上一篇文章自定义viewgroup（3）地址：//www.jb51.net/article/100618.htm
代码：
package com.example.libingyuan.horizontallistview.ScrollViewGroup;
import android.content.Context;
import android.util.AttributeSet;
import android.util.DisplayMetrics;
import android.view.MotionEvent;
import android.view.VelocityTracker;
import android.view.View;
import android.view.ViewConfiguration;
import android.view.ViewGroup;
import android.view.WindowManager;
import android.widget.Scroller;
public class ScrollViewGroup extends ViewGroup {
//滚动计算辅助类
private Scroller mScroller;
//手指落点的X坐标
private float mLastMotionX = 0;
//屏幕宽度
private int screenWidth;
//手指加速度辅助类
private VelocityTracker mVelocityTracker;
//每秒移动的最小dp
private int mMinimumVelocity;
//每秒移动的最大dp
private int mMaximumVelocity;
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) {
//初始化辅助类
mScroller = new Scroller(context);
//获取屏幕宽度
WindowManager manager = (WindowManager) context
.getSystemService(Context.WINDOW_SERVICE);
DisplayMetrics outMetrics = new DisplayMetrics();
manager.getDefaultDisplay().getMetrics(outMetrics);
screenWidth = outMetrics.widthPixels;
//获取最小和最大的移动距离
final ViewConfiguration configuration = ViewConfiguration.get(context);
mMinimumVelocity = configuration.getScaledMinimumFlingVelocity();
mMaximumVelocity = configuration.getScaledMaximumFlingVelocity();
}
@Override
public void computeScroll() {
//判断滚动时候停止
if (mScroller.computeScrollOffset()) {
//滚动到指定的位置
scrollTo(mScroller.getCurrX(), mScroller.getCurrY());
//这句话必须写，否则不能实时刷新
postInvalidate();
}
}
@Override
public boolean onTouchEvent(MotionEvent event) {
// TODO Auto-generated method stub
int action = event.getAction();
//获取现在手指所在的位置的x坐标
float x = event.getX();
//判断触发的时间
switch (action) {
//按下事件
case MotionEvent.ACTION_DOWN:
//初始化或服用加速度测试器
initOrResetVelocityTracker();
//测试器添加按下事件
mVelocityTracker.addMovement(event);
//如果停止滚动则取消动画（即手指按下就停止滚动）
if (!mScroller.isFinished()) {
mScroller.abortAnimation();
}
//获取现在的x坐标
mLastMotionX = event.getX();
break;
//移动事件
case MotionEvent.ACTION_MOVE:
//测试器添加移动事件
if (mVelocityTracker != null) {
mVelocityTracker.addMovement(event);
}
//计算移动的偏移量
float delt = mLastMotionX - x;
//重置手指位置
mLastMotionX = x;
//滚动
scrollBy((int) delt, 0);
break;
//手指抬起事件
case MotionEvent.ACTION_UP:
//测试器添加抬起事件
mVelocityTracker.addMovement(event);
//添加加速度的测试时间，这里是测量1000毫秒内的加速度
mVelocityTracker.computeCurrentVelocity(1000, mMaximumVelocity);
//获取x方向加速度
float pxsec = mVelocityTracker.getXVelocity();
//得到最后一个子View
View lastChild = getChildAt(getChildCount() - 1);
//获取滑动的最大滑动距离（最后一个Child的右边框的坐标减去屏幕的宽度）
int finalyChild = (int) (lastChild.getX() + lastChild.getWidth() - screenWidth);
//如果x的加速度大于系统设定的最小移动距离，就可以惯性滑动
if (Math.abs(pxsec) > mMinimumVelocity)
mScroller.fling(getScrollX(), 0, (int) -pxsec, 0, 0, finalyChild, 0, 0);
//如果滑动的距离小于第一个控件的最左边（0）则回弹至（0,0）点
if (getScrollX() < 0) {
scrollTo(0, 0);
}
//如果滑动的距离大于最大可滑动距离则滑动到最后一个子View
if (getScrollX() >= finalyChild)
scrollTo(finalyChild, 0);
//刷新界面
invalidate();
//清空测试器
recycleVelocityTracker();
break;
default:
break;
}
return true;
}
private void initOrResetVelocityTracker() {
if (mVelocityTracker == null) {
mVelocityTracker = VelocityTracker.obtain();
} else {
mVelocityTracker.clear();
}
}
private void recycleVelocityTracker() {
if (mVelocityTracker != null) {
mVelocityTracker.recycle();
mVelocityTracker = null;
}
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
//重新设置宽高
this.setMeasuredDimension(measureWidth(widthMeasureSpec, heightMeasureSpec), measureHeight(widthMeasureSpec, heightMeasureSpec));
}
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;
}
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;//子View左边的间距
int childWidth;//子View的宽度
int height = getHeight();//屏幕的宽度
int childCount = getChildCount();//子View的数量
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);
}
}
