android 服务中未显示通知

Question

我有这项服务可以连接到服务器并获取通知但不幸的是它没有显示任何通知这是服务 class :

public class NotificationService extends Service {
    @Nullable
    @Override
    public IBinder onBind(Intent intent) {
        return null;
    }
    public void startNotificationListener()
    {
      //start's a new thread
    new Thread(new Runnable() {
        @Override
        public void run() {
          //fetching notifications from server
         //if there is notifications then call this method
        ShowNotification();
        }
    }).start();
    @Override
    public void onCreate()
    {
        startNotificationListener();
        super.onCreate();
    }
    @Override
    public int onStartCommand(Intent intent,int flags,int startId)
    {
        return super.onStartCommand(intent,flags,startId);
    }
    @Override
    public void onDestroy()
    {
        super.onDestroy();
    }
    public void ShowNotification()
    {
      NotificationManager notificationManager =
                    (NotificationManager) getSystemService(Service.NOTIFICATION_SERVICE);
            Notification notification = new NotificationCompat.Builder(getBaseContext(),"notification_id")
                    .setSmallIcon(R.drawable.icon)
                    .setContentTitle("title")
                    .setContentText("content")
                    .setDefaults(NotificationCompat.DEFAULT_SOUND)
                    .build();
            notificationManager.notify(0, notification);
       //the notification is not showing

    }
}

调用 ShowNotification 时通知没有显示，我试过将 ShowNotification 的代码粘贴到主要 activity 的 oncreate 中，就像那样

@Override
    protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
          NotificationManager notificationManager =
                (NotificationManager) getSystemService(Service.NOTIFICATION_SERVICE);
        Notification notification = new NotificationCompat.Builder(getBaseContext(),"n")
                .setSmallIcon(R.drawable.icon)
                .setContentTitle("Title")
                .setContentText("Content Text"))
                .setDefaults(NotificationCompat.DEFAULT_SOUND)
                .build();
        notificationManager.notify(0, notification);
    }

而且有效。

我是否总是需要从 activity 创建通知？如果没有，如何从服务创建通知？

P.S: the service will run even if the app is not running

Answer 1

是的，您可以根据您的代码从 service.but 创建通知 startNotificationListener() 的右括号在下面的代码后丢失

new Thread(new Runnable() { @Override public void run() { //fetching notifications from server //if there is notifications then call this method ShowNotification(); } }).start();

并且您必须在 </application> 之前在 AndroidManifest.Xml 文件中注册服务。

<service android:name=".NotificationService"/>

之后，您必须按照以下方式从您的 activity 开始服务。

startService(new Intent(this,NotificationService.class));

有您的服务代码：

public class NotificationService extends Service {

public void startNotificationListener() {
    //start's a new thread
    new Thread(new Runnable() {
        @Override
        public void run() {
            //fetching notifications from server
            //if there is notifications then call this method
            ShowNotification();
        }
    }).start();
}
@Override
public void onCreate()
{
    startNotificationListener();
    super.onCreate();
}
@Override
public int onStartCommand(Intent intent,int flags,int startId)
{
    return super.onStartCommand(intent,flags,startId);
}
@Override
public void onDestroy()
{
    super.onDestroy();
}

@Nullable
@Override
public IBinder onBind(Intent intent) {
    return null;
}

public void ShowNotification()
{
    NotificationManager notificationManager =
            (NotificationManager) getSystemService(Service.NOTIFICATION_SERVICE);
    Notification notification = new NotificationCompat.Builder(getBaseContext(),"notification_id")
            .setSmallIcon(R.mipmap.ic_launcher)
            .setContentTitle("title")
            .setContentText("content")
            .setDefaults(NotificationCompat.DEFAULT_SOUND)
            .build();
    notificationManager.notify(0, notification);
    //the notification is not showing

}

}

您将获得 notification.please 检查屏幕截图

Answer 2

尝试使用通知渠道...可能就是问题所在。

Starting in Android 8.0 (API level 26), all notifications must be assigned to a channel or it will not appear.

https://developer.android.com/guide/topics/ui/notifiers/notifications.html#ManageChannels

        // The id of the channel.
        String CHANNEL_ID = "my_channel_01";
        NotificationCompat.Builder mBuilder =
                new NotificationCompat.Builder(MainActivity.this).setChannel(CHANNEL_ID)
                        .setSmallIcon(R.mipmap.ic_launcher)
                        .setContentTitle("My notification")
                        .setContentText("Hello World!");
        // Creates an explicit intent for an Activity in your app
        Intent resultIntent = new Intent(this, MainActivity.class);

        // The stack builder object will contain an artificial back stack for the
        // started Activity.
        // This ensures that navigating backward from the Activity leads out of
        // your app to the Home screen.
        TaskStackBuilder stackBuilder = TaskStackBuilder.create(this);
        // Adds the back stack for the Intent (but not the Intent itself)
        stackBuilder.addParentStack(MainActivity.class);
        // Adds the Intent that starts the Activity to the top of the stack
        stackBuilder.addNextIntent(resultIntent);
        PendingIntent resultPendingIntent =
                stackBuilder.getPendingIntent(
                        0,
                        PendingIntent.FLAG_UPDATE_CURRENT
                );
        mBuilder.setContentIntent(resultPendingIntent);
        NotificationManager mNotificationManager =
                (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);

        // mNotificationId is a unique integer your app uses to identify the
        // notification. For example, to cancel the notification, you can pass its ID
        // number to NotificationManager.cancel().
        mNotificationManager.notify(0, mBuilder.build());

https://github.com/fida1989/NotificationDemo

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