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);
}

@SuppressWarnings("unused")
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
    // For simple implementation, or internal size is always 0.
    // We depend on the container to specify the layout size of
    // our view. We can't really know what it is since we will be
    // adding and removing different arbitrary views and do not
    // want the layout to change as this happens.
    setMeasuredDimension(getDefaultSize(0, widthMeasureSpec), getDefaultSize(0, heightMeasureSpec));

    // Children are just made to fill our space.
    int childWidthSize = getMeasuredWidth();
    int childHeightSize = getMeasuredHeight();
    //高度和宽度一样


    heightMeasureSpec = widthMeasureSpec = MeasureSpec.makeMeasureSpec(childWidthSize, MeasureSpec.EXACTLY);

    super.onMeasure(widthMeasureSpec, heightMeasureSpec);
}

}