android - 使用服务绑定(bind)从服务更新 Activity TextView

Question

我有一个读取 GPS 纬度和经度的服务。我想从服务的 locationlistener 的 onLocationChanged 更新 Activity 。

我怎样才能实现它？我一直在阅读 Service Bound但看起来它只是为了 Activity 调用服务中的方法而不是服务调用 Activity 中的textView。难道绑定(bind)服务不是可以实现的吗？

Answer 1

你应该使用 LocalBroadcastManager从您的服务中发送一个 Intent 返回给 Activity。

例如，包含单个 TextView 的 Activity 可以像这样设置一个 BroadcastReceiver:

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));
    }
}

一个基本的服务可以如下广播所有位置变化:

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;
    }
}