如何使用Google可视化setSelection（）防止无限循环？

I'm running into a situation using the Google visualization API for charts. When the user clicks on a chart item, it calls an event handler that opens a popup (but in the example below, just does an alert). it works, but only once; after you click on the item, it remains selected and so does not fire the event handler again (which is listening for a 'select' event).I'm running into a situation using the Google v