java - Android smoothScrollToPosition 无法正常工作

Question

我使用此函数滚动到水平回收器 View 内的选定位置。问题是，如果我滚动回收器然后单击某个项目，它不会转到 View 的中心。相反，如果我不滚动回收器，它就会起作用。当我单击某个项目时，我正在使用此方法。该位置是适配器位置。

override fun scrollToSelected(position: Int, isLeftScroll: Boolean) {
if(!isLeftScroll || position == 0) contactRV.layoutManager?.smoothScrollToPosition(contactRV, RecyclerView.State(), position +1)
    else contactRV.layoutManager?.smoothScrollToPosition(contactRV, RecyclerView.State(), position-1)

我应该怎么做才能解决这个问题？

Answer 1

您将通过实现RecyclerView.SmoothScroller的方法onTargetFound(View, State, Action)来实现。

/**
 * Called when the target position is laid out. This is the last callback SmoothScroller
 * will receive and it should update the provided {@link Action} to define the scroll
 * details towards the target view.
 * @param targetView    The view element which render the target position.
 * @param state         Transient state of RecyclerView
 * @param action        Action instance that you should update to define final scroll action
 *                      towards the targetView
 */
abstract protected void onTargetFound(View targetView, State state, Action action);

特别是在 LinearLayoutManager 和 LinearSmoothScroller 中:

public class CenterLayoutManager extends LinearLayoutManager {

    public CenterLayoutManager(Context context) {
        super(context);
    }

    public CenterLayoutManager(Context context, int orientation, boolean reverseLayout) {
        super(context, orientation, reverseLayout);
    }

    public CenterLayoutManager(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) {
        super(context, attrs, defStyleAttr, defStyleRes);
    }

    @Override
    public void smoothScrollToPosition(RecyclerView recyclerView, RecyclerView.State state, int position) {
        RecyclerView.SmoothScroller smoothScroller = new CenterSmoothScroller(recyclerView.getContext());
        smoothScroller.setTargetPosition(position);
        startSmoothScroll(smoothScroller);
    }

    private static class CenterSmoothScroller extends LinearSmoothScroller {

        CenterSmoothScroller(Context context) {
            super(context);
        }

        @Override
        public int calculateDtToFit(int viewStart, int viewEnd, int boxStart, int boxEnd, int snapPreference) {
            return (boxStart + (boxEnd - boxStart) / 2) - (viewStart + (viewEnd - viewStart) / 2);
        }
    }
}