仿淘宝京东拖拽商品详情页上下滚动黏滞效果

比较常用的效果，有现成的，如此甚好！：）

import android.content.Context;import android.content.res.TypedArray;import android.support.v4.view.ViewCompat;import android.support.v4.view.ViewPager;import android.util.AttributeSet;import android.view.MotionEvent;import android.view.VelocityTracker;import android.view.View;import android.view.ViewConfiguration;import android.view.ViewGroup;import android.view.animation.DecelerateInterpolator;import android.widget.LinearLayout;import android.widget.Scroller;import com.snail.labaffinity.R;import com.snail.labaffinity.adapter.SlideFragmentPagerAdapter;/** * 1 ViewPager+TabLayout as content * 2 FragmentTabHost+Fragment as content * 3 bug :can not assertain which View is inTouch */public class DragScrollDetailsLayout extends LinearLayout {    public interface OnSlideFinishListener {        void onStatueChanged(CurrentTargetIndex status);    }    public enum CurrentTargetIndex {        UPSTAIRS,        DOWNSTAIRS;        public static CurrentTargetIndex valueOf(int index) {            return 1 == index ? DOWNSTAIRS : UPSTAIRS;        }    }    private static final float DEFAULT_PERCENT = 0.3f;    private static final int DEFAULT_DURATION = 400;    private int mMaxFlingVelocity;    private int mMiniFlingVelocity;    private int mDefaultPanel = 0;    private int mDuration = DEFAULT_DURATION;    private float mTouchSlop;    private float mDownMotionY;    private float mDownMotionX;    private float mInitialInterceptY;    public void setPercent(float percent) {        mPercent = percent;    }    private float mPercent = DEFAULT_PERCENT;    /**     * flag for listview or scrollview ,if child overscrolled ,do not judge view region 滚过头了，还是可以滚动     */    private boolean mChildHasScrolled;    private View mUpstairsView;    private View mDownstairsView;    private View mCurrentTargetView;    private Scroller mScroller;    private VelocityTracker mVelocityTracker;    private OnSlideFinishListener mOnSlideDetailsListener;    private CurrentTargetIndex mCurrentViewIndex = CurrentTargetIndex.UPSTAIRS;    public DragScrollDetailsLayout(Context context) {        this(context, null);    }    public DragScrollDetailsLayout(Context context, AttributeSet attrs) {        this(context, attrs, 0);    }    public DragScrollDetailsLayout(Context context, AttributeSet attrs, int defStyleAttr) {        super(context, attrs, defStyleAttr);        TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.DragScrollDetailsLayout, defStyleAttr, 0);        mPercent = a.getFloat(R.styleable.DragScrollDetailsLayout_percent, DEFAULT_PERCENT);        mDuration = a.getInt(R.styleable.DragScrollDetailsLayout_duration, DEFAULT_DURATION);        mDefaultPanel = a.getInt(R.styleable.DragScrollDetailsLayout_default_panel, 0);        a.recycle();        mScroller = new Scroller(getContext(),new DecelerateInterpolator());        mTouchSlop = ViewConfiguration.get(getContext()).getScaledTouchSlop();        mMaxFlingVelocity = ViewConfiguration.get(getContext()).getScaledMaximumFlingVelocity();        mMiniFlingVelocity = ViewConfiguration.get(getContext()).getScaledMinimumFlingVelocity();        setOrientation(VERTICAL);    }    public void setOnSlideDetailsListener(OnSlideFinishListener listener) {        this.mOnSlideDetailsListener = listener;    }    @Override    protected void onFinishInflate() {        super.onFinishInflate();        final int childCount = getChildCount();        if (1 >= childCount) {            throw new RuntimeException("SlideDetailsLayout only accept childs more than 1!!");        }        mUpstairsView = getChildAt(0);        mDownstairsView = getChildAt(1);    }    /**     * requestDisallowInterceptTouchEvent guarantee DragScrollDetailsLayout intercept event as wish     */    @Override    public boolean dispatchTouchEvent(MotionEvent ev) {        requestDisallowInterceptTouchEvent(false);        return super.dispatchTouchEvent(ev);    }    /**     * intercept rules：     * 1. The vertical displacement is larger than the horizontal displacement;     * 2. Panel stauts is UPSTAIRS：  slide up     * 3. Panel status is DOWNSTAIRS：slide down     * 4. child can requestDisallowInterceptTouchEvent();     */    @Override    public boolean onInterceptTouchEvent(MotionEvent ev) {        switch (ev.getActionMasked()) {            case MotionEvent.ACTION_DOWN:                mDownMotionX = ev.getX();                mDownMotionY = ev.getY();                if (mVelocityTracker == null) {                    mVelocityTracker = VelocityTracker.obtain();                }                mVelocityTracker.clear();                mChildHasScrolled=false;                break;            case MotionEvent.ACTION_MOVE:                adjustValidDownPoint(ev);                return checkCanInterceptTouchEvent(ev);            default:                break;        }        return false;    }    @Override    public boolean onTouchEvent(MotionEvent ev) {        switch (ev.getActionMasked()) {            case MotionEvent.ACTION_UP:            case MotionEvent.ACTION_CANCEL:                flingToFinishScroll();                recycleVelocityTracker();                break;            case MotionEvent.ACTION_MOVE:                scroll(ev);                break;            default:                break;        }        return true;    }    private boolean checkCanInterceptTouchEvent(MotionEvent ev) {        final float xDiff = ev.getX() - mDownMotionX;        final float yDiff = ev.getY() - mDownMotionY;        if (!canChildScrollVertically((int) yDiff,ev)) {            mInitialInterceptY = (int) ev.getY();            if (Math.abs(yDiff) > mTouchSlop && Math.abs(yDiff) >= Math.abs(xDiff)                    && !(mCurrentViewIndex == CurrentTargetIndex.UPSTAIRS && yDiff > 0                    || mCurrentViewIndex == CurrentTargetIndex.DOWNSTAIRS && yDiff < 0)) {                return true;            }        }        return false;    }    private void adjustValidDownPoint(MotionEvent event) {        if (mCurrentViewIndex == CurrentTargetIndex.UPSTAIRS && event.getY() > mDownMotionY                || mCurrentViewIndex == CurrentTargetIndex.DOWNSTAIRS && event.getY() < mDownMotionY) {            mDownMotionX = event.getX();            mDownMotionY = event.getY();        }    }    private void scroll(MotionEvent event) {        if (mCurrentViewIndex == CurrentTargetIndex.UPSTAIRS) {            if (getScrollY() <= 0 && event.getY() > mInitialInterceptY) {                mInitialInterceptY = (int) event.getY();            }            scrollTo(0, (int) (mInitialInterceptY - event.getY()));        } else {            if (getScrollY() >= mUpstairsView.getMeasuredHeight() && event.getY() < mInitialInterceptY) {                mInitialInterceptY = (int) event.getY();            }            scrollTo(0, (int) (mInitialInterceptY - event.getY() + mUpstairsView.getMeasuredHeight()));        }        mVelocityTracker.addMovement(event);    }    private void recycleVelocityTracker() {        if (mVelocityTracker != null) {            mVelocityTracker.clear();            mVelocityTracker.recycle();            mVelocityTracker = null;        }    }    /**     * if speed is enough even though offset is not enough go     */    private void flingToFinishScroll() {        final int pHeight = mUpstairsView.getMeasuredHeight();        final int threshold = (int) (pHeight * mPercent);        float scrollY = getScrollY();        if (CurrentTargetIndex.UPSTAIRS == mCurrentViewIndex) {            if (scrollY <= 0) {                scrollY = 0;            } else if (scrollY <= threshold) {                if (needFlingToToggleView()) {                    scrollY = pHeight - getScrollY();                    mCurrentViewIndex = CurrentTargetIndex.DOWNSTAIRS;                } else                    scrollY = -getScrollY();            } else {                scrollY = pHeight - getScrollY();                mCurrentViewIndex = CurrentTargetIndex.DOWNSTAIRS;            }        } else if (CurrentTargetIndex.DOWNSTAIRS == mCurrentViewIndex) {            if (pHeight - scrollY <= threshold) {                if (needFlingToToggleView()) {                    scrollY = -getScrollY();                    mCurrentViewIndex = CurrentTargetIndex.UPSTAIRS;                } else                    scrollY = pHeight - scrollY;            } else if (scrollY < pHeight) {                scrollY = -getScrollY();                mCurrentViewIndex = CurrentTargetIndex.UPSTAIRS;            }        }        mScroller.startScroll(0, getScrollY(), 0, (int) scrollY, mDuration);        if (mOnSlideDetailsListener != null) {            mOnSlideDetailsListener.onStatueChanged(mCurrentViewIndex);        }        postInvalidate();    }    private boolean needFlingToToggleView() {        mVelocityTracker.computeCurrentVelocity(1000, mMaxFlingVelocity);        if (mCurrentViewIndex == CurrentTargetIndex.UPSTAIRS) {            if (-mVelocityTracker.getYVelocity() > mMiniFlingVelocity) {                return true;            }        } else {            if (mVelocityTracker.getYVelocity() > mMiniFlingVelocity) {                return true;            }        }        return false;    }    private View getCurrentTargetView() {        return mCurrentViewIndex == CurrentTargetIndex.UPSTAIRS                ? mUpstairsView : mDownstairsView;    }    @Override    public void computeScroll() {        super.computeScroll();        if (mScroller.computeScrollOffset()) {            scrollTo(0, mScroller.getCurrY());            postInvalidate();        }    }    /***     * 复用已经实现的View，省却了测量布局之类的麻烦     */    @Override    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {        super.onMeasure(widthMeasureSpec, heightMeasureSpec);        measureChildren(widthMeasureSpec, heightMeasureSpec);        setMeasuredDimension(getMeasuredWidth(), getMeasuredHeight());    }    protected boolean canChildScrollVertically(int offSet,MotionEvent ev) {        mCurrentTargetView = getCurrentTargetView();        return canScrollVertically(mCurrentTargetView, -offSet, ev);    }    /***     * judge is event  is in current view     * 判断MotionEvent是否处于View上面     */    protected boolean isTransformedTouchPointInView(MotionEvent ev, View view) {        float x = ev.getRawX();        float y = ev.getRawY();        int[] rect = new int[2];        view.getLocationInWindow(rect);        float localX = x - rect[0];        float localY = y - rect[1];        return localX >= 0 && localX < (view.getRight() - view.getLeft())                && localY >= 0 && localY < (view.getBottom() - view.getTop());    }    /***     * first    can view self  ScrollVertically     * seconde  if View is ViewPager only judge current page     * third    if view is viewgroup check it`s children     */    private boolean canScrollVertically(View view, int offSet, MotionEvent ev) {        if (!mChildHasScrolled && !isTransformedTouchPointInView(ev, view)) {            return false;        }        if (ViewCompat.canScrollVertically(view, offSet)) {            mChildHasScrolled = true;            return true;        }        if (view instanceof ViewPager) {            return canViewPagerScrollVertically((ViewPager) view, offSet, ev);        }        if (view instanceof ViewGroup) {            ViewGroup vGroup = (ViewGroup) view;            for (int i = 0; i < vGroup.getChildCount(); i++) {                if (canScrollVertically(vGroup.getChildAt(i), offSet, ev)) {                    mChildHasScrolled = true;                    return true;                }            }        }        return false;    }    private boolean canViewPagerScrollVertically(ViewPager viewPager, int offset,MotionEvent ev) {        View showView = ((SlideFragmentPagerAdapter) viewPager.getAdapter()).getPrimaryItem();        return showView != null && canScrollVertically(showView, offset, ev);    }    @Override    protected void onScrollChanged(int l, int t, int oldl, int oldt) {        super.onScrollChanged(l, t, oldl, oldt);    }}

<declare-styleable name="DragScrollDetailsLayout">        <!-- float value for indicate the moment of switch panel-->        <attr name="percent" format="float"/>        <!-- how long the animation keep-->        <attr name="duration" format="integer"/>        <!-- default panel to show after init-->        <attr name="default_panel" format="enum">            <enum name="front" value="0"/>            <enum name="behind" value="1"/>        </attr>    </declare-styleable>

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自定义商品详情页
http://blog.csdn.net/qq_22271479/article/details/68490868