package com.simple.carpool.view;import android.content.Context;
import android.support.v4.view.GestureDetectorCompat;
import android.support.v4.view.NestedScrollingChild;
import android.support.v4.view.NestedScrollingChildHelper;
import android.support.v4.view.NestedScrollingParent;
import android.support.v4.view.NestedScrollingParentHelper;
import android.support.v4.view.ScrollingView;
import android.support.v4.view.ViewCompat;
import android.support.v4.widget.ScrollerCompat;
import android.util.AttributeSet;
import android.util.Log;
import android.view.GestureDetector;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewGroup;import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;/*** Created by xl on 2016/11/22.*/public class FlingNestedScrollView extends ViewGroup implements NestedScrollingParent, NestedScrollingChild, ScrollingView {private NestedScrollingParentHelper parentHelper;private NestedScrollingChildHelper childHelper;//手势判断private GestureDetectorCompat mGestureDetector;//惯性滑动计算private ScrollerCompat scroller;private View nestedScrollingView;private OnScrollChangeListener listener;private final int[] mScrollConsumed = new int[2];private final int[] mNestedOffsets = new int[2];private int windowOffsetY = 0;private List<View> nestedScrollingChildList = new ArrayList<>();private int currentFlingY = 0;public FlingNestedScrollView(Context context) {this(context, null);}public FlingNestedScrollView(Context context, AttributeSet attrs) {this(context, attrs, 0);}public FlingNestedScrollView(Context context, AttributeSet attrs, int defStyleAttr) {super(context, attrs, defStyleAttr);setOverScrollMode(View.OVER_SCROLL_NEVER);parentHelper = new NestedScrollingParentHelper(this);childHelper = new NestedScrollingChildHelper(this);setNestedScrollingEnabled(true);scroller = ScrollerCompat.create(context);mGestureDetector = new GestureDetectorCompat(getContext(), new MyGestureListener());}public void setOnScrollChangeListener(OnScrollChangeListener listener) {this.listener = listener;}@Overrideprotected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {super.onMeasure(widthMeasureSpec, heightMeasureSpec);View view = getChildAt(0);if (view == null || !(view instanceof ViewGroup)) {throw new IllegalArgumentException("must have one child ViewGroup");}measureChild(view, widthMeasureSpec, heightMeasureSpec);ViewGroup viewGroup = (ViewGroup) view;for (int i = 0; i < viewGroup.getChildCount(); i++) {View child = viewGroup.getChildAt(i);measureChild(child, widthMeasureSpec, heightMeasureSpec);}}@Overrideprotected void onLayout(boolean changed, int l, int t, int r, int b) {View view = getChildAt(0);if (view == null || !(view instanceof ViewGroup)) {throw new IllegalArgumentException("must have one child ViewGroup");}ViewGroup viewGroup = (ViewGroup) view;int parentHeight = getMeasuredHeight();int top = 0;int width = r - l;for (int i = 0; i < viewGroup.getChildCount(); i++) {View child = viewGroup.getChildAt(i);LayoutParams layoutParams = child.getLayoutParams();if (layoutParams.height == LayoutParams.MATCH_PARENT) {layoutParams.height = parentHeight;} else {int childMeasuredHeight = child.getMeasuredHeight();layoutParams.height = childMeasuredHeight;}child.setLayoutParams(layoutParams);child.layout(0, top, width, top + layoutParams.height);top += layoutParams.height;}viewGroup.layout(0, 0, width, top);}@Overrideprotected void onFinishInflate() {super.onFinishInflate();View view = getChildAt(0);if (view == null || !(view instanceof ViewGroup)) {throw new IllegalArgumentException("must have one child ViewGroup");}nestedScrollingChildList.clear();ViewGroup viewGroup = (ViewGroup) view;getAllNestedChildren(viewGroup);Log.i("carpool", "Children count:" + nestedScrollingChildList.size());Collections.sort(nestedScrollingChildList, new SortComparator());}private void onScrollChange(View view, int scroll) {if(listener != null) listener.onScrollChange(view, scroll);}//获取本身滑动高度private int getScrollHeight() {int height = getHeight() - getPaddingTop() - getPaddingBottom();int bottom = getChildAt(0).getHeight();return bottom - height;}//获取所有可以滑动的NestedScrollChildprivate void getAllNestedChildren(ViewGroup viewGroup) {for (int i = 0, len = viewGroup.getChildCount(); i < len; i++) {View child = viewGroup.getChildAt(i);if(ViewCompat.isNestedScrollingEnabled(child) && child instanceof ScrollingView) {nestedScrollingChildList.add(child);} else if(child instanceof ViewGroup) {getAllNestedChildren((ViewGroup) child);}}}//子view是否显示，不显示则不计算private boolean isShownInVertical(View view) {if(!view.isShown()) return false;int[] position = new int[2];view.getLocationOnScreen(position);int screenLeft = position[0];int screenRight = screenLeft + view.getWidth();if(screenRight < getWidth() / 3 || screenLeft > getWidth() / 3 * 2) {return false;}return true;}//滑动子view，如果子view正在滑动则返回，否则会引起循环调用，nestedChild会“歘”一下就滑到底部private void scrollViewYTo(View view, int y) {onScrollChange(view, y);if(view == nestedScrollingView) return;int currentScroll = getViewScrollY(view);view.scrollBy(0, y - currentScroll);}private void scrollViewYBy(View view, int dy) {onScrollChange(view, getViewScrollY(view) + dy);
//        if(view == nestedScrollingView) return;view.scrollBy(0, dy);}private void scrollYTo(int dy) {onScrollChange(this, dy);super.scrollTo(0, dy);}private void scrollYBy(int dy) {int scrollYTo = getScrollY() + dy;onScrollChange(this, scrollYTo);super.scrollBy(0, dy);}//获取view相对于root的坐标private int getYWithView(View view, View parent) {int[] position = new int[2];view.getLocationOnScreen(position);int viewTop = position[1];parent.getLocationOnScreen(position);int parentTop = position[1];return viewTop - parentTop;}//获取view相对于root的topprivate int getTopWithView(View view, View parent) {int parentY = getYWithView(view, parent);return getViewScrollY(parent) + parentY;}//获取子view当前滑动位置private int getViewScrollY(View view) {if(view instanceof ScrollingView) {return ((ScrollingView)view).computeVerticalScrollOffset();} else {return view.getScrollY();}}//------------------------------------scrollBy(因为在滑动过程中，scrollingview不知道自己的最大高度，所以不能使用全局坐标！)----------//全局滑动，包括子scrollingview//true:消费，false：未消费private boolean nestedScrollBy(int dy) {if(dy == 0) return true;int scrollY = getScrollY();int scrollMax = getScrollHeight();//有正在滑动的子viewView currentScrollChild = getCurrentScrollChild(dy);if(currentScrollChild != null) {//如果两者相等，返回false，让其自己消费，以免循环调用//按逻辑来说，还应该判断currentScrollChild是否是nestedScrollingView的子控件//但是子控件的scrollBy好像并不会再次触发onPreNestedScroll,暂未发现bug//所以就先这么写吧if(currentScrollChild == nestedScrollingView) {onScrollChange(currentScrollChild, getViewScrollY(currentScrollChild) + dy);return false;} else {scrollViewYBy(currentScrollChild, dy);return true;}}//将会滑动到子viewView nextScrollChild = getNextScrollChild(dy);if(nextScrollChild != null) {scrollYBy(getYWithView(nextScrollChild, this));return true;}//仅滑动自己if(dy < 0 && scrollY == 0) return false;if(dy > 0 && scrollY == scrollMax) return false;if(scrollY + dy <= 0) scrollYTo(0);else if(scrollY + dy >= scrollMax) scrollYTo(scrollMax);else scrollYBy(dy);return true;}//获取正在滑动的viewprivate View getCurrentScrollChild(int dy) {for(View child: nestedScrollingChildList) {int childY = getYWithView(child, this);if(childY == 0 && isShownInVertical(child)) {if(canScrollVertically(child, dy)) return child;}}return null;}//获取下一个将会自滑动的view//consumed: index0: parentscroll, index1: viewscrollprivate View getNextScrollChild(int dy) {View view = null;int viewY = 0;for(View child: nestedScrollingChildList) {int childY = getYWithView(child, this);if(dy > 0 && childY > 0) {view = child;viewY = childY;break;} else if(dy < 0 && childY < 0) {view  = child;viewY = childY;}}if(view == null) return null;if(!canScrollVertically(view, dy)) return null;if((dy < 0 && dy - viewY < 0) || (dy > 0 && dy - viewY > 0)) {return view;}return null;}//子View是否能够滑动private boolean canScrollVertically(View view, int scrollY) {if(scrollY > 0 && ViewCompat.canScrollVertically(view, 1)) {return true;} else if(scrollY < 0 && ViewCompat.canScrollVertically(view, -1)) {return true;}return false;}//-----------------------------------scrollBy(end)------------------------------------------//惯性滑动private void flingY(int velocityY) {if (getChildCount() > 0) {currentFlingY = 0;scroller.fling(0, 0, 0, velocityY, 0, 0, Integer.MIN_VALUE,Integer.MAX_VALUE);invalidate();}}@Overridepublic void computeScroll() {if (scroller.computeScrollOffset()) {int y = scroller.getCurrY();nestedScrollBy(y - currentFlingY);currentFlingY = y;invalidate();}}@Overridepublic void scrollBy(int x, int y) {nestedScrollBy(y);}//---------------------------NestedScrollParent----------------------------------
    @Overridepublic boolean onStartNestedScroll(View child, View target, int nestedScrollAxes) {Log.i("carpool", "start");if(!nestedScrollingChildList.contains(target)) {onFinishInflate();}nestedScrollingView = target;scroller.abortAnimation();return (nestedScrollAxes & SCROLL_AXIS_VERTICAL) != 0;}@Overridepublic void onNestedScrollAccepted(View child, View target, int nestedScrollAxes) {Log.i("carpool", "accept");parentHelper.onNestedScrollAccepted(child, target, nestedScrollAxes);}@Overridepublic void onStopNestedScroll(View target) {Log.i("carpool", "stop");if(nestedScrollingView == target) nestedScrollingView = null;parentHelper.onStopNestedScroll(target);}@Overridepublic void onNestedScroll(View target, int dxConsumed, int dyConsumed, int dxUnconsumed, int dyUnconsumed) {}@Overridepublic void onNestedPreScroll(View target, int dx, int dy, int[] consumed) {boolean isConsumed = nestedScrollBy(dy);if(isConsumed) {consumed[0] = 0;consumed[1] = dy;}}@Overridepublic boolean onNestedFling(View target, float velocityX, float velocityY, boolean consumed) {return false;}@Overridepublic boolean onNestedPreFling(View target, float velocityX, float velocityY) {Log.i("carpool", "fling");flingY((int) velocityY);return true;}@Overridepublic int getNestedScrollAxes() {return parentHelper.getNestedScrollAxes();}//---------------------------NestedScrollParent(End)-----------------------------//---------------------------NestedScrollChild----------------------------------
@Overridepublic void setNestedScrollingEnabled(boolean enabled) {childHelper.setNestedScrollingEnabled(enabled);}@Overridepublic boolean isNestedScrollingEnabled() {return childHelper.isNestedScrollingEnabled();}@Overridepublic boolean startNestedScroll(int axes) {return childHelper.startNestedScroll(axes);}@Overridepublic void stopNestedScroll() {childHelper.stopNestedScroll();}@Overridepublic boolean hasNestedScrollingParent() {return childHelper.hasNestedScrollingParent();}@Overridepublic boolean dispatchNestedScroll(int dxConsumed, int dyConsumed, int dxUnconsumed, int dyUnconsumed, int[] offsetInWindow) {return childHelper.dispatchNestedScroll(dxConsumed, dyConsumed, dxUnconsumed, dyUnconsumed, offsetInWindow);}@Overridepublic boolean dispatchNestedPreScroll(int dx, int dy, int[] consumed, int[] offsetInWindow) {return childHelper.dispatchNestedPreScroll(dx, dy, consumed, offsetInWindow);}@Overridepublic boolean dispatchNestedFling(float velocityX, float velocityY, boolean consumed) {return childHelper.dispatchNestedFling(velocityX, velocityY, consumed);}@Overridepublic boolean dispatchNestedPreFling(float velocityX, float velocityY) {return childHelper.dispatchNestedPreFling(velocityX, velocityY);}//---------------------------NestedScrollChild(End)-----------------------------//---------------------------ScrollingView---------------------------
    @Overridepublic int computeHorizontalScrollRange() {return 0;}public int computeHorizontalScrollOffset() {return 0;}public int computeHorizontalScrollExtent() {return 0;}public int computeVerticalScrollRange() {return getChildAt(0).getHeight();}public int computeVerticalScrollOffset() {return getScrollY();}public int computeVerticalScrollExtent() {return getHeight() - getPaddingTop() - getPaddingBottom();}//--------------------------ScrollingView(End)------------------------------
@Overridepublic boolean onTouchEvent(MotionEvent event) {event.offsetLocation(0, windowOffsetY);mGestureDetector.onTouchEvent(event);if(event.getAction() == MotionEvent.ACTION_UP) {windowOffsetY = 0;stopNestedScroll();}return true;}private class MyGestureListener implements GestureDetector.OnGestureListener {@Overridepublic boolean onDown(MotionEvent e) {scroller.abortAnimation();startNestedScroll(ViewCompat.SCROLL_AXIS_VERTICAL);windowOffsetY = 0;return true;}@Overridepublic void onShowPress(MotionEvent e) {}@Overridepublic boolean onSingleTapUp(MotionEvent e) {return false;}@Overridepublic boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {int dx = (int) distanceX;int dy = (int) distanceY;dispatchNestedPreScroll(dx, dy, mScrollConsumed, mNestedOffsets);windowOffsetY += mNestedOffsets[1];dy -= mScrollConsumed[1];if(dy == 0) return true;else nestedScrollBy(dy);return true;}@Overridepublic void onLongPress(MotionEvent e) {}@Overridepublic boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {if(!dispatchNestedPreFling(-velocityX, -velocityY)) {dispatchNestedFling(-velocityX, -velocityY, true);flingY((int) -velocityY);}return true;}}public class SortComparator implements Comparator<View> {@Overridepublic int compare(View lhs, View rhs) {return getTopWithView(lhs, FlingNestedScrollView.this) - getTopWithView(rhs, FlingNestedScrollView.this);}}public interface OnScrollChangeListener {void onScrollChange(View view, int scroll);}
}