ListBox.ScrollAlwaysVisible ListBox.ScrollAlwaysVisible ListBox.ScrollAlwaysVisible ListBox.ScrollAlwaysVisible Property

定義

取得或設定值,指出是否永遠顯示垂直捲軸。Gets or sets a value indicating whether the vertical scroll bar is shown at all times.

public:
 property bool ScrollAlwaysVisible { bool get(); void set(bool value); };
public bool ScrollAlwaysVisible { get; set; }
member this.ScrollAlwaysVisible : bool with get, set
Public Property ScrollAlwaysVisible As Boolean

屬性值

如果應該永遠顯示垂直捲軸,則為 true,否則為 falsetrue if the vertical scroll bar should always be displayed; otherwise, false. 預設為 falseThe default is false.

範例

下列程式碼範例ListBox示範如何DrawMode將屬性設定為OwnerDrawVariable值並處理DrawItemMeasureItem事件, 藉以進行主控繪製。The following code example demonstrates an owner-drawn ListBox by setting the DrawMode property to the OwnerDrawVariable value and handling the DrawItem and MeasureItem events. 它也會示範如何BorderStyle設定ScrollAlwaysVisible和屬性, 以及AddRange如何使用方法。It also demonstrates setting the BorderStyle and ScrollAlwaysVisible properties and using the AddRange method.

若要執行此範例, 請將它貼入匯入System.Drawing命名空間System.Windows.Forms和命名空間的空白表單中。To run this example, paste it in an empty form that imports the System.Drawing namespace and the System.Windows.Forms namespace. InitializeOwnerDrawnListBox表單的函式或Load事件處理方法呼叫。Call InitializeOwnerDrawnListBox from the form's constructor or Load event-handling method.

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

備註

屬性會指出是否永遠顯示垂直捲動條, 即使ListBox中的專案數不需要顯示垂直捲動條也一樣。 ScrollAlwaysVisibleThe ScrollAlwaysVisible property indicates whether a vertical scroll bar is always displayed, even if the number of items in the ListBox does not require displaying the vertical scroll bar. 根據預設, ListBox只有在有足夠的專案可供顯示時, 才會顯示垂直捲動條。By default, a ListBox only shows a vertical scroll bar when there are enough items to warrant displaying. 若為多行ScrollAlwaysVisible ,屬性工作表示會顯示水準捲軸。ListBoxFor a multicolumn ListBox, the ScrollAlwaysVisible property indicates that a horizontal scroll bar is displayed. 不論多行的這個屬性ListBox值為何, 一律不會顯示垂直捲動條。A vertical scroll bar is never displayed regardless of the value of this property for a multicolumn ListBox.

適用於

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