C#ListView鼠标滚轮没有焦点

private void listView1_MouseWheel(object sender, MouseEventArgs e)
{
    int scrollSize = 20; // 自定义滚动大小
    if (e.Delta > 0)
    {
        listView1.TopItem = listView1.TopItem.PrevItem;
    }
    else
    {
        listView1.TopItem = listView1.TopItem.NextItem;
    }
}

public Form1()
{
    InitializeComponent();
    listView1.MouseWheel += listView1_MouseWheel;
}