通过Firebase函数发送FCM通知的持续性错误

Question

我正在尝试使用Firebase函数向使用Java编写的Android应用程序中的用户发送通知，但我仍然在Firebase功能控制台日志中收到此错误：

          Error: Messaging payload contains an invalid value for the "notification.title" property. Values must be strings.
at FirebaseMessagingError.Error (native)
at FirebaseMessagingError.FirebaseError [as constructor] (/user_code/node_modules/firebase-admin/lib/utils/error.js:25:28)
at new FirebaseMessagingError (/user_code/node_modules/firebase-admin/lib/utils/error.js:130:23)
at /user_code/node_modules/firebase-admin/lib/messaging/messaging.js:486:27
at Array.forEach (native)
at /user_code/node_modules/firebase-admin/lib/messaging/messaging.js:483:32
at Array.forEach (native)
at Messaging.validateMessagingPayload (/user_code/node_modules/firebase-admin/lib/messaging/messaging.js:476:21)
at /user_code/node_modules/firebase-admin/lib/messaging/messaging.js:313:37
at process._tickDomainCallback (internal/process/next_tick.js:135:7)

这是我的功能：

const functions = require('firebase-functions');
const admin = require('firebase-admin');

admin.initializeApp(functions.config().firebase);

exports.pushNotification = functions.database.ref('/messages/send').onWrite( 
event => {
console.log('Push notification event triggered');

event.data.adminRef.parent.once('value').then((snapshot) => {
var valueObject = snapshot.val();

const payload = {
    notification: {
        title: JSON.stringify(valueObject.title),
        body: JSON.stringify(valueObject.message),
        click_action: ".WebsiteActivityNotification",
        sound: "default"
    },
    data: {
        title: JSON.stringify(valueObject.title),
        message: JSON.stringify(valueObject.message),
        link: JSON.stringify(valueObject.link)
    }
};
const options = {
    priority: "high",
    timeToLive: 60 * 60 * 24 //24 hours
};
return admin.messaging().sendToTopic("notifications", payload, options);

});

});

以下是我的Firebase数据库结构：

/messages
    link: "..."
    message: "..."
    title: "..."
    send: "..."

这是我的服务：

import android.app.Notification;
import android.app.NotificationManager;
import android.app.PendingIntent;
import android.content.Context;
import android.content.Intent;
import android.media.RingtoneManager;
import android.net.Uri;
import android.support.v4.app.NotificationCompat;
import android.util.Log;

import com.google.firebase.messaging.FirebaseMessagingService;
import com.google.firebase.messaging.RemoteMessage;

public class FCMService extends FirebaseMessagingService {

private static final String TAG = "MyFirebaseMsgService";

@Override
public void onMessageReceived(RemoteMessage remoteMessage) {

    String notificationTitle = null, notificationBody = null;
    String dataTitle = null, dataMessage = null, dataLink = null;

    if (remoteMessage.getData().size() > 0) {
        Log.d(TAG, "Message data payload: " + remoteMessage.getData().get("message"));
        dataTitle = remoteMessage.getData().get("title");
        dataMessage = remoteMessage.getData().get("message");
        dataLink = remoteMessage.getData().get("link");
    }

    if (remoteMessage.getNotification() != null) {
        Log.d(TAG, "Message Notification Body: " + remoteMessage.getNotification().getBody());
        notificationTitle = remoteMessage.getNotification().getTitle();
        notificationBody = remoteMessage.getNotification().getBody();
    }

    sendNotification(notificationTitle, notificationBody, dataTitle, dataMessage, dataLink);
}

private void sendNotification(String notificationTitle, String notificationBody, String dataTitle, String dataMessage, String dataLink) {
    Intent intent = new Intent(this, WebsiteActivityNotification.class);
    intent.putExtra("title", dataTitle);
    intent.putExtra("message", dataMessage);
    intent.putExtra("link", dataLink);
    intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
    PendingIntent pendingIntent = PendingIntent.getActivity(this, 0 /* Request code */, intent,
            PendingIntent.FLAG_ONE_SHOT);

    Uri defaultSoundUri= RingtoneManager.getDefaultUri(RingtoneManager.TYPE_NOTIFICATION);
    NotificationCompat.Builder notificationBuilder = new NotificationCompat.Builder(this)
            .setSmallIcon(R.mipmap.ic_launcher)
            .setContentTitle(notificationTitle)
            .setStyle(new NotificationCompat.BigTextStyle().bigText(notificationBody))
            .setContentText(notificationBody)
            .setAutoCancel(true)
            .setPriority(Notification.PRIORITY_HIGH)
            .setDefaults(Notification.FLAG_AUTO_CANCEL | Notification.DEFAULT_LIGHTS | Notification.DEFAULT_VIBRATE | Notification.DEFAULT_SOUND)
            .setContentIntent(pendingIntent);

    NotificationManager notificationManager =
            (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);

    notificationManager.notify(0 /* ID of notification */, notificationBuilder.build());
}
}

在Manifest中打开标记的活动：

<activity
    android:name=".WebsiteActivityNotification"
    android:label="@string/app_name"
    android:theme="@style/AppTheme.NoActionBar">
    <intent-filter>
        <action android:name=".WebsiteActivityNotification" />
        <category android:name="android.intent.category.DEFAULT" />
    </intent-filter>
</activity>

Manifest中的服务标签：

<service android:name=".FCMService">
    <intent-filter>
        <action android:name="com.google.firebase.MESSAGING_EVENT"/>
    </intent-filter>
</service>

<service android:name=".FirebaseIDService">
    <intent-filter>
        <action android:name="com.google.firebase.INSTANCE_ID_EVENT"/>
    </intent-filter>
</service>  

仍然没有工作...... 每个答案都受到欢迎。非常感谢你！