android - requestLocationUpdates 从未调用过

Question

我只需要一次 GPS 中的实际位置。在此代码中，永远不会调用 onLocationChanged，我不明白为什么。正如我所说:

mLocationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, this);

它应该每 0 秒和每 0 米运行一次。如何更改代码以使其正常工作？

public class MapActivity extends FragmentActivity implements
        LocationListener {

    private final String TAG = getClass().getSimpleName();
    private GoogleMap mMap;
    private Location loc;
    private Context ctx;
    private radius;
    LocationManager mLocationManager;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        mLocationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
        mLocationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, this);
        ctx = MapActivity.this;
        radius = getRadius();

        mMap = initMap();

    }

    @Override
    public void onLocationChanged(Location location) {
        // TODO Auto-generated method stub
        if (location != null) {
            loc = location;
            Log.v("Location Changed", location.getLatitude() + " and "
                    + location.getLongitude());
            mLocationManager.removeUpdates(this);
myPlaces = new GetPlaces(ctx, GAS_STATION, mMap, loc, radius);
        myPlaces.execute();
            Log.e(TAG, "location : " + loc);
        }
    }
    @Override
    public void onProviderDisabled(String provider) {
    }
    @Override
    public void onProviderEnabled(String provider) {
    }
    @Override
    public void onStatusChanged(String provider, int status, Bundle extras) {
    }

编辑:我将调用移至 loc:

myPlaces = new GetPlaces(ctx, GAS_STATION, mMap, loc, radius);
        myPlaces.execute();
            Log.e(TAG, "location : " + loc);

在 onLocationChange 中。这样，我就不会再得到 nullpointerException，但我可以等待超过 20 秒才能获取位置。不太好...如果有人知道如何快速修复!

Answer 1

我所做的是在 onCreate 之前添加 2 个监听器，不仅是 gps，还有网络:

在此处找到代码:Location Manager's requestLocationUpdates called only once

private final LocationListener gpsLocationListener =new LocationListener(){

    @Override
    public void onStatusChanged(String provider, int status, Bundle extras) {
        final String tvTxt = textView.getText().toString();
        switch (status) {
        case LocationProvider.AVAILABLE:
            textView.setText(tvTxt + "GPS available again\n");
            break;
        case LocationProvider.OUT_OF_SERVICE:
            textView.setText(tvTxt + "GPS out of service\n");
            break;
        case LocationProvider.TEMPORARILY_UNAVAILABLE:
            textView.setText(tvTxt + "GPS temporarily unavailable\n");
            break;
        }
    }

    @Override
    public void onProviderEnabled(String provider) {
        textView.setText(textView.getText().toString()
                + "GPS Provider Enabled\n");
    }

    @Override
    public void onProviderDisabled(String provider) {
        textView.setText(textView.getText().toString()
                + "GPS Provider Disabled\n");
    }

    @Override
    public void onLocationChanged(Location location) {
        locationManager.removeUpdates(networkLocationListener);
        textView.setText(textView.getText().toString()
                + "New GPS location: "
                + String.format("%9.6f", location.getLatitude()) + ", "
                + String.format("%9.6f", location.getLongitude()) + "\n");
    }
};
private final LocationListener networkLocationListener =
                                                    new LocationListener(){

    @Override
    public void onStatusChanged(String provider, int status, Bundle extras){
        final String tvTxt = textView.getText().toString();
        switch (status) {
        case LocationProvider.AVAILABLE:
            textView.setText(tvTxt + "Network location available again\n");
            break;
        case LocationProvider.OUT_OF_SERVICE:
            textView.setText(tvTxt + "Network location out of service\n");
            break;
        case LocationProvider.TEMPORARILY_UNAVAILABLE:
            textView.setText(tvTxt
                    + "Network location temporarily unavailable\n");
            break;
        }
    }

    @Override
    public void onProviderEnabled(String provider) {
        textView.setText(textView.getText().toString()
                + "Network Provider Enabled\n");
    }

    @Override
    public void onProviderDisabled(String provider) {
        textView.setText(textView.getText().toString()
                + "Network Provider Disabled\n");
    }

    @Override
    public void onLocationChanged(Location location) {
        textView.setText(textView.getText().toString()
                + "New network location: "
                + String.format("%9.6f", location.getLatitude()) + ", "
                + String.format("%9.6f", location.getLongitude()) + "\n");
    }
};

并在回调方法中激活它们:

@Override
protected void onResume() {
    super.onResume();
    locationManager.requestLocationUpdates(
            LocationManager.NETWORK_PROVIDER, 0, 0,
            networkLocationListener);
    locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER,
            0, 0, gpsLocationListener);
}

@Override
protected void onPause() {
    super.onPause();
    locationManager.removeUpdates(networkLocationListener);
    locationManager.removeUpdates(gpsLocationListener);
}

然后效果很好!我认为只有 GPS 是不够的，因为修复可以持续很长时间!