为什么地图视图上的叠加层未显示？

Question

我按照google hellomapview教程中的说明操作.我得到了一个有效的mapview等.但是没有显示添加到地图中的两个项目.它似乎在某处,因为在指定位置点击会显示添加到项目中的消息.

编辑

这是我的源代码.它应该非常接近谷歌教程源代码.

public class MapOverlay extends ItemizedOverlay<OverlayItem> {

private List<OverlayItem> overlays = new ArrayList<OverlayItem>();
private Context context;

public MapOverlay(Drawable defaultMarker, Context context) {
    super(defaultMarker);
    overlays = new ArrayList<OverlayItem>();
    this.context = context;
}

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

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

public void addOverlay(OverlayItem overlay) {
    overlays.add(overlay);
    this.populate();
}

@Override
protected boolean onTap(int index) {
  OverlayItem item = overlays.get(index);
  AlertDialog.Builder dialog = new AlertDialog.Builder(this.context);
  dialog.setTitle(item.getTitle());
  dialog.setMessage(item.getSnippet());
  dialog.show();
  return true;
}

}

public class MapsActivity 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);

    MapOverlay overlay = new MapOverlay(this.getResources().getDrawable(
            R.drawable.androidmarker), this);

    overlay.addOverlay(new OverlayItem(new GeoPoint(19240000,-99120000), "Blubb", "See?"));
    mapView.getOverlays().add(overlay);
}

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

谷歌教程的源代码是否可以在某处获得？

Answer 1

问题是我忘了设置drawable的边界.似乎如果mapview不知道如何对齐图像,它根本不会显示它.

我改变了构造函数中的第一行:

super(defaultMarker);

至

super(boundCenterBottom(defaultMarker));

并且知道它的工作完美.