在類庫(kù)中的定義為:
復(fù)制代碼 代碼如下:
[UIPermissionAttribute(SecurityAction.Demand, Clipboard = UIPermissionClipboard.OwnClipboard)]
public DragDropEffects DoDragDrop(
Object data,
DragDropEffects allowedEffects
)
其中data參數(shù)為要拖放的數(shù)據(jù)，如果拖動(dòng)操作需要于另一個(gè)進(jìn)程的應(yīng)用程序相互操作，data代表的數(shù)據(jù)應(yīng)該是基本托管類(String,BitMap,或MetaFile),或者是實(shí)現(xiàn) ISerializable 或IDataObject的對(duì)象。 allowedEffects參數(shù)表示拖放的效果，為一個(gè)枚舉值（DragDropEffects）.返回值也為DragDropEffects枚舉值。
當(dāng)開(kāi)始調(diào)用DoDragDrop方法拖動(dòng)一個(gè)數(shù)據(jù)對(duì)象時(shí)，DoDragDrops在拖放過(guò)程中，檢測(cè)當(dāng)前光標(biāo)位置下的控件是不是有效的放置目標(biāo)。如果當(dāng)前光標(biāo)下的控件是有效的放置目標(biāo)，則GiveFeedBack事件以指定的拖放效果引發(fā)。在檢測(cè)當(dāng)前位置光標(biāo)是否為有效的拖放目標(biāo)時(shí)，DoDragDrops方法同時(shí)跟蹤光標(biāo)位置，鍵盤狀態(tài)和鼠標(biāo)狀態(tài)的更改。
(1)如果用于移出了一個(gè)窗口，則引發(fā)DragLeave事件。
（2）如果移入了另外一個(gè)控件，則引發(fā)該控件的DragEnter事件。
?。?）如果鼠標(biāo)移動(dòng)，但是停留在一個(gè)控件中，則引發(fā)DragOver事件。
如果檢測(cè)到更改了鍵盤或者鼠標(biāo)狀態(tài),則引發(fā)拖放源的QueryContinueDrag事件, 并根據(jù)事件的QueryContinueDragEventArgs的Action屬性值確定繼續(xù)拖動(dòng)，放置數(shù)據(jù)或取消操作。
（1）如果Action屬性指定為Continue，則將引發(fā)DragOver事件。
(2)如果Action屬性指定為Drop，則將放置效果返回給源，以便應(yīng)用程序?qū)?shù)據(jù)進(jìn)行適當(dāng)?shù)牟僮鳎焕?，如果是移?dòng)操作，則剪切數(shù)據(jù)。
(3)如果是DragAction的值為Cancel,則引發(fā)DragLeave事件
從csdn上摘抄一段示例代碼:
下面的代碼示例演示在兩個(gè) ListBox 控件之間的拖放操作。當(dāng)拖動(dòng)動(dòng)作啟動(dòng)時(shí)，該示例調(diào)用 DoDragDrop 方法。在 MouseDown 事件期間，如果從鼠標(biāo)位置起鼠標(biāo)移動(dòng)的距離大于 SystemInformation..::.DragSize，則啟動(dòng)拖動(dòng)動(dòng)作。IndexFromPoint 方法用于確定在 MouseDown 事件期間要拖動(dòng)的項(xiàng)的索引。
該示例還演示如何對(duì)拖放操作使用自定義光標(biāo)。該示例要求應(yīng)用程序目錄中存在兩個(gè)光標(biāo)文件：3dwarro.cur 和 3dwno.cur，分別用于自定義拖動(dòng)光標(biāo)和禁止停放光標(biāo)。如果選中 UseCustomCursorsCheckCheckBox，則使用自定義光標(biāo)。自定義光標(biāo)在 GiveFeedback 事件處理程序中設(shè)置。
鍵盤狀態(tài)在右 ListBox 的 DragOver 事件處理程序中計(jì)算，以確定基于 Shift、Ctrl、Alt 或 Ctrl+Alt 鍵的狀態(tài)將發(fā)生哪種拖動(dòng)操作。放置動(dòng)作在 ListBox 中發(fā)生的位置也在 DragOver 事件期間確定。如果要放置的數(shù)據(jù)不是 String，則 DragDropEffects 中將把 DragEventArgs.sEffect 設(shè)置為 None。最后，停放狀態(tài)在 DropLocationLabelLabel 中顯示。
要放置的用于右 ListBox 的數(shù)據(jù)在 DragDrop 事件處理程序中確定，并且在 ListBox 中的適當(dāng)位置添加該 String 值。如果拖動(dòng)操作移動(dòng)到窗體邊框的外面，則 QueryContinueDrag 事件處理程序中將取消拖放操作
復(fù)制代碼 代碼如下:
using System;
using System.Drawing;
using System.Windows.Forms;
namespace Snip_DragNDrop
{
public class Form1 : System.Windows.Forms.Form
{
private System.Windows.Forms.ListBox ListDragSource;
private System.Windows.Forms.ListBox ListDragTarget;
private System.Windows.Forms.CheckBox UseCustomCursorsCheck;
private System.Windows.Forms.Label DropLocationLabel;
private int indexOfItemUnderMouseToDrag;
private int indexOfItemUnderMouseToDrop;
private Rectangle dragBoxFromMouseDown;
private Point screenOffset;
private Cursor MyNoDropCursor;
private Cursor MyNormalCursor;
/// The main entry point for the application.
[STAThread]
static void Main()
{
Application.Run(new Form1());
}
public Form1()
{
this.ListDragSource = new System.Windows.Forms.ListBox();
this.ListDragTarget = new System.Windows.Forms.ListBox();
this.UseCustomCursorsCheck = new System.Windows.Forms.CheckBox();
this.DropLocationLabel = new System.Windows.Forms.Label();
this.SuspendLayout();
// ListDragSource
this.ListDragSource.Items.AddRange(new object[] {"one", "two", "three", "four",
"five", "six", "seven", "eight",
"nine", "ten"});
this.ListDragSource.Location = new System.Drawing.Point(10, 17);
this.ListDragSource.Size = new System.Drawing.Size(120, 225);
this.ListDragSource.MouseDown += new System.Windows.Forms.MouseEventHandler(this.ListDragSource_MouseDown);
this.ListDragSource.QueryContinueDrag += new System.Windows.Forms.QueryContinueDragEventHandler(this.ListDragSource_QueryContinueDrag);
this.ListDragSource.MouseUp += new System.Windows.Forms.MouseEventHandler(this.ListDragSource_MouseUp);
this.ListDragSource.MouseMove += new System.Windows.Forms.MouseEventHandler(this.ListDragSource_MouseMove);
this.ListDragSource.GiveFeedback += new System.Windows.Forms.GiveFeedbackEventHandler(this.ListDragSource_GiveFeedback);
// ListDragTarget
this.ListDragTarget.AllowDrop = true;
this.ListDragTarget.Location = new System.Drawing.Point(154, 17);
this.ListDragTarget.Size = new System.Drawing.Size(120, 225);
this.ListDragTarget.DragOver += new System.Windows.Forms.DragEventHandler(this.ListDragTarget_DragOver);
this.ListDragTarget.DragDrop += new System.Windows.Forms.DragEventHandler(this.ListDragTarget_DragDrop);
this.ListDragTarget.DragEnter += new System.Windows.Forms.DragEventHandler(this.ListDragTarget_DragEnter);
this.ListDragTarget.DragLeave += new System.EventHandler(this.ListDragTarget_DragLeave);
// UseCustomCursorsCheck
this.UseCustomCursorsCheck.Location = new System.Drawing.Point(10, 243);
this.UseCustomCursorsCheck.Size = new System.Drawing.Size(137, 24);
this.UseCustomCursorsCheck.Text = "Use Custom Cursors";
// DropLocationLabel
this.DropLocationLabel.Location = new System.Drawing.Point(154, 245);
this.DropLocationLabel.Size = new System.Drawing.Size(137, 24);
this.DropLocationLabel.Text = "None";
// Form1
this.ClientSize = new System.Drawing.Size(292, 270);
this.Controls.AddRange(new System.Windows.Forms.Control[] {this.ListDragSource,
this.ListDragTarget, this.UseCustomCursorsCheck,
this.DropLocationLabel});
this.Text = "drag-and-drop Example";
this.ResumeLayout(false);
}
private void ListDragSource_MouseDown(object sender, System.Windows.Forms.MouseEventArgs e)
{
// Get the index of the item the mouse is below.
indexOfItemUnderMouseToDrag = ListDragSource.IndexFromPoint(e.X, e.Y);
if (indexOfItemUnderMouseToDrag != ListBox.NoMatches) {
// Remember the point where the mouse down occurred. The DragSize indicates
// the size that the mouse can move before a drag event should be started.
Size dragSize = SystemInformation.DragSize;
// Create a rectangle using the DragSize, with the mouse position being
// at the center of the rectangle.
dragBoxFromMouseDown = new Rectangle(new Point(e.X - (dragSize.Width /2),
e.Y - (dragSize.Height /2)), dragSize);
} else
// Reset the rectangle if the mouse is not over an item in the ListBox.
dragBoxFromMouseDown = Rectangle.Empty;
}
private void ListDragSource_MouseUp(object sender, System.Windows.Forms.MouseEventArgs e) {
// Reset the drag rectangle when the mouse button is raised.
dragBoxFromMouseDown = Rectangle.Empty;
}
private void ListDragSource_MouseMove(object sender, System.Windows.Forms.MouseEventArgs e)
{
if ((e.Button MouseButtons.Left) == MouseButtons.Left) {
// If the mouse moves outside the rectangle, start the drag.
if (dragBoxFromMouseDown != Rectangle.Empty
!dragBoxFromMouseDown.Contains(e.X, e.Y)) {
// Create custom cursors for the drag-and-drop operation.
try {
MyNormalCursor = new Cursor("3dwarro.cur");
MyNoDropCursor = new Cursor("3dwno.cur");
} catch {
// An error occurred while attempting to load the cursors, so use
// standard cursors.
UseCustomCursorsCheck.Checked = false;
}finally {
// The screenOffset is used to account for any desktop bands
// that may be at the top or left side of the screen when
// determining when to cancel the drag drop operation.
screenOffset = SystemInformation.WorkingArea.Location;
// Proceed with the drag-and-drop, passing in the list item.
DragDropEffects dropEffect = ListDragSource.DoDragDrop(ListDragSource.Items[indexOfItemUnderMouseToDrag], DragDropEffects.All | DragDropEffects.Link);
// If the drag operation was a move then remove the item.
if (dropEffect == DragDropEffects.Move) {
ListDragSource.Items.RemoveAt(indexOfItemUnderMouseToDrag);
// Selects the previous item in the list as long as the list has an item.
if (indexOfItemUnderMouseToDrag > 0)
ListDragSource.SelectedIndex = indexOfItemUnderMouseToDrag -1;
else if (ListDragSource.Items.Count > 0)
// Selects the first item.
ListDragSource.SelectedIndex =0;
}
// Dispose of the cursors since they are no longer needed.
if (MyNormalCursor != null)
MyNormalCursor.Dispose();
if (MyNoDropCursor != null)
MyNoDropCursor.Dispose();
}
}
}
}
private void ListDragSource_GiveFeedback(object sender, System.Windows.Forms.GiveFeedbackEventArgs e)
{
// Use custom cursors if the check box is checked.
if (UseCustomCursorsCheck.Checked) {
// Sets the custom cursor based upon the effect.
e.UseDefaultCursors = false;
if ((e.Effect DragDropEffects.Move) == DragDropEffects.Move)
Cursor.Current = MyNormalCursor;
else
Cursor.Current = MyNoDropCursor;
}
}
private void ListDragTarget_DragOver(object sender, System.Windows.Forms.DragEventArgs e)
{
// Determine whether string data exists in the drop data. If not, then
// the drop effect reflects that the drop cannot occur.
if (!e.Data.GetDataPresent(typeof(System.String))) {
e.Effect = DragDropEffects.None;
DropLocationLabel.Text = "None - no string data.";
return;
}
// Set the effect based upon the KeyState.
if ((e.KeyState (8+32)) == (8+32)
(e.AllowedEffect DragDropEffects.Link) == DragDropEffects.Link) {
// KeyState 8 + 32 = CTL + ALT
// Link drag-and-drop effect.
e.Effect = DragDropEffects.Link;
} else if ((e.KeyState 32) == 32
(e.AllowedEffect DragDropEffects.Link) == DragDropEffects.Link) {
// ALT KeyState for link.
e.Effect = DragDropEffects.Link;
} else if ((e.KeyState 4) == 4
(e.AllowedEffect DragDropEffects.Move) == DragDropEffects.Move) {
// SHIFT KeyState for move.
e.Effect = DragDropEffects.Move;
} else if ((e.KeyState 8) == 8
(e.AllowedEffect DragDropEffects.Copy) == DragDropEffects.Copy) {
// CTL KeyState for copy.
e.Effect = DragDropEffects.Copy;
} else if ((e.AllowedEffect DragDropEffects.Move) == DragDropEffects.Move) {
// By default, the drop action should be move, if allowed.
e.Effect = DragDropEffects.Move;
} else
e.Effect = DragDropEffects.None;
// Get the index of the item the mouse is below.
// The mouse locations are relative to the screen, so they must be
// converted to client coordinates.
indexOfItemUnderMouseToDrop =
ListDragTarget.IndexFromPoint(ListDragTarget.PointToClient(new Point(e.X, e.Y)));
// Updates the label text.
if (indexOfItemUnderMouseToDrop != ListBox.NoMatches){
DropLocationLabel.Text = "Drops before item #" + (indexOfItemUnderMouseToDrop + 1);
} else
DropLocationLabel.Text = "Drops at the end.";
}
private void ListDragTarget_DragDrop(object sender, System.Windows.Forms.DragEventArgs e)
{
// Ensure that the list item index is contained in the data.
if (e.Data.GetDataPresent(typeof(System.String))) {
Object item = (object)e.Data.GetData(typeof(System.String));
// Perform drag-and-drop, depending upon the effect.
if (e.Effect == DragDropEffects.Copy ||
e.Effect == DragDropEffects.Move) {
// Insert the item.
if (indexOfItemUnderMouseToDrop != ListBox.NoMatches)
ListDragTarget.Items.Insert(indexOfItemUnderMouseToDrop, item);
else
ListDragTarget.Items.Add(item);
}
}
// Reset the label text.
DropLocationLabel.Text = "None";
}
private void ListDragSource_QueryContinueDrag(object sender, System.Windows.Forms.QueryContinueDragEventArgs e) {
// Cancel the drag if the mouse moves off the form.
ListBox lb = sender as ListBox;
if (lb != null) {
Form f = lb.FindForm();
// Cancel the drag if the mouse moves off the form. The screenOffset
// takes into account any desktop bands that may be at the top or left
// side of the screen.
if (((Control.MousePosition.X - screenOffset.X) f.DesktopBounds.Left) ||
((Control.MousePosition.X - screenOffset.X) > f.DesktopBounds.Right) ||
((Control.MousePosition.Y - screenOffset.Y) f.DesktopBounds.Top) ||
((Control.MousePosition.Y - screenOffset.Y) > f.DesktopBounds.Bottom)) {
e.Action = DragAction.Cancel;
}
}
}
private void ListDragTarget_DragEnter(object sender, System.Windows.Forms.DragEventArgs e) {
// Reset the label text.
DropLocationLabel.Text = "None";
}
private void ListDragTarget_DragLeave(object sender, System.EventArgs e) {
// Reset the label text.
DropLocationLabel.Text = "None";
}
}
}
對(duì)用這種拖放操作和微軟的服務(wù)，容器模式的關(guān)系，留在以后再學(xué)習(xí)。
