android.support.v4.view.ViewCompat#NestedScrollType ( )源码实例Demo

/**
 * Stop a nested scroll in progress.
 *
 * <p>This is a delegate method. Call it from your {@link android.view.View View} subclass
 * method/{@link android.support.v4.view.NestedScrollingChild2} interface method with the same
 * signature to implement the standard policy.</p>
 */
public void stopNestedScroll(@ViewCompat.NestedScrollType int type) {
    ViewParent parent = getNestedScrollingParentForType(type);
    if (parent != null) {
        ViewParentCompat.onStopNestedScroll(parent, mView, type);
        setNestedScrollingParentForType(type, null);
    }
}
 

public boolean dispatchNestedScroll(int dxConsumed, int dyConsumed,
                                    int dxUnconsumed, int dyUnconsumed, @Nullable int[] offsetInWindow,
                                    @ViewCompat.NestedScrollType int type) {
    if (isNestedScrollingEnabled()) {
        //获取实现了NestedScrollingParent2或NestedScrollingParent的祖辈控件，如果没有则为null
        final ViewParent parent = getNestedScrollingParentForType(type);
        if (parent == null) {
            //没有实现NestedScrollingParent2或NestedScrollingParent的祖辈控件，则不作任何处理
            return false;
        }

        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];
            }

            //将嵌套滑动事件分发给祖辈控件的onNestedScroll方法
            ViewParentCompat.onNestedScroll(parent, mView, dxConsumed,
                    dyConsumed, dxUnconsumed, dyUnconsumed, type);

            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;
}
 

private ViewParent getNestedScrollingParentForType(@ViewCompat.NestedScrollType int type) {
    switch (type) {
        case TYPE_TOUCH:
            return mNestedScrollingParentTouch;
        case TYPE_NON_TOUCH:
            return mNestedScrollingParentNonTouch;
    }
    return null;
}
 

private void setNestedScrollingParentForType(@ViewCompat.NestedScrollType int type, ViewParent p) {
    switch (type) {
        case TYPE_TOUCH:
            mNestedScrollingParentTouch = p;
            break;
        case TYPE_NON_TOUCH:
            mNestedScrollingParentNonTouch = p;
            break;
    }
}
 

public boolean dispatchNestedPreScroll(int dx, int dy, @Nullable int[] consumed,
                                       @Nullable int[] offsetInWindow, @ViewCompat.NestedScrollType int type) {
    if (isNestedScrollingEnabled()) {
        //获取实现了NestedScrollingParent2或NestedScrollingParent的祖辈控件，如果没有则为null
        final ViewParent parent = getNestedScrollingParentForType(type);
        if (parent == null) {
            //没有实现NestedScrollingParent2或NestedScrollingParent的祖辈控件，则不作任何处理
            return false;
        }

        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;

            //将嵌套滑动事件分发给祖辈控件的onNestedPreScroll方法
            ViewParentCompat.onNestedPreScroll(parent, mView, dx, dy, consumed, type);

            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;
}
 

/**
 * Check if this view has a nested scrolling parent view currently receiving events for
 * a nested scroll in progress with the given type.
 *
 * <p>This is a delegate method. Call it from your {@link android.view.View View} subclass
 * method/{@link android.support.v4.view.NestedScrollingChild} interface method with the same
 * signature to implement the standard policy.</p>
 *
 * @return true if this view has a nested scrolling parent, false otherwise
 */
public boolean hasNestedScrollingParent(@ViewCompat.NestedScrollType int type) {
    return getNestedScrollingParentForType(type) != null;
}
 

/**
 * when scrooll, it would call back
 *
 * @param isUp isScroollUp
 * @param dy   child.getTanslationY
 * @param type touch or not touch, TYPE_TOUCH, TYPE_NON_TOUCH
 */
void onScrollChange(boolean isUp, int dy, @ViewCompat.NestedScrollType int type);
 

/**
 * when scrooll, it would call back
 *
 * @param isUp
 * @param dy   child.getTanslationY
 * @param type
 */
void onScrollChange(boolean isUp, int dy, @ViewCompat.NestedScrollType int type);