Android自定义ViewGroup横向布局（1）

package com.example.libingyuan.horizontallistview.ScrollViewGroup;

import android.content.Context;
import android.util.AttributeSet;
import android.view.View;
import android.view.ViewGroup;

/**
 * 自定义ViewGroup
 * 很简单的横向布局，把所有的子View都横着排列起来，不可滚动
 */
public class ScrollViewGroup extends ViewGroup{
  public ScrollViewGroup(Context context) {
    this(context,null);
  }

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

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

  @Override
  protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
    //重新设置宽高
    this.setMeasuredDimension(measureWidth(widthMeasureSpec,heightMeasureSpec),measureHeight(widthMeasureSpec,heightMeasureSpec));
  }
   /**
   * 测量宽度
   */
  private int measureWidth(int widthMeasureSpec, int heightMeasureSpec) {
    // 宽度
    int sizeWidth = MeasureSpec.getSize(widthMeasureSpec);
    //宽度的类型
    int modeWidth = MeasureSpec.getMode(widthMeasureSpec);
    //父控件的宽（wrap_content）
    int width = 0;
    //子View的个数
    int childCount = getChildCount();

    //重新测量子view的宽度，以及最大高度
    for (int i = 0; i < childCount; i++) {
      //获取子View
      View child = getChildAt(i);
      //测量子View，无论什么模式，这句必须有否则界面不显示子View（一片空白）
      measureChild(child, widthMeasureSpec, heightMeasureSpec);
      //得到子View的边距
      MarginLayoutParams lp = (MarginLayoutParams) child.getLayoutParams();
      //得到宽度
      int childWidth = child.getMeasuredWidth() + lp.leftMargin + lp.rightMargin;
      //宽度累加
      width += childWidth;
    }
    //返回宽度
    return modeWidth == MeasureSpec.EXACTLY ? sizeWidth : width;
  }

  /**
   * 测量高度
   */
  private int measureHeight(int widthMeasureSpec, int heightMeasureSpec) {
    //高度
    int sizeHeight = MeasureSpec.getSize(heightMeasureSpec);
    //高度的模式
    int modeHeight = MeasureSpec.getMode(heightMeasureSpec);
    //父控件的高（wrap_content）
    int height = 0;
    //子View的个数
    int childCount = getChildCount();

    //重新测量子view的宽度，以及最大高度
    for (int i = 0; i < childCount; i++) {
      //得到子View
      View child = getChildAt(i);
      //测量
      measureChild(child, widthMeasureSpec, heightMeasureSpec);
      //得到边距
      MarginLayoutParams lp = (MarginLayoutParams) child.getLayoutParams();
      //得到高度
      int childHeight = child.getMeasuredHeight() + lp.topMargin + lp.bottomMargin;
      //累加高度
      height += childHeight;
    }
    //求平均高度
    height = height / childCount;
    //返回高度
    return modeHeight == MeasureSpec.EXACTLY ? sizeHeight : height;
  }

  @Override
  protected void onLayout(boolean changed, int l, int t, int r, int b) {
    int childLeft=0;//子View左边的距离
    int childWidth;//子View的宽度
    int height=getHeight();
    int childCount=getChildCount();
    for (int i = 0; i < childCount; i++) {
      View child=getChildAt(i);
      MarginLayoutParams lp= (MarginLayoutParams) child.getLayoutParams();
      childWidth=child.getMeasuredWidth()+lp.leftMargin+lp.rightMargin;
      //最主要的一句话
      child.layout(childLeft,0,childLeft+childWidth,height);
      childLeft+=childWidth;
    }
  }

  @Override
  public LayoutParams generateLayoutParams(AttributeSet attrs) {
    return new MarginLayoutParams(getContext(),attrs);
  }
}