scrollBy scrollTo使用方法

在View.java中

 /**     * The offset, in pixels, by which the content of this view is scrolled     * horizontally.该视图相对于起始位置的X轴偏移量     * {@hide}     */    @ViewDebug.ExportedProperty(category = "scrolling")    protected int mScrollX;    /**     * The offset, in pixels, by which the content of this view is scrolled     * vertically.该视图相对于起始位置的Y轴偏移量     * {@hide}     */    @ViewDebug.ExportedProperty(category = "scrolling")    protected int mScrollY;

  /**     * Return the scrolled left position of this view. This is the left edge of     * the displayed part of your view. You do not need to draw any pixels     * farther left, since those are outside of the frame of your view on     * screen.     *     * @return The left edge of the displayed part of your view, in pixels.     */    public final int getScrollX() {        return mScrollX;    }    /**     * Return the scrolled top position of this view. This is the top edge of     * the displayed part of your view. You do not need to draw any pixels above     * it, since those are outside of the frame of your view on screen.     *     * @return The top edge of the displayed part of your view, in pixels.     */    public final int getScrollY() {        return mScrollY;    }

/**     * Set the scrolled position of your view. This will cause a call to     * {@link #onScrollChanged(int, int, int, int)} and the view will be     * invalidated. 当前内容偏移至(x, y)位置     * @param x the x position to scroll to     * @param y the y position to scroll to     */    public void scrollTo(int x, int y) {       //偏移位置发生了变化        if (mScrollX != x || mScrollY != y) {            int oldX = mScrollX;            int oldY = mScrollY;            mScrollX = x;            mScrollY = y;            invalidateParentCaches();            onScrollChanged(mScrollX, mScrollY, oldX, oldY);            if (!awakenScrollBars()) {                invalidate(true);            }        }    }    /**     * Move the scrolled position of your view. This will cause a call to     * {@link #onScrollChanged(int, int, int, int)} and the view will be     * invalidated. 当前内容偏移(x, y)个单位     * @param x the amount of pixels to scroll by horizontally     * @param y the amount of pixels to scroll by vertically     */    public void scrollBy(int x, int y) {        scrollTo(mScrollX + x, mScrollY + y);    }

例如：

1. 

初始布局如下，绿色为LinearLayout,，橘色为TextView，左上为(0,0)点

当调用LinearLayout.scrollTo(100,0)时，相当于滚动条X方向移动到100位置，Y方向不移动，实质LinearLayout中的内容即TextView向左移动，效果如下

2. LinearLayout.scrollBy(100,0)实质也是调用的scrollTo