ItemizedOverlay问题(HelloMapView教程)

Question

我在Android开发者网站上遇到了Hello Map Views教程的问题:http://developer.android.com/resources/tutorials/views/hello-mapview.html

我的第一个问题是,在单击覆盖项时,应用程序将崩溃.通过确保将上下文传递给我创建的ItemizedOverlay类来解决此问题...

解决此问题后,叠加层的图标不会显示在地图中.我可以单击叠加层所在的地图并显示对话框.不幸的是,我看不到图标.我确保我引用的图像是位于R.java资源文件中的对象.事实上,在经历相同的问题后,我的确切问题是由以下线程的海报提出的.不幸的是他的第二个问题从未得到解 上下文空指针

这是我的MapView类:

package com.mapsExample;

import java.util.List;

import android.content.Context;
import android.graphics.drawable.Drawable;
import android.os.Bundle;

import com.google.android.maps.GeoPoint;
import com.google.android.maps.MapActivity;
import com.google.android.maps.MapView;
import com.google.android.maps.Overlay;
import com.google.android.maps.OverlayItem;

public class HelloMaps extends MapActivity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        MapView mapView = (MapView) findViewById(R.id.mapview);
        mapView.setBuiltInZoomControls(true);
        List<Overlay> mapOverlays = mapView.getOverlays();
        Drawable drawable = this.getResources().getDrawable(R.drawable.androidmarker);
        HelloItemizedOverlay itemizedoverlay = new HelloItemizedOverlay(drawable, this);
        GeoPoint point = new GeoPoint(19240000,-99120000);
        OverlayItem overlayitem = new OverlayItem(point, "Hola, Mundo!", "I'm in Mexico City!");
        itemizedoverlay.addOverlay(overlayitem);
        mapOverlays.add(itemizedoverlay);
    }

    @Override
    protected boolean isRouteDisplayed() {
        return false;
    }
}

我的ItemizedOverlay类:

package com.mapsExample;
import java.util.ArrayList;

import android.app.AlertDialog;
import android.content.Context;
import android.graphics.drawable.Drawable;

import com.google.android.maps.ItemizedOverlay;
import com.google.android.maps.OverlayItem;


public class HelloItemizedOverlay extends ItemizedOverlay {

 private ArrayList<OverlayItem> mOverlays = new ArrayList<OverlayItem>();
 Context mContext;


 public HelloItemizedOverlay(Drawable defaultMarker) {
   super(boundCenterBottom(defaultMarker));
 }

 public HelloItemizedOverlay(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;
 }

}

同样,如果我没有将'this'传递给ItemizedOverlay构造函数,则会显示图标但无法单击.任何帮助深表感谢.提前致谢!

Answer 1

将第二个构造函数中的超级调用更改为:

超级(boundCenterBottom(defaultMarker));

应该工作!