我正在尝试使用MapView创建如何获取。我创建了一个Fragment和一个XML来使用它。问题是当我尝试打开时,MapView会抛出 NullPointerException ,但我无法解释原因。
我怎么解决?
XML
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent">
<com.google.android.gms.maps.MapView
android:id="@+id/mapView"
android:layout_width="match_parent"
android:layout_height="160dp"
android:layout_marginRight="10dp" />
</LinearLayout>
片段
public class FormComoChegarEmpresa extends Fragment{
MapView mapView;
private GoogleMap googleMap;
private final String TAG = getClass().getSimpleName() + "->";
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
((CustomDrawerLayout)getActivity()).getSupportActionBar().hide();
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.como_chegar_empresa, container, false);
mapView = (MapView)view.findViewById(R.id.mapView);
return view;
}
@Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
setMapView();
}
private void setMapView() {
try {
MapsInitializer.initialize(getActivity().getApplicationContext());
} catch (Exception e) {
e.printStackTrace();
}
googleMap = mapView.getMap();
// latitude and longitude
double latitude = 17.385044;
double longitude = 78.486671;
// create marker
MarkerOptions marker = new MarkerOptions().position(
new LatLng(latitude, longitude)).title("Hello Maps");
// Changing marker icon
marker.icon(BitmapDescriptorFactory
.defaultMarker(BitmapDescriptorFactory.HUE_ROSE));
// adding marker
googleMap.addMarker(marker);
CameraPosition cameraPosition = new CameraPosition.Builder()
.target(new LatLng(17.385044, 78.486671)).zoom(12).build();
googleMap.animateCamera(CameraUpdateFactory
.newCameraPosition(cameraPosition));
// Perform any camera updates here
}
}
异常
java.lang.NullPointerException
at br.com.package.myapp.frags.FormComoChegarEmpresa.setMapView(FormComoChegarEmpresa.java:80)
at br.com.package.myapp.frags.FormComoChegarEmpresa.onActivityCreated(FormComoChegarEmpresa.java:56)
at android.support.v4.app.Fragment.performActivityCreated(Fragment.java:1794)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:967)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1126)
at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:739)
at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1489)
at android.support.v4.app.FragmentManagerImpl$1.run(FragmentManager.java:454)
at android.os.Handler.handleCallback(Handler.java:733)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:157)
at android.app.ActivityThread.main(ActivityThread.java:5356)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1265)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1081)
at dalvik.system.NativeStart.main(Native Method)
答案 0 :(得分:6)
我第一次尝试GoogleMap和MapView时遇到了同样的问题。
问题在于,当您启动地图时,需要一段时间才能加载(它在后台执行)。从MapView获取实例时,GoogleMap的值仍为null(未初始化)。
您需要在此处使用OnMapLoadedCallback。在googleMap
之后立即将此回调的实例添加到googleMap = mapView.getMap();
。回调主体有一个名为onMapLoaded()
的函数,您可以在其中放置以下代码:
googleMap.addMarker(marker);
CameraPosition cameraPosition = new CameraPosition.Builder()
.target(new LatLng(17.385044, 78.486671)).zoom(12).build();
googleMap.animateCamera(CameraUpdateFactory
.newCameraPosition(cameraPosition));
以及'googleMap.<member>'
之类的东西。我正在添加下面编辑的代码,以方便您使用。
private void setMapView() {
try {
MapsInitializer.initialize(getActivity().getApplicationContext());
} catch (Exception e) {
e.printStackTrace();
}
googleMap = mapView.getMap();
googleMap.setOnMapLoadedCallback(new OnMapLoadedCallback()
{
@Override
public void onMapLoaded()
{
// latitude and longitude
double latitude = 17.385044;
double longitude = 78.486671;
// create marker
MarkerOptions marker = new MarkerOptions().position(
new LatLng(latitude, longitude)).title("Hello Maps");
// Changing marker icon
marker.icon(BitmapDescriptorFactory
.defaultMarker(BitmapDescriptorFactory.HUE_ROSE));
// adding marker
googleMap.addMarker(marker);
CameraPosition cameraPosition = new CameraPosition.Builder()
.target(new LatLng(17.385044, 78.486671)).zoom(12).build();
googleMap.animateCamera(CameraUpdateFactory
.newCameraPosition(cameraPosition));
// Perform any camera updates here
}
});
}