C＃在拖放时实现ListView中的自动滚动

Posted 2021-05-04

如何在Winforms ListView中实现自动滚动（例如，当您靠近顶部或底部时ListView滚动）？我一直在谷歌上寻找运气很少。我不敢相信这不是开箱即用的！在此先感谢戴夫

答案

可以使用ListViewItem.EnsureVisible方法完成滚动。您需要确定当前拖动的项目是否位于列表视图的可见边界，而不是第一个/最后一个。

private static void RevealMoreItems(object sender, DragEventArgs e)
{
    var listView = (ListView)sender;

    var point = listView.PointToClient(new Point(e.X, e.Y));
    var item = listView.GetItemAt(point.X, point.Y);
    if (item == null)
        return;

    var index = item.Index;
    var maxIndex = listView.Items.Count;
    var scrollZoneHeight = listView.Font.Height;

    if (index > 0 && point.Y < scrollZoneHeight)
    {
        listView.Items[index - 1].EnsureVisible();
    }
    else if (index < maxIndex && point.Y > listView.Height - scrollZoneHeight)
    {
        listView.Items[index + 1].EnsureVisible();
    }
}

然后将此方法连接到DragOver事件。

targetListView.DragOver += RevealMoreItems;

targetListView.DragOver += (sender, e) =>
{
    e.Effect = DragDropEffects.Move;
};

另一答案

感谢链接（http://www.knowdotnet.com/articles/listviewdragdropscroll.html），我C＃ised它

class ListViewBase:ListView
{
    private Timer tmrLVScroll;
    private System.ComponentModel.IContainer components;
    private int mintScrollDirection;
    [DllImport("user32.dll", CharSet = CharSet.Auto)]
    private static extern int SendMessage(IntPtr hWnd, int wMsg, IntPtr wParam, IntPtr lParam);
    const int WM_VSCROLL = 277; // Vertical scroll
    const int SB_LINEUP = 0; // Scrolls one line up
    const int SB_LINEDOWN = 1; // Scrolls one line down

    public ListViewBase()
    {
        InitializeComponent();
    }
    protected void InitializeComponent()
    {
        this.components = new System.ComponentModel.Container();
        this.tmrLVScroll = new System.Windows.Forms.Timer(this.components);
        this.SuspendLayout();
        // 
        // tmrLVScroll
        // 
        this.tmrLVScroll.Tick += new System.EventHandler(this.tmrLVScroll_Tick);
        // 
        // ListViewBase
        // 
        this.DragOver += new System.Windows.Forms.DragEventHandler(this.ListViewBase_DragOver);
        this.ResumeLayout(false);

    }

    protected void ListViewBase_DragOver(object sender, DragEventArgs e)
    {
        Point position = PointToClient(new Point(e.X, e.Y));

        if (position.Y <= (Font.Height / 2))
        {
            // getting close to top, ensure previous item is visible
            mintScrollDirection = SB_LINEUP;
            tmrLVScroll.Enabled = true;
        }else if (position.Y >= ClientSize.Height - Font.Height / 2)
        { 
            // getting close to bottom, ensure next item is visible
            mintScrollDirection = SB_LINEDOWN;
            tmrLVScroll.Enabled = true;
        }else{
            tmrLVScroll.Enabled = false;
        }
    }

    private void tmrLVScroll_Tick(object sender, EventArgs e)
    {
        SendMessage(Handle, WM_VSCROLL, (IntPtr)mintScrollDirection, IntPtr.Zero);
    }
}

另一答案

看看ObjectListView。它做到了这一点。如果您不想使用ObjectListView本身，您可以阅读代码并使用它。

另一答案

只是未来googlers的一个注释：要使用更复杂的控件（如DataGridView），请参阅this thread。