API v2 中的地图视图和相机更新

Question

为什么 CameraUpdateFactory 类在我的项目中不起作用？如果应用执行以下命令，则会崩溃： CameraUpdate pino= CameraUpdateFactory.newLatLng（new LatLng（location.getLatitude（）， location.getLongitude（）））;如果我删除该行（当然还有下一行），代码将成功启动并显示地图。我需要mapView，我需要使用新的api v2。我以这种方式在布局中声明地图视图：

        <com.google.android.gms.maps.MapView
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:map="http://schemas.android.com/apk/res-auto"
    android:id="@+id/mappa"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_alignParentBottom="true"
    android:layout_below="@+id/buttonBar"
    map:uiZoomControls="false"
     />

然后在mainActivity中.java我写了这个：

    public class MainActivity extends FragmentActivity    implements LocationListener, LocationSource { 
public static boolean locatingMe=true;
public GoogleMap mappa;
public MapView mapView;
private OnLocationChangedListener onLocationChangedListener;
private LocationManager locationManager;


@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    mapView = (MapView) findViewById(R.id.mappa);
    mapView.onCreate(savedInstanceState);

        locationManager = (LocationManager) getSystemService(LOCATION_SERVICE);
    //You may want to pass a different provider in as the first arg here
    //depending on the location accuracy that you desire
    //see LocationManager.getBestProvider()
    Criteria locationCriteria = new Criteria();
    locationCriteria.setAccuracy(Criteria.NO_REQUIREMENT);
    locationManager.requestLocationUpdates(locationManager.getBestProvider(locationCriteria, true), 1L, 2F, this);
    if (mappa == null) {
        mappa=mapView.getMap();
        //This is how you register the LocationSource
        mappa.setLocationSource(this);
        mappa.getUiSettings().setMyLocationButtonEnabled(false);
        mappa.setMyLocationEnabled(true);
    }

}
@Override
public void onPause()
{
    if(locationManager != null)
    {
        locationManager.removeUpdates(this);
    }
    mapView.onPause();
    super.onPause();
}
@Override
public void onResume()
{
      checkGooglePlayServicesAvailability();
      checkGps();
      mapView.onResume();
      super.onResume();
}
@Override
protected void onDestroy() {
    mapView.onDestroy();
    super.onDestroy();
}
@Override
public void onLowMemory() {
    super.onLowMemory();
    mapView.onLowMemory();
}
@Override
public void activate(OnLocationChangedListener listener) 
{
    onLocationChangedListener = listener;
}
@Override
public void deactivate() 
{
    onLocationChangedListener = null;
}
@Override
public void onLocationChanged(Location location) 
{
    if( onLocationChangedListener != null )
    {
        onLocationChangedListener.onLocationChanged( location );
        //Move the camera to the user's location once it's available!
        //only if locatingMe is true
        if (locatingMe) {
            if (mappa!=null){
                CameraUpdate pino= CameraUpdateFactory.newLatLng(new LatLng(location.getLatitude(), location.getLongitude()));
                        mappa.animateCamera(pino);
            }
        }
    }
}
@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();
}

日志猫中的错误如下：

 Caused by: java.lang.NullPointerException: CameraUpdateFactory is not initialized.

Answer 1

我通过在"onCreate"上添加以下行来解决问题：

 try {
     MapsInitializer.initialize(this);
 } catch (GooglePlayServicesNotAvailableException e) {
     e.printStackTrace();
 }

原因是需要启动CameraUpdateFactory（即使从文档中似乎使用mapview它应该自动初始化）

我甚至将"公共类 MainActivity 扩展 FragmentActivity"替换为"公共类 MainActivity 扩展活动"。但我认为这最后一件事是不需要的。.

Answer 2

如果我使用：

try {
 MapsInitializer.initialize(this);
} catch (GooglePlayServicesNotAvailableException e) {
 e.printStackTrace();
}

异常给我这个错误：

Unreachable catch block for GooglePlayServicesNotAvailableException.

此异常永远不会从 try 语句正文中抛出"。

我只使用：

MapsInitializer.initialize(this);

:)