流失布局

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

public MyViewSelect(Context context, AttributeSet attrs) {
    this(context, attrs, 0);
}

public MyViewSelect(Context context, AttributeSet attrs, int defStyleAttr) {
    super(context, attrs, defStyleAttr);
}

@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
    //测量所有孩子的宽高
    measureChildren(widthMeasureSpec, heightMeasureSpec);
    //最大的宽度，也就是FlowLayout父布局的宽度
    int widthSize = MeasureSpec.getSize(widthMeasureSpec);
    int widthMode = MeasureSpec.getMode(widthMeasureSpec);
    int heightSize = MeasureSpec.getSize(heightMeasureSpec);
    int heightMode = MeasureSpec.getMode(heightMeasureSpec);

    int width = 0;
    int height = 0;
    int lineWidth = 0;
    int lineHeight = 0;
    int totalHeight = 0;
    View childView;
    int childWidth = 0;
    int childHeight = 0;

    for (int i = 0; i < getChildCount(); i++) {
        childView = getChildAt(i);
        childWidth = childView.getMeasuredWidth();

        if (childWidth > widthSize) {
            throw new IllegalArgumentException("子view宽度不能大于FlowLayout宽度");
        }

        childHeight = childView.getMeasuredHeight();
        if (lineWidth + childWidth > widthSize) {
            //换行width就是最大宽,只要又换行的情况出现，说明流式布局的宽度已经不够用了
            width = widthSize;
            //totalHeight不包含最后一行高度
            int preLineHeight = lineHeight;
            totalHeight += preLineHeight;
            lineHeight = childHeight;
            lineWidth = childWidth;

        } else {
            //不换行
            lineWidth += childWidth;
            //当前行的高度
            lineHeight = Math.max(lineHeight, childHeight);

            //假如只有一行，那测量的宽度就是当前行宽,如果又换行那就去最大宽
            width = Math.max(width, lineWidth);
        }

        //当结束遍历的时候要加上最后一行的高度
        if (i == getChildCount() - 1) {
            totalHeight += lineHeight;
            height = totalHeight;
        }

    }

    width = widthMode == MeasureSpec.EXACTLY ? widthSize : width;
    height = heightMode == MeasureSpec.EXACTLY ? heightSize : height;

    //确定最终测量的宽高
    setMeasuredDimension(width, height);
}

@Override
protected void onLayout(boolean changed, int l, int t, int r, int b) {
    int lineWidth = 0;
    int lineHeight = 0;
    int totalHeight = 0;
    View childView;
    int childWidth = 0;
    int childHeight = 0;

    for (int i = 0; i < getChildCount(); i++) {
        childView = getChildAt(i);
        childWidth = childView.getMeasuredWidth();
        childHeight = childView.getMeasuredHeight();
        if (lineWidth + childWidth > getMeasuredWidth()) {
            //换行
            //totalHeight不包含最后一行高度
            totalHeight += childHeight;
            lineWidth = 0;
            layoutChildView(childView, lineWidth, totalHeight, lineWidth + childWidth, totalHeight + childHeight);

            //换行width就是最大宽
            lineHeight = childHeight;
            lineWidth = childWidth;
        } else {
            //不换行
            layoutChildView(childView, lineWidth, totalHeight, lineWidth + childWidth, totalHeight + childHeight);
            lineWidth += childWidth;
            //当前行的高度
            lineHeight = Math.max(lineHeight, childHeight);
        }
    }

}

public void layoutChildView(View child, int l, int t, int r, int b) {
    child.layout(l, t, r, b);
}