当 RecyclerView 元素为其高度设置动画时，如何正确绘制 ItemDecoration？

Question

我有一个使用 LinearLayoutManager（垂直）的 RecyclerView。我想要完成的是让项目装饰（全宽和 1px 高）分隔线在视图移动（translationY() 正确处理）以及视图改变其高度时与视图一起动画。在我下面的当前代码中，分隔线将在动画期间跳转到视图底部的未来位置，而不是当前底部。有什么方法可以考虑动画期间物品装饰的高度变化以使动画看起来更好？

我正在通过在 RecyclerView 的适配器上使用 notifyItemChanged() 来更改视图高度。

public class DividerItemDecoration extends RecyclerView.ItemDecoration {
    private Drawable mDivider;

    public DividerItemDecoration(Context context) {
        mDivider = context.getResources().getDrawable(R.drawable.line_divider);
    }

    @Override
    public void onDrawOver(Canvas c, RecyclerView parent, RecyclerView.State state) {
        int right = parent.getWidth();
        int dividerHeight = mDivider.getIntrinsicHeight();

        int childCount = parent.getChildCount();
        for (int i = 0; i < childCount - 1; i++) {
            View child = parent.getChildAt(i);
            View nextChild = parent.getChildAt(i + 1);

            RecyclerView.LayoutParams layoutParams1 =
                    (RecyclerView.LayoutParams) child.getLayoutParams();
            RecyclerView.LayoutParams layoutParams2 =
                    (RecyclerView.LayoutParams) nextChild.getLayoutParams();
            int left = 0;
            if (layoutParams1 != null && layoutParams2 != null) {
                left = Math.min(layoutParams1.leftMargin, layoutParams2.leftMargin);
            }

            int ty = (int) (child.getTranslationY() + 0.5f);
            int top = child.getBottom() + ty;
            int bottom = top + dividerHeight;

            mDivider.setBounds(
                    left,
                    top,
                    right,
                    bottom);
            mDivider.draw(c);
        }
    }
}

Answer 1

我有同样的问题。通过在 onDraw 方法中添加孩子的过渡到计算来解决这个问题，如下所示：

@Override
public void onDraw(Canvas c, RecyclerView parent, RecyclerView.State state) {
    int left = parent.getPaddingLeft();
    int right = parent.getWidth() - parent.getPaddingRight();

    int childCount = parent.getChildCount();
    for (int i = 0; i < childCount - 1; i++) {
        View child = parent.getChildAt(i);
        RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child.getLayoutParams();
        //Here is the trick!
        int top = child.getBottom() + params.bottomMargin  + Math.round(child.getTranslationY());
        int bottom = top + mDivider.getIntrinsicHeight();
        mDivider.setBounds(left, top, right, bottom);
        mDivider.draw(c);
    }
}