ListBox.MeasureItem Olay

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 

Olay Türü

Örnekler

Aşağıdaki kod örneği, özelliğini OwnerDrawVariable olarak ayarlayıp DrawMode ve MeasureItem olaylarını işleyerek DrawItem sahip tarafından çizilmiş ListBox bir örneği gösterir. Ayrıca ve ScrollAlwaysVisible özelliklerini ayarlamayı BorderStyle ve yöntemini kullanmayı AddRange gösterir.

Bu örneği çalıştırmak için ad alanını ve ad alanını içeri aktaran System.Drawing boş bir forma yapıştırın System.Windows.Forms . Formun oluşturucusundan veya Load olay işleme yönteminden çağrısıInitializeOwnerDrawnListBox.

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

Açıklamalar

Bir öğenin olayda DrawItem çizilmeden önce oluşturulacağı boyutu belirtmek üzere bu olay için bir olay işleyicisi oluşturabilirsiniz. Olay yalnızca özelliği olarak ayarlandığında OwnerDrawVariableoluşturulurDrawMode.

Bir öğenin geçerli yüksekliği üst ListBox sınırı 255 pikseldir. ItemHeight bu olayı işlerken özelliğini MeasureItemEventArgs 255'ten büyük bir değere ayarlamak beklenmeyen sonuçlar verebilir.

Olayları işleme hakkında daha fazla bilgi için bkz. Olayları İşleme ve Oluşturma.

Şunlara uygulanır

Ayrıca bkz.

• ItemHeight