Question

我正在使用谷歌地图指出用户的位置。我无法在应用上找到任何标记。标记应指向当前位置。使用与链接中相同的代码。

https://www.androidtutorialpoint.com/intermediate/android-map-app-showing-current-location-android/

这是我没有标记的屏幕

我的整个主要活动代码是：

public class parentTracker extends FragmentActivity implements OnMapReadyCallback,
        GoogleApiClient.ConnectionCallbacks,
        GoogleApiClient.OnConnectionFailedListener,
        LocationListener {

    private GoogleMap mMap;
    GoogleApiClient mGoogleApiClient;
    Location mLastLocation;
    Marker mCurrLocationMarker;
    LocationRequest mLocationRequest;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_parent_tracker);
        SupportMapFragment mapFragment = (SupportMapFragment) getSupportFragmentManager()
                .findFragmentById(R.id.map);
        mapFragment.getMapAsync(this);
        // Obtain the SupportMapFragment and get notified when the map is ready to be used.

    }


    @Override
    protected void onPause() {
        super.onPause();


    }

    @Override
    public void onMapReady(GoogleMap googleMap) {

        mMap = googleMap;
        mMap.setMapType(GoogleMap.MAP_TYPE_NORMAL);

        buildGoogleApiClient();
        if (ActivityCompat.checkSelfPermission(this, android.Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, android.Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
            // TODO: Consider calling
            //    ActivityCompat#requestPermissions
            // here to request the missing permissions, and then overriding
            //   public void onRequestPermissionsResult(int requestCode, String[] permissions,
            //                                          int[] grantResults)
            // to handle the case where the user grants the permission. See the documentation
            // for ActivityCompat#requestPermissions for more details.
            return;
        }
        mMap.setMyLocationEnabled(true);
        mGoogleApiClient.connect();


    }

    protected synchronized void buildGoogleApiClient() {

        mGoogleApiClient = new GoogleApiClient.Builder(this)
                .addConnectionCallbacks(this)
                .addOnConnectionFailedListener(this)
                .addApi(LocationServices.API)
                .build();
        mGoogleApiClient.connect();

    }

    @Override
    public void onLocationChanged(Location location) {

        mLastLocation = location;
        if (mCurrLocationMarker != null) {
            mCurrLocationMarker.remove();
        }



        //Place current location marker
        LatLng latLng = new LatLng(location.getLatitude(), location.getLongitude());
        MarkerOptions markerOptions = new MarkerOptions();
        markerOptions.position(latLng);
        markerOptions.title("Current Position");
        markerOptions.icon(BitmapDescriptorFactory.defaultMarker(BitmapDescriptorFactory.HUE_MAGENTA));
        mCurrLocationMarker = mMap.addMarker(markerOptions);

        //move map camera
        mMap.moveCamera(CameraUpdateFactory.newLatLng(latLng));
        mMap.animateCamera(CameraUpdateFactory.zoomTo(11));

        //stop location updates
        if (mGoogleApiClient != null) {
            LocationServices.FusedLocationApi.removeLocationUpdates(mGoogleApiClient, (com.google.android.gms.location.LocationListener) this);
        }


    }

    @Override
    public void onStatusChanged(String provider, int status, Bundle extras) {

    }

    @Override
    public void onProviderEnabled(String provider) {

    }

    @Override
    public void onProviderDisabled(String provider) {

    }

    @Override
    public void onConnected(Bundle bundle) {

        mLocationRequest = new LocationRequest();
        mLocationRequest.setInterval(1000);
        mLocationRequest.setFastestInterval(1000);
        mLocationRequest.setPriority(LocationRequest.PRIORITY_BALANCED_POWER_ACCURACY);

        if (ActivityCompat.checkSelfPermission(this, android.Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, android.Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
            // TODO: Consider calling
            //    ActivityCompat#requestPermissions
            // here to request the missing permissions, and then overriding
            //   public void onRequestPermissionsResult(int requestCode, String[] permissions,
            //                                          int[] grantResults)
            // to handle the case where the user grants the permission. See the documentation
            // for ActivityCompat#requestPermissions for more details.
            return;
        }
        LocationServices.FusedLocationApi.requestLocationUpdates(mGoogleApiClient, mLocationRequest, (com.google.android.gms.location.LocationListener) this);


    }

    @Override
    public void onConnectionSuspended(int i) {

    }

    @Override
    public void onConnectionFailed(@NonNull ConnectionResult connectionResult) {



    }

    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
            switch (requestCode) {
                case MY_PERMISSIONS_REQUEST_LOCATION: {
                    // If request is cancelled, the result arrays are empty.
                    if (grantResults.length > 0
                            && grantResults[0] == PackageManager.PERMISSION_GRANTED) {

                        // permission was granted. Do the
                        // contacts-related task you need to do.
                        if (ContextCompat.checkSelfPermission(this,
                                android.Manifest.permission.ACCESS_FINE_LOCATION)
                                == PackageManager.PERMISSION_GRANTED) {

                            if (mGoogleApiClient == null) {
                                buildGoogleApiClient();
                            }
                            mMap.setMyLocationEnabled(true);
                        }

                    } else {

                        // Permission denied, Disable the functionality that depends on this permission.
                        Toast.makeText(this, "permission denied", Toast.LENGTH_LONG).show();
                    }
                    return;
                }

                // other 'case' lines to check for other permissions this app might request.
                // You can add here other case statements according to your requirement.
            }
    }


    public static final int MY_PERMISSIONS_REQUEST_LOCATION = 99;
    public boolean checkLocationPermission(){
        if (ContextCompat.checkSelfPermission(this,
                android.Manifest.permission.ACCESS_FINE_LOCATION)
                != PackageManager.PERMISSION_GRANTED) {

            // Asking user if explanation is needed
            if (ActivityCompat.shouldShowRequestPermissionRationale(this,
                    android.Manifest.permission.ACCESS_FINE_LOCATION)) {

                // Show an explanation to the user *asynchronously* -- don't block
                // this thread waiting for the user's response! After the user
                // sees the explanation, try again to request the permission.

                //Prompt the user once explanation has been shown
                ActivityCompat.requestPermissions(this,
                        new String[]{android.Manifest.permission.ACCESS_FINE_LOCATION},
                        MY_PERMISSIONS_REQUEST_LOCATION);


            } else {
                // No explanation needed, we can request the permission.
                ActivityCompat.requestPermissions(this,
                        new String[]{android.Manifest.permission.ACCESS_FINE_LOCATION},
                        MY_PERMISSIONS_REQUEST_LOCATION);
            }
            return false;
        } else {
            return true;
        }

    }
}

Answer 1

您应首先在onMapReady方法中添加标记。否则，只有在移动并接收新位置后才会看到您的标记。

Answer 2

您确定在OnLocationChanged中获得了有效的位置吗？如果是这样，那么你可以尝试使用refreshMap（）方法（下面指定），以便在地图上放置任何标记：

// Map
private GoogleMap mMap;

// Method that clears all previous markers in the map and put a new marker with the new location coordinates.
private void refreshMap(Location location) {

    // Just double-checking that the map is correctly set and that we have a valid location.
    if (mMap == null || location== null) return;

    // Clearing the map.
    mMap.clear();

    // If there is a valid Latitude and Longitude, then show the marker in that position.
    if (location.getLatitude() != 0.00 || location.getLongitude() != 0.00) {
        LatLng coordinates = new LatLng(location.getLatitude(), location.getLongitude());
        mMap.addMarker(new MarkerOptions().position(coordinates).title("Current Position"));
        mMap.moveCamera(CameraUpdateFactory.newLatLngZoom(coordinates, 16));
    }
}

// OnLocationChanged
@Override
public void onLocationChanged(Location location) {
    refreshMap(location);
}

// Setting of the variable mMap when the GoogleMap is ready.
@Override
public void onMapReady(GoogleMap googleMap) {
    mMap = googleMap;
}

注意：有时，“LocationServices.FusedLocationApi.requestLocationUpdates（）”返回的第一个位置将是最后一个已知位置。因此，我建议您继续收听位置更新，并在不同于“最后已知位置”的位置到达时停止。您可以使用从Fused Location获取Last Known位置的方法来比较坐标。

Answer 3

是因为未启用您的移动位置信息。启用它，代码将起作用

标记没有在地图上显示

3 个答案: