Maps in TabActivity overlaps each other

Question

I have implemented the TabActivity in which there are 3 tabs. And each tab contains a map view. When I switch the tabs,

The map of one tab is shown on the top of map of other tap.

This is my code for maps inside tabs:

    GoogleMap map;
public void mapshow(String Message,int mapId) {

    // google map start
    SupportMapFragment fragment;
    fragment =(SupportMapFragment)getSupportFragmentManager().findFragmentById(mapId);

    // Getting reference to Google Map
    map = fragment.getMap();

    // Clear all the markers from the Google Map
    map.clear();

    MarkerOptions markerOptions = new MarkerOptions();
    LatLng point = new LatLng(latitude, longitude);

    // Setting position for the marker
    markerOptions.position(point);

    // Setting custom icon for the marker
    markerOptions.icon(BitmapDescriptorFactory
            .fromResource(R.drawable.marker));

    // Setting title for the info window
    markerOptions.title(Message);
    // markerOptions.snippet("Showing a demo map marker.");

    map.setMapType(GoogleMap.MAP_TYPE_NORMAL);

    // Move the camera to the user's location and zoom in!
    map.animateCamera(CameraUpdateFactory.newLatLngZoom(new LatLng(
            latitude, longitude), 14.0f));

    // Adding the marker to the map
    Marker marker = map.addMarker(markerOptions);
    marker.showInfoWindow();
    map.setOnMarkerClickListener(this);
    map.getUiSettings().setZoomControlsEnabled(false);
    // end google

}

So how to hide the previously selected tab's map when I switch the tab?