Android自定义viewgroup可滚动布局 GestureDetector手势监听（5）

这篇效果和上一篇：//www.jb51.net/article/100638.htm的效果是一样的，但是不再在OnTouchEvent中写代码，而是使用系统自带的类GestureDetector来监听手势以及滑动事件等等，它内置了滑动，点击，长按等事件，而且有快速滑动，比较方便，比自己写的细节处理要好。

代码：

package com.example.libingyuan.horizontallistview.ScrollViewGroup;
import android.content.Context;
import android.util.AttributeSet;
import android.util.DisplayMetrics;
import android.view.GestureDetector;
import android.view.MotionEvent;
import android.view.View;
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;
 //屏幕宽度
 private int screenWidth;
 //可以移动的最大距离
 private int mMaxDistance;
 //自定义手势监听类
 private ScrollTouchLisener mTouchLisener;
 //手势监听
 private GestureDetector mDetector;
 
 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;
  //手势指示器初始化
  mTouchLisener = new ScrollTouchLisener();
  mDetector = new GestureDetector(context, mTouchLisener);
 }
 
 @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) {
  mDetector.onTouchEvent(event);
  if (event.getAction() == MotionEvent.ACTION_UP) {
   this.onUp(event);
  }
  return true;
 }
 
 @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);
 }
 
 public boolean onDown(MotionEvent e) {
  //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();
  }
  return false;
 }
 
 public boolean onUp(MotionEvent e) {
  //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);
  mMaxDistance = finalyChild;
  //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();
  return false;
 }
 
 public void onShowPress(MotionEvent e) {
 }
 
 public boolean onSingleTapUp(MotionEvent e) {
  return false;
 }
 
 public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {
  //滚动
  scrollBy((int) distanceX, 0);
  return false;
 }
 // ACTION_DOWN 、长按不滑动
 public void onLongPress(MotionEvent e) {
 }
 
 public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
  mScroller.fling(getScrollX(), 0, (int) -velocityX, 0, 0, mMaxDistance, 0, 0);
  return false;
 }
 
 private class ScrollTouchLisener implements GestureDetector.OnGestureListener {
  //按下事件
  @Override
  public boolean onDown(MotionEvent e) {
   return ScrollViewGroup.this.onDown(e);
  }
  //单击事件
  @Override
  public void onShowPress(MotionEvent e) {
   ScrollViewGroup.this.onShowPress(e);
  }
  //手指抬起事件
  @Override
  public boolean onSingleTapUp(MotionEvent e) {
   return ScrollViewGroup.this.onSingleTapUp(e);
  }
  //滚动事件
  @Override
  public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {
   return ScrollViewGroup.this.onScroll(e1, e2, distanceX, distanceY);
  }
  //长按事件
  @Override
  public void onLongPress(MotionEvent e) {
   ScrollViewGroup.this.onLongPress(e);
  }
  //滑动事件
  @Override
  public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
   return ScrollViewGroup.this.onFling(e1, e2, velocityX, velocityY);
  }
 }
}

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