Keyboard Show Hide Problem

The keyboard event is only attached to native textfield object.

I am having problem in a html textfield in the webview. When I clicked on the html textfield in the webview, the keyboard will show on top of my webview and I am not able to see all the textbox at the bottom of the web.

Is there anyway to detect if the keyboard show up? so I could adjust the height or the position of the webview when the keyboard show or hide?

And how can I know the height of the keyboard?

Thanks