使用服务绑定从服务更新Activity TextView [英] Updating Activity TextView from service using Service binding

问题描述

我有一项读取GPS纬度和经度的服务.我想从服务的locationlistener的onLocationChanged更新活动.

I have a service for reading GPS latitude and longitude. I would like to update the activity from the service's locationlistener's onLocationChanged.

如何实现?我一直在阅读服务绑定，但看起来像是仅用于活动调用服务中的方法，而不用于服务调用活动中的textView.绑定服务无法实现吗?

How can I achieve it? I have been reading on Service Bound but it looks like it is only for activity to invoke the methods in service but not service invoke textView in Activity. Is binding service is not possible to achieve it?

推荐答案

您应使用您的服务中的LocalBroadcastManager 类，将Intent发送回Activity.

You should use the LocalBroadcastManager class from within your Service to send an Intent back to the Activity.

例如，包含单个TextView的Activity可以像这样设置BroadcastReceiver:

For Example, An Activity containing a single TextView can set up a BroadcastReceiver like such:

public class MainActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        final TextView textView = (TextView) findViewById(R.id.main_activity_text_view);

        LocalBroadcastManager.getInstance(this).registerReceiver(
                new BroadcastReceiver() {
                    @Override
                    public void onReceive(Context context, Intent intent) {
                        double latitude = intent.getDoubleExtra(LocationBroadcastService.EXTRA_LATITUDE, 0);
                        double longitude = intent.getDoubleExtra(LocationBroadcastService.EXTRA_LONGITUDE, 0);
                        textView.setText("Lat: " + latitude + ", Lng: " + longitude);
                    }
                }, new IntentFilter(LocationBroadcastService.ACTION_LOCATION_BROADCAST)
        );
    }

    @Override
    protected void onResume() {
        super.onResume();
        startService(new Intent(this, LocationBroadcastService.class));
    }

    @Override
    protected void onPause() {
        super.onPause();
        stopService(new Intent(this, LocationBroadcastService.class));
    }
}

基本的Service可以广播以下所有位置更改:

And a basic Service can broadcast all location changes as follows:

public class LocationBroadcastService extends Service {

    public static final String
            ACTION_LOCATION_BROADCAST = LocationBroadcastService.class.getName() + "LocationBroadcast",
            EXTRA_LATITUDE = "extra_latitude",
            EXTRA_LONGITUDE = "extra_longitude";

    private static final int
            MIN_TIME = 2000,
            MIN_DISTANCE = 1;

    @Override
    public void onCreate() {
        super.onCreate();
        LocationManager locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
        sendBroadcastMessage(locationManager.getLastKnownLocation(LocationManager.NETWORK_PROVIDER));
        locationManager.requestLocationUpdates(LocationManager.NETWORK_PROVIDER, MIN_TIME, MIN_DISTANCE,
                new LocationListener() {
                    @Override
                    public void onLocationChanged(Location location) {
                        sendBroadcastMessage(location);
                    }

                    @Override
                    public void onStatusChanged(String provider, int status, Bundle extras) {

                    }

                    @Override
                    public void onProviderEnabled(String provider) {

                    }

                    @Override
                    public void onProviderDisabled(String provider) {

                    }
                }
        );
    }

    private void sendBroadcastMessage(Location location) {
        if (location != null) {
            Intent intent = new Intent(ACTION_LOCATION_BROADCAST);
            intent.putExtra(EXTRA_LATITUDE, location.getLatitude());
            intent.putExtra(EXTRA_LONGITUDE, location.getLongitude());
            LocalBroadcastManager.getInstance(this).sendBroadcast(intent);
        }
    }


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

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