Android自定义ViewGroup实现可滚动的横向布局（2）

上一篇文章自定义viewgroup（1）地址：https://www.jb51.net/article/100608.htm

这里直接代码：

package com.example.libingyuan.horizontallistview.ScrollViewGroup;

import android.content.Context;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Scroller;

/**
* 自定义ViewGroup
* 在横向布局的基础上，增加啦滚动效果，但是没有边界限制
*/
public class ScrollViewGroup extends ViewGroup {
 private Scroller mScroller;
 private float mLastMotionX = 0;

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);
   init(context);
 }

private void init(Context context) {
   mScroller = new Scroller(context);
 }

@Override
 public void computeScroll() {
   if (mScroller.computeScrollOffset()) {
     scrollTo(mScroller.getCurrX(), mScroller.getCurrY());
     postInvalidate();
   }
 }

@Override
 public boolean onTouchEvent(MotionEvent event) {
   // TODO Auto-generated method stub
   int action = event.getAction();
   float x = event.getX();
   switch (action) {
     case MotionEvent.ACTION_DOWN:
       if (!mScroller.isFinished()) {
         mScroller.abortAnimation();
       }
       mLastMotionX = event.getX();
       break;
     case MotionEvent.ACTION_MOVE:
       float delt = mLastMotionX - x;
       mLastMotionX = x;
       scrollBy((int) delt, 0);
       break;
     case MotionEvent.ACTION_UP:
       invalidate();
       break;

default:
       break;
   }

return true;
 }

@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);
   int modeWidth = MeasureSpec.getMode(widthMeasureSpec);
   //父控件的宽（wrap_content）
   int width = 0;
   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++) {
     View child = getChildAt(i);
     measureChild(child, widthMeasureSpec, heightMeasureSpec);
     MarginLayoutParams lp = (MarginLayoutParams) child.getLayoutParams();
     int childWidth = child.getMeasuredWidth() + lp.leftMargin + lp.rightMargin;
     width += childWidth;
   }
   return modeWidth == MeasureSpec.EXACTLY ? sizeWidth : width;
 }

/**
  * 测量高度
  */
 private int measureHeight(int widthMeasureSpec, int heightMeasureSpec) {
   //高度
   int sizeHeight = MeasureSpec.getSize(heightMeasureSpec);
   int modeHeight = MeasureSpec.getMode(heightMeasureSpec);
   //父控件的高（wrap_content）
   int height = 0;
   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++) {
     View child = getChildAt(i);
     measureChild(child, widthMeasureSpec, heightMeasureSpec);
     MarginLayoutParams lp = (MarginLayoutParams) child.getLayoutParams();
     int childHeight = child.getMeasuredHeight() + lp.topMargin + lp.bottomMargin;
     height += childHeight;
   }
   height = height / childCount;
   return modeHeight == MeasureSpec.EXACTLY ? sizeHeight : height;
 }

@Override
 protected void onLayout(boolean changed, int l, int t, int r, int b) {
   int childLeft = 0;
   int childWidth;
   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;
     child.layout(childLeft, 0, childLeft + childWidth, height);
     childLeft += childWidth;
   }
 }

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