//①實例一個Scroller,它有三個構造方法如下  //public Scroller (Context context)  //public Scroller (Context context, Interpolator interpolator)//傳入一個時間插值器  //public Scroller (Context context, Interpolator interpolator, boolean flywheel)  Scroller mScroller=new Scroller(context);  //②使用Scroller  //startScroll()傳入一些參數：開始位置，結束位置，開始時間滑動到結束位置的完成時間。  mScrooler.startScroll(int startX,int startY,int endx,int endY,int duration);  invalidate();//在ViewGroup中,invalidate()方法會導致computeScroll()方法的執行  //③在computeScroll()的方法中判斷：mScroller是否結束，如果沒有結束就調用scrollTo()讓view處于正確的位置  @Override  public void computeScroll() {   //computeScrollOffset()判斷是否還在滾動，如果還在滾動,會獲取到某一時刻view應該所在的位置，刷新Scroller中mCurrX，mCurrY的值，并且return true;   if (mScroller.computeScrollOffset()) {    scrollTo(mScroller.getCurrX(), mScroller.getCurrY());    //更新界面    postInvalidate();   }   super.computeScroll();  }

package com.liujian.chart;/** * Scroller練習，一個簡單的ViewPager * @author : liujian * @since : 2017/12/17 */public class ScrollLayout extends ViewGroup { private Scroller mScroller; //當前設備滑動的最小距離 private int mTouchSlop; private int leftBorder;//布局內容的左邊界 private int rightBorder;//布局內容的右邊界 private float mRawXDown; private float mRawXMove; private float mRawXLastMove; public ScrollLayout(Context context) {  super(context);  initView(context); } public ScrollLayout(Context context, @Nullable AttributeSet attrs) {  super(context, attrs);  initView(context); } public ScrollLayout(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {  super(context, attrs, defStyleAttr);  initView(context); } private void initView(Context context) {  mTouchSlop = ViewConfiguration.get(getContext()).getScaledTouchSlop();  mScroller = new Scroller(getContext()); } @Override protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {  super.onMeasure(widthMeasureSpec, heightMeasureSpec);  //為ScrollLayout中的某一個子View給出一個建議的測量大小和測量模式  measureChildren(widthMeasureSpec, heightMeasureSpec); } @Override protected void onLayout(boolean changed, int l, int t, int r, int b) {  int childCount = getChildCount();  for (int i = 0; i < childCount; i++) {   View view = getChildAt(i);   view.layout(i * view.getMeasuredWidth(), 0, (i + 1) * view.getMeasuredWidth(), view.getMeasuredHeight());  }  leftBorder = getChildAt(0).getLeft();  rightBorder = getChildAt(getChildCount() - 1).getRight(); } @Override public boolean onInterceptTouchEvent(MotionEvent ev) {  switch (ev.getAction()) {   case MotionEvent.ACTION_DOWN:    mRawXDown = ev.getRawX();    mRawXLastMove = mRawXDown;    break;   case MotionEvent.ACTION_MOVE:    mRawXMove = ev.getRawX();    mRawXLastMove = mRawXMove;    float distance = Math.abs(mRawXMove - mRawXDown);    //左右滑動時，攔截子view的觸摸事件    if (distance > mTouchSlop) {     return true;    }    break;   case MotionEvent.ACTION_UP:    break;  }  return super.onInterceptTouchEvent(ev); } @SuppressLint("ClickableViewAccessibility") @Override public boolean onTouchEvent(MotionEvent event) {  switch (event.getAction()) {   case MotionEvent.ACTION_MOVE:    mRawXMove = event.getRawX();    int distanceX = (int) (mRawXLastMove - mRawXMove);    //對邊界異常情況的處理    if (getScrollX() + distanceX < leftBorder) {     scrollBy(leftBorder, 0);    }    if (getScrollX() + getWidth() + distanceX > rightBorder) {     scrollBy(rightBorder - getWidth(), 0);    }    scrollBy(distanceX, 0);    mRawXLastMove = mRawXMove;    break;   case MotionEvent.ACTION_UP:    //當前所在的page頁面    int targetIndex = (getScrollX() + getWidth() / 2) / getWidth();    int dx = targetIndex * getWidth() - getScrollX();    Log.i("TAG", "dx: " + dx);    Log.i("TAG", "getScrollX: " + getScrollX());    Log.i("TAG", "getWidth: " + getWidth());    // 第二步，調用startScroll()方法來初始化滾動數據并刷新界面    mScroller.startScroll(getScrollX(), 0, dx, 0);    invalidate();    break;  }  return super.onTouchEvent(event); } @Override public void computeScroll() {  if (mScroller.computeScrollOffset()) {   scrollTo(mScroller.getCurrX(), mScroller.getCurrY());   invalidate();  } }}