問題描述

我有一個小問題.我想要制作可以在多個 FlowLayoutPanel 之間拖動生成的標簽的程序.但最近幾天我試圖讓拖放工作.我嘗試了許多教程、示例等，但總是有些不同，我無法僅提取基本代碼.

I have small problem. I want make program where I can drag generated labels between multiple FlowLayoutPanels. But last few days I have tried to make drag and drop working. I tried many tutorials, examples etc. but it is always something bit diferent and I am not able extract only basic code.

類似于 這個程序 但它在 Visual Basic 中，我需要它在 C# 中.我知道這可能很簡單，但我是新手.

It is similar to this program but it is in Visual Basic and I need it in C#. I know it is maybe very simple, but I am newbie.

感謝您的幫助.

推薦答案

真正的 Drag&Drop 在應用程序之間最有用，也許在 Forms 之間也是最有用的.

Real Drag&Drop ist most useful between applications and maybe also between Forms.

假設您想在同一 Form 上的 FLPs 之間拖動 Labels，下面的代碼應該可以幫助您進行操作..

Assuming you want to drag Labels between FLPs on the same Form, the code below should get you going..

它需要兩個 FlowLayoutPanels，分別稱為 FLP1 和 FLP2，并首先使用一些 Labels 對其進行初始化.

It takes two FlowLayoutPanels called FLP1 and FLP2 and starts by initializing them with a few Labels.

注意我添加到每個 Label 以模擬 Drag&Drop 動作的三個 鼠標事件！

Note the three mouse events I add to each Label to emulate a Drag&Drop action!

private void Form1_Load(object sender, EventArgs e)
{
    // create a few Label with varying Colors for testing..
    fillFLP(FLP1, 88);
    fillFLP(FLP2, 111);
}

void fillFLP(FlowLayoutPanel FLP, int cc)
{
    for (int i = 0; i < 24; i++)
    {
        Label l = new Label();
        // the next 3 lines optional and only are there for testing!
        l.AutoSize = false;      
        l.Text = FLP.Name + " " +  i.ToString("00");
        l.BackColor = Color.FromArgb(255, cc * 2 - i, 255 - 5 * i, cc + 5 * i); 
        // add controls and set mouse events:
        FLP.Controls.Add(l);
        l.MouseDown += l_MouseDown;
        l.MouseMove += l_MouseMove;
        l.MouseUp += l_MouseUp;
    }
}


// the currently moved Label:
Label mvLabel = null;

void l_MouseDown(object sender, MouseEventArgs e)
{
    // keep reference
    mvLabel = (Label)sender;
}

void l_MouseMove(object sender, MouseEventArgs e)
{
    // if we are dragging a label:
    if (mvLabel != null)
    {
        // mouse pos in window coords
        Point  mvPoint = this.PointToClient(Control.MousePosition);
        // the label is still in the FLP, so we start the drg action:
        if (mvLabel.Parent != this)
        {
            mvLabel.Parent = this;
            mvLabel.Location = mvPoint;
            mvLabel.BringToFront();
        }
        else
        {   
            // we are already in the form, so we just move
            mvLabel.Location = mvPoint;
        }
    }
}

void l_MouseUp(object sender, MouseEventArgs e)
{
    // are we over a FLP? and if so which?
    Point MP = Control.MousePosition;
    FlowLayoutPanel FLP = null;

    Point mLoc1 = FLP1.PointToClient(MP);
    Point mLoc2 = FLP2.PointToClient(MP);

    if (FLP1.ClientRectangle.Contains(mLoc1)) FLP = FLP1;
    else if (FLP2.ClientRectangle.Contains(mLoc2)) FLP = FLP2;
    else return;  // no! nothing we can do..

    // yes, now find out if we are over a label..
    // ..or over an empty area
    mvLabel.SendToBack();
    Control cc = FLP.GetChildAtPoint(FLP.PointToClient(MP));
    // if we are over the FLP we can insert at the beginning or the end:
    // int mvIndex = 0; // to the beginning
    int mvIndex = FLP.Controls.Count; // to the end
    // we are over a Label, so we insert before it:
    if (cc != null) mvIndex = FLP.Controls.IndexOf(cc);

    // move the Label into the FLP
    FLP.Controls.Add(mvLabel);
    // move it to the right position:
    FLP.Controls.SetChildIndex(mvLabel, mvIndex);
    // let go of the reference
    mvLabel = null;

}

這使您可以在兩個 FLP 之間以及通過將 onto 拖放到 FLP 內來回拖放 Lablesstrong> 標簽.