How to upload files inside WebView?

I have an app that 开发者_如何学Goloads a WebView. Inside the WebView the page that's loaded has a file upload control (html input=file). The button is visible and it says "Choose File", however if you click the button nothing happens. If you are using the default Android browser and load this same page and click the button, it brings up a window letting you choose a file from your gallery, files, etc. Why doesn't it work from the WebView?

I figure I need to override something but I don't know what that might be. Basically I want to be able to upload photos from inside my app just like I can already do from my web app that runs in the browser. The native app/webview version should work the same but clicking the 'Choose File' button doesn't do anything.

Thanks.