方形布局SquareLayout

 public class SquareLayout extends RelativeLayout {
     public SquareLayout(Context context, AttributeSet attrs, int defStyle) {
         super(context, attrs, defStyle);
     }

     public SquareLayout(Context context, AttributeSet attrs) {
         super(context, attrs);
     }

     public SquareLayout(Context context) {
         super(context);
     }

     @Override
     protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
         setMeasuredDimension(getDefaultSize(0, widthMeasureSpec),
                 getDefaultSize(0, heightMeasureSpec));
         int childWidthSize = getMeasuredWidth();
         int childHeightSize = getMeasuredHeight();
         // 高度和宽度一样
         heightMeasureSpec = widthMeasureSpec = MeasureSpec.makeMeasureSpec(
                 childWidthSize, MeasureSpec.EXACTLY);
         super.onMeasure(widthMeasureSpec, heightMeasureSpec);
     }
 }