Question

I have a map activity which displays the map, I want to add a marker when I touch on the screen ..

This is my Activity …

package com.adhamenaya.android;

import java.util.List;

import android.content.Context;
import android.graphics.drawable.Drawable;
import android.location.Location;
import android.location.LocationListener;
import android.location.LocationManager;
import android.os.Bundle;
import android.view.MotionEvent;
import android.widget.Toast;

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

public class MapApp extends MapActivity {

    private MapView mapView;
    private MapController mapController;
    private LocationManager locationManager;
    private Context context;
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        context=this;
        initLayout();
        initMap();
    }

    private void initLayout(){
         mapView = (MapView) findViewById(R.id.mapview);
         //blueIcon = (Drawable)this.getResources().getDrawable(R.drawable.blueicon);

    }
    private void initMap(){
        mapView.setBuiltInZoomControls(true);
        mapView.setStreetView(true);
        mapController=mapView.getController();
        mapController.setZoom(10);// 1 is world view
        locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
        locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER,0, 0, new GeoUpdateHandler());

    }


    @Override
    protected boolean isRouteDisplayed() {
        // TODO Auto-generated method stub
        return false;
    }

    class GeoUpdateHandler implements LocationListener {

        @Override
        public void onLocationChanged(Location location) {
            int lat=(int)(location.getLatitude()*1E6);
            int lng=(int)(location.getLongitude()*1E6);

            GeoPoint point=new GeoPoint(lat,lng);
            //GeoPoint point = new GeoPoint(19240000,-99120000);

            mapController.animateTo(point);
            mapController.setCenter(point);
            Drawable redIcon = context.getResources().getDrawable(R.drawable.redicon);
            List<Overlay> mapOverlays = mapView.getOverlays();
            MyItemizedOverlay itemizedoverlay = new MyItemizedOverlay(redIcon);
            OverlayItem overlayitem = new OverlayItem(point, "Hello !", "I'm here");
            itemizedoverlay.addOverlay(overlayitem);
            mapOverlays.add(itemizedoverlay);
        }

        @Override
        public void onProviderDisabled(String arg0) {
            // TODO Auto-generated method stub

        }

        @Override
        public void onProviderEnabled(String arg0) {
            // TODO Auto-generated method stub

        }

        @Override
        public void onStatusChanged(String arg0, int arg1, Bundle arg2) {
            // TODO Auto-generated method stub

        }
        public boolean onTouchEvent(MotionEvent event){
            int x=(int)event.getX();
            int y=(int)event.getY();
            Toast.makeText(context, x, Toast.LENGTH_LONG).show();
            GeoPoint point = mapView.getProjection().fromPixels(x, y);

            Drawable redIcon = context.getResources().getDrawable(R.drawable.blueicon);
            List<Overlay> mapOverlays = mapView.getOverlays();
            MyItemizedOverlay itemizedoverlay = new MyItemizedOverlay(redIcon);
            OverlayItem overlayitem = new OverlayItem(point, "New Place", "I clicked here !");
            itemizedoverlay.addOverlay(overlayitem);
            mapOverlays.add(itemizedoverlay);
            return false;
        }

}
}

Edit : This is the class for ItemizedOverlay, where I have implemented onTap() method , but nothing happens …

package com.adhamenaya.android;

import java.util.ArrayList;

import android.app.AlertDialog;
import android.content.Context;
import android.graphics.drawable.Drawable;
import android.view.MotionEvent;
import android.widget.Toast;

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

public class MyItemizedOverlay extends ItemizedOverlay{

    private ArrayList<OverlayItem> mOverlays = new ArrayList<OverlayItem>();
    private Context mContext;
    public MyItemizedOverlay(Drawable defaultMarker) {
          super(boundCenterBottom(defaultMarker));
    }

    public MyItemizedOverlay(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;
    }
     @Override
        public boolean onTouchEvent(MotionEvent event, MapView mapView) {
         int x=(int)event.getX();
            int y=(int)event.getY();
            Toast.makeText(mContext, x, Toast.LENGTH_LONG).show();
            return super.onTouchEvent(event, mapView);
        }


}

Answer 1

Hello, MapView! tutorial covers showing markers on MapView. In the tutorial markers are added as soon as the activity starts, but you can also add markers at later time, for example, when user touches screen. If you try this approach, you’ll likely want to override onTap in your subclass of ItemizedOverlay.

Update:

If you follow the tutorial, you’ll have your own subclass of ItemizedOverlay. onTap is one of its methods. Now that I look at the documentation, unfortunately onTap(GeoPoint p, MapView mapView) is not public or protected so you cannot override it.

What you can do, is have another overlay, solely for detecting taps. Instead of subclassing ItemizedOverlay, subclass Overlay.

private class TapOverlay extends Overlay {
    public boolean onTap(GeoPoint p, MapView mapView) {
        // code that adds item in your ItemizedOverlay
        // goes here

        return true;
    }
}