Firebase云功能和Android推送通知

Question

I have this problem, I am creating an android application that is connected to Firebase. Then I have my Raspberry Pi connected to Firebase, the data sent from the Pi is GPS coordinates specifically latitude and longitude. The main application that I want to create has a Push Notification function when data on the Firebase has been changed or the coordinates on the main node has been changed. Here is the screenshot of my Firebase Data:

Firebase Database Screenshot

My problem is this, the cloud function that I created has found errors that I don't understand or I'm just overseeing it. I've looked up in the Firebase documentation, sample codes from articles and I guess nothing just seemed to work for me. Here is the code for the cloud function and the error I got when I just manually type in data in Firebase.

const functions = require('firebase-functions');
const admin = require('firebase-admin');
admin.initializeApp(functions.config().firebase);

exports.sendLocationNotification = functions.database.ref("/GPS/{gps_id}").onWrite((event)=>{

var latitude = event.data.child('latitude'); 

var longitude = event.data.child('longitude');        

if(!latitude.changed() && !longitude.changed()){

return console.log('The database has been reset');
    } 

const payload = {        
    notification:{            
            title: "Location Monitor",            
            body: "Your motorcycle has moved",            
            icon: "default",            
            sound: "default"
        }
    };


    const options = {        
            priority: "high",
            timeToLive: 60 * 60 * 24
    };

        return admin.messaging().sendToTopic("Location_Notification", payload, options)

});

The next one is with the Android Application, even though my Firebase FCM is in the gradle:app, then I manually send a message in the Firebase console, the application doesn't receive any messages on the avd or phone installed with the app. Here's a code for my MessagingService to handle foreground notifications:

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;

import java.util.Map;

public class MyFirebaseMessagingService extends FirebaseMessagingService {

    private static final String TAG = "FirebaseMessgingService";

    @Override

    public void onMessageReceived(RemoteMessage remoteMessage){

        if(remoteMessage.getData().size()>0){
            Map<String, String> payload = remoteMessage.getData();

            showNotification(payload);

        }

    }

    private void showNotification(Map<String, String> payload) {

        Intent intent = new Intent(this, Tracking.class);
        intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
        PendingIntent pendingIntent = PendingIntent.getActivity(this,0,intent, PendingIntent.FLAG_ONE_SHOT);

        Uri defaultSoundUri = RingtoneManager.getDefaultUri(RingtoneManager.TYPE_NOTIFICATION);
        NotificationCompat.Builder notificationBuilder = (NotificationCompat.Builder) new NotificationCompat.Builder(this)
                .setAutoCancel(true)
                .setSmallIcon(R.drawable.track)
                .setContentIntent(pendingIntent)
                .setContentTitle(payload.get("Title"))
                .setContentText(payload.get("Body"))
                .setSound(defaultSoundUri);

        NotificationManager notificationManager = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);
        notificationManager.notify(0,notificationBuilder.build());

    }

}

Then here's my android manifest:

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="">

    <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".Splash">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity android:name=".Menu" />
        <!--
             The API key for Google Maps-based APIs is defined as a string resource.
             (See the file "res/values/google_maps_api.xml").
             Note that the API key is linked to the encryption key used to sign the APK.
             You need a different API key for each encryption key, including the release key that is used to
             sign the APK for publishing.
             You can define the keys for the debug and release targets in src/debug/ and src/release/. 
        -->
        <meta-data
            android:name="com.google.android.geo.API_KEY"
            android:value="@string/google_maps_key" />
        <meta-data
            android:name="com.google.firebase.messaging.default_notification_icon"
            android:resource="@drawable/track"/>
        <service android:name=".MyFirebaseMessagingService">
            <intent-filter>
                <action android:name="com.google.firebase.MESSAGING_EVENT"/>
            </intent-filter>
        </service>
        <activity
            android:name=".Tracking"
            android:label="@string/title_activity_tracking" />
        <activity
            android:name=".Tracing"
            android:label="@string/title_activity_tracing" />
        <activity android:name=".Tips" />
        <activity android:name=".Instruction" />
        <activity android:name=".About"></activity>
    </application>

</manifest>

This is my gradle:app

apply plugin: 'com.android.application'

android {
    compileSdkVersion 26
    defaultConfig {
        applicationId ""
        minSdkVersion 15
        targetSdkVersion 26
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])
    implementation 'com.android.support:appcompat-v7:26.1.0'
    implementation 'com.android.support.constraint:constraint-layout:1.0.2'
    implementation 'com.google.android.gms:play-services-maps:11.0.4'
    implementation 'com.google.firebase:firebase-database:11.0.4'
    implementation 'com.google.firebase:firebase-messaging:11.0.4'
    testImplementation 'junit:junit:4.12'
    androidTestImplementation 'com.android.support.test:runner:1.0.1'
    androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.1'
    compile 'com.github.Hitomis:CircleMenu:v1.1.0'
}


apply plugin: 'com.google.gms.google-services'

Here's a the error that keeps on appearing:

TypeError: Cannot read property 'child' of undefined
    at exports.sendLocationNotification.functions.database.ref.onWrite (/user_code/index.js:13:30)
    at Object.<anonymous> (/user_code/node_modules/firebase-functions/lib/cloud-functions.js:112:27)
    at next (native)
    at /user_code/node_modules/firebase-functions/lib/cloud-functions.js:28:71
    at __awaiter (/user_code/node_modules/firebase-functions/lib/cloud-functions.js:24:12)
    at cloudFunction (/user_code/node_modules/firebase-functions/lib/cloud-functions.js:82:36)
    at /var/tmp/worker/worker.js:700:26
    at process._tickDomainCallback (internal/process/next_tick.js:135:7)

Answer 1

As per the Firebase documentation for the onWrite method, it's passed:

a functions.Change containing a non-null functions.database.DataSnapshot and an optional non-null functions.EventContext )

However in your function you're expecting an event object, which results empty.

Following the sample code available here , you could re-write your function like so:

exports.makeUppercase = functions.database.ref("/GPS/{gps_id}")
    .onWrite((change, context) => {

      // You can get the previous value for latitude and longitude
      var previousLatitude = change.before.ref.parent.child('latitude'); 
      var previousLongitude = change.before.ref.parent.child('longitude');

      // And the new values
      var newLatitude = change.after.ref.parent.child('latitude'); 
      var newLongitude = change.after.ref.parent.child('longitude');

      // And perform your logic from here
      ...

      return admin.messaging().sendToTopic("Location_Notification", payload, options);
    });

I haven't checked the Android issue you mentioned but I guess that since the Firebase Function was failing, the return statement didn't execute and no notification was sent at all.