android gridlayout 分割线

要为 Android GridLayout 添加分割线，可以通过创建自定义的 GridItemDecoration 类来实现。这个类需要继承自 RecyclerView.ItemDecoration，然后重写其中的 onDraw() 和 getItemOffsets() 方法。

下面是一个示例代码，可以为 GridLayout 添加水平和垂直方向的分割线：

public class GridItemDecoration extends RecyclerView.ItemDecoration {
    private int horizontalSpacing;
    private int verticalSpacing;
    private Paint dividerPaint;

    public GridItemDecoration(int horizontalSpacing, int verticalSpacing, int dividerColor) {
        this.horizontalSpacing = horizontalSpacing;
        this.verticalSpacing = verticalSpacing;
        dividerPaint = new Paint();
        dividerPaint.setColor(dividerColor);
        dividerPaint.setStyle(Paint.Style.FILL);
    }

    @Override
    public void onDraw(Canvas c, RecyclerView parent, RecyclerView.State state) {
        int childCount = parent.getChildCount();
        int rowCount = parent.getAdapter().getItemCount() / parent.getChildCount();
        int lastRowChildCount = parent.getAdapter().getItemCount() % parent.getChildCount();

        for (int i = 0; i < childCount; i++) {
            View child = parent.getChildAt(i);
            int childAdapterPosition = parent.getChildAdapterPosition(child);
            int row = childAdapterPosition / rowCount;
            int column = childAdapterPosition % rowCount;

            if (row != 0) { // 绘制垂直方向的分割线
                int left = child.getLeft() - horizontalSpacing / 2;
                int right = child.getRight() + horizontalSpacing / 2;
                int top = child.getTop() - verticalSpacing;
                int bottom = child.getTop();
                c.drawRect(left, top, right, bottom, dividerPaint);
            }

            if (column != 0) { // 绘制水平方向的分割线
                int left = child.getLeft() - horizontalSpacing;
                int right = child.getLeft();
                int top = child.getTop() - verticalSpacing / 2;
                int bottom = child.getBottom() + verticalSpacing / 2;
                c.drawRect(left, top, right, bottom, dividerPaint);
            }

            // 绘制右边和底部的边框
            if (column == rowCount - 1 && lastRowChildCount == 0) {
                int left = child.getRight() - horizontalSpacing / 2;
                int right = child.getRight() + horizontalSpacing / 2;
                int top = child.getTop() - verticalSpacing;
                int bottom = child.getBottom() + verticalSpacing;
                c.drawRect(left, top, right, bottom, dividerPaint);
            }
            if (row == parent.getAdapter().getItemCount() / rowCount - 1) {
                int left = child.getLeft() - horizontalSpacing;
                int right = child.getRight() + horizontalSpacing;
                int top = child.getBottom() - verticalSpacing / 2;
                int bottom = child.getBottom() + verticalSpacing / 2;
                c.drawRect(left, top, right, bottom, dividerPaint);
            }
        }
    }

    @Override
    public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
        outRect.set(horizontalSpacing, verticalSpacing, horizontalSpacing, verticalSpacing);
    }
}

使用方式：

GridLayout gridLayout = findViewById(R.id.grid_layout);
gridLayout.addItemDecoration(new GridItemDecoration(16, 16, Color.GRAY));

其中，16 表示水平和垂直方向的间距，Color.GRAY 表示分割线的颜色。