GoogleMaps MapView在Android中崩溃onTap?
我目前正在编写一个应用程序,显示一个显示谷歌地图的MapView。我使用了http://developer.android.com/resources/tutorials/views/hello-mapview.html中的“hello map view”教程,这个工程到目前为止:地图显示,居中和放大正确,即使我添加的OverlayItems显示正确。GoogleMaps MapView在Android中崩溃onTap?
但是,当我在我加入那些覆盖项目中的一个点击,应用程序崩溃,一个空指针异常:
07-23 16:24:48.167: ERROR/AndroidRuntime(2530): java.lang.NullPointerException
07-23 16:24:48.167: ERROR/AndroidRuntime(2530): at com.android.internal.app.AlertController$AlertParams.<init>(AlertController.java:753)
07-23 16:24:48.167: ERROR/AndroidRuntime(2530): at android.app.AlertDialog$Builder.<init>(AlertDialog.java:273)
07-23 16:24:48.167: ERROR/AndroidRuntime(2530): at net.xenonite.wifiloc.act_map$MapItemizedOverlay.onTap(act_map.java:182)
07-23 16:24:48.167: ERROR/AndroidRuntime(2530): at com.google.android.maps.ItemizedOverlay.onTap(ItemizedOverlay.java:453)
07-23 16:24:48.167: ERROR/AndroidRuntime(2530): at com.google.android.maps.OverlayBundle.onTap(OverlayBundle.java:83)
07-23 16:24:48.167: ERROR/AndroidRuntime(2530): at com.google.android.maps.MapView$1.onSingleTapUp(MapView.java:347)
07-23 16:24:48.167: ERROR/AndroidRuntime(2530): at com.google.android.maps.GestureDetector.onTouchEvent(GestureDetector.java:533)
07-23 16:24:48.167: ERROR/AndroidRuntime(2530): at com.google.android.maps.MapView.onTouchEvent(MapView.java:647)
07-23 16:24:48.167: ERROR/AndroidRuntime(2530): at android.view.View.dispatchTouchEvent(View.java:3709)
07-23 16:24:48.167: ERROR/AndroidRuntime(2530): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:874)
07-23 16:24:48.167: ERROR/AndroidRuntime(2530): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:924)
07-23 16:24:48.167: ERROR/AndroidRuntime(2530): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:924)
07-23 16:24:48.167: ERROR/AndroidRuntime(2530): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:924)
07-23 16:24:48.167: ERROR/AndroidRuntime(2530): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:924)
07-23 16:24:48.167: ERROR/AndroidRuntime(2530): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:924)
07-23 16:24:48.167: ERROR/AndroidRuntime(2530): at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:924)
07-23 16:24:48.167: ERROR/AndroidRuntime(2530): at com.android.internal.policy.impl.PhoneWindow$DecorView.superDispatchTouchEvent(PhoneWindow.java:1695)
07-23 16:24:48.167: ERROR/AndroidRuntime(2530): at com.android.internal.policy.impl.PhoneWindow.superDispatchTouchEvent(PhoneWindow.java:1116)
07-23 16:24:48.167: ERROR/AndroidRuntime(2530): at android.app.Activity.dispatchTouchEvent(Activity.java:2068)
07-23 16:24:48.167: ERROR/AndroidRuntime(2530): at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchTouchEvent(PhoneWindow.java:1679)
07-23 16:24:48.167: ERROR/AndroidRuntime(2530): at android.view.ViewRoot.handleMessage(ViewRoot.java:1708)
07-23 16:24:48.167: ERROR/AndroidRuntime(2530): at android.os.Handler.dispatchMessage(Handler.java:99)
07-23 16:24:48.167: ERROR/AndroidRuntime(2530): at android.os.Looper.loop(Looper.java:123)
07-23 16:24:48.167: ERROR/AndroidRuntime(2530): at android.app.ActivityThread.main(ActivityThread.java:4595)
07-23 16:24:48.167: ERROR/AndroidRuntime(2530): at java.lang.reflect.Method.invokeNative(Native Method)
07-23 16:24:48.167: ERROR/AndroidRuntime(2530): at java.lang.reflect.Method.invoke(Method.java:521)
07-23 16:24:48.167: ERROR/AndroidRuntime(2530): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:860)
07-23 16:24:48.167: ERROR/AndroidRuntime(2530): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:618)
07-23 16:24:48.167: ERROR/AndroidRuntime(2530): at dalvik.system.NativeStart.main(Native Method)
我的代码大多是从教程复制:
public class act_map extends MapActivity
{
@Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.map);
intent = getIntent();
lat = intent.getDoubleExtra("lat", 0.0);
lng = intent.getDoubleExtra("lng", 0.0);
MapView = (MapView) findViewById(R.id.act_map_mapview);
List<Overlay> mapOverlays = MapView.getOverlays();
Drawable positionMarker
= getResources().getDrawable(R.drawable.act_map_androidmarker);
MapItemizedOverlay itemizedOverlay
= new MapItemizedOverlay(positionMarker);
geoPoint = new GeoPoint((int) (lat * 1000000), (int) (lng * 1000000));
Pointer = new OverlayItem(geoPoint, "Thats me!", "wohooo");
itemizedOverlay.addOverlay(Pointer);
mapOverlays.add(itemizedOverlay);
MapView.setSatellite(false);
MapController = MapView.getController();
MapController.setCenter(geoPoint);
MapController.setZoom(18);
MapView.setBuiltInZoomControls(true);
MapView.displayZoomControls(true);
}
@Override
protected boolean isRouteDisplayed()
{
return false;
}
public boolean onKeyDown(int keyCode, KeyEvent event)
{
if (keyCode == KeyEvent.KEYCODE_I)
{
MapView.getController().setZoom(MapView.getZoomLevel() + 1);
return true;
}
else if (keyCode == KeyEvent.KEYCODE_O)
{
MapView.getController().setZoom(MapView.getZoomLevel() - 1);
return true;
}
else if (keyCode == KeyEvent.KEYCODE_S)
{
MapView.setSatellite(true);
return true;
}
else if (keyCode == KeyEvent.KEYCODE_M)
{
MapView.setSatellite(false);
return true;
}
return false;
}
public class MapItemizedOverlay extends ItemizedOverlay<OverlayItem>
{
private ArrayList<OverlayItem> mOverlays = new ArrayList<OverlayItem>();
private Context mContext;
public MapItemizedOverlay(Drawable defaultMarker)
{
super(boundCenterBottom(defaultMarker));
}
public MapItemizedOverlay(Drawable defaultMarker, Context context)
{
super(defaultMarker);
mContext = context;
}
public void addOverlay(OverlayItem overlay)
{
mOverlays.add(overlay);
populate();
}
@Override
protected OverlayItem createItem(int i)
{
return mOverlays.get(i);
}
@Override
public int size()
{
return mOverlays.size();
}
@Override
protected boolean onTap(int index)
{
OverlayItem item = mOverlays.get(index);
AlertDialog.Builder dialog = new AlertDialog.Builder(mContext);
dialog.setTitle(item.getTitle());
dialog.setMessage(item.getSnippet());
dialog.show();
return true;
}
}
如何我解决这个问题吗?
mContext
是null
。由于您的叠加层是活动的内部类,因此请在您的AlertDialog
构造函数调用中将mContext
替换为act_map.this
。
我也有过与Android的MapView教程的一个问题。当我点击该图标时,屏幕会崩溃(空mContext将被传递):
上述修正没有为我工作。相反,我改变了下面的代码行从MapActivity类从:
HelloItemizedOverlay itemizedoverlay = new HelloItemizedOverlay(drawable);
这样:
HelloItemizedOverlay itemizedoverlay = new HelloItemizedOverlay(drawable, this);
您还需要通过添加boundCenterBottom
修复构造其丢失:
public HelloItemizedOverlay(Drawable defaultMarker, Context context) {
super(boundCenterBottom(defaultMarker));
mContext = context;
}
(已有美丽的截图,但不能发表,因为我是新的:P)
希望可以帮助其他仍然存在教程问题并修复其应用程序的人!
有完全相同的问题,这固定它。他们的教程中如何存在这样一个明显的错误? – wbarksdale 2011-11-25 04:22:00
+1是的,这也是我的修复。 – 2011-11-27 04:09:37
也在mapoverlay构造函数中调用populate()
thanx!这解决了问题! – xenonite 2010-07-29 13:53:28
如果它不在内部班级,那又怎样? – 2011-02-03 19:51:46