java - 在 onMessageReceived() 中执行操作 - Firebase 云消息传递

Question

我试图在监听 onMessageReceived() 中的有效负载后执行一个操作，我想要实现的操作在其方法中有一个 ProgressBar ，因此它会抛出一个空指针异常。

下面是我的方法onMessageReceived()。

@Override
    public void onMessageReceived(RemoteMessage remoteMessage) {
        if (remoteMessage.getNotification() != null) {
            Handler handler = new Handler(Looper.getMainLooper());
            handler.post(new Runnable() {
                public void run() {
                    roomAvailabilityHelper = new RoomAvailabilityHelper("");
                    roomAvailabilityHelper.endCurrentMeeting(new RoomAvailabilityActivity());
                    roomAvailabilityHelper.autoRefreshTimer(new RoomAvailabilityActivity());
                    Toast.makeText(getApplicationContext(),
                            "Am working", Toast.LENGTH_SHORT).show();
                    Log.d("Updated ->","Calendar updated");
                }
            });
        }
    }

然后，autoRefreshTimer() 和 endCurrentMeeting() 在 RoomAvailabilityHelper` 类中可用。以下是方法。

 public static void endCurrentMeeting(RoomAvailabilityActivity activity) {
            activity.progressBar.setVisibility(VISIBLE);
            RoomAvailabilityHelper.updateRoomCalendarEvents(activity.mDisposables,
                    false, activity, 2000);
            activity.runOnUiThread(() -> new Handler().postDelayed(() -> {
                MeetingRoomDetailFragment meetingRoomDetailFragment = (MeetingRoomDetailFragment)
                        activity.getSupportFragmentManager()
                                .findFragmentById(R.id.frame_room_availability_details);
                if (meetingRoomDetailFragment != null && activity.sharedPreferences.getString(
                        CountryActivity.SHARED_ROOM_CHECKED_IN, null) == null) {
                    meetingRoomDetailFragment.displayCheckInScreen();
                }
                activity.progressBar.setVisibility(View.GONE);
            }, 3000));
        }


    public static void autoRefreshTimer(RoomAvailabilityActivity activity) {
            final int timedPeriod = 300000;
            final Handler handler = new Handler();
            handler.postDelayed(() -> {
                endCurrentMeeting(activity);
                autoRefreshTimer(activity);
            }, timedPeriod);
        }

下面是错误:

java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ProgressBar.setVisibility(int)' on a null object reference
        at com.andela.mrm.room_availability.RoomAvailabilityHelper.endCurrentMeeting(RoomAvailabilityHelper.java:280)
        at com.andela.mrm.notifications.Notifications$1.run(Notifications.java:40)
        at android.os.Handler.handleCallback(Handler.java:739)
        at android.os.Handler.dispatchMessage(Handler.java:95)
        at android.os.Looper.loop(Looper.java:145)
        at android.app.ActivityThread.main(ActivityThread.java:6939)
        at java.lang.reflect.Method.invoke(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:372)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1404)

所以我正在寻找一种在onMessageReceived()中连接Activity的方法，但我无法得到它。这就是为什么由于 Activity，ProgressBar 上出现空指针异常，

Answer 1

我建议使用 LocalBroadcastManager 。因此，当您在 Firebase 服务文件中的 onMessageReceived() 中收到事件时，它会触发 Activity 中的函数 并在 Activity 中调用您的函数。

在 ProgressBar 的 Activity 中

private BroadcastReceiver pushMessageBroadCastReceiver;
//here receive the broadcast from Firebase message,then your thing

//add this inside onCreate()
pushMessageBroadCastReceiver = new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent intent) {
            if (intent.getAction().equals(AppConfig.PUSH_NOTIFICATION)) {

                //Here your receive the data from onMessageReceived()
                //do your thing here
                Log.d("Activity","Is triggerred here")
            }
        }
    };

@Override
protected void onResume() {
        super.onResume();
        LocalBroadcastManager.getInstance(this).registerReceiver(pushMessageBroadCastReceiver,
                new IntentFilter(AppConfig.PUSH_NOTIFICATION));
    }

@Override
protected void onPause() {
super.onPause();
    LocalBroadcastManager.getInstance(this).unregisterReceiver(pushMessageBroadCastReceiver);
    }

在你的AppConfig类中(如果没有，创建一个)

// broadcast receiver intent filters
 public static final String PUSH_NOTIFICATION = "pushNotification";

在您的onMessageReceived()中添加以下代码，从这里触发您的 Activity 中的LocalBroadcastManager:

@Override
public void onMessageReceived(RemoteMessage remoteMessage) {

    //here you trigger the LocalBroadcastManager in your activity
    Intent pushNotification = new Intent(AppConfig.PUSH_NOTIFICATION);
    LocalBroadcastManager.getInstance(this).sendBroadcast(pushNotification);

}