifications == null)
        return;

    //remove all notification created by library(super.handleIntent(intent))
    for (StatusBarNotification tmp : activeNotifications) {
        Log.d("FCM StatusBarNotification", 
            "StatusBarNotification tag/id: " + tmp.getTag() + " / " + tmp.getId());
        String tag = tmp.getTag();
        int id = tmp.getId();

        //trace the library source code, follow the rule to remove it.
        if (tag != null && tag.contains("FCM-Notification"))
            notificationManager.cancel(tag, id);
    }
}

public class MyFirebaseMessagingService extends FirebaseMessagingService {

private static int notificationCount=0;

@Override
public void handleIntent(Intent intent) {
    //add a log, and you'll see the method will be triggered all the time (both foreground and background).
    Log.d( "FCM", "handleIntent");

    //if you don't know the format of your FCM message,
    //just print it out, and you'll know how to parse it
    Bundle bundle = intent.getExtras();
    if (bundle != null) {
        for (String key : bundle.keySet()) {
            Object value = bundle.get(key);
            Log.d("FCM", "Key: " + key + " Value: " + value);
        }
    }

    //the background notification is created by super method
    //but you can't remove the super method. 
    //the super method do other things, not just creating the notification
    super.handleIntent(intent);

    //remove the Notificaitons
    removeFirebaseOrigianlNotificaitons();

    if (bundle ==null)
        return;

    //pares the message
    CloudMsg cloudMsg = parseCloudMsg(bundle);

    //if you want take the data to Activity, set it
    Bundle myBundle = new Bundle();
    myBundle.putSerializable(TYPE_FCM_PLATFORM, cloudMsg);
    Intent myIntent = new Intent(this, NotificationActivity.class);
    myIntent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
    myIntent.putExtras(myBundle);
    PendingIntent pendingIntent = PendingIntent.getActivity(this, notificationCount, myIntent, PendingIntent.FLAG_UPDATE_CURRENT);

    //set the Notification
    NotificationCompat.Builder notificationBuilder = new NotificationCompat.Builder(this)
            .setSmallIcon(R.mipmap.icon)
            .setContentTitle(cloudMsg.getTitle())
            .setContentText(cloudMsg.getMessage())
            .setAutoCancel(true)
            .setContentIntent(pendingIntent);

    NotificationManager notificationManager = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);
    notificationManager.notify(notificationCount++, notificationBuilder.build());
}



/**
 * parse the message which is from FCM
 * @param bundle
 */
private CloudMsg parseCloudMsg(Bundle bundle) {
    String title = null, msg=null;

    //if the message is sent from Firebase platform, the key will be that
    msg = (String) bundle.get("gcm.notification.body");

    if(bundle.containsKey("gcm.notification.title"))
    title = (String) bundle.get("gcm.notification.title");

    //parse your custom message
    String testValue=null;
    testValue =  (String) bundle.get("testKey");

    //package them into a object(CloudMsg is your own structure), it is easy to send to Activity.
    CloudMsg cloudMsg = new CloudMsg(title, msg, testValue);
    return cloudMsg;
}


/**
 * remove the notification created by "super.handleIntent(intent)"
 */
    private void removeFirebaseOrigianlNotificaitons() {

    //check notificationManager is available
    NotificationManager notificationManager = 
        (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);
    if (notificationManager == null )
        return;

    //check api level for getActiveNotifications()
    if (Build.VERSION.SDK_INT < Build.VERSION_CODES.M) {
        //if your Build version is less than android 6.0
        //we can remove all notifications instead. 
        //notificationManager.cancelAll();
        return;
     }

    //check there are notifications
    StatusBarNotification[] activeNotifications = 
        notificationManager.getActiveNotifications();
    if (activeNotifications == null)
        return;

    //remove all notification created by library(super.handleIntent(intent))
    for (StatusBarNotification tmp : activeNotifications) {
        Log.d("FCM StatusBarNotification", 
            "tag/id: " + tmp.getTag() + " / " + tmp.getId());
        String tag = tmp.getTag();
        int id = tmp.getId();

        //trace the library source code, follow the rule to remove it.
        if (tag != null && tag.contains("FCM-Notification"))
            notificationManager.cancel(tag, id);
    }
}
}