java - 如何显示来自广播接收器的通知？

Question

我正在从服务注册广播接收器。如果设备位置关闭，我需要向用户显示通知，代码工作正常，但接收器不会创建通知。我可以看到有关更改位置状态的 logcat 消息，但未创建通知，请检查问题!还有什么办法可以更新服务当前的通知吗？

这是服务:

public class LockService extends Service {
BroadcastReceiver mReceiver;
Handler handler;
LocationManager locationManager;

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

private static final int NOTIF_ID = 1;

@Override
public void onCreate() {

    final IntentFilter filter = new IntentFilter(Intent.ACTION_SCREEN_ON);
    filter.addAction(Intent.ACTION_SCREEN_OFF);
    filter.addAction(Intent.ACTION_USER_PRESENT);
    filter.addAction(LocationManager.PROVIDERS_CHANGED_ACTION);
    mReceiver = new com.example.fizatanveerkhan.citycops.ScreenReceiver();
    registerReceiver(mReceiver, filter);
    super.onCreate();

}
private void startForeground() {
    startForeground(NOTIF_ID, getMyActivityNotification(""));
}


@Override
public int onStartCommand(Intent intent, int flags, int startId) {
    this.startForeground();
    return super.onStartCommand(intent, flags, startId);
}

@Override
public void onDestroy() {

    if (mReceiver != null) {
        unregisterReceiver(mReceiver);
        mReceiver = null;

        Log.i("onDestroy Reciever", "Called");

    }
    super.onDestroy();

}

public class LocalBinder extends Binder {
    LockService getService() {
        return LockService.this;
    }
}

private Notification getMyActivityNotification(String text) {

    CharSequence title = "new";



    Notification notification = null;
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
        String NOTIFICATION_CHANNEL_ID = " com.example.fizatanveerkhan.citycops";
        String channelName = "My Background Service";
        NotificationChannel chan = new NotificationChannel(NOTIFICATION_CHANNEL_ID, channelName, NotificationManager.IMPORTANCE_NONE);
        chan.setLightColor(Color.BLUE);
        chan.setLockscreenVisibility(Notification.VISIBILITY_PRIVATE);
        NotificationManager manager = (NotificationManager) getApplicationContext().getSystemService(Context.NOTIFICATION_SERVICE);
        assert manager != null;
        manager.createNotificationChannel(chan);

        NotificationCompat.Builder notificationBuilder = new NotificationCompat.Builder(this, NOTIFICATION_CHANNEL_ID);
        notification = notificationBuilder.setOngoing(true)
                .setSmallIcon(R.drawable.abc)
                .setContentTitle("Service running")
                .setContentText("new")
                .setPriority(NotificationManager.IMPORTANCE_MIN)
                .setCategory(Notification.CATEGORY_SERVICE)
                .build();

    }
    return notification;
}
     /*  public void updateNotification() {
    String text = "Some text that will update the notification";

    Notification notification = getMyActivityNotification(text);

    NotificationManager mNotificationManager = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);
    mNotificationManager.notify(NOTIF_ID, notification);
      }*/


   }

这是广播接收器:

public class ScreenReceiver extends BroadcastReceiver {

public static boolean wasScreenOn = true;


private static final int POWER_OFF_TIMEOUT = 500;
private Handler handler = new Handler();
private Runnable powerOffCounterReset = new PowerOfTimeoutReset();
private int countPowerOff = 0;
private boolean screenOff;
//private LockService updateService = new LockService();

private final static String TAG = "LocationProviderChanged";

boolean isGpsEnabled;
boolean isNetworkEnabled;
@Override
public void onReceive(final Context context, final Intent intent) {
    if (intent.getAction().matches("android.location.PROVIDERS_CHANGED")) {
        Log.i(TAG, "Location Providers changed");

        LocationManager locationManager = (LocationManager) context.getSystemService(Context.LOCATION_SERVICE);
        isGpsEnabled = locationManager.isProviderEnabled(LocationManager.GPS_PROVIDER);
        isNetworkEnabled = locationManager.isProviderEnabled(LocationManager.NETWORK_PROVIDER);

        //Start your Activity if location was enabled:
        if (isGpsEnabled || isNetworkEnabled) {

            Log.i(TAG, "Location Providers on");
       }

       else {

              Log.i(TAG, "Location Providers off");
            Notification notification = null;
            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
                String NOTIFICATION_CHANNEL_ID = " com.example.fizatanveerkhan.citycops";
                String channelName = "My Background Service";
                NotificationChannel chan = new NotificationChannel(NOTIFICATION_CHANNEL_ID, channelName, NotificationManager.IMPORTANCE_NONE);
                chan.setLightColor(Color.BLUE);
                chan.setLockscreenVisibility(Notification.VISIBILITY_PRIVATE);
                NotificationManager manager = (NotificationManager) context.getSystemService(Context.NOTIFICATION_SERVICE);
                assert manager != null;
                manager.createNotificationChannel(chan);

                NotificationCompat.Builder notificationBuilder = new NotificationCompat.Builder(context, NOTIFICATION_CHANNEL_ID);
                notification = notificationBuilder.setOngoing(true)
                        .setSmallIcon(R.drawable.abc)
                        .setContentTitle("Service running")
                        .setContentText("new")
                        .setPriority(NotificationManager.IMPORTANCE_MIN)
                        .setCategory(Notification.CATEGORY_SERVICE)
                        .build();
                NotificationManager mNotificationManager = (NotificationManager) context.getSystemService(Context.NOTIFICATION_SERVICE);
                mNotificationManager.notify(1, notification);

            }
        }
    }

我可以看到有关更改位置状态的 logcat 消息，但未创建通知

Answer 1

将通知代码更改为此解决了问题

          if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
                String NOTIFICATION_CHANNEL_ID = " 
            com.example.fizatanveerkhan.citycops";
                CharSequence name =  "My Background Service";
                String description =  "My Background Service";
                int importance = NotificationManager.IMPORTANCE_DEFAULT;
                NotificationChannel channel = new NotificationChannel(NOTIFICATION_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 = context.getSystemService(NotificationManager.class);
                notificationManager.createNotificationChannel(channel);

                NotificationCompat.Builder notificationBuilder = new NotificationCompat.Builder(context, NOTIFICATION_CHANNEL_ID);
                notification = notificationBuilder.setOngoing(true)
                        .setSmallIcon(R.drawable.abc)
                        .setContentTitle("Service running")
                        .setContentText("new")
                        .setPriority(NotificationManager.IMPORTANCE_MIN)
                        .setCategory(Notification.CATEGORY_SERVICE)
                        .build();
                NotificationManagerCompat notificationManagerq = 
           NotificationManagerCompat.from(context);

        // notificationId is a unique int for each notification that you must define
                notificationManagerq.notify(1, notificationBuilder.build());

                   }