Procedura: visualizzare un segno di inserimento in un controllo ListView per Windows Form
Aggiornamento: novembre 2007
Il segno di inserimento nel controllo ListView indica agli utenti il punto in cui verranno inseriti gli elementi trascinati. Quando un utente trascina un elemento in un punto intermedio tra due elementi, il segno di inserimento indica la nuova posizione prevista dell'elemento.
.gif "Nota") Nota: |
|---|
La funzionalità del segno di inserimento è disponibile solo in Windows XP Home Edition, Windows XP Professional, Windows Server 2003 quando l'applicazione chiama il metodo Application.EnableVisualStyles. Nei sistemi operativi precedenti, qualsiasi codice relativo al segno di inserimento non ha alcun effetto e il segno di inserimento non verrà visualizzato. Per ulteriori informazioni, vedere ListViewInsertionMark. |
Nell'immagine seguente viene visualizzato un segno di inserimento:
.gif)
Nell'esempio di codice riportato di seguito viene illustrato l'utilizzo di questa funzionalità.
Esempio
Imports System
Imports System.Drawing
Imports System.Windows.Forms
Public Class ListViewInsertionMarkExample
Inherits Form
Private myListView As ListView
Public Sub New()
' Initialize myListView.
myListView = New ListView()
myListView.Dock = DockStyle.Fill
myListView.View = View.LargeIcon
myListView.MultiSelect = False
myListView.ListViewItemSorter = New ListViewIndexComparer()
' Initialize the insertion mark.
myListView.InsertionMark.Color = Color.Green
' Add items to myListView.
myListView.Items.Add("zero")
myListView.Items.Add("one")
myListView.Items.Add("two")
myListView.Items.Add("three")
myListView.Items.Add("four")
myListView.Items.Add("five")
' Initialize the drag-and-drop operation when running
' under Windows XP or a later operating system.
If OSFeature.Feature.IsPresent(OSFeature.Themes)
myListView.AllowDrop = True
AddHandler myListView.ItemDrag, AddressOf myListView_ItemDrag
AddHandler myListView.DragEnter, AddressOf myListView_DragEnter
AddHandler myListView.DragOver, AddressOf myListView_DragOver
AddHandler myListView.DragLeave, AddressOf myListView_DragLeave
AddHandler myListView.DragDrop, AddressOf myListView_DragDrop
End If
' Initialize the form.
Me.Text = "ListView Insertion Mark Example"
Me.Controls.Add(myListView)
End Sub 'New
<STAThread()> _
Shared Sub Main()
Application.EnableVisualStyles()
Application.Run(New ListViewInsertionMarkExample())
End Sub 'Main
' Starts the drag-and-drop operation when an item is dragged.
Private Sub myListView_ItemDrag(sender As Object, e As ItemDragEventArgs)
myListView.DoDragDrop(e.Item, DragDropEffects.Move)
End Sub 'myListView_ItemDrag
' Sets the target drop effect.
Private Sub myListView_DragEnter(sender As Object, e As DragEventArgs)
e.Effect = e.AllowedEffect
End Sub 'myListView_DragEnter
' Moves the insertion mark as the item is dragged.
Private Sub myListView_DragOver(sender As Object, e As DragEventArgs)
' Retrieve the client coordinates of the mouse pointer.
Dim targetPoint As Point = myListView.PointToClient(New Point(e.X, e.Y))
' Retrieve the index of the item closest to the mouse pointer.
Dim targetIndex As Integer = _
myListView.InsertionMark.NearestIndex(targetPoint)
' Confirm that the mouse pointer is not over the dragged item.
If targetIndex > -1 Then
' Determine whether the mouse pointer is to the left or
' the right of the midpoint of the closest item and set
' the InsertionMark.AppearsAfterItem property accordingly.
Dim itemBounds As Rectangle = myListView.GetItemRect(targetIndex)
If targetPoint.X > itemBounds.Left + (itemBounds.Width / 2) Then
myListView.InsertionMark.AppearsAfterItem = True
Else
myListView.InsertionMark.AppearsAfterItem = False
End If
End If
' Set the location of the insertion mark. If the mouse is
' over the dragged item, the targetIndex value is -1 and
' the insertion mark disappears.
myListView.InsertionMark.Index = targetIndex
End Sub 'myListView_DragOver
' Removes the insertion mark when the mouse leaves the control.
Private Sub myListView_DragLeave(sender As Object, e As EventArgs)
myListView.InsertionMark.Index = -1
End Sub 'myListView_DragLeave
' Moves the item to the location of the insertion mark.
Private Sub myListView_DragDrop(sender As Object, e As DragEventArgs)
' Retrieve the index of the insertion mark;
Dim targetIndex As Integer = myListView.InsertionMark.Index
' If the insertion mark is not visible, exit the method.
If targetIndex = -1 Then
Return
End If
' If the insertion mark is to the right of the item with
' the corresponding index, increment the target index.
If myListView.InsertionMark.AppearsAfterItem Then
targetIndex += 1
End If
' Retrieve the dragged item.
Dim draggedItem As ListViewItem = _
CType(e.Data.GetData(GetType(ListViewItem)), ListViewItem)
' Insert a copy of the dragged item at the target index.
' A copy must be inserted before the original item is removed
' to preserve item index values.
myListView.Items.Insert(targetIndex, _
CType(draggedItem.Clone(), ListViewItem))
' Remove the original copy of the dragged item.
myListView.Items.Remove(draggedItem)
End Sub 'myListView_DragDrop
' Sorts ListViewItem objects by index.
Private Class ListViewIndexComparer
Implements System.Collections.IComparer
Public Function Compare(x As Object, y As Object) As Integer _
Implements System.Collections.IComparer.Compare
Return CType(x, ListViewItem).Index - CType(y, ListViewItem).Index
End Function 'Compare
End Class 'ListViewIndexComparer
End Class 'ListViewInsertionMarkExample
using System;
using System.Drawing;
using System.Windows.Forms;
public class ListViewInsertionMarkExample : Form
{
private ListView myListView;
public ListViewInsertionMarkExample()
{
// Initialize myListView.
myListView = new ListView();
myListView.Dock = DockStyle.Fill;
myListView.View = View.LargeIcon;
myListView.MultiSelect = false;
myListView.ListViewItemSorter = new ListViewIndexComparer();
// Initialize the insertion mark.
myListView.InsertionMark.Color = Color.Green;
// Add items to myListView.
myListView.Items.Add("zero");
myListView.Items.Add("one");
myListView.Items.Add("two");
myListView.Items.Add("three");
myListView.Items.Add("four");
myListView.Items.Add("five");
// Initialize the drag-and-drop operation when running
// under Windows XP or a later operating system.
if (OSFeature.Feature.IsPresent(OSFeature.Themes))
{
myListView.AllowDrop = true;
myListView.ItemDrag += new ItemDragEventHandler(myListView_ItemDrag);
myListView.DragEnter += new DragEventHandler(myListView_DragEnter);
myListView.DragOver += new DragEventHandler(myListView_DragOver);
myListView.DragLeave += new EventHandler(myListView_DragLeave);
myListView.DragDrop += new DragEventHandler(myListView_DragDrop);
}
// Initialize the form.
this.Text = "ListView Insertion Mark Example";
this.Controls.Add(myListView);
}
[STAThread]
static void Main()
{
Application.EnableVisualStyles();
Application.Run(new ListViewInsertionMarkExample());
}
// Starts the drag-and-drop operation when an item is dragged.
private void myListView_ItemDrag(object sender, ItemDragEventArgs e)
{
myListView.DoDragDrop(e.Item, DragDropEffects.Move);
}
// Sets the target drop effect.
private void myListView_DragEnter(object sender, DragEventArgs e)
{
e.Effect = e.AllowedEffect;
}
// Moves the insertion mark as the item is dragged.
private void myListView_DragOver(object sender, DragEventArgs e)
{
// Retrieve the client coordinates of the mouse pointer.
Point targetPoint =
myListView.PointToClient(new Point(e.X, e.Y));
// Retrieve the index of the item closest to the mouse pointer.
int targetIndex = myListView.InsertionMark.NearestIndex(targetPoint);
// Confirm that the mouse pointer is not over the dragged item.
if (targetIndex > -1)
{
// Determine whether the mouse pointer is to the left or
// the right of the midpoint of the closest item and set
// the InsertionMark.AppearsAfterItem property accordingly.
Rectangle itemBounds = myListView.GetItemRect(targetIndex);
if ( targetPoint.X > itemBounds.Left + (itemBounds.Width / 2) )
{
myListView.InsertionMark.AppearsAfterItem = true;
}
else
{
myListView.InsertionMark.AppearsAfterItem = false;
}
}
// Set the location of the insertion mark. If the mouse is
// over the dragged item, the targetIndex value is -1 and
// the insertion mark disappears.
myListView.InsertionMark.Index = targetIndex;
}
// Removes the insertion mark when the mouse leaves the control.
private void myListView_DragLeave(object sender, EventArgs e)
{
myListView.InsertionMark.Index = -1;
}
// Moves the item to the location of the insertion mark.
private void myListView_DragDrop(object sender, DragEventArgs e)
{
// Retrieve the index of the insertion mark;
int targetIndex = myListView.InsertionMark.Index;
// If the insertion mark is not visible, exit the method.
if (targetIndex == -1)
{
return;
}
// If the insertion mark is to the right of the item with
// the corresponding index, increment the target index.
if (myListView.InsertionMark.AppearsAfterItem)
{
targetIndex++;
}
// Retrieve the dragged item.
ListViewItem draggedItem =
(ListViewItem)e.Data.GetData(typeof(ListViewItem));
// Insert a copy of the dragged item at the target index.
// A copy must be inserted before the original item is removed
// to preserve item index values.
myListView.Items.Insert(
targetIndex, (ListViewItem)draggedItem.Clone());
// Remove the original copy of the dragged item.
myListView.Items.Remove(draggedItem);
}
// Sorts ListViewItem objects by index.
private class ListViewIndexComparer : System.Collections.IComparer
{
public int Compare(object x, object y)
{
return ((ListViewItem)x).Index - ((ListViewItem)y).Index;
}
}
}
#using <System.dll>
#using <System.Windows.Forms.dll>
#using <System.Drawing.dll>
using namespace System;
using namespace System::Drawing;
using namespace System::Windows::Forms;
public ref class ListViewInsertionMarkExample: public Form
{
private:
ListView^ myListView;
public:
ListViewInsertionMarkExample()
{
// Initialize myListView.
myListView = gcnew ListView;
myListView->Dock = DockStyle::Fill;
myListView->View = View::LargeIcon;
myListView->MultiSelect = false;
myListView->ListViewItemSorter = gcnew ListViewIndexComparer;
// Initialize the insertion mark.
myListView->InsertionMark->Color = Color::Green;
// Add items to myListView.
myListView->Items->Add( "zero" );
myListView->Items->Add( "one" );
myListView->Items->Add( "two" );
myListView->Items->Add( "three" );
myListView->Items->Add( "four" );
myListView->Items->Add( "five" );
// Initialize the drag-and-drop operation when running
// under Windows XP or a later operating system.
if ( System::Environment::OSVersion->Version->Major > 5 || (System::Environment::OSVersion->Version->Major == 5 && System::Environment::OSVersion->Version->Minor >= 1) )
{
myListView->AllowDrop = true;
myListView->ItemDrag += gcnew ItemDragEventHandler( this, &ListViewInsertionMarkExample::myListView_ItemDrag );
myListView->DragEnter += gcnew DragEventHandler( this, &ListViewInsertionMarkExample::myListView_DragEnter );
myListView->DragOver += gcnew DragEventHandler( this, &ListViewInsertionMarkExample::myListView_DragOver );
myListView->DragLeave += gcnew EventHandler( this, &ListViewInsertionMarkExample::myListView_DragLeave );
myListView->DragDrop += gcnew DragEventHandler( this, &ListViewInsertionMarkExample::myListView_DragDrop );
}
// Initialize the form.
this->Text = "ListView Insertion Mark Example";
this->Controls->Add( myListView );
}
private:
// Starts the drag-and-drop operation when an item is dragged.
void myListView_ItemDrag( Object^ /*sender*/, ItemDragEventArgs^ e )
{
myListView->DoDragDrop( e->Item, DragDropEffects::Move );
}
// Sets the target drop effect.
void myListView_DragEnter( Object^ /*sender*/, DragEventArgs^ e )
{
e->Effect = e->AllowedEffect;
}
// Moves the insertion mark as the item is dragged.
void myListView_DragOver( Object^ /*sender*/, DragEventArgs^ e )
{
// Retrieve the client coordinates of the mouse pointer.
Point targetPoint = myListView->PointToClient( Point(e->X,e->Y) );
// Retrieve the index of the item closest to the mouse pointer.
int targetIndex = myListView->InsertionMark->NearestIndex( targetPoint );
// Confirm that the mouse pointer is not over the dragged item.
if ( targetIndex > -1 )
{
// Determine whether the mouse pointer is to the left or
// the right of the midpoint of the closest item and set
// the InsertionMark.AppearsAfterItem property accordingly.
Rectangle itemBounds = myListView->GetItemRect( targetIndex );
if ( targetPoint.X > itemBounds.Left + (itemBounds.Width / 2) )
{
myListView->InsertionMark->AppearsAfterItem = true;
}
else
{
myListView->InsertionMark->AppearsAfterItem = false;
}
}
// Set the location of the insertion mark. If the mouse is
// over the dragged item, the targetIndex value is -1 and
// the insertion mark disappears.
myListView->InsertionMark->Index = targetIndex;
}
// Removes the insertion mark when the mouse leaves the control.
void myListView_DragLeave( Object^ /*sender*/, EventArgs^ /*e*/ )
{
myListView->InsertionMark->Index = -1;
}
// Moves the item to the location of the insertion mark.
void myListView_DragDrop( Object^ /*sender*/, DragEventArgs^ e )
{
// Retrieve the index of the insertion mark;
int targetIndex = myListView->InsertionMark->Index;
// If the insertion mark is not visible, exit the method.
if ( targetIndex == -1 )
{
return;
}
// If the insertion mark is to the right of the item with
// the corresponding index, increment the target index.
if ( myListView->InsertionMark->AppearsAfterItem )
{
targetIndex++;
}
// Retrieve the dragged item.
ListViewItem^ draggedItem = dynamic_cast<ListViewItem^>(e->Data->GetData( ListViewItem::typeid ));
// Insert a copy of the dragged item at the target index.
// A copy must be inserted before the original item is removed
// to preserve item index values.
myListView->Items->Insert( targetIndex, dynamic_cast<ListViewItem^>(draggedItem->Clone()) );
// Remove the original copy of the dragged item.
myListView->Items->Remove( draggedItem );
}
// Sorts ListViewItem objects by index.
ref class ListViewIndexComparer: public System::Collections::IComparer
{
public:
virtual int Compare( Object^ x, Object^ y )
{
return (dynamic_cast<ListViewItem^>(x))->Index - (dynamic_cast<ListViewItem^>(y))->Index;
}
};
};
[STAThread]
int main()
{
Application::EnableVisualStyles();
Application::Run( gcnew ListViewInsertionMarkExample );
}
import System.*;
import System.Drawing.*;
import System.Windows.Forms.*;
public class ListViewInsertionMarkExample extends Form
{
private ListView myListView;
public ListViewInsertionMarkExample()
{
// Initialize myListView.
myListView = new ListView();
myListView.set_Dock(DockStyle.Fill);
myListView.set_View(View.LargeIcon);
myListView.set_MultiSelect(false);
myListView.set_ListViewItemSorter(new ListViewIndexComparer());
// Initialize the insertion mark.
myListView.get_InsertionMark().set_Color(Color.get_Green());
// Add items to myListView.
myListView.get_Items().Add("zero");
myListView.get_Items().Add("one");
myListView.get_Items().Add("two");
myListView.get_Items().Add("three");
myListView.get_Items().Add("four");
myListView.get_Items().Add("five");
// Initialize the drag-and-drop operation when running
// under Windows XP or a later operating system.
if (System.Environment.get_OSVersion().get_Version().get_Major() > 5
|| (System.Environment.get_OSVersion().get_Version().get_Major()
== 5 && System.Environment.get_OSVersion().get_Version().
get_Minor() >= 1)) {
myListView.set_AllowDrop(true);
myListView.add_ItemDrag(new ItemDragEventHandler(
myListView_ItemDrag));
myListView.add_DragEnter(new DragEventHandler(
myListView_DragEnter));
myListView.add_DragOver(new DragEventHandler(myListView_DragOver));
myListView.add_DragLeave(new EventHandler(myListView_DragLeave));
myListView.add_DragDrop(new DragEventHandler(myListView_DragDrop));
}
// Initialize the form.
this.set_Text("ListView Insertion Mark Example");
this.get_Controls().Add(myListView);
} //ListViewInsertionMarkExample
/** @attribute STAThread()
*/
public static void main(String[] args)
{
Application.Run(new ListViewInsertionMarkExample());
} //main
// Starts the drag-and-drop operation when an item is dragged.
private void myListView_ItemDrag(Object sender, ItemDragEventArgs e)
{
myListView.DoDragDrop(e.get_Item(), DragDropEffects.Move);
} //myListView_ItemDrag
// Sets the target drop effect.
private void myListView_DragEnter(Object sender, DragEventArgs e)
{
e.set_Effect(e.get_AllowedEffect());
} //myListView_DragEnter
// Moves the insertion mark as the item is dragged.
private void myListView_DragOver(Object sender, DragEventArgs e)
{
// Retrieve the client coordinates of the mouse pointer.
Point targetPoint = myListView.PointToClient(
new Point(e.get_X(), e.get_Y()));
// Retrieve the index of the item closest to the mouse pointer.
int targetIndex = myListView.get_InsertionMark().
NearestIndex(targetPoint);
// Confirm that the mouse pointer is not over the dragged item.
if (targetIndex > -1) {
// Determine whether the mouse pointer is to the left or
// the right of the midpoint of the closest item and set
// the InsertionMark.AppearsAfterItem property accordingly.
Rectangle itemBounds = myListView.GetItemRect(targetIndex);
if (targetPoint.get_X() > itemBounds.get_Left()
+ itemBounds.get_Width() / 2) {
myListView.get_InsertionMark().set_AppearsAfterItem(true);
}
else {
myListView.get_InsertionMark().set_AppearsAfterItem(false);
}
}
// Set the location of the insertion mark. If the mouse is
// over the dragged item, the targetIndex value is -1 and
// the insertion mark disappears.
myListView.get_InsertionMark().set_Index(targetIndex);
} //myListView_DragOver
// Removes the insertion mark when the mouse leaves the control.
private void myListView_DragLeave(Object sender, EventArgs e)
{
myListView.get_InsertionMark().set_Index(-1);
} //myListView_DragLeave
// Moves the item to the location of the insertion mark.
private void myListView_DragDrop(Object sender, DragEventArgs e)
{
// Retrieve the index of the insertion mark;
int targetIndex = myListView.get_InsertionMark().get_Index();
// If the insertion mark is not visible, exit the method.
if (targetIndex == -1) {
return;
}
// If the insertion mark is to the right of the item with
// the corresponding index, increment the target index.
if (myListView.get_InsertionMark().get_AppearsAfterItem()) {
targetIndex++;
}
// Retrieve the dragged item.
ListViewItem draggedItem = (ListViewItem)(e.get_Data().GetData(
ListViewItem.class.ToType()));
// Insert a copy of the dragged item at the target index.
// A copy must be inserted before the original item is removed
// to preserve item index values.
myListView.get_Items().Insert(targetIndex, (ListViewItem)
draggedItem.Clone());
// Remove the original copy of the dragged item.
myListView.get_Items().Remove(draggedItem);
} //myListView_DragDrop
// Sorts ListViewItem objects by index.
private class ListViewIndexComparer
implements System.Collections.IComparer
{
public int Compare(Object x, Object y)
{
return ((ListViewItem)x).get_Index()
- ((ListViewItem)y).get_Index();
} //Compare
} //ListViewIndexComparer
} //ListViewInsertionMarkExample
Compilazione del codice
Per questo esempio è necessario:
- Riferimenti agli assembly System e System.Windows.Forms.
Per informazioni sulla generazione di questo esempio dalla riga di comando per Visual Basic o Visual C#, vedere Compilazione dalla riga di comando (Visual Basic) o Compilazione dalla riga di comando con csc.exe. È anche possibile generare questo esempio in Visual Studio incollando il codice in un nuovo progetto.
Vedere anche
Attività
Procedura dettagliata: Esecuzione di un'operazione di trascinamento in Windows Form
Concetti
Funzionalità di Windows XP e controlli di Windows Form
Riferimenti
Cenni preliminari sul controllo ListView (Windows Form)