相对布局由RelativeLayout代表，是指参考某一控件组件进行摆放，可以通过控制将组件摆放在一个指定组件的上、下、左、右等位置，可以通过各个组件提供的属性完成。(The relative layout is represented by RelativeLayout is the reference of a control component is placed, can control the components will be placed in a specified compo