LayoutEngine Classe

Definição

Namespace:

System.Windows.Forms.Layout

Assembly:

System.Windows.Forms.dll

Fornece a classe base para implementar mecanismos de layout.

public ref class LayoutEngine abstract

public abstract class LayoutEngine

type LayoutEngine = class

Public MustInherit Class LayoutEngine

Herança

Object

LayoutEngine

Exemplos

O exemplo de código a seguir demonstra o uso da classe para implementar o LayoutEngine comportamento de layout personalizado.

#using <System.Drawing.dll>
#using <System.dll>
#using <System.Windows.Forms.dll>

using namespace System;
using namespace System::Collections::Generic;
using namespace System::Drawing;
using namespace System::Text;
using namespace System::Windows::Forms;
using namespace System::Windows::Forms::Layout;

// This class demonstrates a simple custom layout engine.
public ref class DemoFlowLayout : public LayoutEngine
{
public:
    virtual bool Layout(Object^ container,
        LayoutEventArgs^ layoutEventArgs) override
    {
        Control^ parent = nullptr;
        try
        {
            parent = (Control ^) container;
        }
        catch (InvalidCastException^ ex)
        {
            throw gcnew ArgumentException(
                "The parameter 'container' must be a control", "container", ex);
        }
        // Use DisplayRectangle so that parent.Padding is honored.
        Rectangle parentDisplayRectangle = parent->DisplayRectangle;
        Point nextControlLocation = parentDisplayRectangle.Location;

        for each (Control^ currentControl in parent->Controls)
        {
            // Only apply layout to visible controls.
            if (!currentControl->Visible)
            {
                continue;
            }

            // Respect the margin of the control:
            // shift over the left and the top.
            nextControlLocation.Offset(currentControl->Margin.Left,
                currentControl->Margin.Top);

            // Set the location of the control.
            currentControl->Location = nextControlLocation;

            // Set the autosized controls to their
            // autosized heights.
            if (currentControl->AutoSize)
            {
                currentControl->Size = currentControl->GetPreferredSize(
                    parentDisplayRectangle.Size);
            }

            // Move X back to the display rectangle origin.
            nextControlLocation.X = parentDisplayRectangle.X;

            // Increment Y by the height of the control
            // and the bottom margin.
            nextControlLocation.Y += currentControl->Height +
                currentControl->Margin.Bottom;
        }

        // Optional: Return whether or not the container's
        // parent should perform layout as a result of this
        // layout. Some layout engines return the value of
        // the container's AutoSize property.

        return false;
    }
};

// This class demonstrates a simple custom layout panel.
// It overrides the LayoutEngine property of the Panel
// control to provide a custom layout engine.
public ref class DemoFlowPanel : public Panel
{
private:
    DemoFlowLayout^ layoutEngine;

public:
    DemoFlowPanel()
    {
        layoutEngine = gcnew DemoFlowLayout();
    }

public:
    virtual property System::Windows::Forms::Layout::LayoutEngine^ LayoutEngine
    {
        System::Windows::Forms::Layout::LayoutEngine^ get() override
        {
            if (layoutEngine == nullptr)
            {
                layoutEngine = gcnew DemoFlowLayout();
            }

            return layoutEngine;
        }
    }
};

using System;
using System.Collections.Generic;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using System.Windows.Forms.Layout;

// This class demonstrates a simple custom layout panel.
// It overrides the LayoutEngine property of the Panel
// control to provide a custom layout engine. 
public class DemoFlowPanel : Panel
{
    private DemoFlowLayout layoutEngine;

    public DemoFlowPanel()
    {
    }

    public override LayoutEngine LayoutEngine
    {
        get
        {
            layoutEngine ??= new DemoFlowLayout();

            return layoutEngine;
        }
    }
}

// This class demonstrates a simple custom layout engine.
public class DemoFlowLayout : LayoutEngine
{
    public override bool Layout(
        object container,
        LayoutEventArgs layoutEventArgs)
    {
        Control parent = container as Control;

        // Use DisplayRectangle so that parent.Padding is honored.
        Rectangle parentDisplayRectangle = parent.DisplayRectangle;
        Point nextControlLocation = parentDisplayRectangle.Location;

        foreach (Control c in parent.Controls)
        {
            // Only apply layout to visible controls.
            if (!c.Visible)
            {
                continue;
            }

            // Respect the margin of the control:
            // shift over the left and the top.
            nextControlLocation.Offset(c.Margin.Left, c.Margin.Top);

            // Set the location of the control.
            c.Location = nextControlLocation;

            // Set the autosized controls to their 
            // autosized heights.
            if (c.AutoSize)
            {
                c.Size = c.GetPreferredSize(parentDisplayRectangle.Size);
            }

            // Move X back to the display rectangle origin.
            nextControlLocation.X = parentDisplayRectangle.X;

            // Increment Y by the height of the control 
            // and the bottom margin.
            nextControlLocation.Y += c.Height + c.Margin.Bottom;
        }

        // Optional: Return whether or not the container's 
        // parent should perform layout as a result of this 
        // layout. Some layout engines return the value of 
        // the container's AutoSize property.

        return false;
    }
}

Imports System.Collections.Generic
Imports System.Drawing
Imports System.Text
Imports System.Windows.Forms
Imports System.Windows.Forms.Layout

' This class demonstrates a simple custom layout panel.
' It overrides the LayoutEngine property of the Panel
' control to provide a custom layout engine. 
Public Class DemoFlowPanel
    Inherits Panel

    Private layoutEng As DemoFlowLayout

    Public Sub New()
    End Sub

    Public Overrides ReadOnly Property LayoutEngine() As LayoutEngine
        Get
            If layoutEng Is Nothing Then
                layoutEng = New DemoFlowLayout()
            End If

            Return layoutEng
        End Get
    End Property
End Class

' This class demonstrates a simple custom layout engine.
Public Class DemoFlowLayout
   Inherits LayoutEngine

    Public Overrides Function Layout( _
    ByVal container As Object, _
    ByVal layoutEventArgs As LayoutEventArgs) As Boolean

        Dim parent As Control = container

        ' Use DisplayRectangle so that parent.Padding is honored.
        Dim parentDisplayRectangle As Rectangle = parent.DisplayRectangle
        Dim nextControlLocation As Point = parentDisplayRectangle.Location

        Dim c As Control
        For Each c In parent.Controls

            ' Only apply layout to visible controls.
            If c.Visible <> True Then
                Continue For
            End If

            ' Respect the margin of the control:
            ' shift over the left and the top.
            nextControlLocation.Offset(c.Margin.Left, c.Margin.Top)

            ' Set the location of the control.
            c.Location = nextControlLocation

            ' Set the autosized controls to their 
            ' autosized heights.
            If c.AutoSize Then
                c.Size = c.GetPreferredSize(parentDisplayRectangle.Size)
            End If

            ' Move X back to the display rectangle origin.
            nextControlLocation.X = parentDisplayRectangle.X

            ' Increment Y by the height of the control 
            ' and the bottom margin.
            nextControlLocation.Y += c.Height + c.Margin.Bottom
        Next c

        ' Optional: Return whether or not the container's 
        ' parent should perform layout as a result of this 
        ' layout. Some layout engines return the value of 
        ' the container's AutoSize property.
        Return False

    End Function
End Class

Comentários

Use a LayoutEngine classe quando quiser criar um comportamento de layout personalizado em tempo de execução. Derive sua própria classe da LayoutEngine classe e substitua o método para definir seu Layout comportamento de layout personalizado.

Construtores

LayoutEngine()

Inicializa uma nova instância da classe LayoutEngine.

Métodos

Equals(Object)	Determina se o objeto especificado é igual ao objeto atual. (Herdado de Object)
GetHashCode()	Serve como a função de hash padrão. (Herdado de Object)
GetType()	Obtém o Type da instância atual. (Herdado de Object)
InitLayout(Object, BoundsSpecified)	Inicializa o mecanismo de layout.
Layout(Object, LayoutEventArgs)	Solicita que o mecanismo de layout execute uma operação de layout.
MemberwiseClone()	Cria uma cópia superficial do Object atual. (Herdado de Object)
ToString()	Retorna uma cadeia de caracteres que representa o objeto atual. (Herdado de Object)

Confira também

• Como: Implementar um mecanismo de layout personalizado