Visão geral de ScrollViewer
Content within a user interface is often larger than a computer screen's display area. The ScrollViewer control provides a convenient way to enable scrolling of content in Windows Presentation Foundation (WPF) applications. Este tópico apresenta o ScrollViewer elemento e fornece vários exemplos de uso.
This topic contains the following sections:
The ScrollViewer Control
Physical vs. Logical Scrolling
Defining and Using a ScrollViewer Element
Styling a ScrollViewer
Paginating Documents
Related Topics
The ScrollViewer Control
Existem dois elementos predefinidos que permitem a rolagem em WPF aplicativos: ScrollBar and ScrollViewer. O ScrollViewer encapsula o controle horizontal e vertical ScrollBar elementos e um contêiner de conteúdo (como um Panel elemento) para exibir outros elementos visíveis em uma área rolável. Você deve criar um objeto personalizado para usar o ScrollBar elemento para a rolagem de conteúdo. No entanto, você pode usar o ScrollViewer o elemento por si só porque é uma composição de controle que encapsula ScrollBar funcionalidade.
The ScrollViewer control responds to both mouse and keyboard commands, and defines numerous methods with which to scroll content by predetermined increments. You can use the ScrollChanged event to detect a change in a ScrollViewer state.
A ScrollViewer só pode ter um filho, geralmente um Panel o elemento que pode hospedar um Children a coleção de elementos. The Content property defines the sole child of the ScrollViewer.
Físicos vs.Rolagem lógico
Physical scrolling is used to scroll content by a predetermined physical increment, typically by a value that is declared in pixels. Logical scrolling is used to scroll to the next item in the logical tree. Rolagem físico é o comportamento de rolagem de padrão para a maioria das Panel elementos. WPFoferece suporte a ambos os tipos de rolagem.
The IScrollInfo Interface
The IScrollInfo interface represents the main scrolling region within a ScrollViewer or derived control. The interface defines scrolling properties and methods that can be implemented by Panel elements that require scrolling by logical unit, rather than by a physical increment. Casting an instance of IScrollInfo to a derived Panel and then using its scrolling methods provides a useful way to scroll to the next logical unit in a child collection, rather than by pixel increment. By default, the ScrollViewer control supports scrolling by physical units.
StackPanel and VirtualizingStackPanel both implement IScrollInfo and natively support logical scrolling. For layout controls that natively support logical scrolling, you can still achieve physical scrolling by wrapping the host Panel element in a ScrollViewer and setting the CanContentScroll property to false.
The following code example demonstrates how to cast an instance of IScrollInfo to a StackPanel and use content scrolling methods (LineUp and LineDown) defined by the interface.
Private Sub spLineUp(ByVal sender As Object, ByVal args As RoutedEventArgs)
CType(sp1, IScrollInfo).LineUp()
End Sub
Private Sub spLineDown(ByVal sender As Object, ByVal args As RoutedEventArgs)
CType(sp1, IScrollInfo).LineDown()
End Sub
private void spLineUp(object sender, RoutedEventArgs e)
{
((IScrollInfo)sp1).LineUp();
}
private void spLineDown(object sender, RoutedEventArgs e)
{
((IScrollInfo)sp1).LineDown();
}
Defining and Using a ScrollViewer Element
O exemplo a seguir cria um ScrollViewer em uma janela que contém algum texto e um retângulo. ScrollBaros elementos aparecem somente quando forem necessários. When you resize the window, the ScrollBar elements appear and disappear, due to updated values of the ComputedHorizontalScrollBarVisibility and ComputedVerticalScrollBarVisibility properties.
'Define a ScrollViewer.
Dim myScrollViewer As New ScrollViewer
myScrollViewer.HorizontalScrollBarVisibility = ScrollBarVisibility.Auto
'Add Layout control.
Dim myStackPanel As New StackPanel
myStackPanel.HorizontalAlignment = System.Windows.HorizontalAlignment.Left
myStackPanel.VerticalAlignment = System.Windows.VerticalAlignment.Top
Dim myTextBlock As New TextBlock
myTextBlock.TextWrapping = TextWrapping.Wrap
myTextBlock.Margin = New Thickness(0, 0, 0, 20)
myTextBlock.Text = "Scrolling is enabled when it is necessary. Resize the Window, making it larger and smaller."
Dim myRectangle As New Rectangle
myRectangle.Fill = Brushes.Red
myRectangle.Width = 500
myRectangle.Height = 500
'Add child elements to the parent StackPanel.
myStackPanel.Children.Add(myTextBlock)
myStackPanel.Children.Add(myRectangle)
'Add the StackPanel as the lone Child of the Border
myScrollViewer.Content = myStackPanel
Me.Content = myScrollViewer
// Create the application's main window
mainWindow = new Window ();
mainWindow.Title = "ScrollViewer Sample";
// Define a ScrollViewer
myScrollViewer = new ScrollViewer();
myScrollViewer.HorizontalScrollBarVisibility = ScrollBarVisibility.Auto;
// Add Layout control
myStackPanel = new StackPanel();
myStackPanel.HorizontalAlignment = HorizontalAlignment.Left;
myStackPanel.VerticalAlignment = VerticalAlignment.Top;
TextBlock myTextBlock = new TextBlock();
myTextBlock.TextWrapping = TextWrapping.Wrap;
myTextBlock.Margin = new Thickness(0, 0, 0, 20);
myTextBlock.Text = "Scrolling is enabled when it is necessary. Resize the Window, making it larger and smaller.";
Rectangle myRectangle = new Rectangle();
myRectangle.Fill = Brushes.Red;
myRectangle.Width = 500;
myRectangle.Height = 500;
// Add child elements to the parent StackPanel
myStackPanel.Children.Add(myTextBlock);
myStackPanel.Children.Add(myRectangle);
// Add the StackPanel as the lone Child of the Border
myScrollViewer.Content = myStackPanel;
// Add the Border as the Content of the Parent Window Object
mainWindow.Content = myScrollViewer;
mainWindow.Show ();
// Create the application's main window
mainWindow = gcnew System::Windows::Window();
mainWindow->Title = "ScrollViewer Sample";
// Define a ScrollViewer
myScrollViewer = gcnew ScrollViewer();
myScrollViewer->HorizontalScrollBarVisibility = ScrollBarVisibility::Auto;
// Add Layout control
myStackPanel = gcnew StackPanel();
myStackPanel->HorizontalAlignment = HorizontalAlignment::Left;
myStackPanel->VerticalAlignment = VerticalAlignment::Top;
TextBlock^ myTextBlock = gcnew TextBlock();
myTextBlock->TextWrapping = TextWrapping::Wrap;
myTextBlock->Margin = System::Windows::Thickness(0, 0, 0, 20);
myTextBlock->Text = "Scrolling is enabled when it is necessary. Resize the Window, making it larger and smaller.";
Rectangle^ myRectangle = gcnew Rectangle();
myRectangle->Fill = Brushes::Red;
myRectangle->Width = 500;
myRectangle->Height = 500;
// Add child elements to the parent StackPanel
myStackPanel->Children->Add(myTextBlock);
myStackPanel->Children->Add(myRectangle);
// Add the StackPanel as the lone Child of the Border
myScrollViewer->Content = myStackPanel;
// Add the Border as the Content of the Parent Window Object
mainWindow->Content = myScrollViewer;
mainWindow->Show();
<Page xmlns="https://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="https://schemas.microsoft.com/winfx/2006/xaml"
WindowTitle="ScrollViewer Sample">
<ScrollViewer HorizontalScrollBarVisibility="Auto">
<StackPanel VerticalAlignment="Top" HorizontalAlignment="Left">
<TextBlock TextWrapping="Wrap" Margin="0,0,0,20">Scrolling is enabled when it is necessary.
Resize the window, making it larger and smaller.</TextBlock>
<Rectangle Fill="Red" Width="500" Height="500"></Rectangle>
</StackPanel>
</ScrollViewer>
</Page>
Styling a ScrollViewer
Like all controls in Windows Presentation Foundation, the ScrollViewer can be styled in order to change the default rendering behavior of the control. For additional information on control styling, see Styling and Templating.
Paginating Documents
For document content, an alternative to scrolling is to choose a document container that supports pagination. FlowDocumenté para documentos que são projetados para ser hospedado em um controle de exibição, como FlowDocumentPageViewer, que oferece suporte a paginating de conteúdo em várias páginas, evitando a necessidade de rolagem. DocumentViewerFornece uma solução para visualização FixedDocument o conteúdo, que usa o tradicional de rolagem para exibir o conteúdo fora do território da área de exibição.
For additional information about document formats and presentation options, see Documentos no WPF.