我切换到Android版地图的v2，我正在尝试移植以下功能：
使用MyLocationOverlay，我可以显示设备当前位置（蓝点）。当用户的位置发生变化并且点到达可见区域的边缘时，地图会动画显示，以便点实时成为视图的中心。
在v2中，我使用了SupportMapFragment和getMap（）。setMyLocationEnabled（true）。当前位置显示为蓝点（箭头），但是当设备更改位置时，地图视图不会移动，并且点最终会离开视图。
有什么想法吗？
答案 0 :(得分：24)
您需要将LocationSource添加到GoogleMap并响应onLocationChanged事件。这是一个简单的类，询问用户的位置，然后等待用户的位置可用，并将地图动画为中心位置。
public class MyLocationMapFragmentActivity extends FragmentActivity implements LocationListener, LocationSource
{
/**
* Note that this may be null if the Google Play services APK is not available.
*/
private GoogleMap mMap;
private OnLocationChangedListener mListener;
private LocationManager locationManager;
@Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.basic_map);
locationManager = (LocationManager) getSystemService(LOCATION_SERVICE);
if(locationManager != null)
{
boolean gpsIsEnabled = locationManager.isProviderEnabled(LocationManager.GPS_PROVIDER);
boolean networkIsEnabled = locationManager.isProviderEnabled(LocationManager.NETWORK_PROVIDER);
if(gpsIsEnabled)
{
locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 5000L, 10F, this);
}
else if(networkIsEnabled)
{
locationManager.requestLocationUpdates(LocationManager.NETWORK_PROVIDER, 5000L, 10F, this);
}
else
{
//Show an error dialog that GPS is disabled.
}
}
else
{
//Show a generic error dialog since LocationManager is null for some reason
}
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.basicMap)).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.newLatLng(new LatLng(location.getLatitude(), location.getLongitude())));
}
}
@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();
}
}
这应该跟随用户并在地图改变时将地图保持在中心位置 - 如果您只想在用户“离开屏幕”时将地图居中，那么您可以检查用户是否location位于地图的可见范围内
@Override
public void onLocationChanged(Location location)
{
if( mListener != null )
{
mListener.onLocationChanged( location );
LatLngBounds bounds = this.mMap.getProjection().getVisibleRegion().latLngBounds;
if(!bounds.contains(new LatLng(location.getLatitude(), location.getLongitude())))
{
//Move the camera to the user's location if they are off-screen!
mMap.animateCamera(CameraUpdateFactory.newLatLng(new LatLng(location.getLatitude(), location.getLongitude())));
}
}
}
以下是关于该主题的简短说明： Google Maps Android API V2 MyLocation LocationSource and event handling
<强>更新
我编辑了如何获取用户的位置（请参阅onCreate中的locationManager代码）。我发现使用“getBestProvider”方法并不可靠，只是简单地在多个设备上不起作用。我有几个用户抱怨他们的设备永远找不到他们的位置，无论我做出多么轻松的标准。手动选择GPS或网络似乎普遍适用。
答案 1 :(得分：14)
更新：Google引入了新的LocationClient和关联的LocationListener（OnMyLocationChangeListener界面现已弃用）。因此，现在自动对中摄像头是一项微不足道的任务。
虽然spotdog已经回答了我想分享我自己的例子的问题，但我希望这会帮助Android初学者更好地理解为my-location层制作自定义LocationSource所需的内容。希望你会发现代码有充分的文档/注释。
public class PlaceMapFragment extends SupportMapFragment {
// Note that this may be null if the Google Play services APK is not available.
private GoogleMap mMap;
protected PlaceActivity activity;
private FollowMeLocationSource followMeLocationSource;
private Context mContext;
/* We need the Context in order to get a reference to the Location Manager
* (when instantiating this fragment from your activity use:
* PlaceMapFragment mapFragment = new PlaceMapFragment(this); ) */
public PlaceMapFragment(Context context) {
this.mContext = context;
}
@Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
activity = (PlaceActivity)getActivity();
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// creates our custom LocationSource and initializes some of its members
followMeLocationSource = new FollowMeLocationSource();
/* We can't be guaranteed that the map is available because Google Play services might not be available.
* (un-comment the following line when using this code in a FragmentActivity / Activity
* to try get a reference to the map here !) */
//setUpMapIfNeeded();
}
@Override
public void onResume() {
super.onResume();
/* We query for the best Location Provider everytime this fragment is displayed
* just in case a better provider might have become available since we last displayed it */
followMeLocationSource.getBestAvailableProvider();
// Get a reference to the map/GoogleMap object
setUpMapIfNeeded();
/* Enable the my-location layer (this causes our LocationSource to be automatically activated.)
* While enabled, the my-location layer continuously draws an indication of a user's
* current location and bearing, and displays UI controls that allow a user to interact
* with their location (for example, to enable or disable camera tracking of their location and bearing).*/
mMap.setMyLocationEnabled(true);
}
@Override
public void onPause() {
/* Disable the my-location layer (this causes our LocationSource to be automatically deactivated.) */
mMap.setMyLocationEnabled(false);
super.onPause();
}
/**
* 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
* manipulate the map once when it {@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.
*/
private void setUpMapIfNeeded() {
// Do a null check to confirm that we have not already instantiated the map.
if (mMap == null) {
mMap = getMap();
// Check if we were successful in obtaining the map.
if (mMap != null) {
// The Map is verified. It is now safe to manipulate the map:
// Replace the (default) location source of the my-location layer with our custom LocationSource
mMap.setLocationSource(followMeLocationSource);
// Set default zoom
mMap.moveCamera(CameraUpdateFactory.zoomTo(15f));
}
}
}
/* Our custom LocationSource.
* We register this class to receive location updates from the Location Manager
* and for that reason we need to also implement the LocationListener interface. */
private class FollowMeLocationSource implements LocationSource, LocationListener {
private OnLocationChangedListener mListener;
private LocationManager locationManager;
private final Criteria criteria = new Criteria();
private String bestAvailableProvider;
/* Updates are restricted to one every 10 seconds, and only when
* movement of more than 10 meters has been detected.*/
private final int minTime = 10000; // minimum time interval between location updates, in milliseconds
private final int minDistance = 10; // minimum distance between location updates, in meters
private FollowMeLocationSource() {
// Get reference to Location Manager
locationManager = (LocationManager) mContext.getSystemService(Context.LOCATION_SERVICE);
// Specify Location Provider criteria
criteria.setAccuracy(Criteria.ACCURACY_FINE);
criteria.setPowerRequirement(Criteria.POWER_LOW);
criteria.setAltitudeRequired(true);
criteria.setBearingRequired(true);
criteria.setSpeedRequired(true);
criteria.setCostAllowed(true);
}
private void getBestAvailableProvider() {
/* The preffered way of specifying the location provider (e.g. GPS, NETWORK) to use
* is to ask the Location Manager for the one that best satisfies our criteria.
* By passing the 'true' boolean we ask for the best available (enabled) provider. */
bestAvailableProvider = locationManager.getBestProvider(criteria, true);
}
/* Activates this provider. This provider will notify the supplied listener
* periodically, until you call deactivate().
* This method is automatically invoked by enabling my-location layer. */
@Override
public void activate(OnLocationChangedListener listener) {
// We need to keep a reference to my-location layer's listener so we can push forward
// location updates to it when we receive them from Location Manager.
mListener = listener;
// Request location updates from Location Manager
if (bestAvailableProvider != null) {
locationManager.requestLocationUpdates(bestAvailableProvider, minTime, minDistance, this);
} else {
// (Display a message/dialog) No Location Providers currently available.
}
}
/* Deactivates this provider.
* This method is automatically invoked by disabling my-location layer. */
@Override
public void deactivate() {
// Remove location updates from Location Manager
locationManager.removeUpdates(this);
mListener = null;
}
@Override
public void onLocationChanged(Location location) {
/* Push location updates to the registered listener..
* (this ensures that my-location layer will set the blue dot at the new/received location) */
if (mListener != null) {
mListener.onLocationChanged(location);
}
/* ..and Animate camera to center on that location !
* (the reason for we created this custom Location Source !) */
mMap.animateCamera(CameraUpdateFactory.newLatLng(new LatLng(location.getLatitude(), location.getLongitude())));
}
@Override
public void onStatusChanged(String s, int i, Bundle bundle) {
}
@Override
public void onProviderEnabled(String s) {
}
@Override
public void onProviderDisabled(String s) {
}
}
}
答案 2 :(得分：0)
只需使用OnMyLocationChangeListener，覆盖方法public void onMyLocationChange(Location location)即可。使用GoogleMap.setOnMyLocationChangeListener(your listener)注册您的听众。
public void onMyLocationChange(Location location) {
changeMapLocation(location);
}
private void changeMapLocation(Location location) {
LatLng latlong = new LatLng(location.getLatitude(),
location.getLongitude());
map.moveCamera(CameraUpdateFactory.newLatLngZoom(latlong, 15));
// Zoom in, animating the camera.
map.animateCamera(CameraUpdateFactory.zoomTo(10), 2000, null);
}