如何通过ItemDecoration改变列表项的显示效果

要通过ItemDecoration改变列表项的显示效果，可以创建一个自定义的ItemDecoration类，并重写其onDraw()和onDrawOver()方法来实现想要的效果。例如，可以在onDraw()方法中绘制分隔线或背景色，或者在onDrawOver()方法中绘制悬浮的标签等。然后将该ItemDecoration类应用到RecyclerView中即可。

以下是一个示例代码，演示如何创建一个自定义的ItemDecoration类来绘制分隔线：

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

    public DividerItemDecoration(Context context) {
        divider = ContextCompat.getDrawable(context, R.drawable.divider);
    }

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

        for (int i = 0; i < parent.getChildCount(); i++) {
            View child = parent.getChildAt(i);
            RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child.getLayoutParams();
            int top = child.getBottom() + params.bottomMargin;
            int bottom = top + divider.getIntrinsicHeight();
            divider.setBounds(left, top, right, bottom);
            divider.draw(c);
        }
    }
}

然后在RecyclerView中应用该ItemDecoration类：

RecyclerView recyclerView = findViewById(R.id.recycler_view);
recyclerView.addItemDecoration(new DividerItemDecoration(this));

这样就可以在RecyclerView中显示分隔线了。您可以根据自己的需求和创意，定制不同的ItemDecoration类来改变列表项的显示效果。