这是我的代码。该应用程序非常简单，我所做的只是初始化一个地图，并尝试将活动（实现LocationListener）注册到LocationManager更新。由于某种原因，currentLocation保持为null ...请帮助吗？
public class LocationActivity extends FragmentActivity implements LocationListener{
//Map Variables
private GoogleMap mMap; // Might be null if Google Play services APK is not available.
private int DEFAULT_ZOOM = 17;
private int DEFAULT_MAP_STYLE = GoogleMap.MAP_TYPE_NORMAL;
private Marker currentMarker = null;
private GroundOverlay currentDebrisPic = null;
//General Variables
private String LOCATION_TAG = "LocationActivity";
//Location Variables
private LocationManager locationManager = null;
private String locationProvider = "";
private Location currentLocation = null;
private int LOCATION_UPDATES_TIME_INTERVAL = 2000; //Time between two location updates
private int LOCATION_UPDATES_DISTANCE_INTERVAL = 3;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.location_layout);
setUpMapIfNeeded();
setLocationServices();
//initializeCamera();
}
protected void initializeCamera(){
//Make the Initialization small window visible
TextView initializationTextView = (TextView)findViewById(R.id.InitializationTextView);
ProgressBar initializationProgressBar = (ProgressBar)findViewById(R.id.InitializationProgressBar);
initializationTextView.setVisibility(View.VISIBLE);
initializationProgressBar.setVisibility(View.VISIBLE);
//As progress bar advances,
for(int i = 1; i <= DEFAULT_ZOOM; i++){
CameraUpdate cameraUpdate = getMoveCameraUpdate(currentLocation, i);
mMap.moveCamera(cameraUpdate);
//for(int j = 0; j < 400000; j++);
initializationProgressBar.setProgress((100/DEFAULT_ZOOM) * i);
}
//After zooming is done, make the progress bar invisible again
initializationProgressBar.setVisibility(View.INVISIBLE);
initializationTextView.setVisibility(View.INVISIBLE);
addMarkerAtCurrentLocation();
}
//Generates and returns a new CameraUpdate containing the new position of the camera with zoom 0 and bearing 0;
private CameraUpdate getMoveCameraUpdate(Location location, int zoom){
LatLng newLocation = new LatLng(location.getLatitude(),location.getLongitude());
CameraUpdate cameraUpdate = CameraUpdateFactory.newCameraPosition(new CameraPosition(newLocation, zoom, 0, 0));
return cameraUpdate;
}
//Add marker at current location
protected void addMarkerAtCurrentLocation(){
if(null != currentMarker)
currentMarker.remove();
currentMarker = mMap.addMarker(new MarkerOptions()
.position(new LatLng(currentLocation.getLatitude(), currentLocation.getLongitude()))
.icon(BitmapDescriptorFactory.fromResource(R.drawable.locationmarker))
.title("Your location"));
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.location_menu, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
//If the item titled "Home Menu" was pressed
if(id == R.id.LocationToHome) {
try {
Intent intent = new Intent(this, MainActivity.class);
startActivity(intent);
finish();
Log.d(LOCATION_TAG, "Successfully moved from localization to home menu");
}
catch (Exception ex){
Log.e(LOCATION_TAG, "Can't move to Home Menu\n" + ex.getMessage());
}
}
//If the item titled "Change map type" was pressed,
else if(id == R.id.MapTypeChange){
//Current map is Normal type and should be changed to Hybrid
if(mMap.getMapType() == GoogleMap.MAP_TYPE_NORMAL){
mMap.setMapType(GoogleMap.MAP_TYPE_HYBRID);
item.setTitle("Normal map");
}
//Current map is Hybrid type and should be changed to Normal
else if(mMap.getMapType() == GoogleMap.MAP_TYPE_HYBRID){
mMap.setMapType(GoogleMap.MAP_TYPE_NORMAL);
item.setTitle("Hybrid map");
}
Log.d(LOCATION_TAG, "Map type changed successfully");
}
//Default item in the menu
else if(id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
@Override
protected void onResume() {
super.onResume();
setUpMapIfNeeded();
locationManager.requestLocationUpdates(locationProvider, LOCATION_UPDATES_TIME_INTERVAL, LOCATION_UPDATES_DISTANCE_INTERVAL, this);
addMarkerAtCurrentLocation();
}
@Override
protected void onStop(){
super.onStop();
//To save battery, location updates are not necessary when the map isn't currently showed. When onResume is called,
//the LocationManager is requested to re-set the updates.
locationManager.removeUpdates(this);
}
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 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() {
//Default map type is Hybrid, can be changed in the menu
mMap.setMapType(DEFAULT_MAP_STYLE);
//Auto zoom to a resolution of a few houses, additional zoom can be done manually
CameraUpdate cameraUpdate = CameraUpdateFactory.zoomTo(12);
mMap.animateCamera(cameraUpdate);
//Receive the current location and zoom onto it
}
protected void setLocationServices(){
//Try to open a location service and check if GPS is available. If not, open the GPS settings so that the
//user will be able to enable it manually.
locationManager = (LocationManager)getSystemService(LOCATION_SERVICE);
boolean locationEnabled = locationManager.isProviderEnabled(LocationManager.GPS_PROVIDER);
if (!locationEnabled) {
//Alert!
Intent intent = new Intent(Settings.ACTION_LOCATION_SOURCE_SETTINGS);
startActivity(intent);
}
//Choose best location provider by criteria, when initialized with empty constructor
// gives the best criteria available
Criteria criteria = new Criteria();
locationProvider = locationManager.getBestProvider(criteria, false);
try {
Location location = locationManager.getLastKnownLocation(locationProvider);
onLocationChanged(location);
if(null != location) {
Log.d(LOCATION_TAG, "Location successfully obtained from provider");
onLocationChanged(location);
}
else {
Log.d(LOCATION_TAG, "getLastKnownLocation failed");
}
}
catch (Exception ex){
Log.e(LOCATION_TAG, "Can't obtain location\n" + ex.getMessage());
}
locationManager.requestLocationUpdates(locationProvider, LOCATION_UPDATES_TIME_INTERVAL, LOCATION_UPDATES_DISTANCE_INTERVAL, this);
}
//Called when the location provider updates the current location
@Override
public void onLocationChanged(Location newLocation){
try {
currentLocation = newLocation;
Log.d(LOCATION_TAG, "Location successfully assigned to currentLocation");
//Move marker to current location
addMarkerAtCurrentLocation();
//Log.d(LOCATION_TAG, "Marker added successfully");
}
catch (Exception ex){
Log.e(LOCATION_TAG, "Can't assign new location to currentLocation\n" + ex.getMessage());
}
}
@Override
public void onStatusChanged(String provider, int status, Bundle extras) {
switch(status){
case LocationProvider.OUT_OF_SERVICE:
Toast.makeText(this, "Location provider unavailable, please restart", Toast.LENGTH_LONG).show();
Log.d(LOCATION_TAG, provider + "Location provider out of service");
break;
case LocationProvider.AVAILABLE:
Toast.makeText(this, "Location provider available", Toast.LENGTH_SHORT).show();
Log.d(LOCATION_TAG, provider + "Location provider available");
break;
case LocationProvider.TEMPORARILY_UNAVAILABLE:
Toast.makeText(this, "Location provider temporarily unavailable", Toast.LENGTH_SHORT).show();
Log.d(LOCATION_TAG, provider + "Location provider temporarily unavailable");
break;
}
}
//Called when the provider is enabled by the user.
@Override
public void onProviderEnabled(String provider) {
//Toast.makeText(this, provider + "Location provider enabled", Toast.LENGTH_SHORT);
Log.d(LOCATION_TAG, provider + "Location provider enabled");
}
//Called when the provider is disabled by the user. If requestLocationUpdates is called on an already
//disabled provider, this method is called immediately.
@Override
public void onProviderDisabled(String provider) {
Toast.makeText(this, provider + "Location provider disabled", Toast.LENGTH_SHORT).show();
Log.d(LOCATION_TAG, provider + "Location provider disabled");
}
}
答案 0 :(得分：0)
当您使用V2时，最好让Google处理此问题，V2可以帮助您使用GoogleMap自己的列表工具找到您的位置。
mMap.setMyLocationEnabled(true);
mMap.setOnMyLocationChangeListener(new OnMyLocationChangeListener()
{
@Override
public void onMyLocationChange(Location location)
{
// Do your stuff here
}
});