我知道以前有人问过这个问题，但是我对什么是正确的什么是不正确的看法不一，
我正在尝试使用两个按钮开始和停止来计算我的应用程序中两点之间的距离。
我认为这很简单，在按下开始时获取位置的纬度和经度，然后在按下停止时再次获取它们，计算两者，瞧。然而，它不会计划。
当单击停止按钮以获取反馈时，我在停止按钮上设置了一个对话框，目前我只返回（大概）一个纬度或经度。
我的代码如下::
public class MapRun extends FragmentActivity implements LocationListener,
LocationSource {
private OnLocationChangedListener mListener;
private LocationManager locationManager;
private GoogleMap mMap;
double lat, lng;
static double startLat;
double startLong;
double stopLat;
double stopLong;
public static Location l;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.maprun);
locationManager = (LocationManager) getSystemService(LOCATION_SERVICE);
// Creating a criteria object to retrieve provider
Criteria criteria = new Criteria();
// Getting the name of the best provider
String provider = locationManager.getBestProvider(criteria, true);
// Getting Current Location
Location location = locationManager.getLastKnownLocation(provider);
l = location;
lat = l.getLatitude();
lng = l.getLongitude();
onLocationChanged(location);
locationManager.requestLocationUpdates(provider, 20000, 0, this);
setUpMapIfNeeded();
}
@Override
public void onPause() {
if (locationManager != null) {
locationManager.removeUpdates(this);
}
super.onPause();
}
@Override
public void onResume() {
super.onResume();
setUpMapIfNeeded();
if (locationManager != null) {
mMap.setMyLocationEnabled(true);
}
}
/**
* Sets up the map if it is possible to do so (i.e., the Google Play
* services APK is correctly installed) and the map has not already been
* instantiated.. This will ensure that we only ever call
* {@link #setUpMap()} once when {@link #mMap} is not null.
* <p>
* If it isn't installed {@link SupportMapFragment} (and
* {@link com.google.android.gms.maps.MapView MapView}) will show a prompt
* for the user to install/update the Google Play services APK on their
* device.
* <p>
* A user can return to this Activity after following the prompt and
* correctly installing/updating/enabling the Google Play services. Since
* the Activity may not have been completely destroyed during this process
* (it is likely that it would only be stopped or paused),
* {@link #onCreate(Bundle)} may not be called again so we should call this
* method in {@link #onResume()} to guarantee that it will be called.
*/
private void setUpMapIfNeeded() {
// Do a null check to confirm that we have not already instantiated the
// map.
if (mMap == null) {
// Try to obtain the map from the SupportMapFragment.
mMap = ((SupportMapFragment) getSupportFragmentManager()
.findFragmentById(R.id.map)).getMap();
// Check if we were successful in obtaining the map.
if (mMap != null) {
setUpMap();
}
// This is how you register the LocationSource
mMap.setLocationSource(this);
}
}
/**
* This is where we can add markers or lines, add listeners or move the
* camera. In this case, we just add a marker near Africa.
* <p>
* This should only be called once and when we are sure that {@link #mMap}
* is not null.
*/
private void setUpMap() {
mMap.setMyLocationEnabled(true);
}
@Override
public void activate(OnLocationChangedListener listener) {
mListener = listener;
}
@Override
public void deactivate() {
mListener = null;
}
@Override
public void onLocationChanged(Location location) {
if (mListener != null) {
mListener.onLocationChanged(location);
// Move the camera to the user's location once it's available!
mMap.animateCamera(CameraUpdateFactory.newLatLngZoom(new LatLng(
location.getLatitude(), location.getLongitude()), 16.0f));
}
}
@Override
public void onProviderDisabled(String provider) {
// TODO Auto-generated method stub
Toast.makeText(this, "provider disabled", Toast.LENGTH_SHORT).show();
}
@Override
public void onProviderEnabled(String provider) {
// TODO Auto-generated method stub
Toast.makeText(this, "provider enabled", Toast.LENGTH_SHORT).show();
}
@Override
public void onStatusChanged(String provider, int status, Bundle extras) {
// TODO Auto-generated method stub
Toast.makeText(this, "status changed", Toast.LENGTH_SHORT).show();
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
super.onCreateOptionsMenu(menu);
MenuInflater inflater = getMenuInflater();
inflater.inflate(R.menu.map_menu, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case R.id.startRun:
startRun();
case R.id.stopRun:
stopRun();
return true;
default:
return super.onOptionsItemSelected(item);
}
}
public void startRun() {
;
}
public void stopRun() {
Location startPoint = new Location("Ran From");
startPoint.setLatitude(lat);
startPoint.setLongitude(lng);
Location stopPoint = new Location("Ran To");
stopPoint.setLatitude(stopLat);
stopPoint.setLongitude(stopLong);
float distance = startPoint.distanceTo(stopPoint);
String distStr = String.valueOf(distance);
Dialog d = new Dialog(this);
d.setTitle("distance");
TextView tv = new TextView(this);
tv.setText(distStr);
d.setContentView(tv);
d.show();
}
到目前为止，这是我更新的按钮，我有一个原则，我认为我只是在努力以正确的方式存储和传递变量：
@Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case R.id.startRun:
currentLocation = lat + lng;
startLocation = currentLocation;
case R.id.stopRun:
currentLocation = lat + lng;
stopLocatio
n = 当前位置；
float distance = startLocation.distanceTo(stopLocation);
String distStr = String.valueOf(distance);
Dialog d = new Dialog(this);
d.setTitle("distance");
TextView tv = new TextView(this);
tv.setText(distStr);
d.setContentView(tv);
d.show();
return true;
default:
return super.onOptionsItemSelected(item);
}
我的 OnLocation 改变了：
@Override
public void onLocationChanged(Location location) {
l = location;
lat = l.getLatitude();
lng = l.getLongitude();
if (mListener != null) {
mListener.onLocationChanged(location);
// Move the camera to the user's location once it's available!
mMap.animateCamera(CameraUpdateFactory.newLatLngZoom(new LatLng(
location.getLatitude(), location.getLongitude()), 16.0f));
}
}