Firebase（FCM）：在通知点击时打开活动并传递数据。安卓

应该清楚如何处理Firebase通知和数据的实现。我阅读了很多答案，但似乎无法使其工作。以下是我的步骤：

1.) 我在PHP中将通知和数据传递给Android，看起来还不错：

$msg = array
    (
         "body" => $body,
         "title" => $title,
         "sound" => "mySound"
    );
    $data = array
    (
         "user_id" => $res_id,
         "date" => $date,
         "hal_id" => $hal_id,
         "M_view" => $M_view
    );
    $fields = array
    (
        'registration_ids' => $registrationIds,
        'notification' => $msg,
        'data' => $data
    );
    $headers = array
    (
        'Authorization: key='.API_ACCESS_KEY,
        'Content-Type: application/json'
    );
    $ch = curl_init();
    curl_setopt( $ch,CURLOPT_URL, 'https://android.googleapis.com/gcm/send' );
    curl_setopt( $ch,CURLOPT_POST, true );
    curl_setopt( $ch,CURLOPT_HTTPHEADER, $headers );
    curl_setopt( $ch,CURLOPT_RETURNTRANSFER, true );
    curl_setopt( $ch,CURLOPT_SSL_VERIFYPEER, false );
    curl_setopt( $ch,CURLOPT_POSTFIELDS, json_encode( $fields ) );
    $result = curl_exec($ch );
    curl_close( $ch );

2.) 当通知和数据在Android中接收到时，会显示通知。当我点击该通知时，它会打开应用程序。但是我无法弄清楚在打开应用程序时如何处理数据。应用程序在前台和后台时有几个不同之处。我现在的代码如下：

public class MyFirebaseMessagingService extends FirebaseMessagingService {
private static final String TAG = "MyFirebaseMsgService";
@Override
public void onMessageReceived(RemoteMessage remoteMessage) {
    String user_id = "0";
    String date = "0";
    String cal_id = "0";
    String M_view = "0";
    if (remoteMessage.getData().size() > 0) {
        Log.d(TAG, "Message data payload: " + remoteMessage.getData());
        user_id = remoteMessage.getData().get("user_id");
        date = remoteMessage.getData().get("date");
        hal_id = remoteMessage.getData().get("hal_id");
        M_view = remoteMessage.getData().get("M_view");
    }
    //调用生成通知的方法
    sendNotification(remoteMessage.getNotification().getBody(), user_id, date, hal_id, M_view);
}
private void sendNotification(String messageBody, String user_id, String date, String hal_id, String M_view) {
    Intent intent = new Intent(this, MainActivity.class);
    intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_SINGLE_TOP | Intent.FLAG_ACTIVITY_CLEAR_TOP);
    intent.putExtra("fcm_notification", "Y");
    intent.putExtra("user_id", user_id);
    intent.putExtra("date", date);
    intent.putExtra("hal_id", hal_id);
    intent.putExtra("M_view", M_view);
    int uniqueInt = (int) (System.currentTimeMillis() & 0xff);
    PendingIntent pendingIntent = PendingIntent.getActivity(getApplicationContext(), uniqueInt, intent,
            PendingIntent.FLAG_UPDATE_CURRENT);
    Uri defaultSoundUri= RingtoneManager.getDefaultUri(RingtoneManager.TYPE_NOTIFICATION);
    NotificationCompat.Builder notificationBuilder = new NotificationCompat.Builder(this);
    notificationBuilder.setSmallIcon(R.drawable.ic_launcher)
            .setContentText(messageBody)
            .setAutoCancel(true)
            .setSound(defaultSoundUri)
            .setContentIntent(pendingIntent);
    NotificationManager notificationManager = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);
    notificationManager.notify(0, notificationBuilder.build());
}}

3.) 当我使用上述代码，并且当我点击通知时，它只是在后台打开应用程序。如果应用程序在前台，则在通知点击时它只是取消通知。然而，我希望在两种情况下（前台和后台）都能接收数据并打开特定的Activity。我在MainActivity中有以下代码，但我无法获取数据。fcm_notification、date、hal_id都返回null。

public class MainActivity extends Activity {
 UserFunctions userFunctions;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
}
@Override
protected void onNewIntent(Intent intent) {
    super.onNewIntent(intent);
    setIntent(intent);
    Intent intent_o = getIntent();
}
@Override
protected void onResume() {
    super.onResume();
    userFunctions = new UserFunctions();
    if(userFunctions.isUserLoggedIn(getApplicationContext())){
        Intent intent_o = getIntent();
        String fcm_notification = intent_o.getStringExtra("fcm_notification") ;
        String user_id = intent_o.getStringExtra("user_id");
        String date = intent_o.getStringExtra("date");
        String hal_id = intent_o.getStringExtra("hal_id");
        String M_view = intent_o.getStringExtra("M_view");
        Intent intent = new Intent(this, JobList.class);
        // THIS RETURNS NULL, user_id = null
        System.out.print("FCM" + user_id);
        startActivity(intent);
        finish();
    }else{
        // user is not logged in show login screen
        Intent login = new Intent(this, LoginActivity.class);
        startActivity(login);
        // Closing dashboard screen
        finish();
    }
}}

如果有人能指导或建议如何从Firebase的MainActivity.java中检索数据（无论是在前台还是后台），那将是太棒了。