Android自定义ViewGroup实现淘宝商品详情页

package com.mcoy.snapscrollview; import android.content.Context;import android.util.AttributeSet;import android.util.Log;import android.view.MotionEvent;import android.view.VelocityTracker;import android.view.View;import android.view.ViewConfiguration;import android.view.ViewGroup;import android.widget.Scroller; /** * @author jiangxinxing---mcoy in English *  * 了解此ViewGroup之前， 有两点一定要做到心中有数 * 一个是对Scroller的使用， 另一个是对onInterceptTouchEvent和onTouchEvent要做到很熟悉 * 以下几个网站可以做参考用 * http://blog.csdn.net/bigconvience/article/details/26697645 * http://blog.csdn.net/androiddevelop/article/details/8373782 * http://blog.csdn.net/xujainxing/article/details/8985063 */public class McoySnapPageLayout extends ViewGroup {   。。。。   public interface McoySnapPage { /** * 返回page根节点 *  * @return */ View getRootView();  /** * 是否滑动到最顶端 * 第二页必须自己实现此方法，来判断是否已经滑动到第二页的顶部 * 并决定是否要继续滑动到第一页 */ boolean isAtTop();  /** * 是否滑动到最底部 * 第一页必须自己实现此方法，来判断是否已经滑动到第二页的底部 * 并决定是否要继续滑动到第二页 */ boolean isAtBottom(); }  public interface PageSnapedListener {  /** * @mcoy * 当从某一页滑动到另一页完成时的回调函数 */ void onSnapedCompleted(int derection); }   。。。。。。  /** * 设置上下页面 * @param pageTop * @param pageBottom */ public void setSnapPages(McoySnapPage pageTop, McoySnapPage pageBottom) { mPageTop = pageTop; mPageBottom = pageBottom; addPagesAndRefresh(); }  private void addPagesAndRefresh() { // 设置页面id mPageTop.getRootView().setId(0); mPageBottom.getRootView().setId(1); addView(mPageTop.getRootView()); addView(mPageBottom.getRootView()); postInvalidate(); }  /** * @mcoy add * computeScroll方法会调用postInvalidate()方法， 而postInvalidate()方法中系统 * 又会调用computeScroll方法， 因此会一直在循环互相调用， 循环的终结点是在computeScrollOffset() * 当computeScrollOffset这个方法返回false时，说明已经结束滚动。 *  * 重要：真正的实现此view的滚动是调用scrollTo(mScroller.getCurrX(), mScroller.getCurrY()); */ @Override public void computeScroll() { //先判断mScroller滚动是否完成 if (mScroller.computeScrollOffset()) { if (mScroller.getCurrY() == (mScroller.getFinalY())) { if (mNextDataIndex > mDataIndex) {  mFlipDrection = FLIP_DIRECTION_DOWN;  makePageToNext(mNextDataIndex); } else if (mNextDataIndex < mDataIndex) {  mFlipDrection = FLIP_DIRECTION_UP;  makePageToPrev(mNextDataIndex); }else{  mFlipDrection = FLIP_DIRECTION_CUR; } if(mPageSnapedListener != null){  mPageSnapedListener.onSnapedCompleted(mFlipDrection); } } //这里调用View的scrollTo()完成实际的滚动 scrollTo(mScroller.getCurrX(), mScroller.getCurrY()); //必须调用该方法，否则不一定能看到滚动效果 postInvalidate(); } }  private void makePageToNext(int dataIndex) { mDataIndex = dataIndex;  mCurrentScreen = getCurrentScreen(); }  private void makePageToPrev(int dataIndex) { mDataIndex = dataIndex;  mCurrentScreen = getCurrentScreen(); }  public int getCurrentScreen() { for (int i = 0; i < getChildCount(); i++) { if (getChildAt(i).getId() == mDataIndex) { return i; } } return mCurrentScreen; }  public View getCurrentView() { for (int i = 0; i < getChildCount(); i++) { if (getChildAt(i).getId() == mDataIndex) { return getChildAt(i); } } return null; }  /* * (non-Javadoc) *  * @see * android.view.ViewGroup#onInterceptTouchEvent(android.view.MotionEvent) * 重写了父类的onInterceptTouchEvent()，主要功能是在onTouchEvent()方法之前处理 * touch事件。包括：down、up、move事件。 * 当onInterceptTouchEvent()返回true时进入onTouchEvent()。 */ @Override public boolean onInterceptTouchEvent(MotionEvent ev) { final int action = ev.getAction(); if ((action == MotionEvent.ACTION_MOVE) && (mTouchState != TOUCH_STATE_REST)) { return true; } final float x = ev.getX(); final float y = ev.getY();  switch (action) { case MotionEvent.ACTION_MOVE: // 记录y与mLastMotionY差值的绝对值。   // yDiff大于gapBetweenTopAndBottom时就认为界面拖动了足够大的距离，屏幕就可以移动了。 final int yDiff = (int)(y - mLastMotionY); boolean yMoved = Math.abs(yDiff) > gapBetweenTopAndBottom; if (yMoved) { if(MCOY_DEBUG) {  Log.e(TAG, "yDiff is " + yDiff);  Log.e(TAG, "mPageTop.isFlipToBottom() is " + mPageTop.isAtBottom());  Log.e(TAG, "mCurrentScreen is " + mCurrentScreen);  Log.e(TAG, "mPageBottom.isFlipToTop() is " + mPageBottom.isAtTop()); } if(yDiff < 0 && mPageTop.isAtBottom() && mCurrentScreen == 0   || yDiff > 0 && mPageBottom.isAtTop() && mCurrentScreen == 1){  Log.e("mcoy", "121212121212121212121212");  mTouchState = TOUCH_STATE_SCROLLING; } } break; case MotionEvent.ACTION_DOWN: // Remember location of down touch mLastMotionY = y; Log.e("mcoy", "mScroller.isFinished() is " + mScroller.isFinished()); mTouchState = mScroller.isFinished() ? TOUCH_STATE_REST  : TOUCH_STATE_SCROLLING; break; case MotionEvent.ACTION_CANCEL: case MotionEvent.ACTION_UP: // Release the drag mTouchState = TOUCH_STATE_REST; break; } boolean intercept = mTouchState != TOUCH_STATE_REST; Log.e("mcoy", "McoySnapPageLayout---onInterceptTouchEvent return " + intercept); return intercept; }  /* * (non-Javadoc) *  * @see android.view.View#onTouchEvent(android.view.MotionEvent) * 主要功能是处理onInterceptTouchEvent()返回值为true时传递过来的touch事件 */ @Override public boolean onTouchEvent(MotionEvent ev) { Log.e("mcoy", "onTouchEvent--" + System.currentTimeMillis());  if (mVelocityTracker == null) {   mVelocityTracker = VelocityTracker.obtain();  }  mVelocityTracker.addMovement(ev);   final int action = ev.getAction(); final float x = ev.getX(); final float y = ev.getY(); switch (action) { case MotionEvent.ACTION_DOWN: if (!mScroller.isFinished()) { mScroller.abortAnimation(); } break; case MotionEvent.ACTION_MOVE:  if(mTouchState != TOUCH_STATE_SCROLLING){     // 记录y与mLastMotionY差值的绝对值。     // yDiff大于gapBetweenTopAndBottom时就认为界面拖动了足够大的距离，屏幕就可以移动了。    final int yDiff = (int) Math.abs(y - mLastMotionY);    boolean yMoved = yDiff > gapBetweenTopAndBottom;    if (yMoved) {     mTouchState = TOUCH_STATE_SCROLLING;    }   }   // 手指拖动屏幕的处理   if ((mTouchState == TOUCH_STATE_SCROLLING)) {    // Scroll to follow the motion event    final int deltaY = (int) (mLastMotionY - y);    mLastMotionY = y;    final int scrollY = getScrollY();    if(mCurrentScreen == 0){//显示第一页，只能上拉时使用     if(mPageTop != null && mPageTop.isAtBottom()){     scrollBy(0, Math.max(-1 * scrollY, deltaY));     }    }else{     if(mPageBottom != null && mPageBottom.isAtTop()){     scrollBy(0, deltaY);     }    }   } break; case MotionEvent.ACTION_CANCEL: case MotionEvent.ACTION_UP: // 弹起手指后，切换屏幕的处理 if (mTouchState == TOUCH_STATE_SCROLLING) {  final VelocityTracker velocityTracker = mVelocityTracker;    velocityTracker.computeCurrentVelocity(1000, mMaximumVelocity);    int velocityY = (int) velocityTracker.getYVelocity();    if (Math.abs(velocityY) > SNAP_VELOCITY) {     if( velocityY > 0 && mCurrentScreen == 1 && mPageBottom.isAtTop()){      snapToScreen(mDataIndex-1);     }else if(velocityY < 0 && mCurrentScreen == 0){      snapToScreen(mDataIndex+1);     }else{      snapToScreen(mDataIndex);     }    } else {     snapToDestination();    }    if (mVelocityTracker != null) {     mVelocityTracker.recycle();     mVelocityTracker = null;    } }else{ } mTouchState = TOUCH_STATE_REST; break;  default: break; } return true; }  private void clearOnTouchEvents(){ mTouchState = TOUCH_STATE_REST; if (mVelocityTracker != null) {    mVelocityTracker.recycle();    mVelocityTracker = null;   } }  private void snapToDestination() { // 计算应该去哪个屏 final int flipHeight = getHeight() / 8;    int whichScreen = -1;  final int topEdge = getCurrentView().getTop();   if(topEdge < getScrollY() && (getScrollY()-topEdge) >= flipHeight && mCurrentScreen == 0){   //向下滑动    whichScreen = mDataIndex + 1;  }else if(topEdge > getScrollY() && (topEdge - getScrollY()) >= flipHeight && mCurrentScreen == 1){   //向上滑动   whichScreen = mDataIndex - 1;  }else{   whichScreen = mDataIndex;  }  Log.e(TAG, "snapToDestination mDataIndex = " + mDataIndex);  Log.e(TAG, "snapToDestination whichScreen = " + whichScreen);  snapToScreen(whichScreen); }  private void snapToScreen(int dataIndex) {  if (!mScroller.isFinished())   return;    final int direction = dataIndex - mDataIndex;  mNextDataIndex = dataIndex;  boolean changingScreens = dataIndex != mDataIndex;  View focusedChild = getFocusedChild();  if (focusedChild != null && changingScreens) {   focusedChild.clearFocus();  }  //在这里判断是否已到目标位置~  int newY = 0; switch (direction) { case 1: //需要滑动到第二页 Log.e(TAG, "the direction is 1"); newY = getCurrentView().getBottom(); // 最终停留的位置 break; case -1: //需要滑动到第一页 Log.e(TAG, "the direction is -1"); Log.e(TAG, "getCurrentView().getTop() is "  + getCurrentView().getTop() + " getHeight() is "  + getHeight()); newY = getCurrentView().getTop() - getHeight(); // 最终停留的位置 break; case 0: //滑动距离不够， 因此不造成换页，回到滑动之前的位置 Log.e(TAG, "the direction is 0"); newY = getCurrentView().getTop(); //第一页的top是0， 第二页的top应该是第一页的高度 break; default: break; }  final int cy = getScrollY(); // 启动的位置  Log.e(TAG, "the newY is " + newY + " cy is " + cy);  final int delta = newY - cy; // 滑动的距离，正值是往左滑<—，负值是往右滑—>  mScroller.startScroll(0, cy, 0, delta, Math.abs(delta));  invalidate(); }  }