ExtJs 4 - 在窗口调整大小时调整表单项的大小

I am using ExtJs 4.0.7 and I have just got into a problem. I want to resize the elements in the form(panel) when I resize the window which contains it(or them). It's simple when you don't have columns and You are using an I am using ExtJs 4.0.7 and I have just got into