如何在GridLayout的RecyclerView项目装饰中跳过第一行？

Question

我正在为GridLayout使用这个ItemDecoration类 - > https://github.com/devunwired/recyclerview-playground/blob/master/app/src/main/java/com/example/android/recyclerplayground/GridDividerDecoration.java

但问题是,我在GridLayout中的第一行是一个图像,我将跨度设置为2.

您可以按照以下屏幕截图查看我的屏幕:

如何跳过第一行,以便ItemDecoration没有在图像上绘制？

下面是我用来添加ItemDecoration的代码: -

mRecyclerView.setHasFixedSize(true);
mLayoutManager = new GridLayoutManager(getActivity(), 2);
mLayoutManager.setSpanSizeLookup(new GridLayoutManager.SpanSizeLookup() {
    @Override
    public int getSpanSize(int position) {
        return position == 0 ? 2 : 1;
    }
});
mRecyclerView.setLayoutManager(mLayoutManager);
mAdapter.setHighlightsCallbacks(this);
mRecyclerView.setAdapter(mAdapter);
mRecyclerView.setItemAnimator(new DefaultItemAnimator());
mRecyclerView.addItemDecoration(new GridDividerDecoration(getActivity()));

我还修改了GridDividerDecoration类中的drawHorizo​​ntal方法,只有当imageview为null但仍无法工作时才绘制:

public void drawHorizontal(Canvas c, RecyclerView parent) {

    final int top = parent.getPaddingTop();
    final int bottom = parent.getHeight() - parent.getPaddingBottom();

    final int childCount = parent.getChildCount();

    for (int i = 0; i < childCount; i++) {
        final View child = parent.getChildAt(i);
        if (child.findViewById(R.id.home_imgHeader) == null) {
            final RecyclerView.LayoutParams params =
                    (RecyclerView.LayoutParams) child.getLayoutParams();
            final int left = child.getRight() + params.rightMargin + mInsets;
            final int right = left + mDivider.getIntrinsicWidth();
            mDivider.setBounds(left, top, right, bottom);
            mDivider.draw(c);
        }
    }
}

有帮助吗？

Answer 1

假设你的项目不单独拥有雄厚的背景（即白色是从父），最简单的解决将是代码从移动onDrawOver()到onDraw()。这将在您的子视图内容下方绘制网格线，并将其隐藏在标题图像下方。

否则，您使用的代码假定网格线始终绘制到视图的顶部drawHorizontal()（注意top是一个永远不会改变的值）。您需要修改该函数以考虑第一个项目的底部并在那里开始绘制。就像是：

public void drawHorizontal(Canvas c, RecyclerView parent) {
    final View topView = parent.findViewHolderForAdapterPosition(0);
    int viewBottom = -1;
    if (topView != null) {
        final RecyclerView.LayoutParams params =
            (RecyclerView.LayoutParams) child.getLayoutParams();
        viewBottom = child.getBottom() + params.bottomMargin + mInsets;
    }

    final int top = viewBottom > parent.getPaddingTop() ? viewBottom : parent.getPaddingTop();
    final int bottom = parent.getHeight() - parent.getPaddingBottom();

    … /* Remaining Code */
}