如何在当前视图中计算经度/纬度的存在

Question

我真的很坚持：

我在Android应用程序中的Google地图上绘制了经度/纬度点。 为此，我创建了一个扩展Overlay的类。

我通过以下方式获取当前的经度/纬度部分：

GeoPoint topLeft = proj.fromPixels(0, 0);
GeoPoint bottomRight = proj.fromPixels(width-1, height-1);
int topLat = topLeft.getLatitudeE6();
int topLon = topLeft.getLongitudeE6();
int bottomLat = bottomRight.getLatitudeE6();
int bottomLon = bottomRight.getLongitudeE6();

以下作品（仅适用于纬度）：

if(latLon[0] >= bottomLat && latLon[0] <= topLat){ // do something; }

但这不起作用（经度）：

if(latLon[1] >= topLon && latLon[1] <= bottomLon) { // do something; }

latLon [0]是我要检查的经度latLon [1]是我要检查的经度

有人有主意吗？

格蕾兹！

Answer 1

使用谷歌地图，并在上面插入您的标记。 见下文 ：

public class MapActivity extends GeolocationActivity implements GoogleMap.OnInfoWindowClickListener{

private final String TAG = "MapFragment";


private MapView _mapView;
private GoogleMap _gmap;

/**
 * the logo of the marker on the map
 */
private Bitmap _littlePin;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.map);

    _mapView = (MapView) findViewById(R.id.location_map);
    _mapView.onCreate(savedInstanceState);
    _gmap = _mapView.getMap(); // initalise the map
    if (_gmap != null)
    {
        setUpMap();
    }
}

/**
 * set up the map; Add the market on it with a blue dot for the location of the user in real time
 * @return false if something goes wrong, true otherwise
 * _latitude = latitude of the user, get from the GeolocationActivity
 * _longitude = longitude of the user, get from the GeolocationActivity
 */
private boolean setUpMap()
{
    // Gets to GoogleMap from the MapView and does initialization stuff
    _gmap.getUiSettings().setMyLocationButtonEnabled(false);
    _gmap.setMyLocationEnabled(true);
    if (_gmap == null) {
        Toast.makeText(this, "Google Maps not available",  Toast.LENGTH_LONG).show();
        return false;
    }
    // Needs to call MapsInitializer before doing any CameraUpdateFactory calls
    MapsInitializer.initialize(this);


    BitmapDrawable bitmapDrawable = (BitmapDrawable) getResources().getDrawable(R.drawable.pin); // file stored in /res/drawable/
    Bitmap bitmap = bitmapDrawable.getBitmap();
    _littlePin = Bitmap.createScaledBitmap(bitmap, 96, 96, false); // 96/96px

    _gmap.setOnInfoWindowClickListener(this);// add listener on this class


    // here the _lat and _long should be the user of this cafe, at the moment I am using the one of the user
    this.addMarker("Cafe", "Best cafe in London", new LatLng(_latitude, _longitude));


    // camera, 13 if the zoon, you can change it manually, or dynamically in order to see all your markers
    CameraUpdate cameraUpdate = CameraUpdateFactory.newLatLngZoom(new LatLng(_latitude, _longitude), 13);
    _gmap.animateCamera(cameraUpdate); // zoom effect
    return true;
}

/**
 * Add markers on the map view
 * @param title title of place / marker
 * @param description short description
 * @param position geposition, LatLng object, filled with latitude and longitude.
 */
private void addMarker(String title, String description, LatLng position)
{
    _gmap.addMarker(new MarkerOptions()
            .position(position)
            .title(title)
            .snippet(description)
            .icon(BitmapDescriptorFactory.fromBitmap(_littlePin)));
}

/**
 * The user click on the marker on the map, this callback is called
 * @param marker clicked marker
 */
@Override
public void onInfoWindowClick(Marker marker) {
    Log.d(TAG, "onMarkerClick " + marker.getTitle());
}


@Override
public void onResume() {
    _mapView.onResume();
    super.onResume();
}

@Override
public void onDestroy() {
    super.onDestroy();
    _mapView.onDestroy();
}

@Override
public void onLowMemory() {
    super.onLowMemory();
    _mapView.onLowMemory();
}

}

这是一个可以帮助您的好例子。

带有代码示例的github在这里 。

希望能有所帮助。

Answer 2

经度数从西向西的英格兰0子午线开始为负。 在北美和南美，它们是负面的。