使相机随着位置的变化而移动（Google Maps Api）

Posted 2023-02-23

【中文标题】使相机随着位置的变化而移动（Google Maps Api）

【英文标题】：Make Camera move as Location changes (Google Maps Api)

【发布时间】：2016-04-26 20:09:23

【问题描述】：

我对谷歌地图 api 有疑问。我想要做的是将相机与 Location 一起移动，以便蓝色指示器始终位于中心。

认为放置代码的好地方是在 OnLocationChanged 方法中，但事实并非如此。

我试图在那里运行这段代码：

LatLng latlng = new LatLng(mLastLocation.getLatitude(),mLastLocation.getLongitude());
    CameraUpdate cameraUpdate = CameraUpdateFactory.newLatLngZoom(latlng,17);
    mMap.animateCamera(cameraUpdate);

更新

那么我不能这样做吗？

@Override
public void onLocationChanged(Location location) 
mLocationRequest = LocationRequest.create()
        .setPriority(LocationRequest.PRIORITY_BALANCED_POWER_ACCURACY)
        .setInterval(10 * 1000)
        .setFastestInterval(1 * 1000);

    LatLng latLng = new LatLng(location.getLatitude(),location.getLongitude());
    CameraPosition cameraPosition = new CameraPosition.Builder()
            .target(latLng)
            .zoom(ZOOM)
            .bearing(0)
            .tilt(0)
            .build();
    mMap.animateCamera(CameraUpdateFactory.newCameraPosition(cameraPosition));

【问题讨论】：

这是另一个线程的解决方案：***.com/questions/13742551/…

为什么我不能将以下内容添加到 OnLocationChanged 事件中。:: @Override public void onLocationChanged(Location location) mLocationRequest = LocationRequest.create() .setPriority(LocationRequest.PRIORITY_BALANCED_POWER_ACCURACY) .setInterval(10 * 1000) .setFastestInterval(1 * 1000); mMap.animateCamera(CameraUpdateFactory.newLatLng(new LatLng(location.getLatitude(), location.getLongitude())));

蓝色指示器位置请求是由地图实现的，与您的位置请求相比，它可以在不同的时间间隔给出不同的点。 AFAIK，无法收听地图使用的默认位置提供程序，您需要顺利更新地图摄像头位置。

好的，所以我不能按照我的更新@PabloBaxter 下的代码中显示的那样做

【参考方案1】：

该代码可用于更新您的相机位置，但无法将 Google 地图蓝色指示器精确居中。这是因为蓝点正在侦听的 locationRequest 与您在代码 sn-p 中创建的 locationRequest 不同（这似乎没有做任何事情）。以下代码sn-p来自here

/* 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 preferred 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) 

    

现在，在您的 onMapReady(GoogleMap) 回调中，将其放入：

public void onMapReady(GoogleMap map)
    mMap = map;
    FollowMeLocationSource locationSource = new FollowMeLocationSource();
    locationSource.getBestAvailableProvider();
    mMap.setLocationSource(locationSource);
    mMap.setMyLocationEnabled(true);

根据需要修改此示例，但这应该会为您提供所需的功能。

【讨论】：

我会试试这个。因为就目前而言，我的代码并没有像你说的那样做任何事情。相机根本不动。

我已经测试了代码，我收到错误“java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.Object android.content.Context.getSystemService(java.lang.String) ' 在“locationManager = (LocationManager) mContext.getSystemService(Context.LOCATION_SERVICE);”这一行的空对象引用上@PabloBaxter

您是否将 mContext 分配给包含您的地图的任何上下文？

mContext 在那里。但是现在当我测试是否调用了 OnLocationChanged 时，它永远不会被调用。

放一个日志语句，并检查“activate()”是否被调用。另外，请检查您是否也在手机上启用了位置信息。