ListBox.MeasureItem Événement
Définition
Important
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Se produit lorsqu’un propriétaire ListBox est créé et que les tailles des éléments de liste sont déterminées.
public:
event System::Windows::Forms::MeasureItemEventHandler ^ MeasureItem;public event System.Windows.Forms.MeasureItemEventHandler MeasureItem;public event System.Windows.Forms.MeasureItemEventHandler? MeasureItem;member this.MeasureItem : System.Windows.Forms.MeasureItemEventHandler Public Custom Event MeasureItem As MeasureItemEventHandler Type d'événement
Exemples
L’exemple de code suivant illustre un dessin propriétaire en ListBox définissant la DrawMode propriété sur OwnerDrawVariable et en gérant les événements et MeasureItem les DrawItem événements. Il illustre également la définition des BorderStyle propriétés et ScrollAlwaysVisible l’utilisation de la AddRange méthode.
Pour exécuter cet exemple, collez-le dans un formulaire vide qui importe l’espace System.Drawing de noms et l’espace System.Windows.Forms de noms. Appel InitializeOwnerDrawnListBox à partir du constructeur ou Load de la méthode de gestion des événements du formulaire.
internal:
System::Windows::Forms::ListBox^ ListBox1;
private:
void InitializeOwnerDrawnListBox()
{
this->ListBox1 = gcnew System::Windows::Forms::ListBox;
// Set the location and size.
ListBox1->Location = Point(20,20);
ListBox1->Size = System::Drawing::Size( 240, 240 );
// Populate the ListBox.ObjectCollection property
// with several strings, using the AddRange method.
array<Object^>^temp0 = {"System.Windows.Forms","System.Drawing","System.Xml","System.Net","System.Runtime.Remoting","System.Web"};
this->ListBox1->Items->AddRange( temp0 );
// Turn off the scrollbar.
ListBox1->ScrollAlwaysVisible = false;
// Set the border style to a single, flat border.
ListBox1->BorderStyle = BorderStyle::FixedSingle;
// Set the DrawMode property to the OwnerDrawVariable value.
// This means the MeasureItem and DrawItem events must be
// handled.
ListBox1->DrawMode = DrawMode::OwnerDrawVariable;
ListBox1->MeasureItem += gcnew MeasureItemEventHandler( this, &Form1::ListBox1_MeasureItem );
ListBox1->DrawItem += gcnew DrawItemEventHandler( this, &Form1::ListBox1_DrawItem );
this->Controls->Add( this->ListBox1 );
}
// Handle the DrawItem event for an owner-drawn ListBox.
void ListBox1_DrawItem( Object^ /*sender*/, DrawItemEventArgs^ e )
{
// If the item is the selected item, then draw the rectangle
// filled in blue. The item is selected when a bitwise And
// of the State property and the DrawItemState.Selected
// property is true.
if ( (e->State & DrawItemState::Selected) == DrawItemState::Selected )
{
e->Graphics->FillRectangle( Brushes::CornflowerBlue, e->Bounds );
}
else
{
// Otherwise, draw the rectangle filled in beige.
e->Graphics->FillRectangle( Brushes::Beige, e->Bounds );
}
// Draw a rectangle in blue around each item.
e->Graphics->DrawRectangle( Pens::Blue, e->Bounds );
// Draw the text in the item.
e->Graphics->DrawString( ListBox1->Items[ e->Index ]->ToString(), this->Font, Brushes::Black, (float)e->Bounds.X, (float)e->Bounds.Y );
// Draw the focus rectangle around the selected item.
e->DrawFocusRectangle();
}
// Handle the MeasureItem event for an owner-drawn ListBox.
void ListBox1_MeasureItem( Object^ sender, MeasureItemEventArgs^ e )
{
// Cast the sender object back to ListBox type.
ListBox^ theListBox = dynamic_cast<ListBox^>(sender);
// Get the string contained in each item.
String^ itemString = dynamic_cast<String^>(theListBox->Items[ e->Index ]);
// Split the string at the " . " character.
array<Char>^temp1 = {'.'};
array<String^>^resultStrings = itemString->Split( temp1 );
// If the string contains more than one period, increase the
// height by ten pixels; otherwise, increase the height by
// five pixels.
if ( resultStrings->Length > 2 )
{
e->ItemHeight += 10;
}
else
{
e->ItemHeight += 5;
}
}
internal System.Windows.Forms.ListBox ListBox1;
private void InitializeOwnerDrawnListBox()
{
this.ListBox1 = new System.Windows.Forms.ListBox();
// Set the location and size.
ListBox1.Location = new Point(20, 20);
ListBox1.Size = new Size(240, 240);
// Populate the ListBox.ObjectCollection property
// with several strings, using the AddRange method.
this.ListBox1.Items.AddRange(new object[]{"System.Windows.Forms",
"System.Drawing", "System.Xml", "System.Net", "System.Runtime.Remoting",
"System.Web"});
// Turn off the scrollbar.
ListBox1.ScrollAlwaysVisible = false;
// Set the border style to a single, flat border.
ListBox1.BorderStyle = BorderStyle.FixedSingle;
// Set the DrawMode property to the OwnerDrawVariable value.
// This means the MeasureItem and DrawItem events must be
// handled.
ListBox1.DrawMode = DrawMode.OwnerDrawVariable;
ListBox1.MeasureItem +=
new MeasureItemEventHandler(ListBox1_MeasureItem);
ListBox1.DrawItem += new DrawItemEventHandler(ListBox1_DrawItem);
this.Controls.Add(this.ListBox1);
}
// Handle the DrawItem event for an owner-drawn ListBox.
private void ListBox1_DrawItem(object sender, DrawItemEventArgs e)
{
// If the item is the selected item, then draw the rectangle
// filled in blue. The item is selected when a bitwise And
// of the State property and the DrawItemState.Selected
// property is true.
if ((e.State & DrawItemState.Selected) == DrawItemState.Selected)
{
e.Graphics.FillRectangle(Brushes.CornflowerBlue, e.Bounds);
}
else
{
// Otherwise, draw the rectangle filled in beige.
e.Graphics.FillRectangle(Brushes.Beige, e.Bounds);
}
// Draw a rectangle in blue around each item.
e.Graphics.DrawRectangle(Pens.Blue, e.Bounds);
// Draw the text in the item.
e.Graphics.DrawString(ListBox1.Items[e.Index].ToString(),
this.Font, Brushes.Black, e.Bounds.X, e.Bounds.Y);
// Draw the focus rectangle around the selected item.
e.DrawFocusRectangle();
}
// Handle the MeasureItem event for an owner-drawn ListBox.
private void ListBox1_MeasureItem(object sender,
MeasureItemEventArgs e)
{
// Cast the sender object back to ListBox type.
ListBox theListBox = (ListBox) sender;
// Get the string contained in each item.
string itemString = (string) theListBox.Items[e.Index];
// Split the string at the " . " character.
string[] resultStrings = itemString.Split('.');
// If the string contains more than one period, increase the
// height by ten pixels; otherwise, increase the height by
// five pixels.
if (resultStrings.Length>2)
{
e.ItemHeight += 10;
}
else
{
e.ItemHeight += 5;
}
}
Friend WithEvents ListBox1 As System.Windows.Forms.ListBox
Private Sub InitializeOwnerDrawnListBox()
Me.ListBox1 = New System.Windows.Forms.ListBox
' Set the location and size.
ListBox1.Location = New Point(20, 20)
ListBox1.Size = New Size(240, 240)
' Populate the ListBox.ObjectCollection property
' with several strings, using the AddRange method.
Me.ListBox1.Items.AddRange(New Object() _
{"System.Windows.Forms", "System.Drawing", "System.Xml", _
"System.Net", "System.Runtime.Remoting", "System.Web"})
' Turn off the scrollbar.
ListBox1.ScrollAlwaysVisible = False
' Set the border style to a single, flat border.
ListBox1.BorderStyle = BorderStyle.FixedSingle
' Set the DrawMode property to the OwnerDrawVariable value.
' This means the MeasureItem and DrawItem events must be
' handled.
ListBox1.DrawMode = DrawMode.OwnerDrawVariable
Me.Controls.Add(Me.ListBox1)
End Sub
' Handle the DrawItem event for an owner-drawn ListBox.
Private Sub ListBox1_DrawItem(ByVal sender As Object, _
ByVal e As DrawItemEventArgs) Handles ListBox1.DrawItem
' If the item is the selected item, then draw the rectangle filled in
' blue. The item is selected when a bitwise And of the State property
' and the DrawItemState.Selected property is true.
If (e.State And DrawItemState.Selected = DrawItemState.Selected) Then
e.Graphics.FillRectangle(Brushes.CornflowerBlue, e.Bounds)
Else
' Otherwise, draw the rectangle filled in beige.
e.Graphics.FillRectangle(Brushes.Beige, e.Bounds)
End If
' Draw a rectangle in blue around each item.
e.Graphics.DrawRectangle(Pens.Blue, e.Bounds)
' Draw the text in the item.
e.Graphics.DrawString(Me.ListBox1.Items(e.Index), Me.Font, _
Brushes.Black, e.Bounds.X, e.Bounds.Y)
' Draw the focus rectangle around the selected item.
e.DrawFocusRectangle()
End Sub
' Handle the MeasureItem event for an owner-drawn ListBox.
Private Sub ListBox1_MeasureItem(ByVal sender As Object, _
ByVal e As MeasureItemEventArgs) Handles ListBox1.MeasureItem
' Cast the sender object back to ListBox type.
Dim theListBox As ListBox = CType(sender, ListBox)
' Get the string contained in each item.
Dim itemString As String = CType(theListBox.Items(e.Index), String)
' Split the string at the " . " character.
Dim resultStrings() As String = itemString.Split(".")
' If the string contains more than one period, increase the
' height by ten pixels; otherwise, increase the height by
' five pixels.
If (resultStrings.Length > 2) Then
e.ItemHeight += 10
Else
e.ItemHeight += 5
End If
End Sub
Remarques
Vous pouvez créer un gestionnaire d’événements pour cet événement pour spécifier la taille d’un élément avant qu’il ne soit dessiné dans l’événement DrawItem . L’événement est déclenché uniquement lorsque la DrawMode propriété est définie sur OwnerDrawVariable.
La hauteur maximale valide d’un ListBox élément est de 255 pixels. La définition de la propriété sur une valeur supérieure à 255 lors de la ItemHeight gestion de MeasureItemEventArgs cet événement peut produire des résultats inattendus.
Pour plus d'informations sur la gestion des événements, voir gestion et déclenchement d’événements.
