Give it a unique id, then verify if it already exists before creating it, otherwise just show it, something like
function onMenuItemClick() {
var wnd = Ext.getCmp('myUniqueWindow');
if (!wnd) {
wnd = Ext.create('Ext.window.Window', {
id: 'myUniqueWindow',
title: 'Unique Window',
height: 200,
width: 400,
layout: 'fit',
closeAction: 'hide', // This is really important otherwise closing it will destroy the window!
items: { // Let's put an empty grid in just to illustrate fit layout
xtype: 'grid',
border: false,
columns: [{
header: 'Hello World'
}], // One header just for show. There's no data,
store: Ext.create('Ext.data.ArrayStore', {}) // A dummy empty data store
}
});
} else {
wnd.getEl().highlight()
}
wnd.show();
}
You can see a working sample here