我正在研究GoogleMap。我从谷歌开发者网站获得代码。我很难在应用程序启动时设置当前位置。
我成功实施到onMyLocationButtonClick()，当我点击时，它会将我带到我当前的位置。但我正在实施别的东西。
我需要在地图视图开始时显示我当前的位置。有什么想法吗？
package com.jatinderbhola.mymapapp;
import com.google.android.gms.common.ConnectionResult;
import com.google.android.gms.common.GooglePlayServicesUtil;
import com.google.android.gms.common.api.GoogleApiClient;
import com.google.android.gms.location.LocationServices;
import com.google.android.gms.maps.CameraUpdate;
import com.google.android.gms.maps.CameraUpdateFactory;
import com.google.android.gms.maps.GoogleMap;
import com.google.android.gms.maps.GoogleMap.OnMyLocationButtonClickListener;
import com.google.android.gms.maps.OnMapReadyCallback;
import com.google.android.gms.maps.SupportMapFragment;
import com.google.android.gms.maps.model.CameraPosition;
import com.google.android.gms.maps.model.CircleOptions;
import com.google.android.gms.maps.model.LatLng;
import com.google.android.gms.maps.model.MarkerOptions;
import android.Manifest;
import android.app.Dialog;
import android.content.Context;
import android.content.pm.PackageManager;
import android.location.Criteria;
import android.location.Location;
import android.location.LocationListener;
import android.location.LocationManager;
import android.os.Bundle;
import android.support.annotation.NonNull;
import android.support.v4.app.ActivityCompat;
import android.support.v4.content.ContextCompat;
import android.support.v7.app.AppCompatActivity;
import android.widget.Toast;
/**
* This demo shows how GMS Location can be used to check for changes to the users location. The
* "My Location" button uses GMS Location to set the blue dot representing the users location.
* Permission for {@link android.Manifest.permission#ACCESS_FINE_LOCATION} is requested at run
* time. If the permission has not been granted, the Activity is finished with an error message.
*/
public class MapsActivity extends AppCompatActivity
implements
OnMyLocationButtonClickListener,
OnMapReadyCallback,
ActivityCompat.OnRequestPermissionsResultCallback,
LocationListener {
/**
* Request code for location permission request.
*
* @see #onRequestPermissionsResult(int, String[], int[])
*/
private static final int LOCATION_PERMISSION_REQUEST_CODE = 1;
/**
* Flag indicating whether a requested permission has been denied after returning in
* {@link #onRequestPermissionsResult(int, String[], int[])}.
*/
private boolean mPermissionDenied = false;
private GoogleMap mMap;
private LocationManager locationManager;
private String provider;
private GoogleMap googleMap;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_maps);
//
//setUpMap();
SupportMapFragment mapFragment =
(SupportMapFragment) getSupportFragmentManager().findFragmentById(R.id.map);
mapFragment.getMapAsync(this);
}
@Override
public void onMapReady(GoogleMap map) {
mMap = map;
mMap.setOnMyLocationButtonClickListener(this);
enableMyLocation();
}
private void setUpMap() {
mMap.addMarker(new MarkerOptions().position(new LatLng(0, 0)).title("Marker").snippet("Snippet"));
// Enable MyLocation Layer of Google Map
mMap.setMyLocationEnabled(true);
// Get LocationManager object from System Service LOCATION_SERVICE
LocationManager locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
// Create a criteria object to retrieve provider
Criteria criteria = new Criteria();
// Get the name of the best provider
String provider = locationManager.getBestProvider(criteria, true);
// Get Current Location
Location myLocation = locationManager.getLastKnownLocation(provider);
// set map type
mMap.setMapType(GoogleMap.MAP_TYPE_NORMAL);
// Get latitude of the current location
double latitude = myLocation.getLatitude();
// Get longitude of the current location
double longitude = myLocation.getLongitude();
// Create a LatLng object for the current location
LatLng latLng = new LatLng(latitude, longitude);
// Show the current location in Google Map
mMap.moveCamera(CameraUpdateFactory.newLatLng(latLng));
// Zoom in the Google Map
mMap.animateCamera(CameraUpdateFactory.zoomTo(14));
mMap.addMarker(new MarkerOptions().position(new LatLng(latitude, longitude)).title("You are here!").snippet("Consider yourself located"));
}
/**
* Enables the My Location layer if the fine location permission has been granted.
*/
private void enableMyLocation() {
if (ContextCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION)
!= PackageManager.PERMISSION_GRANTED) {
// Permission to access the location is missing.
PermissionUtils.requestPermission(this, LOCATION_PERMISSION_REQUEST_CODE,
Manifest.permission.ACCESS_FINE_LOCATION, true);
setUpMap();
} else if (mMap != null) {
// Access to the location has been granted to the app.
mMap.setMyLocationEnabled(true);
}
}
@Override
public boolean onMyLocationButtonClick() {
Toast.makeText(this, "MyLocation button clicked"+mMap.getMyLocation().getLatitude(), Toast.LENGTH_SHORT).show();
// Return false so that we don't consume the event and the default behavior still occurs
// (the camera animates to the user's current position).
LatLng sydney = new LatLng(mMap.getMyLocation().getLatitude(), mMap.getMyLocation().getLongitude());
mMap.addMarker(new MarkerOptions().position(sydney).title("HOME"));
mMap.moveCamera(CameraUpdateFactory.newLatLng(sydney));
return false;
}
@Override
public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions,
@NonNull int[] grantResults) {
if (requestCode != LOCATION_PERMISSION_REQUEST_CODE) {
return;
}
if (PermissionUtils.isPermissionGranted(permissions, grantResults,
Manifest.permission.ACCESS_FINE_LOCATION)) {
// Enable the my location layer if the permission has been granted.
enableMyLocation();
} else {
// Display the missing permission error dialog when the fragments resume.
mPermissionDenied = true;
}
}
@Override
protected void onResumeFragments() {
super.onResumeFragments();
if (mPermissionDenied) {
// Permission was not granted, display error dialog.
showMissingPermissionError();
mPermissionDenied = false;
}
}
/**
* Displays a dialog with error message explaining that the location permission is missing.
*/
private void showMissingPermissionError() {
PermissionUtils.PermissionDeniedDialog
.newInstance(true).show(getSupportFragmentManager(), "dialog");
}
@Override
public void onLocationChanged(Location location) {
}
@Override
public void onStatusChanged(String provider, int status, Bundle extras) {
}
@Override
public void onProviderEnabled(String provider) {
}
@Override
public void onProviderDisabled(String provider) {
}
}
我尝试使用setUpMap（）但会导致跟随错误。我是android的新手。
02-05 15:35:11.303 19034-19034/com.jatinderbhola.mymapapp E/AndroidRuntime: FATAL EXCEPTION: main Process: com.jatinderbhola.mymapapp, PID: 19034
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.jatinderbhola.mymapapp/com.jatinderbhola.mymapapp.MapsActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'com.google.android.gms.maps.model.Marker com.google.android.gms.maps.GoogleMap.addMarker(com.google.android.gms.maps.model.MarkerOptions)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2416)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
at android.app.ActivityThread.-wrap11(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5417)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'com.google.android.gms.maps.model.Marker com.google.android.gms.maps.GoogleMap.addMarker(com.google.android.gms.maps.model.MarkerOptions)' on a null object reference
at com.jatinderbhola.mymapapp.MapsActivity.setUpMap(MapsActivity.java:83)
at com.jatinderbhola.mymapapp.MapsActivity.onCreate(MapsActivity.java:70)
at android.app.Activity.performCreate(Activity.java:6237)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1107)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2369)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
at android.app.ActivityThread.-wrap11(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5417)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
提前致谢。
答案 0 :(得分：0)
mMap.animateCamera(CameraUpdateFactory.newLatLngZoom(new LatLng(getLatitude(),
getLongitude()), 10.0f), 4000, null);
mMap.setMapType(GoogleMap.MAP_TYPE_NORMAL);
myMarker = mMap.addMarker(new MarkerOptions()
.position(new LatLng(getLatitude(), getLongitude()))
.title("My Position").draggable(true));
使用getLatitude（）和getLongitude（）是我检索GPS坐标的私有方法，我在我的活动的onCreate上使用上面的代码向我显示以我的位置为中心点的地图。
答案 1 :(得分：0)
您需要将相机设置为您的位置动画。你可以这样做。在你启动地图后就没法了。
location = locationManager.getLastKnownLocation(LocationManager.NETWORK_PROVIDER);
if(location != null){
CameraUpdate position = CameraUpdateFactory.newLatLng(new LatLng(location.getLatitude(),location.getLongitude()));
mMap.animateCamera(position);
}
CameraUpdate zoom= CameraUpdateFactory.zoomTo(15);
mMap.animateCamera(zoom);
这对模拟器无效。如果您有实际的手机，请使用此功能。
String provider = locationManager.getBestProvider(criteria, true);
或使用手动提供商。
locationManager.NETWORK_PROVIDER OR GPS_PROVIDER