Android :: Resize Based On Orientation.

I need to have my view resize itself based on the orientation. After extensive googling (maybe i was using the wrong terms) I could find nothing telling me how to detect when the orientation was changed. Here is my layout file: how do I have it automatically resize itself? I want each item (the EditText and the WebView) to fill half the screen (not counting the title/notification bars). I set the height to absolute and not wrap_content because wrap_content defaults to 1 line for EditText and nothing for WebView. and fill_parent has the EditText on top of the WebView.