CoordinatorLayout和Behavior和嵌套滑动（

点击 拖动一段距离 抬起

 ......
    case MotionEvent.ACTION_MOVE:
        final int activePointerIndex = MotionEventCompat.findPointerIndex(ev, mActivePointerId);
            if (activePointerIndex == -1) {
                Log.e(TAG, "Invalid pointerId=" + mActivePointerId + " in onTouchEvent");
                break;
            }

            final int y = (int) MotionEventCompat.getY(ev, activePointerIndex);
            int deltaY = mLastMotionY - y;
            if (dispatchNestedPreScroll(0, deltaY, mScrollConsumed, mScrollOffset)) {
                deltaY -= mScrollConsumed[1];
                vtev.offsetLocation(0, mScrollOffset[1]);
                mNestedYOffset += mScrollOffset[1];
            }
            if (!mIsBeingDragged && Math.abs(deltaY) > mTouchSlop) {
                final ViewParent parent = getParent();
                if (parent != null) {
                    parent.requestDisallowInterceptTouchEvent(true);
                }
                mIsBeingDragged = true;
                if (deltaY > 0) {
                    deltaY -= mTouchSlop;
                } else {
                    deltaY += mTouchSlop;
                }
            }
            if (mIsBeingDragged) {
                // Scroll to follow the motion event
                mLastMotionY = y - mScrollOffset[1];

                final int oldY = getScrollY();
                final int range = getScrollRange();
                final int overscrollMode = ViewCompat.getOverScrollMode(this);
                boolean canOverscroll = overscrollMode == ViewCompat.OVER_SCROLL_ALWAYS ||
                        (overscrollMode == ViewCompat.OVER_SCROLL_IF_CONTENT_SCROLLS && range > 0);

                // Calling overScrollByCompat will call onOverScrolled, which
                // calls onScrollChanged if applicable.
                if (overScrollByCompat(0, deltaY, 0, getScrollY(), 0, range, 0, 0, true) 
                    && !hasNestedScrollingParent()) {
                    // Break our velocity if we hit a scroll barrier.
                    mVelocityTracker.clear();
                }
    
                final int scrolledDeltaY = getScrollY() - oldY;
                final int unconsumedY = deltaY - scrolledDeltaY;
                if (dispatchNestedScroll(0, scrolledDeltaY, 0, unconsumedY, mScrollOffset)) {
                    mLastMotionY -= mScrollOffset[1];
                    vtev.offsetLocation(0, mScrollOffset[1]);
                    mNestedYOffset += mScrollOffset[1];
                } else if (canOverscroll) {
                    ensureGlows();
                    final int pulledToY = oldY + deltaY;
                    if (pulledToY < 0) {
                        mEdgeGlowTop.onPull((float) deltaY / getHeight(),
                            MotionEventCompat.getX(ev, activePointerIndex) / getWidth());
                        if (!mEdgeGlowBottom.isFinished()) {
                            mEdgeGlowBottom.onRelease();
                        }
                    } else if (pulledToY > range) {
                        mEdgeGlowBottom.onPull((float) deltaY / getHeight(),
                            1.f - MotionEventCompat.getX(ev, activePointerIndex)
                                / getWidth());
                        if (!mEdgeGlowTop.isFinished()) {
                            mEdgeGlowTop.onRelease();
                        }
                    }
                    if (mEdgeGlowTop != null
                        && (!mEdgeGlowTop.isFinished() || !mEdgeGlowBottom.isFinished())) {
                        ViewCompat.postInvalidateOnAnimation(this);
                    }
                }
            }
            ......
            break;   

第12行dispatchNestedPreScroll(0, deltaY, mScrollConsumed, mScrollOffset)。

    @Override
    public boolean dispatchNestedPreScroll(int dx, int dy, int[] consumed, int[] offsetInWindow) {
        return mChildHelper.dispatchNestedPreScroll(dx, dy, consumed, offsetInWindow);
    } 

mChildHelper.dispatchNestedPreScroll()。

public boolean dispatchNestedPreScroll(int dx, int dy, int[] consumed, int[] offsetInWindow) {
        if (isNestedScrollingEnabled() && mNestedScrollingParent != null) {
            if (dx != 0 || dy != 0) {
                int startX = 0;
                int startY = 0;
                if (offsetInWindow != null) {
                    mView.getLocationInWindow(offsetInWindow);
                    startX = offsetInWindow[0];
                    startY = offsetInWindow[1];
                }

                if (consumed == null) {
                    if (mTempNestedScrollConsumed == null) {
                        mTempNestedScrollConsumed = new int[2];
                    }
                    consumed = mTempNestedScrollConsumed;
                }
                consumed[0] = 0;
                consumed[1] = 0;
                ViewParentCompat.onNestedPreScroll(mNestedScrollingParent, mView, dx, dy, consumed);

                if (offsetInWindow != null) {
                    mView.getLocationInWindow(offsetInWindow);
                    offsetInWindow[0] -= startX;
                    offsetInWindow[1] -= startY;
                }
                return consumed[0] != 0 || consumed[1] != 0;
            } else if (offsetInWindow != null) {
                offsetInWindow[0] = 0;
                offsetInWindow[1] = 0;
            }
        }
        return false;
    }  

mNestedScrollingParent​为空，所以返回false。
再回到onTouchEvent()。当滑动距离达到一定长度后，mIsBeingDragged为true。
scrollView的滚动

overScrollByCompat(0, deltaY, 0, getScrollY(), 0, range, 0,
                            0, true)​ 

之后调dispatchNestedPreScroll(0, deltaY, mScrollConsumed, mScrollOffset)​。

    public boolean dispatchNestedScroll(int dxConsumed, int dyConsumed,
            int dxUnconsumed, int dyUnconsumed, int[] offsetInWindow) {
        if (isNestedScrollingEnabled() && mNestedScrollingParent != null) {
            if (dxConsumed != 0 || dyConsumed != 0 || dxUnconsumed != 0 || dyUnconsumed != 0) {
                int startX = 0;
                int startY = 0;
                if (offsetInWindow != null) {
                    mView.getLocationInWindow(offsetInWindow);
                    startX = offsetInWindow[0];
                    startY = offsetInWindow[1];
                }

                ViewParentCompat.onNestedScroll(mNestedScrollingParent, mView, dxConsumed,
                        dyConsumed, dxUnconsumed, dyUnconsumed);

                if (offsetInWindow != null) {
                    mView.getLocationInWindow(offsetInWindow);
                    offsetInWindow[0] -= startX;
                    offsetInWindow[1] -= startY;
                }
                return true;
            } else if (offsetInWindow != null) {
                // No motion, no dispatch. Keep offsetInWindow up to date.
                offsetInWindow[0] = 0;
                offsetInWindow[1] = 0;
            }
        }
        return false;
    } 

因为mNestedScrollingParent为空，所以什么都没干。
接下来就是ACTION_UP,和前面一样。