我已经在 Android Studio 中的谷歌地图活动片段上尝试了下面给出的代码，我什至已经在我的手机上编译并运行了它，但我的位置没有显示出来。请帮助我找到我的代码中的错误。
package com.example.ambulance;
import ...
public class MapsActivity extends AppCompatActivity implements OnMapReadyCallback {
private GoogleMap googleMap;
private FusedLocationProviderClient fusedLocationProviderClient;
private int REQUEST_ACCESS = 5445;
private boolean firstTimeFlag = true;
private Marker currentLocationMarker;
private static Location currentLocation;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_maps);
SupportMapFragment supportMapFragment = (SupportMapFragment) getSupportFragmentManager().findFragmentById(R.id.google_map);
supportMapFragment.getMapAsync(this);
}
@Override
public void onMapReady(GoogleMap googleMap)
{
this.googleMap = googleMap;
}
@Override
protected void onResume()
{
super.onResume();
if(isGooglePlayServicesAvailable())
{
fusedLocationProviderClient = LocationServices.getFusedLocationProviderClient(this);
startLocationUpdates();
}
}
private boolean isGooglePlayServicesAvailable()
{
GoogleApiAvailability googleApiAvailability = GoogleApiAvailability.getInstance();
int status = googleApiAvailability.isGooglePlayServicesAvailable(this);
if(ConnectionResult.SUCCESS == status)
return true;
else
{
if(googleApiAvailability.isUserResolvableError(status))
Toast.makeText(this, "Please Install Google Play Services to Use this Application", Toast.LENGTH_LONG).show();
}
return false;
}
private void startLocationUpdates()
{
LocationRequest locationRequest = LocationRequest.create();
locationRequest.setPriority(LocationRequest.PRIORITY_HIGH_ACCURACY);
locationRequest.setInterval(300);
locationRequest.setSmallestDisplacement(1);
if(Build.VERSION.SDK_INT >= Build.VERSION_CODES.M)
{
if(ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED)
ActivityCompat.requestPermissions(MapsActivity.this, new String[] {Manifest.permission.ACCESS_FINE_LOCATION}, REQUEST_ACCESS);
return;
}
fusedLocationProviderClient.requestLocationUpdates(locationRequest, mLocationCallback, Looper.myLooper());
}
//Here we are defining the mLocationCallback object, that is used in the previous function.
private final LocationCallback mLocationCallback = new LocationCallback(){
@Override
public void onLocationResult(LocationResult locationResult)
{
super.onLocationResult(locationResult);
if(locationResult.getLastLocation() == null)
return;
currentLocation = locationResult.getLastLocation();
if(firstTimeFlag && googleMap != null)
{
animateCamera(currentLocation);
firstTimeFlag = true;
}
showMarker(currentLocation);
}
};
private void animateCamera(@NonNull Location location)
{
LatLng latLng = new LatLng(location.getLatitude(), location.getLongitude());
googleMap.animateCamera(CameraUpdateFactory.newCameraPosition(getCameraPositionWithBearing(latLng)));
}
@NonNull
private CameraPosition getCameraPositionWithBearing(LatLng latLng) {
return new CameraPosition.Builder().target(latLng).zoom(16).build();
}
private void showMarker(@NonNull Location currentLocation)
{
LatLng latLng = new LatLng(currentLocation.getLatitude(), currentLocation.getLongitude());
if(currentLocationMarker == null)
currentLocationMarker = googleMap.addMarker(new MarkerOptions().icon(BitmapDescriptorFactory.defaultMarker()).position(latLng));
else
MarkerAnimation.animateMarkerToGB(currentLocationMarker, latLng, new LatLngInterpolator.Spherical());
}
}
package com.example.ambulance;
import ...
public interface LatLngInterpolator
{
LatLng interpolate(float fraction, LatLng a, LatLng b);
class Spherical implements LatLngInterpolator
{
/* From github.com/googlemaps/android-maps-utils */
@Override
public LatLng interpolate(float fraction, LatLng from, LatLng to)
{
//http://en.wikipedia.org/wiki/Slerp
double fromLat = toRadians(from.latitude);
double fromLng = toRadians(from.longitude);
double toLat = toRadians(to.latitude);
double toLng = toRadians(to.longitude);
double cosFromLat = cos(fromLat);
double cosToLat = cos(toLat);
//Computes Spherical interpolation co-efficients.
double angle = computeAngleBetween(fromLat, fromLng, toLat, toLng);
double sinAngle = sin(angle);
if (sinAngle < 1E-6)
return from;
double a = sin((1 - fraction) * angle) / sinAngle;
double b = sin(fraction * angle) / sinAngle;
//Converts from polar to vector and interpolate.
double x = a * cosFromLat * cos(fromLat) + b * cosToLat * cos(toLng);
double y = a * cosFromLat * sin(fromLng) + b * cosToLat * sin(toLng);
double z = a * sin(fromLat) + b * sin(toLat);
//Converts interpolated vectors back to polar.
double lat = atan2(z, sqrt(x*x + y*y));
double lng = atan2(y, x);
return new LatLng(toDegrees(lat), toDegrees(lng));
}
private double computeAngleBetween(double fromLat, double fromLng, double toLat, double toLng)
{
//Haversine's Formula
double dLat = fromLat - toLat;
double dLng = fromLng - toLng;
return 2 * asin(sqrt(pow(sin(dLat / 2), 2) + cos(fromLat) * cos(toLat * pow(sin(dLng / 2), 2))));
}
}
}
package com.example.ambulance;
import ...
public class MarkerAnimation {
public static void animateMarkerToGB(final Marker marker, final LatLng finalPosition, final LatLngInterpolator latLngInterpolator) {
final LatLng startPosition = marker.getPosition();
final Handler handler = new Handler();
final long start = SystemClock.uptimeMillis();
final Interpolator interpolator = new AccelerateDecelerateInterpolator();
final float durationInMs = 2000;
handler.post(new Runnable() {
long elapsed;
float t;
float v;
@Override
public void run() {
//Calculator Progress Using Interpolator.
elapsed = SystemClock.uptimeMillis() - start;
t = elapsed / durationInMs;
v = interpolator.getInterpolation(t);
marker.setPosition(latLngInterpolator.interpolate(v, startPosition, finalPosition));
//Repeat till progress is complete.
if (t < 1) {
//Post again 16ms later.
handler.postDelayed(this, 16);
}
}
});
}
}
这是我正在使用的代码。另外，我已经在 AndroidManifest.xml 文件中授予了必要的权限。