RecycleView将指定item滚动到顶部

Recycleview滑动方法

• smoothScrollBy()

/**
 * Animate a scroll by the given amount of pixels along either axis.
 *
 * @param dx Pixels to scroll horizontally
 * @param dy Pixels to scroll vertically
 */
public void smoothScrollBy(@Px int dx, @Px int dy) {
    smoothScrollBy(dx, dy, null);
}

需要提供滑动的距离,具有平滑效果

• smoothScrollToPosition()

/**
 * Starts a smooth scroll to an adapter position.
 * <p>
 * To support smooth scrolling, you must override
 * {@link LayoutManager#smoothScrollToPosition(RecyclerView, State, int)} and create a
 * {@link SmoothScroller}.
 * <p>
 * {@link LayoutManager} is responsible for creating the actual scroll action. If you want to
 * provide a custom smooth scroll logic, override
 * {@link LayoutManager#smoothScrollToPosition(RecyclerView, State, int)} in your
 * LayoutManager.
 *
 * @param position The adapter position to scroll to
 * @see LayoutManager#smoothScrollToPosition(RecyclerView, State, int)
 */
public void smoothScrollToPosition(int position) {
    if (mLayoutSuppressed) {
        return;
    }
    if (mLayout == null) {
        Log.e(TAG, "Cannot smooth scroll without a LayoutManager set. "
                + "Call setLayoutManager with a non-null argument.");
        return;
    }
    mLayout.smoothScrollToPosition(this, mState, position);
}

这个方法只保证指定的item被滑动到屏幕中，意味着自下往上滑的话，可以将指定item置顶，但是如果已经在屏幕中的话，那他就不会起作用，并且如果是自上往下滑的话，则置顶的item就会被滑到底部
具有平滑效果

• scrollToPosition()

/**
 * Convenience method to scroll to a certain position.
 *
 * RecyclerView does not implement scrolling logic, rather forwards the call to
 * {@link RecyclerView.LayoutManager#scrollToPosition(int)}
 * @param position Scroll to this adapter position
 * @see RecyclerView.LayoutManager#scrollToPosition(int)
 */
public void scrollToPosition(int position) {
    if (mLayoutSuppressed) {
        return;
    }
    stopScroll();
    if (mLayout == null) {
        Log.e(TAG, "Cannot scroll to position a LayoutManager set. "
                + "Call setLayoutManager with a non-null argument.");
        return;
    }
    mLayout.scrollToPosition(position);
    awakenScrollBars();
}

没有任何效果的移动到指定position

LayoutManager滑动方法

• scrollToPositionWithOffset

这种方式是定位到指定项如果该项可以置顶就将其置顶显示

参看demo:
实现滚动方案:
https://github.com/z-chu/RecyclerView-Scroll-Sample
平滑滚动方案:
https://github.com/SilentSword2020/RecyclerViewScrollTop