Android：如何在双击时添加标记以进行地图显示？

Question

我想这样做，以便在地图上双击时会添加一个新标记。我该怎么做呢？我还想知道如何在点击上显示描述，就像我已经拥有的标记一样。越具体越好。

MainActivity.java：

package Food.Pack.HomeScreen;

import android.app.Activity;
import android.content.Intent;
import android.graphics.drawable.Drawable;
import android.os.Bundle;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import com.google.android.maps.GeoPoint;
import com.google.android.maps.MapActivity;
import com.google.android.maps.MapController;
import com.google.android.maps.MapView;
import com.google.android.maps.MyLocationOverlay;
import com.google.android.maps.Overlay;
import com.google.android.maps.OverlayItem;
import de.android1.overlaymanager.ManagedOverlay;
import java.util.List;


public class MainActivity extends MapActivity
{
    MapView mapView;
    MapController mc;
    GeoPoint p;
    Overlay overlayManager;


    @Override
    protected boolean isRouteDisplayed() {
        return false;


    }

    /** 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);
   mc = mapView.getController();
        String coordinates[] = {"40", "-100"};
        double lat = Double.parseDouble(coordinates[0]);
        double lng = Double.parseDouble(coordinates[1]);

        p = new GeoPoint(
            (int) (lat * 1E6),
            (int) (lng * 1E6));

        mc.animateTo(p);
        mc.setZoom(17);
        mapView.invalidate();

        List<Overlay> mapOverlays = mapView.getOverlays();
 Drawable drawable = this.getResources().getDrawable(R.drawable.marker2);
 HelloItemizedOverlay itemizedoverlay = new HelloItemizedOverlay(drawable,this);
 GeoPoint point = new GeoPoint(30443769,-91158458);
 OverlayItem overlayitem = new OverlayItem(point, "Baton Rouge", "Louisiana");

 GeoPoint point2 = new GeoPoint(17385812,78480667);
 OverlayItem overlayitem2 = new OverlayItem(point2, "Hyderabad", "India");

 itemizedoverlay.addOverlay(overlayitem);
 itemizedoverlay.addOverlay(overlayitem2);

 mapOverlays.add(itemizedoverlay);


 }

    }

ItemizedOverlay.java：

package Food.Pack.HomeScreen;
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 ItemizedOverlay extends ItemizedOverlay<OverlayItem>
{
 private ArrayList<OverlayItem> mOverlays = new ArrayList<OverlayItem>();
 private Context mContext;

 public ItemizedOverlay(Drawable defaultMarker, Context context)
 {
 super(boundCenterBottom(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;
 }
}