android应用中怎么利用onLayout()实现一个流式布局

package com.example.my_view;import android.content.Context;import android.util.AttributeSet;import android.view.View;import android.view.ViewGroup;public class FlowLayout extends ViewGroup {  public FlowLayout(Context context) {    super(context);  }  public FlowLayout(Context context, AttributeSet attrs) {    super(context, attrs);  }    @Override  protected void onLayout(boolean changed, int l, int t, int r, int b) {    //获得子控件的数量    int childCount = getChildCount();    //当前子控件的左边坐标    int cl = 0;    //当前子控件的上边坐标    int ct = 0;    //ViewGroup整体宽度    int width = r - l;    //行高    int lineHeight = 0;    //遍历所有子控件    for(int i = 0; i < childCount; i++){      //获取当前控件      View childAt = getChildAt(i);      //获取宽度      int cw = childAt.getMeasuredWidth();      //获取高度      int ch = childAt.getMeasuredHeight();      //当前控件右边      int cr = cl + cw;      //当前控件下边      int cb = ct + ch;      //判断是否换行      if(cr > width){        //如果换行重新计算上下左右地值        cl = 0;        cr = cl + cw;        ct += lineHeight;        cb = ct + ch;        //换行后，第一个控件作为最大行高        lineHeight = ch;      }else{        //如果不换行，需要计算最大高度        lineHeight = Math.max(lineHeight,ch);      }      childAt.layout(cl,ct,cr,cb);      //横向向后移动一个，前面控件的右边作为后面控件的左边      cl = cr;    }  }  @Override  protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {    super.onMeasure(widthMeasureSpec, heightMeasureSpec);    //测量所有子控件    measureChildren(widthMeasureSpec, heightMeasureSpec);  }}