android - 使最后一个 RecyclerView 项填充 RecyclerView 中的空间（如果数据计数为奇数）

Question

到目前为止，我一直在尝试创建一个 recyclerView，但现在我遇到了一个问题。

我需要让它看起来像这样

我需要使它像列表一样网格，但是我无法将它们并排放置。

其次，如果最后一项是“单独”，我需要最后一项来填充两个空格。

有任何想法吗？

Answer 1

我需要让它像列表一样网格

您可以使用RecyclerViewwith来实现它GridLayoutManager。例如，

// Initialize the view
recyclerView=(RecyclerView)findViewById(R.id.recyclerView);
// Here 2 is the number of columns
GridLayoutManager llm = new GridLayoutManager(this, 2);
recyclerView.setLayoutManager(llm);
recyclerView.setHasFixedSize(true);

如果最后一项是“单独”，我需要最后一项来填充两个空格

要自定义网格项，我们可以使用ItemDecoration. 在您的情况下，最后一个项目（如果它是单独的）应该具有父宽度。我们可以通过检查最后一项的位置来实现这一点。

现在，代码：

活动中

recyclerView=(RecyclerView)findViewById(R.id.recyclerView);
GridLayoutManager llm = new GridLayoutManager(this, 2);
recyclerView.setLayoutManager(llm);
recyclerView.setHasFixedSize(true);
recyclerView.addItemDecoration(new GridItemDecoration());
// And set adapter

GridItemDecoration.java

public class GridItemDecoration extends RecyclerView.ItemDecoration
{
    private int mHorizontalSpacing = 10;
    private int mVerticalSpacing = 10;

    @Override
    public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state)
    {
        super.getItemOffsets(outRect, view, parent, state);
        // Only handle the vertical situation
        int position = parent.getChildPosition(view);
        if (parent.getLayoutManager() instanceof GridLayoutManager)
        {
            GridLayoutManager layoutManager = (GridLayoutManager) parent.getLayoutManager();
            int spanCount, column;
            // Check the last item and is alone. Then set the parent's width
            if (position == parent.getAdapter().getItemCount() - 1 && position % 2 == 0)
            {
                spanCount = 1;
                outRect.left = mHorizontalSpacing;
                outRect.right = parent.getWidth() - mHorizontalSpacing;
            }
            else
            {
                spanCount = layoutManager.getSpanCount();
                column = position % spanCount;
                outRect.left = mHorizontalSpacing * (spanCount - column) / spanCount;
                outRect.right = mHorizontalSpacing * (column + 1) / spanCount;
            }

            if (position < spanCount)
            {
                outRect.top = mVerticalSpacing;
            }
            outRect.bottom = mVerticalSpacing;
        }
    }
}

Answer 2

对于设置不同的跨度计数，您可以使用GridLayoutManager标准功能setSpanSizeLookup。

在 Kotlin 中实现最后一项的填充屏幕宽度：

// Count of columns (I set it in integer resources for screen optimisation)
val spanCount = resources.getInteger(R.integer.column_count)

val layoutManager = GridLayoutManager(context, spanCount)
layoutManager.spanSizeLookup = object : SpanSizeLookup() {
    override fun getSpanSize(position: Int): Int {
        val isLastItem = position == adapter.getItemList().lastIndex

        return if (isLastItem) {
            /**
             * Return this for full width of screen.
             * It will be always equal 1, dividing only to avoid numbers in code.
             */
            spanCount / spanCount
        } else {
            // Return this for place item in your column.
            spanCount
        }
    }
}

---

另外，如果你有很多复杂的适配器，你可以使用这个实现，例如：

val spanCount = resources.getInteger(R.integer.column_count_profile)
val layoutManager = GridLayoutManager(context, spanCount)
layoutManager.spanSizeLookup = object : SpanSizeLookup() {
    override fun getSpanSize(position: Int): Int {
        val item = adapter.getItemList().getOrNull(position) ?: return spanCount
        return when (item) {
            is ScreenItem.Header -> spanCount
            is ScreenItem.Status -> spanCount
            is ScreenItem.Progress -> spanCount
            is ScreenItem.Empty -> spanCount
            is ScreenItem.Item -> spanCount / spanCount
            is ScreenItem.Load -> spanCount / spanCount
        }
    }
}

在哪里，里面是这样的ScreenItem：sealed class

sealed class ScreenItem{
    object Header : ScreenItem()
    data class Status(var content: ContentItem) : ScreenItem()
    object Progress : ScreenItem()
    object Empty : ScreenItem()
    data class Item(val content: AnotherContentItem) : ScreenItem()
    object Load : ScreenItem()
}