如何在xml中编写此代码？

Question

我如何编写此代码：

protected void onCreate(Bundle savedInstanceState) {
    Display display = getWindowManager().getDefaultDisplay();
    Point screenSize = new Point();
    display.getSize(screenSize);
    Button button1 = (Button)findViewById(R.id.button1);
    LayoutParams params = new LayoutParams(screenSize.x/3-(10*2), screenSize.x/3-(10*2));
    button1.setLayoutParams(params);
}                                    

在xml中？