Question

我似乎拥有Drag-n-Drop所需的所有功能，但是当我尝试将某个控件从一个控件拖到另一个控件时，我的代码不会被调用。

我创建了一个用于创建数据的测试类：

class TestClass
{

    public TestClass()
    {
        Name = "Blank";
        Id = -1;
    }

    public String Name { get; set; }

    public int Id { get; set; }

    public object Data { get; set; }

    public override String ToString()
    {
        return String.Format("{0}: {1}", Id, Name);
    }

}

我创建了一个包含2个列表视图控件的空表单listView1和listView2：

我为所有Drag-n-Drop方法创建了事件处理程序，并在它们上添加了断点：

private void Form_DragDrop(object sender, DragEventArgs e)
{
    e.Effect = DragDropEffects.Copy;
    if (e.Data.GetDataPresent(typeof(TestClass)))
    {
        var item = e.Data.GetData(typeof(TestClass)) as TestClass;
        if (item != null)
        {
            // ?
        }
    }
}

private void Form_DragEnter(object sender, DragEventArgs e)
{
    e.Effect = DragDropEffects.Copy;
    if (sender.Equals(listView2))
    {
        e.Effect = DragDropEffects.All;
        if (e.Data != null)
        {
            var format = GetString(e);
            Console.WriteLine("{0} has a(n) {1} entering it.", listView2.Name, format);
        }
    }
}

private void Form_DragLeave(object sender, EventArgs e)
{
    if (sender.Equals(listView2))
    {

    }
}

private void Form_DragOver(object sender, DragEventArgs e)
{
    // Code Project Article 9017 says DragOver fires repeatedly, even if the mouse does not move.
    if ((e.X != _lastX) || (e.Y != _lastY))
    {
        _lastX = e.X;
        _lastY = e.Y;
        if (e.Data.GetDataPresent(typeof(TestClass)))
        {

        }
        else
        {
            e.Effect = DragDropEffects.None;
        }
    }
}

private void Form_GiveFeedback(Object sender, GiveFeedbackEventArgs e)
{
    if (sender.Equals(listView2))
    {
        // ?
    }
}

private void Form_QueryContinueDrag(object sender, QueryContinueDragEventArgs e)
{
    var listView = sender as ListView;
    if (listView != null)
    {

    }
}

private String GetString(DragEventArgs e)
{
    var result = String.Empty;
    if ((e.AllowedEffect & DragDropEffects.Copy) == DragDropEffects.Copy)
    {
        var formats = e.Data.GetFormats();
        foreach (var format in formats)
        {
            Console.WriteLine("Data is in the format of [{0}].", format);
            result = format;
        }
    }
    return result;
}

我在构造函数InitializeComponent();之后连接了两个控件：

public ListViewsForm()
{
    InitializeComponent();
    // Setup ListView 1:
    listView1.AllowDrop = true;
    listView1.DragDrop += Form_DragDrop;
    listView1.DragEnter += Form_DragEnter;
    listView1.DragLeave += Form_DragLeave;
    listView1.DragOver += Form_DragOver;
    listView1.GiveFeedback += Form_GiveFeedback;
    listView1.QueryContinueDrag += Form_QueryContinueDrag;
    listView1.Dock = DockStyle.Fill;
    listView1.View = View.List;
    // Setup ListView 2:
    listView2.AllowDrop = true;
    listView2.DragDrop += Form_DragDrop;
    listView2.DragEnter += Form_DragEnter;
    listView2.DragLeave += Form_DragLeave;
    listView2.DragOver += Form_DragOver;
    listView2.GiveFeedback += Form_GiveFeedback;
    listView2.QueryContinueDrag += Form_QueryContinueDrag;
    listView2.Dock = DockStyle.Fill;
    // Create some data:
    var group1 = new ListViewGroup("Known Colors");
    foreach (KnownColor known in Enum.GetValues(typeof(KnownColor)))
    {
        var item = new TestClass()
        {
            Name = known.ToString(),
            Id = (int)known,
            Data = known,
        };
        var color = Color.FromKnownColor(known);
        var lvi = new ListViewItem(item.ToString(), group1) {
            BackColor = Color.FromArgb(color.ToArgb() ^ 0xffffff),
            ForeColor = color,
            Tag = item,
        };
        listView1.Items.Add(lvi);
    }
}

每当我运行项目时，一切都很好，但是任何将项目从LEFT侧拖到RIGHT侧的尝试都不起作用。没有一个破发点被击中。没有任何事情发生。

我遗漏了什么？

Answer 1

您缺少一个方便的事件和开始拖动操作的方法：

listView1.ItemDrag += listView1_ItemDrag;

void listView1_ItemDrag(object sender, ItemDragEventArgs e) {
  DoDragDrop(e.Item, DragDropEffects.Copy);
}

Windows窗体拖放功能

1 个答案: