我正在使用firebase云功能在我的应用程序中显示通知，而我面临的唯一问题是当应用程序关闭或后台通知未显示弹出窗口时。应用程序中使用了提醒通知，我确实收到了通知，但通知不会像应用程序在前台时那样弹出。我已将频道和通知的优先级设置为高，但仍然不起作用。
我的服务级别：

@Override
    public void onMessageReceived(RemoteMessage remoteMessage) {
        super.onMessageReceived(remoteMessage);
        Log.d("msg", "onMessageReceived: " + remoteMessage.getData().get("message"));
        Intent intent = new Intent(this, WebViewActivity.class);
        intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
        PendingIntent pendingIntent = PendingIntent.getActivity(this, 0, intent, PendingIntent.FLAG_ONE_SHOT);
        String channelId = "Default";
        NotificationCompat.Builder builder = new  NotificationCompat.Builder(this, channelId)
                .setSmallIcon(R.drawable.app_logo)
                .setContentTitle(remoteMessage.getNotification().getTitle())
                .setContentText(remoteMessage.getNotification().getBody())
                .setAutoCancel(true).setContentIntent(pendingIntent)
                .setDefaults(DEFAULT_SOUND | DEFAULT_VIBRATE)
                .setPriority(Notification.PRIORITY_MAX);
        NotificationManager manager = (NotificationManager) getSystemService(NOTIFICATION_SERVICE);
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
            NotificationChannel channel = new NotificationChannel(channelId, "Default channel", NotificationManager.IMPORTANCE_HIGH);
            channel.setShowBadge(true);
             channel.setLockscreenVisibility(Notification.VISIBILITY_PUBLIC);
            manager.createNotificationChannel(channel);
        }
        manager.notify(0, builder.build());
    }

显示

<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="com.noderon.riscalert.WebViewActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity android:name="com.noderon.riscalert.MainActivity">
        </activity>
        <service
            android:name=".NotificationService">
            <intent-filter>
                <action android:name="com.google.firebase.MESSAGING_EVENT"/>
            </intent-filter>
        </service>
    </application>

任何帮助都将不胜感激。谢谢