C＃在FlowLayoutPanels中拖放標籤

Question

我有一個小問題。我想讓程序可以在多個FlowLayoutPanel之間拖動生成的標籤。但最近幾天我試圖做拖放工作。我嘗試了很多教程，例子等，但它總是有點不同，我不能僅提取基本代碼。

它與this program類似，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。

謝謝你的幫助。

Answer 1

實際Drag&Drop在應用程序之間最有用，也可能在Forms之間。

假設你想在同一FormFLPs之間拖動Labels，下面的代碼應該讓你去..

它有兩個FlowLayoutPanels用幾個Labels初始化它們稱爲FLP1和FLP2和開始。

注意三個鼠標事件我添加到每個Label來模擬Drag&Drop行動！

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; 

} 

這使您可以拖放Lables並通過降低到Labels來回兩者之間FLPs也內FLPs。

注意，如果你想允許下探Labels之間，仍然有位置，你將需要一些額外的行..