RecyclerView 项目动画：仅对最初可见的项目进行动画处理

Question

我有以下代码为 RecyclerView 项目设置动画。这很好用，但是如果我向下滚动，它会为所有出现的项目设置动画。

我想要的是类似于 Google Play 音乐应用中的行为，其中动画仅针对最初可见的项目播放。由于没有动画适配器，因此应显示通过滚动可见的项目。知道如何归档此行为吗？

  public class RecyclerViewAnimationAdapter : RecyclerView.Adapter
    {
        private int m_LastPosition = -1;

        public override void OnBindViewHolder(RecyclerView.ViewHolder holder, int position)
        {
            base.OnBindViewHolder(holder, position);

            animateItem(position, holder.ItemView);
        }

        public override void OnViewDetachedFromWindow(Object holder)
        {
            base.OnViewDetachedFromWindow(holder);

            var viewToAnimate = ((RecyclerView.ViewHolder) holder).ItemView;

            viewToAnimate.ClearAnimation();
        }

        private void animateItem(int position, View viewToAnimate)
        {
            if (position > m_LastPosition)
            {
                var animation = AnimationUtils.LoadAnimation(Application.Context, Resource.Animation.slide_in_bottom);

                viewToAnimate.StartAnimation(animation);

                m_LastPosition = position;
            }
        }
    }

Answer 1

我在 Android Studio 中测试了这个方法，它有效，它应该也适用于你，只需稍作调整：

class YourAdapter extends RecyclerView.Adapter{
    private int lastPosition = -1;
    private boolean isAnimation;

    YourAdapter(... )
    {
       ...
       this.isAnimation = true;
    }
    ....


    private void switchAnimation(boolean isAnimation)
    {
        this.isAnimation = isAnimation;
    }


    private void animateItem(int position, View viewToAnimate)
    {
        if (position > m_LastPosition && isAnimation)
        {
            var animation = AnimationUtils.LoadAnimation(Application.Context, Resource.Animation.slide_in_bottom);

            viewToAnimate.StartAnimation(animation);

            lastPosition = position;
        }
    }

}

然后在您的 LayoutManager 中覆盖方法 onLayoutChildren（您必须将代码适应 C#）：

layoutManager = new LinearLayoutManager(this, LinearLayoutManager.VERTICAL, false){
        @Override
        public void onLayoutChildren(RecyclerView.Recycler recycler, RecyclerView.State state) {
            super.onLayoutChildren(recycler, state);
            myAdapter.switchAnimation(false);
        }
    };

如果有帮助，请告诉我 ;)