Control.DoDragDrop Metodo
Definizione
Importante
Alcune informazioni sono relative alla release non definitiva del prodotto, che potrebbe subire modifiche significative prima della release definitiva. Microsoft non riconosce alcuna garanzia, espressa o implicita, in merito alle informazioni qui fornite.
Overload
| DoDragDrop(Object, DragDropEffects, Bitmap, Point, Boolean) |
Avvia un'operazione di trascinamento. |
| DoDragDrop(Object, DragDropEffects) |
Inizia un'operazione di trascinamento e rilascio. |
DoDragDrop(Object, DragDropEffects, Bitmap, Point, Boolean)
Avvia un'operazione di trascinamento.
public:
System::Windows::Forms::DragDropEffects DoDragDrop(System::Object ^ data, System::Windows::Forms::DragDropEffects allowedEffects, System::Drawing::Bitmap ^ dragImage, System::Drawing::Point cursorOffset, bool useDefaultDragImage);public System.Windows.Forms.DragDropEffects DoDragDrop (object data, System.Windows.Forms.DragDropEffects allowedEffects, System.Drawing.Bitmap? dragImage, System.Drawing.Point cursorOffset, bool useDefaultDragImage);member this.DoDragDrop : obj * System.Windows.Forms.DragDropEffects * System.Drawing.Bitmap * System.Drawing.Point * bool -> System.Windows.Forms.DragDropEffectsPublic Function DoDragDrop (data As Object, allowedEffects As DragDropEffects, dragImage As Bitmap, cursorOffset As Point, useDefaultDragImage As Boolean) As DragDropEffectsParametri
- data
- Object
- allowedEffects
- DragDropEffects
- dragImage
- Bitmap
- cursorOffset
- Point
- useDefaultDragImage
- Boolean
Restituisce
Valore ricavato dall'enumerazione DragDropEffects che rappresenta l'effetto finale ottenuto durante l'operazione di trascinamento.
Commenti
Il allowedEffects parametro determina quali operazioni di trascinamento possono verificarsi. Se l'operazione di trascinamento deve interagire con le applicazioni in un altro processo, data deve essere una classe gestita di base (String, Bitmapo ) o Metafilealcuni Object che implementano ISerializable. data può anche essere qualsiasi Object che implementa IDataObject. dragImage è la bitmap che verrà visualizzata durante l'operazione di trascinamento e cursorOffset specifica la posizione del cursore all'interno dragImagedi , che è un offset dall'angolo superiore sinistro. Specificare true per useDefaultDragImage usare un'immagine di trascinamento della finestra a livelli con dimensioni pari a 96x96; in caso contrario false. Si noti che i bordi esterni di vengono uniti se la larghezza o l'altezza dell'immagine dragImage superano i 300 pixel.
Poiché DoDragDrop(Object, DragDropEffects, Bitmap, Point, Boolean) esegue sempre il passaggio di moltiplicazione RGB nel calcolo del valore alfa, è consigliabile passare sempre un Bitmap senza miscela alfa premultiplied. Nessun errore comporterà il passaggio di un Bitmap oggetto con la fusione alfa premultiplied, ma questo metodo lo moltiplica nuovamente, raddoppiando il valore alfa risultante.
Si applica a
DoDragDrop(Object, DragDropEffects)
Inizia un'operazione di trascinamento e rilascio.
public:
System::Windows::Forms::DragDropEffects DoDragDrop(System::Object ^ data, System::Windows::Forms::DragDropEffects allowedEffects);public System.Windows.Forms.DragDropEffects DoDragDrop (object data, System.Windows.Forms.DragDropEffects allowedEffects);member this.DoDragDrop : obj * System.Windows.Forms.DragDropEffects -> System.Windows.Forms.DragDropEffectsPublic Function DoDragDrop (data As Object, allowedEffects As DragDropEffects) As DragDropEffectsParametri
- data
- Object
Dati da trascinare.
- allowedEffects
- DragDropEffects
Uno dei valori di DragDropEffects.
Restituisce
Valore ricavato dall'enumerazione DragDropEffects che rappresenta l'effetto finale ottenuto durante l'operazione di trascinamento.
Esempio
Nell'esempio di codice seguente viene illustrata un'operazione di trascinamento della selezione tra due ListBox controlli. Nell'esempio viene chiamato il DoDragDrop metodo all'avvio dell'azione di trascinamento. L'azione di trascinamento inizia se il mouse è stato spostato più che SystemInformation.DragSize dalla posizione del mouse durante l'evento MouseDown . Il IndexFromPoint metodo viene usato per determinare l'indice dell'elemento da trascinare durante l'evento MouseDown .
L'esempio illustra anche l'uso di cursori personalizzati per l'operazione di trascinamento. L'esempio richiede che due file 3dwarro.cur di cursore e 3dwno.cur, esistano rispettivamente nella directory dell'applicazione, per il trascinamento personalizzato e i cursori senza rilascio. I cursori personalizzati verranno usati se viene UseCustomCursorsCheckCheckBox controllato. I cursori personalizzati vengono impostati nel GiveFeedback gestore eventi.
Lo stato della tastiera viene valutato nel DragOver gestore eventi per il diritto ListBox, per determinare quale operazione di trascinamento sarà in base allo stato dei tasti MAIUSC, CTRL, ALT o CTRL+ALT. La posizione in ListBox cui si verificherebbe l'eliminazione viene determinata anche durante l'evento DragOver . Se i dati da eliminare non sono un Stringoggetto , l'oggetto DragEventArgs.Effect è impostato su None in DragDropEffects. Infine, lo stato dell'eliminazione DropLocationLabelLabelviene visualizzato in .
I dati da eliminare per il diritto ListBox sono determinati nel DragDrop gestore eventi e il String valore viene aggiunto al posto appropriato in ListBox. Se l'operazione di trascinamento si sposta all'esterno dei limiti del modulo, l'operazione di trascinamento viene annullata nel QueryContinueDrag gestore eventi.
using namespace System;
using namespace System::Drawing;
using namespace System::Windows::Forms;
namespace Snip_DragNDrop
{
public ref class Form1: public System::Windows::Forms::Form
{
private:
System::Windows::Forms::ListBox^ ListDragSource;
System::Windows::Forms::ListBox^ ListDragTarget;
System::Windows::Forms::CheckBox^ UseCustomCursorsCheck;
System::Windows::Forms::Label ^ DropLocationLabel;
Int32 indexOfItemUnderMouseToDrag;
Int32 indexOfItemUnderMouseToDrop;
Rectangle dragBoxFromMouseDown;
Point screenOffset;
System::Windows::Forms::Cursor^ MyNoDropCursor;
System::Windows::Forms::Cursor^ MyNormalCursor;
public:
Form1()
{
this->ListDragSource = gcnew System::Windows::Forms::ListBox;
this->ListDragTarget = gcnew System::Windows::Forms::ListBox;
this->UseCustomCursorsCheck = gcnew System::Windows::Forms::CheckBox;
this->DropLocationLabel = gcnew System::Windows::Forms::Label;
this->SuspendLayout();
// ListDragSource
array<Object^>^temp0 = {"five","six","seven","eight","nine","ten"};
this->ListDragSource->Items->AddRange( temp0 );
this->ListDragSource->Location = System::Drawing::Point( 10, 17 );
this->ListDragSource->Size = System::Drawing::Size( 120, 225 );
this->ListDragSource->MouseDown += gcnew System::Windows::Forms::MouseEventHandler( this, &Form1::ListDragSource_MouseDown );
this->ListDragSource->QueryContinueDrag += gcnew System::Windows::Forms::QueryContinueDragEventHandler( this, &Form1::ListDragSource_QueryContinueDrag );
this->ListDragSource->MouseUp += gcnew System::Windows::Forms::MouseEventHandler( this, &Form1::ListDragSource_MouseUp );
this->ListDragSource->MouseMove += gcnew System::Windows::Forms::MouseEventHandler( this, &Form1::ListDragSource_MouseMove );
this->ListDragSource->GiveFeedback += gcnew System::Windows::Forms::GiveFeedbackEventHandler( this, &Form1::ListDragSource_GiveFeedback );
// ListDragTarget
this->ListDragTarget->AllowDrop = true;
this->ListDragTarget->Location = System::Drawing::Point( 154, 17 );
this->ListDragTarget->Size = System::Drawing::Size( 120, 225 );
this->ListDragTarget->DragOver += gcnew System::Windows::Forms::DragEventHandler( this, &Form1::ListDragTarget_DragOver );
this->ListDragTarget->DragDrop += gcnew System::Windows::Forms::DragEventHandler( this, &Form1::ListDragTarget_DragDrop );
this->ListDragTarget->DragEnter += gcnew System::Windows::Forms::DragEventHandler( this, &Form1::ListDragTarget_DragEnter );
this->ListDragTarget->DragLeave += gcnew System::EventHandler( this, &Form1::ListDragTarget_DragLeave );
// UseCustomCursorsCheck
this->UseCustomCursorsCheck->Location = System::Drawing::Point( 10, 243 );
this->UseCustomCursorsCheck->Size = System::Drawing::Size( 137, 24 );
this->UseCustomCursorsCheck->Text = "Use Custom Cursors";
// DropLocationLabel
this->DropLocationLabel->Location = System::Drawing::Point( 154, 245 );
this->DropLocationLabel->Size = System::Drawing::Size( 137, 24 );
this->DropLocationLabel->Text = "None";
// Form1
this->ClientSize = System::Drawing::Size( 292, 270 );
array<System::Windows::Forms::Control^>^formControls = {this->ListDragSource,this->ListDragTarget,this->UseCustomCursorsCheck,this->DropLocationLabel};
this->Controls->AddRange( formControls );
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 = this->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.
System::Drawing::Size dragSize = SystemInformation::DragSize;
// Create a rectangle using the DragSize, with the mouse position being
// at the center of the rectangle.
dragBoxFromMouseDown = Rectangle(Point(e->X - (dragSize.Width / 2),e->Y - (dragSize.Height / 2)),dragSize);
}
else
dragBoxFromMouseDown = Rectangle::Empty;
// Reset the rectangle if the mouse is not over an item in the ListBox.
}
void ListDragSource_MouseUp( Object^ /*sender*/, System::Windows::Forms::MouseEventArgs^ /*e*/ )
{
// Reset the drag rectangle when the mouse button is raised.
dragBoxFromMouseDown = Rectangle::Empty;
}
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 = gcnew System::Windows::Forms::Cursor( "3dwarro.cur" );
MyNoDropCursor = gcnew System::Windows::Forms::Cursor( "3dwno.cur" );
}
catch ( Exception^ )
{
// An error occurred while attempting to load the cursors, so use
// the standard cursors.
this->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 = this->ListDragSource->DoDragDrop( ListDragSource->Items[ indexOfItemUnderMouseToDrag ], static_cast<DragDropEffects>(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 != nullptr )
delete MyNormalCursor;
if ( MyNoDropCursor != nullptr )
delete MyNoDropCursor;
}
}
}
}
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;
}
}
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( System::String::typeid ) )
{
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 = CTRL + 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) )
{
// CTRL 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( Point(e->X,e->Y) ) );
// Updates the label text.
if ( indexOfItemUnderMouseToDrop != ListBox::NoMatches )
{
DropLocationLabel->Text = String::Concat( "Drops before item # ", (indexOfItemUnderMouseToDrop + 1) );
}
else
DropLocationLabel->Text = "Drops at the end.";
}
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( System::String::typeid ) )
{
Object^ item = dynamic_cast<Object^>(e->Data->GetData( System::String::typeid ));
// 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";
}
void ListDragSource_QueryContinueDrag( Object^ sender, System::Windows::Forms::QueryContinueDragEventArgs^ e )
{
// Cancel the drag if the mouse moves off the form.
ListBox^ lb = dynamic_cast<ListBox^>(sender);
if ( lb != nullptr )
{
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;
}
}
}
void ListDragTarget_DragEnter( Object^ /*sender*/, System::Windows::Forms::DragEventArgs^ /*e*/ )
{
// Reset the label text.
DropLocationLabel->Text = "None";
}
void ListDragTarget_DragLeave( Object^ /*sender*/, System::EventArgs^ /*e*/ )
{
// Reset the label text.
DropLocationLabel->Text = "None";
}
};
}
/// The main entry point for the application.
[STAThread]
int main()
{
Application::Run( gcnew Snip_DragNDrop::Form1 );
}
using System;
using System.Drawing;
using System.Windows.Forms;
namespace Snip_DragNDrop
{
public class Form1 : Form
{
private ListBox ListDragSource;
private ListBox ListDragTarget;
private CheckBox UseCustomCursorsCheck;
private 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 ListBox();
this.ListDragTarget = new ListBox();
this.UseCustomCursorsCheck = new CheckBox();
this.DropLocationLabel = new Label();
this.SuspendLayout();
// ListDragSource
this.ListDragSource.Items.AddRange(new object[] {"one", "two", "three", "four",
"five", "six", "seven", "eight",
"nine", "ten"});
this.ListDragSource.Location = new Point(10, 17);
this.ListDragSource.Size = new Size(120, 225);
this.ListDragSource.MouseDown += this.ListDragSource_MouseDown;
this.ListDragSource.QueryContinueDrag += this.ListDragSource_QueryContinueDrag;
this.ListDragSource.MouseUp += this.ListDragSource_MouseUp;
this.ListDragSource.MouseMove += this.ListDragSource_MouseMove;
this.ListDragSource.GiveFeedback += this.ListDragSource_GiveFeedback;
// ListDragTarget
this.ListDragTarget.AllowDrop = true;
this.ListDragTarget.Location = new Point(154, 17);
this.ListDragTarget.Size = new Size(120, 225);
this.ListDragTarget.DragOver += this.ListDragTarget_DragOver;
this.ListDragTarget.DragDrop += this.ListDragTarget_DragDrop;
this.ListDragTarget.DragEnter += this.ListDragTarget_DragEnter;
this.ListDragTarget.DragLeave += this.ListDragTarget_DragLeave;
// UseCustomCursorsCheck
this.UseCustomCursorsCheck.Location = new Point(10, 243);
this.UseCustomCursorsCheck.Size = new Size(137, 24);
this.UseCustomCursorsCheck.Text = "Use Custom Cursors";
// DropLocationLabel
this.DropLocationLabel.Location = new Point(154, 245);
this.DropLocationLabel.Size = new Size(137, 24);
this.DropLocationLabel.Text = "None";
// Form1
this.ClientSize = new Size(292, 270);
this.Controls.AddRange(new Control[] {
this.ListDragSource,
this.ListDragTarget,
this.UseCustomCursorsCheck,
this.DropLocationLabel});
this.Text = "drag-and-drop Example";
this.ResumeLayout(false);
}
private void ListDragSource_MouseDown(object sender, 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, MouseEventArgs e)
{
// Reset the drag rectangle when the mouse button is raised.
dragBoxFromMouseDown = Rectangle.Empty;
}
private void ListDragSource_MouseMove(object sender, 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, 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, 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 = CTRL + 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)
{
// CTRL 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, DragEventArgs e)
{
// Ensure that the list item index is contained in the data.
if (e.Data.GetDataPresent(typeof(System.String)))
{
Object item = 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, 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, DragEventArgs e)
{
// Reset the label text.
DropLocationLabel.Text = "None";
}
private void ListDragTarget_DragLeave(object sender, EventArgs e)
{
// Reset the label text.
DropLocationLabel.Text = "None";
}
}
}
Imports System.Drawing
Imports System.Windows.Forms
Public NotInheritable Class Form1
Inherits Form
Friend WithEvents ListDragSource As ListBox
Friend WithEvents ListDragTarget As ListBox
Friend WithEvents UseCustomCursorsCheck As CheckBox
Friend WithEvents DropLocationLabel As Label
Private indexOfItemUnderMouseToDrag As Integer
Private indexOfItemUnderMouseToDrop As Integer
Private dragBoxFromMouseDown As Rectangle
Private screenOffset As Point
Private MyNoDropCursor As Cursor
Private MyNormalCursor As Cursor
<STAThread()>
Public Shared Sub Main()
Application.Run(New Form1())
End Sub
Public Sub New()
MyBase.New()
Me.ListDragSource = New ListBox()
Me.ListDragTarget = New ListBox()
Me.UseCustomCursorsCheck = New CheckBox()
Me.DropLocationLabel = New Label()
Me.SuspendLayout()
' ListDragSource
Me.ListDragSource.Items.AddRange(New Object() {"one", "two", "three", "four",
"five", "six", "seven", "eight",
"nine", "ten"})
Me.ListDragSource.Location = New Point(10, 17)
Me.ListDragSource.Size = New Size(120, 225)
' ListDragTarget
Me.ListDragTarget.AllowDrop = True
Me.ListDragTarget.Location = New Point(154, 17)
Me.ListDragTarget.Size = New Size(120, 225)
' UseCustomCursorsCheck
Me.UseCustomCursorsCheck.Location = New Point(10, 243)
Me.UseCustomCursorsCheck.Size = New Size(137, 24)
Me.UseCustomCursorsCheck.Text = "Use Custom Cursors"
' DropLocationLabel
Me.DropLocationLabel.Location = New Point(154, 245)
Me.DropLocationLabel.Size = New Size(137, 24)
Me.DropLocationLabel.Text = "None"
' Form1
Me.ClientSize = New Size(292, 270)
Me.Controls.AddRange(New Control() {Me.ListDragSource,
Me.ListDragTarget,
Me.UseCustomCursorsCheck,
Me.DropLocationLabel})
Me.Text = "drag-and-drop Example"
Me.ResumeLayout(False)
End Sub
Private Sub ListDragSource_MouseDown(ByVal sender As Object, ByVal e As MouseEventArgs) Handles ListDragSource.MouseDown
' Get the index of the item the mouse is below.
indexOfItemUnderMouseToDrag = ListDragSource.IndexFromPoint(e.X, e.Y)
If (indexOfItemUnderMouseToDrag <> ListBox.NoMatches) Then
' 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.
Dim dragSize As Size = 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
End If
End Sub
Private Sub ListDragSource_MouseUp(ByVal sender As Object, ByVal e As MouseEventArgs) Handles ListDragSource.MouseUp
' Reset the drag rectangle when the mouse button is raised.
dragBoxFromMouseDown = Rectangle.Empty
End Sub
Private Sub ListDragSource_MouseMove(ByVal sender As Object, ByVal e As MouseEventArgs) Handles ListDragSource.MouseMove
If ((e.Button And MouseButtons.Left) = MouseButtons.Left) Then
' If the mouse moves outside the rectangle, start the drag.
If (Rectangle.op_Inequality(dragBoxFromMouseDown, Rectangle.Empty) And
Not dragBoxFromMouseDown.Contains(e.X, e.Y)) Then
' Creates 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.
Dim dropEffect As DragDropEffects = ListDragSource.DoDragDrop(
ListDragSource.Items(indexOfItemUnderMouseToDrag),
DragDropEffects.All Or DragDropEffects.Link)
' If the drag operation was a move then remove the item.
If (dropEffect = DragDropEffects.Move) Then
ListDragSource.Items.RemoveAt(indexOfItemUnderMouseToDrag)
' Select the previous item in the list as long as the list has an item.
If (indexOfItemUnderMouseToDrag > 0) Then
ListDragSource.SelectedIndex = indexOfItemUnderMouseToDrag - 1
ElseIf (ListDragSource.Items.Count > 0) Then
' Selects the first item.
ListDragSource.SelectedIndex = 0
End If
End If
' Dispose the cursors since they are no longer needed.
If (Not MyNormalCursor Is Nothing) Then _
MyNormalCursor.Dispose()
If (Not MyNoDropCursor Is Nothing) Then _
MyNoDropCursor.Dispose()
End Try
End If
End If
End Sub
Private Sub ListDragSource_GiveFeedback(ByVal sender As Object, ByVal e As GiveFeedbackEventArgs) Handles ListDragSource.GiveFeedback
' Use custom cursors if the check box is checked.
If (UseCustomCursorsCheck.Checked) Then
' Set the custom cursor based upon the effect.
e.UseDefaultCursors = False
If ((e.Effect And DragDropEffects.Move) = DragDropEffects.Move) Then
Cursor.Current = MyNormalCursor
Else
Cursor.Current = MyNoDropCursor
End If
End If
End Sub
Private Sub ListDragTarget_DragOver(ByVal sender As Object, ByVal e As DragEventArgs) Handles ListDragTarget.DragOver
' Determine whether string data exists in the drop data. If not, then
' the drop effect reflects that the drop cannot occur.
If Not (e.Data.GetDataPresent(GetType(System.String))) Then
e.Effect = DragDropEffects.None
DropLocationLabel.Text = "None - no string data."
Return
End If
' Set the effect based upon the KeyState.
If ((e.KeyState And (8 + 32)) = (8 + 32) And
(e.AllowedEffect And DragDropEffects.Link) = DragDropEffects.Link) Then
' KeyState 8 + 32 = CTRL + ALT
' Link drag-and-drop effect.
e.Effect = DragDropEffects.Link
ElseIf ((e.KeyState And 32) = 32 And
(e.AllowedEffect And DragDropEffects.Link) = DragDropEffects.Link) Then
' ALT KeyState for link.
e.Effect = DragDropEffects.Link
ElseIf ((e.KeyState And 4) = 4 And
(e.AllowedEffect And DragDropEffects.Move) = DragDropEffects.Move) Then
' SHIFT KeyState for move.
e.Effect = DragDropEffects.Move
ElseIf ((e.KeyState And 8) = 8 And
(e.AllowedEffect And DragDropEffects.Copy) = DragDropEffects.Copy) Then
' CTRL KeyState for copy.
e.Effect = DragDropEffects.Copy
ElseIf ((e.AllowedEffect And DragDropEffects.Move) = DragDropEffects.Move) Then
' By default, the drop action should be move, if allowed.
e.Effect = DragDropEffects.Move
Else
e.Effect = DragDropEffects.None
End If
' Gets 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) Then
DropLocationLabel.Text = "Drops before item #" & (indexOfItemUnderMouseToDrop + 1)
Else
DropLocationLabel.Text = "Drops at the end."
End If
End Sub
Private Sub ListDragTarget_DragDrop(ByVal sender As Object, ByVal e As DragEventArgs) Handles ListDragTarget.DragDrop
' Ensures that the list item index is contained in the data.
If (e.Data.GetDataPresent(GetType(System.String))) Then
Dim item As Object = CType(e.Data.GetData(GetType(System.String)), System.Object)
' Perform drag-and-drop, depending upon the effect.
If (e.Effect = DragDropEffects.Copy Or
e.Effect = DragDropEffects.Move) Then
' Insert the item.
If (indexOfItemUnderMouseToDrop <> ListBox.NoMatches) Then
ListDragTarget.Items.Insert(indexOfItemUnderMouseToDrop, item)
Else
ListDragTarget.Items.Add(item)
End If
End If
' Reset the label text.
DropLocationLabel.Text = "None"
End If
End Sub
Private Sub ListDragSource_QueryContinueDrag(ByVal sender As Object, ByVal e As QueryContinueDragEventArgs) Handles ListDragSource.QueryContinueDrag
' Cancel the drag if the mouse moves off the form.
Dim lb As ListBox = CType(sender, ListBox)
If (lb IsNot Nothing) Then
Dim f As Form = 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) Or
((Control.MousePosition.X - screenOffset.X) > f.DesktopBounds.Right) Or
((Control.MousePosition.Y - screenOffset.Y) < f.DesktopBounds.Top) Or
((Control.MousePosition.Y - screenOffset.Y) > f.DesktopBounds.Bottom)) Then
e.Action = DragAction.Cancel
End If
End If
End Sub
Private Sub ListDragTarget_DragEnter(ByVal sender As Object, ByVal e As DragEventArgs) Handles ListDragTarget.DragEnter
' Reset the label text.
DropLocationLabel.Text = "None"
End Sub
Private Sub ListDragTarget_DragLeave(ByVal sender As Object, ByVal e As EventArgs) Handles ListDragTarget.DragLeave
' Reset the label text.
DropLocationLabel.Text = "None"
End Sub
End Class
Nell'esempio di codice seguente viene illustrato come usare l'enumerazione DragDropEffects per specificare come trasferire i dati tra i controlli coinvolti in un'operazione di trascinamento. In questo esempio è necessario che il modulo includa un controllo e un RichTextBoxListBox controllo e che il ListBox controllo sia popolato con un elenco di nomi di file validi. Quando l'utente trascina un nome di file nel RichTextBox controllo, viene generato l'evento del DragEnter controllo. All'interno del gestore eventi, la Effect proprietà dell'oggetto DragEventArgs viene inizializzata per DragDropEffects indicare che i dati a cui fa riferimento il percorso del file devono essere copiati nel RichTextBox controllo.
private:
void Form1_Load( Object^ /*sender*/, EventArgs^ /*e*/ )
{
// Sets the AllowDrop property so that data can be dragged onto the control.
richTextBox1->AllowDrop = true;
// Add code here to populate the ListBox1 with paths to text files.
}
void listBox1_MouseDown( Object^ sender, System::Windows::Forms::MouseEventArgs^ e )
{
// Determines which item was selected.
ListBox^ lb = (dynamic_cast<ListBox^>(sender));
Point pt = Point(e->X,e->Y);
int index = lb->IndexFromPoint( pt );
// Starts a drag-and-drop operation with that item.
if ( index >= 0 )
{
lb->DoDragDrop( lb->Items[ index ], DragDropEffects::Link );
}
}
void richTextBox1_DragEnter( Object^ /*sender*/, DragEventArgs^ e )
{
// If the data is text, copy the data to the RichTextBox control.
if ( e->Data->GetDataPresent( "Text" ) )
e->Effect = DragDropEffects::Copy;
}
void richTextBox1_DragDrop( Object^ /*sender*/, DragEventArgs^ e )
{
// Loads the file into the control.
richTextBox1->LoadFile( dynamic_cast<String^>(e->Data->GetData( "Text" )), System::Windows::Forms::RichTextBoxStreamType::RichText );
}
private void Form1_Load(object sender, EventArgs e)
{
// Sets the AllowDrop property so that data can be dragged onto the control.
richTextBox1.AllowDrop = true;
// Add code here to populate the ListBox1 with paths to text files.
}
private void listBox1_MouseDown(object sender, System.Windows.Forms.MouseEventArgs e)
{
// Determines which item was selected.
ListBox lb =( (ListBox)sender);
Point pt = new Point(e.X,e.Y);
int index = lb.IndexFromPoint(pt);
// Starts a drag-and-drop operation with that item.
if(index>=0)
{
lb.DoDragDrop(lb.Items[index].ToString(), DragDropEffects.Link);
}
}
private void richTextBox1_DragEnter(object sender, DragEventArgs e)
{
// If the data is text, copy the data to the RichTextBox control.
if(e.Data.GetDataPresent("Text"))
e.Effect = DragDropEffects.Copy;
}
private void richTextBox1_DragDrop(object sender, DragEventArgs e)
{
// Loads the file into the control.
richTextBox1.LoadFile((String)e.Data.GetData("Text"), System.Windows.Forms.RichTextBoxStreamType.RichText);
}
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
' Sets the AllowDrop property so that data can be dragged onto the control.
RichTextBox1.AllowDrop = True
' Add code here to populate the ListBox1 with paths to text files.
End Sub
Private Sub RichTextBox1_DragEnter(ByVal sender As Object, ByVal e As System.Windows.Forms.DragEventArgs) Handles RichTextBox1.DragEnter
' If the data is text, copy the data to the RichTextBox control.
If (e.Data.GetDataPresent("Text")) Then
e.Effect = DragDropEffects.Copy
End If
End Sub
Private Overloads Sub RichTextBox1_DragDrop(ByVal sender As Object, ByVal e As System.Windows.Forms.DragEventArgs) Handles RichTextBox1.DragDrop
' Loads the file into the control.
RichTextBox1.LoadFile(e.Data.GetData("Text"), System.Windows.Forms.RichTextBoxStreamType.RichText)
End Sub
Private Sub ListBox1_MouseDown(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles ListBox1.MouseDown
Dim Lb As ListBox
Dim Pt As New Point(e.X, e.Y)
Dim Index As Integer
' Determines which item was selected.
Lb = sender
Index = Lb.IndexFromPoint(Pt)
' Starts a drag-and-drop operation with that item.
If Index >= 0 Then
Lb.DoDragDrop(Lb.Items(Index), DragDropEffects.Link)
End If
End Sub
Commenti
Il allowedEffects parametro determina quali operazioni di trascinamento possono verificarsi. Se l'operazione di trascinamento deve interagire con le applicazioni in un altro processo, i dati devono essere una classe gestita di base (String, , o ) o un oggetto che implementa ISerializable o MetafileIDataObject. Bitmap
Di seguito vengono illustrate le modalità e le circostanze in cui vengono generati eventi relativi a operazioni di trascinamento.
Il DoDragDrop metodo determina il controllo nella posizione del cursore corrente. Verifica quindi se il controllo è una destinazione di rilascio valida.
Se il controllo è una destinazione di rilascio valida, l'evento GiveFeedback viene generato con l'effetto trascinamento specificato. Per un elenco degli effetti di trascinamento e rilascio, vedere l'enumerazione DragDropEffects.
Viene tenuta traccia delle modifiche apportate alla posizione del cursore del mouse, allo stato della tastiera e allo stato dei pulsanti del mouse.
Se l'utente si sposta al di fuori di una finestra, verrà generato un evento DragLeave.
Se il mouse viene spostato su un altro controllo, verrà generato l'evento DragEnter per tale controllo.
Se il mouse viene spostato ma sempre all'interno dello stesso controllo, verrà generato l'evento DragOver.
Se si verifica una modifica nello stato del pulsante della tastiera o del mouse, l'evento QueryContinueDrag viene generato e determina se continuare il trascinamento, eliminare i dati o annullare l'operazione in base al valore della Action proprietà dell'evento QueryContinueDragEventArgs.
Se il valore di DragAction è
Continue, l'evento DragOver viene generato per continuare l'operazione e l'evento GiveFeedback viene generato con il nuovo effetto in modo che sia possibile impostare commenti visivi appropriati. Per un elenco degli effetti di trascinamento validi, vedere l'enumerazione DragDropEffects.Nota
Gli DragOver eventi e GiveFeedback vengono associati in modo che, quando il mouse si sposta attraverso la destinazione di rilascio, l'utente riceve il feedback più aggiornato sulla posizione del mouse.
Se il valore di è
Drop, il valore dell'effetto drop viene restituito all'origine, in modo che l'applicazione di origine possa eseguire l'operazione appropriata sui dati di DragAction origine, ad esempio tagliare i dati se l'operazione è stata spostata.Se il valore di DragAction è
Cancel, viene generato l'evento DragLeave .
Nota
Il DoDragDrop metodo rileva tutte le eccezioni e rethrow solo le eccezioni di sicurezza o critiche seguenti:
SecurityException
NullReferenceException
StackOverflowException
OutOfMemoryException
ThreadAbortException
ExecutionEngineException
IndexOutOfRangeException
Accessviolationexception
Vedi anche
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