如何从java文件更改XML按钮属性？

I am attempting to change the text displayed on a button from my java file, and am not having much luck. After searching for awhile on various forums, and doing google searches, I have learned to create a new button and then use button.setText. However, after my application would suddenly end, displaying a message about being forced to quit, I decided to do some debugging. I found the problem to be in this Java class.I am attempting to change the text displayed on