The source code

    Ext.onReady(function(){

        var mapwin;
        var button = Ext.get('show-btn');

        button.on('click', function(){
            // create the window on the first click and reuse on subsequent clicks
            if(!mapwin){

                mapwin = new Ext.Window({
                    layout: 'fit',
                    title: 'GMap Window',
                    closeAction: 'hide',
                    width:400,
                    height:400,
                    x: 40,
                    y: 60,
                    items: {
                        xtype: 'gmappanel',
                        region: 'center',
                        zoomLevel: 14,
                        gmapType: 'map',
                        mapConfOpts: ['enableScrollWheelZoom','enableDoubleClickZoom','enableDragging'],
                        mapControls: ['GSmallMapControl','GMapTypeControl','NonExistantControl'],
                        setCenter: {
                            geoCodeAddr: '4 Yawkey Way, Boston, MA, 02215-3409, USA',
                            marker: {title: 'Fenway Park'}
                        },
                        markers: [{
                            lat: 42.339641,
                            lng: -71.094224,
                            marker: {title: 'Boston Museum of Fine Arts'},
                            listeners: {
                                click: function(e){
                                    Ext.Msg.alert('Its fine', 'and its art.');
                                }
                            }
                        },{
                            lat: 42.339419,
                            lng: -71.09077,
                            marker: {title: 'Northeastern University'}
                        }]
                    }
                });

            }

            mapwin.show();

        });

     });