Question

谷歌地图中的标记上有onTap问题。

这是错误

05-31 21:46:21.420: E/AndroidRuntime(5541): java.lang.NullPointerException
05-31 21:46:21.420: E/AndroidRuntime(5541):     at com.android.internal.app.AlertController$AlertParams.(AlertController.java:753)
05-31 21:46:21.420: E/AndroidRuntime(5541):     at android.app.AlertDialog$Builder.(AlertDialog.java:273)
05-31 21:46:21.420: E/AndroidRuntime(5541):     at my.class.HelloMapView$LocationOverlay.onTap(HelloMapView.java:1361)

这是my.class.HelloMapView错误的代码$ LocationOverlay.onTap（HelloMapView.java:1361）

    public class LocationOverlay extends ItemizedOverlay<OverlayItem>  {
    //public class LocationOverlay extends ItemizedOverlay{
        private ArrayList<OverlayItem> overLayList = new ArrayList<OverlayItem>();
        private MapView mapView;
        public String pickedlat;
        public String pickedlng;
        private Context mContext;


        public LocationOverlay(MapView mapView, Drawable defaultMarker, Context context) {
            //super(null);
             super(boundCenterBottom(defaultMarker));
             mContext = context;
            this.mapView = mapView; // need it for onTap
            populate();

        }

        @Override
        protected OverlayItem createItem(int i) {
             return overLayList.get(i);
        }

        @Override
        public int size() {
             return overLayList.size();
        }

        public void addOverlayItem(OverlayItem overlayItem) {
             if(!overLayList.contains(overlayItem)){
                  overLayList.add(overlayItem);
                  setLastFocusedIndex(-1);
                  populate();     
             }

           //  populate();
        }

        @Override 
        protected boolean onTap(int pIndex) 
        { 
          OverlayItem item = overLayList.get(pIndex); 
          AlertDialog.Builder dialog = new AlertDialog.Builder(mContext); 
          dialog.setTitle(item.getTitle()); 
          dialog.setMessage(item.getSnippet()); 
          dialog.show(); 
          return true; 
        }

错误日志中引用的行是

AlertDialog.Builder对话框=新的AlertDialog.Builder（mContext）;

我可以通过谷歌搜索猜测它，可能是mContext没有通过...但我不能正确...

请帮忙

Answer 1

检查对构造函数的调用，可能会在那里传递null值。您可以使用this关键字，因为Activity是Contex的子类，所以

LocationOverlay locationOverlay = new LocationOverlay(mapView, getResources().getDrawable(R.drawable.polis), this);

或者如果您从Fragment调用，请使用getActivity（）方法

LocationOverlay locationOverlay = new LocationOverlay(mapView, getResources().getDrawable(R.drawable.polis), this.getActivity());

map-marker上的onTap给我NullPointerException

1 个答案: