Java 应用处于前台状态时无法接收来自FCM的通知

我是Android和编程新手，我正在创建一个应用程序，该应用程序在后台接收来自FCM的消息并正常工作，因此，我添加了一个FirebaseMessagingService类，该类在onMessageReceived方法中接收通知，并跟踪google文档，但当应用程序处于前台状态时，通知仍然不起作用，我遵循了每一步，无法找出代码中的问题在哪里，因为日志对我没有帮助，我也没有收到任何错误，除了这一个，我不知道它是否是问题的根源，如果问题： 分析GCM事件java.lang.NumberFormatException中的时间戳时出错：s==null

这是我的MyFirebaseMessagingService类

import android.app.NotificationManager;
import android.app.PendingIntent;
import android.content.BroadcastReceiver;
import android.content.Intent;
import android.support.v4.app.NotificationCompat;
import android.support.v4.app.NotificationManagerCompat;

import com.app.muhammadgamal.swapy.R;
import com.google.firebase.messaging.RemoteMessage;

public class MyFirebaseMessagingService extends com.google.firebase.messaging.FirebaseMessagingService {

    @Override
    public void onMessageReceived(RemoteMessage remoteMessage) {
        super.onMessageReceived(remoteMessage);

        String click_Action = remoteMessage.getNotification().getClickAction();


        String messageTitle = remoteMessage.getNotification().getTitle();
        String messageBody = remoteMessage.getNotification().getBody();


        NotificationCompat.Builder mBuilder = new NotificationCompat.Builder(this, getString(R.string.default_notification_channel_id))
                .setSmallIcon(R.drawable.ic_main_logo)
                .setContentTitle(messageTitle)
                .setContentText(messageBody)
                .setPriority(NotificationCompat.PRIORITY_DEFAULT);


        Intent intent = new Intent(click_Action);
        PendingIntent pendingIntent = PendingIntent.getActivity(this, 0, intent, PendingIntent.FLAG_UPDATE_CURRENT);
        mBuilder.setContentIntent(pendingIntent);


        int mNotificationID = (int)System.currentTimeMillis();
        NotificationManager manager = (NotificationManager)getSystemService(NOTIFICATION_SERVICE);
        manager.notify(mNotificationID,mBuilder.build());

    }
}

还有我的清单文件

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

    <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
    <uses-permission android:name="android.permission.INTERNET" />
    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
    <uses-permission android:name="android.permission.ACCESS_WIFI_STATE" />

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_main_logo"
        android:label="@string/app_name"
        android:roundIcon="@drawable/ic_main_logo"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity
            android:name=".Activities.SignInActivity"
            android:theme="@style/AppTheme.NoActionBar">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity
            android:name=".Activities.SignUpActivity"
            android:theme="@style/AppTheme.NoActionBar" />
        <activity
            android:name=".Activities.ProfileActivity"
            android:theme="@style/AppTheme.NoActionBar" />
        <activity
            android:name=".Activities.NavDrawerActivity"
            android:theme="@style/AppTheme.NoActionBar" />
        <activity
            android:name=".Activities.SwapCreationActivity"
            android:theme="@style/AppTheme.NoActionBar" />

        <activity android:name=".Activities.ReceivedSwapRequest">
            <intent-filter>
                <action android:name="com.app.muhammadgamal.swapy.Activities.ReceivedSwapRequest_NOTIFICATION_TASK"></action>
                <category android:name="android.intent.category.DEFAULT"></category>
            </intent-filter>
        </activity>

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

    </application>

</manifest>

---

我发现了问题，因为我使用的是Android O，没有设置通知的频道ID，如果你想在Android 8.0或更高版本上接收通知，这是必须的

下面是解决方案代码

 private void createNotificationChannel() {
    // Create the NotificationChannel, but only on API 26+ because
    // the NotificationChannel class is new and not in the support library
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
        CharSequence name = getString(R.string.channel_name);
        String description = getString(R.string.channel_description);
        int importance = NotificationManager.IMPORTANCE_DEFAULT;
        NotificationChannel channel = new NotificationChannel(CHANNEL_ID, name, importance);
        channel.setDescription(description);
        // Register the channel with the system; you can't change the importance
        // or other notification behaviors after this
        NotificationManager notificationManager = getSystemService(NotificationManager.class);
        notificationManager.createNotificationChannel(channel);
    }
}

---

您在哪里包含了解决此问题的上述代码？感谢MyFirebaseMessagingService类—负责接收通知的类

 private void createNotificationChannel() {
    // Create the NotificationChannel, but only on API 26+ because
    // the NotificationChannel class is new and not in the support library
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
        CharSequence name = getString(R.string.channel_name);
        String description = getString(R.string.channel_description);
        int importance = NotificationManager.IMPORTANCE_DEFAULT;
        NotificationChannel channel = new NotificationChannel(CHANNEL_ID, name, importance);
        channel.setDescription(description);
        // Register the channel with the system; you can't change the importance
        // or other notification behaviors after this
        NotificationManager notificationManager = getSystemService(NotificationManager.class);
        notificationManager.createNotificationChannel(channel);
    }
}