DrawListViewItemEventArgs Classe

Definizione

Fornisce i dati per l'evento DrawItem.Provides data for the DrawItem event.

public ref class DrawListViewItemEventArgs : EventArgs
public class DrawListViewItemEventArgs : EventArgs
type DrawListViewItemEventArgs = class
    inherit EventArgs
Public Class DrawListViewItemEventArgs
Inherits EventArgs
Ereditarietà
DrawListViewItemEventArgs

Esempio

Nell'esempio di codice riportato di seguito viene illustrato come fornire un disegno personalizzato per un controllo ListView.The following code example demonstrates how to provide custom drawing for a ListView control. Il controllo ListView nell'esempio ha uno sfondo sfumato.The ListView control in the example has a gradient background. Gli elementi secondari con valori negativi hanno un primo piano rosso e uno sfondo nero.Subitems with negative values have a red foreground and a black background.

Un gestore per l'evento ListView.DrawItem disegna lo sfondo per interi elementi.A handler for the ListView.DrawItem event draws the background for entire items. Un gestore per l'evento ListView.DrawSubItem disegna i valori di testo e il testo e lo sfondo degli elementi secondari con valori negativi.A handler for the ListView.DrawSubItem event draws the text values and both the text and background for subitems that have negative values. Un gestore per l'evento DrawColumnHeader disegna ogni intestazione di colonna.A handler for the DrawColumnHeader event draws each column header.

Un componente ContextMenu consente di passare dalla visualizzazione dettagli alla visualizzazione elenco e viceversa.A ContextMenu component provides a way to switch between the details view and the list view. Nella visualizzazione elenco viene attivato solo l'evento ListView.DrawItem.In the list view, only the ListView.DrawItem event is fired. In questo caso, il testo e lo sfondo vengono entrambi disegnati nel gestore dell'evento ListView.DrawItem.In this case, the text and background are both drawn in the ListView.DrawItem event handler.

using System;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Globalization;
using System.Windows.Forms;

public class ListViewOwnerDraw : Form
{
    private ListView listView1 = new ListView();
    private ContextMenu contextMenu1 = new ContextMenu();

    public ListViewOwnerDraw()
    {
        // Initialize the ListView control.
        listView1.BackColor = Color.Black;
        listView1.ForeColor = Color.White;
        listView1.Dock = DockStyle.Fill;
        listView1.View = View.Details;
        listView1.FullRowSelect = true;

        // Add columns to the ListView control.
        listView1.Columns.Add("Name", 100, HorizontalAlignment.Center);
        listView1.Columns.Add("First", 100, HorizontalAlignment.Center);
        listView1.Columns.Add("Second", 100, HorizontalAlignment.Center);
        listView1.Columns.Add("Third", 100, HorizontalAlignment.Center);

        // Create items and add them to the ListView control.
        ListViewItem listViewItem1 = new ListViewItem(new string[] { "One", "20", "30", "-40" }, -1);
        ListViewItem listViewItem2 = new ListViewItem(new string[] { "Two", "-250", "145", "37" }, -1);
        ListViewItem listViewItem3 = new ListViewItem(new string[] { "Three", "200", "800", "-1,001" }, -1);
        ListViewItem listViewItem4 = new ListViewItem(new string[] { "Four", "not available", "-2", "100" }, -1);
        listView1.Items.AddRange(new ListViewItem[] { listViewItem1, listViewItem2, listViewItem3, listViewItem4 });

        // Initialize the shortcut menu and 
        // assign it to the ListView control.
        contextMenu1.MenuItems.Add("List",
            new EventHandler(menuItemList_Click));
        contextMenu1.MenuItems.Add("Details",
            new EventHandler(menuItemDetails_Click));
        listView1.ContextMenu = contextMenu1;

        // Configure the ListView control for owner-draw and add 
        // handlers for the owner-draw events.
        listView1.OwnerDraw = true;
        listView1.DrawItem += new
            DrawListViewItemEventHandler(listView1_DrawItem);
        listView1.DrawSubItem += new
            DrawListViewSubItemEventHandler(listView1_DrawSubItem);
        listView1.DrawColumnHeader += new
            DrawListViewColumnHeaderEventHandler(listView1_DrawColumnHeader);

        // Add a handler for the MouseUp event so an item can be 
        // selected by clicking anywhere along its width.
        listView1.MouseUp += new MouseEventHandler(listView1_MouseUp);

        // Add handlers for various events to compensate for an 
        // extra DrawItem event that occurs the first time the mouse 
        // moves over each row. 
        listView1.MouseMove += new MouseEventHandler(listView1_MouseMove);
        listView1.ColumnWidthChanged += new ColumnWidthChangedEventHandler(listView1_ColumnWidthChanged);
        listView1.Invalidated += new InvalidateEventHandler(listView1_Invalidated);

        // Initialize the form and add the ListView control to it.
        this.ClientSize = new Size(450, 150);
        this.FormBorderStyle = FormBorderStyle.FixedSingle;
        this.MaximizeBox = false;
        this.Text = "ListView OwnerDraw Example";
        this.Controls.Add(listView1);
    }

    // Clean up any resources being used.        
    protected override void Dispose(bool disposing)
    {
        if (disposing)
        {
            contextMenu1.Dispose();
        }
        base.Dispose(disposing);
    }

    [STAThread]
    static void Main()
    {
        Application.EnableVisualStyles();
        Application.Run(new ListViewOwnerDraw());
    }

    // Sets the ListView control to the List view.
    private void menuItemList_Click(object sender, EventArgs e)
    {
        listView1.View = View.List;
        listView1.Invalidate();
    }

    // Sets the ListView control to the Details view.
    private void menuItemDetails_Click(object sender, EventArgs e)
    {
        listView1.View = View.Details;

        // Reset the tag on each item to re-enable the workaround in
        // the MouseMove event handler.
        foreach (ListViewItem item in listView1.Items)
        {
            item.Tag = null;
        }
    }

    // Selects and focuses an item when it is clicked anywhere along 
    // its width. The click must normally be on the parent item text.
    private void listView1_MouseUp(object sender, MouseEventArgs e)
    {
        ListViewItem clickedItem = listView1.GetItemAt(5, e.Y);
        if (clickedItem != null)
        {
            clickedItem.Selected = true;
            clickedItem.Focused = true;
        }
    }

    // Draws the backgrounds for entire ListView items.
    private void listView1_DrawItem(object sender,
        DrawListViewItemEventArgs e)
    {
        if ((e.State & ListViewItemStates.Selected) != 0)
        {
            // Draw the background and focus rectangle for a selected item.
            e.Graphics.FillRectangle(Brushes.Maroon, e.Bounds);
            e.DrawFocusRectangle();
        }
        else
        {
            // Draw the background for an unselected item.
            using (LinearGradientBrush brush =
                new LinearGradientBrush(e.Bounds, Color.Orange,
                Color.Maroon, LinearGradientMode.Horizontal))
            {
                e.Graphics.FillRectangle(brush, e.Bounds);
            }
        }

        // Draw the item text for views other than the Details view.
        if (listView1.View != View.Details)
        {
            e.DrawText();
        }
    }

    // Draws subitem text and applies content-based formatting.
    private void listView1_DrawSubItem(object sender,
        DrawListViewSubItemEventArgs e)
    {
        TextFormatFlags flags = TextFormatFlags.Left;

        using (StringFormat sf = new StringFormat())
        {
            // Store the column text alignment, letting it default
            // to Left if it has not been set to Center or Right.
            switch (e.Header.TextAlign)
            {
                case HorizontalAlignment.Center:
                    sf.Alignment = StringAlignment.Center;
                    flags = TextFormatFlags.HorizontalCenter;
                    break;
                case HorizontalAlignment.Right:
                    sf.Alignment = StringAlignment.Far;
                    flags = TextFormatFlags.Right;
                    break;
            }

            // Draw the text and background for a subitem with a 
            // negative value. 
            double subItemValue;
            if (e.ColumnIndex > 0 && Double.TryParse(
                e.SubItem.Text, NumberStyles.Currency,
                NumberFormatInfo.CurrentInfo, out subItemValue) &&
                subItemValue < 0)
            {
                // Unless the item is selected, draw the standard 
                // background to make it stand out from the gradient.
                if ((e.ItemState & ListViewItemStates.Selected) == 0)
                {
                    e.DrawBackground();
                }

                // Draw the subitem text in red to highlight it. 
                e.Graphics.DrawString(e.SubItem.Text,
                    listView1.Font, Brushes.Red, e.Bounds, sf);

                return;
            }

            // Draw normal text for a subitem with a nonnegative 
            // or nonnumerical value.
            e.DrawText(flags);
        }
    }

    // Draws column headers.
    private void listView1_DrawColumnHeader(object sender,
        DrawListViewColumnHeaderEventArgs e)
    {
        using (StringFormat sf = new StringFormat())
        {
            // Store the column text alignment, letting it default
            // to Left if it has not been set to Center or Right.
            switch (e.Header.TextAlign)
            {
                case HorizontalAlignment.Center:
                    sf.Alignment = StringAlignment.Center;
                    break;
                case HorizontalAlignment.Right:
                    sf.Alignment = StringAlignment.Far;
                    break;
            }

            // Draw the standard header background.
            e.DrawBackground();

            // Draw the header text.
            using (Font headerFont =
                        new Font("Helvetica", 10, FontStyle.Bold))
            {
                e.Graphics.DrawString(e.Header.Text, headerFont,
                    Brushes.Black, e.Bounds, sf);
            }
        }
        return;
    }

    // Forces each row to repaint itself the first time the mouse moves over 
    // it, compensating for an extra DrawItem event sent by the wrapped 
    // Win32 control. This issue occurs each time the ListView is invalidated.
    private void listView1_MouseMove(object sender, MouseEventArgs e)
    {
        ListViewItem item = listView1.GetItemAt(e.X, e.Y);
        if (item != null && item.Tag == null)
        {
            listView1.Invalidate(item.Bounds);
            item.Tag = "tagged";
        }
    }

    // Resets the item tags. 
    void listView1_Invalidated(object sender, InvalidateEventArgs e)
    {
        foreach (ListViewItem item in listView1.Items)
        {
            if (item == null) return;
            item.Tag = null;
        }
    }

    // Forces the entire control to repaint if a column width is changed.
    void listView1_ColumnWidthChanged(object sender, 
        ColumnWidthChangedEventArgs e)
    {
        listView1.Invalidate();
    }
}
Imports System.Drawing
Imports System.Drawing.Drawing2D
Imports System.Globalization
Imports System.Windows.Forms

Public Class ListViewOwnerDraw
    Inherits Form
    Private WithEvents listView1 As New ListView()
    Private WithEvents contextMenu1 As New ContextMenu()
    Private WithEvents listMenuItem As New MenuItem("List")
    Private WithEvents detailsMenuItem As New MenuItem("Details")

    Public Sub New()

        ' Initialize the shortcut menu. 
        contextMenu1.MenuItems.AddRange(New MenuItem() _
            {Me.listMenuItem, Me.detailsMenuItem})

        ' Initialize the ListView control.
        With Me.listView1
            .BackColor = Color.Black
            .ForeColor = Color.White
            .Dock = DockStyle.Fill
            .View = View.Details
            .FullRowSelect = True
            .OwnerDraw = True
            .ContextMenu = Me.contextMenu1
        End With

        ' Add columns to the ListView control.
        With Me.listView1.Columns
            .Add("Name", 100, HorizontalAlignment.Center)
            .Add("First", 100, HorizontalAlignment.Center)
            .Add("Second", 100, HorizontalAlignment.Center)
            .Add("Third", 100, HorizontalAlignment.Center)
        End With

        ' Create items and add them to the ListView control.
        Dim listViewItem1 As New ListViewItem(New String() _
            {"One", "20", "30", "-40"}, -1)
        Dim listViewItem2 As New ListViewItem(New String() _
            {"Two", "-250", "145", "37"}, -1)
        Dim listViewItem3 As New ListViewItem(New String() _
            {"Three", "200", "800", "-1,001"}, -1)
        Dim listViewItem4 As New ListViewItem(New String() _
            {"Four", "not available", "-2", "100"}, -1)
        Me.listView1.Items.AddRange(New ListViewItem() _
            {listViewItem1, listViewItem2, listViewItem3, listViewItem4})

        ' Initialize the form and add the ListView control to it.
        With Me
            .ClientSize = New Size(450, 150)
            .FormBorderStyle = FormBorderStyle.FixedSingle
            .MaximizeBox = False
            .Text = "ListView OwnerDraw Example"
            .Controls.Add(Me.listView1)
        End With

    End Sub

    ' Clean up any resources being used.        
    Protected Overrides Sub Dispose(ByVal disposing As Boolean)
        If disposing Then
            contextMenu1.Dispose()
        End If
        MyBase.Dispose(disposing)
    End Sub

    <STAThread()> _
    Shared Sub Main()
        Application.Run(New ListViewOwnerDraw())
    End Sub

    ' Sets the ListView control to the List view.
    Private Sub menuItemList_Click(ByVal sender As Object, _
        ByVal e As EventArgs) _
        Handles listMenuItem.Click

        Me.listView1.View = View.List

    End Sub

    ' Sets the ListView control to the Details view.
    Private Sub menuItemDetails_Click(ByVal sender As Object, _
        ByVal e As EventArgs) _
        Handles detailsMenuItem.Click

        Me.listView1.View = View.Details

        ' Reset the tag on each item to re-enable the workaround 
        ' in the MouseMove event handler.
        For Each item As ListViewItem In listView1.Items
            item.Tag = Nothing
        Next

    End Sub

    ' Selects and focuses an item when it is clicked anywhere along 
    ' its width. The click must normally be on the parent item text.
    Private Sub listView1_MouseUp(ByVal sender As Object, _
        ByVal e As MouseEventArgs) _
        Handles listView1.MouseUp

        Dim clickedItem As ListViewItem = Me.listView1.GetItemAt(5, e.Y)
        If (clickedItem IsNot Nothing) Then
            clickedItem.Selected = True
            clickedItem.Focused = True
        End If

    End Sub

    ' Draws the backgrounds for entire ListView items.
    Private Sub listView1_DrawItem(ByVal sender As Object, _
        ByVal e As DrawListViewItemEventArgs) _
        Handles listView1.DrawItem

        If Not (e.State And ListViewItemStates.Selected) = 0 Then

            ' Draw the background for a selected item.
            e.Graphics.FillRectangle(Brushes.Maroon, e.Bounds)
            e.DrawFocusRectangle()

        Else

            ' Draw the background for an unselected item.
            Dim brush As New LinearGradientBrush(e.Bounds, Color.Orange, _
                Color.Maroon, LinearGradientMode.Horizontal)
            Try
                e.Graphics.FillRectangle(brush, e.Bounds)
            Finally
                brush.Dispose()
            End Try

        End If

        ' Draw the item text for views other than the Details view.
        If Not Me.listView1.View = View.Details Then
            e.DrawText()
        End If

    End Sub

    ' Draws subitem text and applies content-based formatting.
    Private Sub listView1_DrawSubItem(ByVal sender As Object, _
        ByVal e As DrawListViewSubItemEventArgs) _
        Handles listView1.DrawSubItem

        Dim flags As TextFormatFlags = TextFormatFlags.Left

        Dim sf As New StringFormat()
        Try

            ' Store the column text alignment, letting it default
            ' to Left if it has not been set to Center or Right.
            Select Case e.Header.TextAlign
                Case HorizontalAlignment.Center
                    sf.Alignment = StringAlignment.Center
                    flags = TextFormatFlags.HorizontalCenter
                Case HorizontalAlignment.Right
                    sf.Alignment = StringAlignment.Far
                    flags = TextFormatFlags.Right
            End Select

            ' Draw the text and background for a subitem with a 
            ' negative value. 
            Dim subItemValue As Double
            If e.ColumnIndex > 0 AndAlso _
                Double.TryParse(e.SubItem.Text, NumberStyles.Currency, _
                NumberFormatInfo.CurrentInfo, subItemValue) AndAlso _
                subItemValue < 0 Then

                ' Unless the item is selected, draw the standard 
                ' background to make it stand out from the gradient.
                If (e.ItemState And ListViewItemStates.Selected) = 0 Then
                    e.DrawBackground()
                End If

                ' Draw the subitem text in red to highlight it. 
                e.Graphics.DrawString(e.SubItem.Text, _
                    Me.listView1.Font, Brushes.Red, e.Bounds, sf)

                Return

            End If

            ' Draw normal text for a subitem with a nonnegative 
            ' or nonnumerical value.
            e.DrawText(flags)

        Finally
            sf.Dispose()
        End Try

    End Sub

    ' Draws column headers.
    Private Sub listView1_DrawColumnHeader(ByVal sender As Object, _
        ByVal e As DrawListViewColumnHeaderEventArgs) _
        Handles listView1.DrawColumnHeader

        Dim sf As New StringFormat()
        Try

            ' Store the column text alignment, letting it default
            ' to Left if it has not been set to Center or Right.
            Select Case e.Header.TextAlign
                Case HorizontalAlignment.Center
                    sf.Alignment = StringAlignment.Center
                Case HorizontalAlignment.Right
                    sf.Alignment = StringAlignment.Far
            End Select

            ' Draw the standard header background.
            e.DrawBackground()

            ' Draw the header text.
            Dim headerFont As New Font("Helvetica", 10, FontStyle.Bold)
            Try
                e.Graphics.DrawString(e.Header.Text, headerFont, _
                    Brushes.Black, e.Bounds, sf)
            Finally
                headerFont.Dispose()
            End Try

        Finally
            sf.Dispose()
        End Try

    End Sub

    ' Forces each row to repaint itself the first time the mouse moves over 
    ' it, compensating for an extra DrawItem event sent by the wrapped 
    ' Win32 control.
    Private Sub listView1_MouseMove(ByVal sender As Object, _
        ByVal e As MouseEventArgs) _
        Handles listView1.MouseMove

        Dim item As ListViewItem = listView1.GetItemAt(e.X, e.Y)
        If item IsNot Nothing AndAlso item.Tag Is Nothing Then
            listView1.Invalidate(item.Bounds)
            item.Tag = "tagged"
        End If

    End Sub

    ' Resets the item tags. 
    Private Sub listView1_Invalidated(ByVal sender As Object, _
        ByVal e As InvalidateEventArgs) Handles listView1.Invalidated

        For Each item As ListViewItem In listView1.Items
            If item Is Nothing Then Return
            item.Tag = Nothing
        Next

    End Sub

    ' Forces the entire control to repaint if a column width is changed.
    Private Sub listView1_ColumnWidthChanged(ByVal sender As Object, _
        ByVal e As ColumnWidthChangedEventArgs) Handles listView1.ColumnWidthChanged

        listView1.Invalidate()

    End Sub

End Class

Commenti

L'evento ListView.DrawItem consente di personalizzare l'aspetto di un controllo ListView utilizzando il disegno del proprietario.The ListView.DrawItem event enables you to customize the appearance of a ListView control using owner drawing.

L'evento ListView.DrawItem viene generato da un controllo ListView quando la proprietà ListView.OwnerDraw è impostata su true.The ListView.DrawItem event is raised by a ListView control when the ListView.OwnerDraw property is set to true. Il DrawListViewItemEventArgs passato al gestore eventi contiene informazioni sulle ListViewItem da creare e fornisce anche metodi che consentono di creare l'elemento.The DrawListViewItemEventArgs passed to the event handler contains information about the ListViewItem to draw and also provides methods to help you draw the item.

Utilizzare le proprietà State o Item per recuperare le informazioni sull'elemento da creare.Use the State or Item properties to retrieve information about the item to draw. Utilizzare la proprietà DrawListViewItemEventArgs.ItemIndex per recuperare l'indice dell'elemento.Use the DrawListViewItemEventArgs.ItemIndex property to retrieve the index of the item.

Utilizzare la proprietà Graphics per eseguire il disegno effettivo all'interno dell'area specificata dalla proprietà Bounds.Use the Graphics property to do the actual drawing within the area specified by the Bounds property. Per creare elementi di ListView standard che non necessitano di personalizzazione, usare i metodi DrawBackground, DrawTexte DrawFocusRectangle.To draw standard ListView elements that do not need customization, use the DrawBackground, DrawText, and DrawFocusRectangle methods.

Nota

Per evitare problemi con lo sfarfallio della grafica quando il disegno del proprietario, eseguire l'override del controllo ListView e impostare la proprietà DoubleBuffered su true.To avoid issues with graphics flickering when owner drawing, override the ListView control and set the DoubleBuffered property to true. Questa funzionalità è disponibile solo in Windows XP e nella famiglia Windows Server 2003 quando l'applicazione chiama il metodo Application.EnableVisualStyles.This feature is available only on Windows XP and the Windows Server 2003 family when your application calls the Application.EnableVisualStyles method.

Costruttori

DrawListViewItemEventArgs(Graphics, ListViewItem, Rectangle, Int32, ListViewItemStates)

Inizializza una nuova istanza della classe DrawListViewItemEventArgs.Initializes a new instance of the DrawListViewItemEventArgs class.

Proprietà

Bounds

Ottiene le dimensioni e la posizione dell'oggetto ListViewItem da creare.Gets the size and location of the ListViewItem to draw.

DrawDefault

Ottiene o imposta una proprietà che indica se nel controllo ListView verrà utilizzata la creazione predefinita per l'elemento ListViewItem.Gets or sets a property indicating whether the ListView control will use the default drawing for the ListViewItem.

Graphics

Ottiene l'oggetto Graphics utilizzato per creare l'oggetto ListViewItem.Gets the Graphics used to draw the ListViewItem.

Item

Ottiene l'oggetto ListViewItem da disegnare.Gets the ListViewItem to draw.

ItemIndex

Ottiene l'indice dell'elemento ListViewItem all'interno dell'insieme Items dell'oggetto ListView che lo contiene.Gets the index of the ListViewItem within the Items collection of the containing ListView.

State

Ottiene lo stato corrente dell'elemento ListViewItem da creare.Gets the current state of the ListViewItem to draw.

Metodi

DrawBackground()

Crea lo sfondo di ListViewItem utilizzandone il colore di sfondo corrente.Draws the background of the ListViewItem using its current background color.

DrawFocusRectangle()

Crea un rettangolo di attivazione per l'elemento ListViewItem se è in stato attivo.Draws a focus rectangle for the ListViewItem if it has focus.

DrawText()

Crea il testo di ListViewItem utilizzandone il colore di primo piano corrente.Draws the text of the ListViewItem using its current foreground color.

DrawText(TextFormatFlags)

Crea il testo di ListViewItem utilizzando il relativo colore di primo piano corrente e i valori di formattazione TextFormatFlags specificati.Draws the text of the ListViewItem using its current foreground color and formatting it with the specified TextFormatFlags values.

Equals(Object)

Determina se l'oggetto specificato è uguale all'oggetto corrente.Determines whether the specified object is equal to the current object.

(Ereditato da Object)
GetHashCode()

Funge da funzione hash predefinita.Serves as the default hash function.

(Ereditato da Object)
GetType()

Ottiene l'oggetto Type dell'istanza corrente.Gets the Type of the current instance.

(Ereditato da Object)
MemberwiseClone()

Crea una copia superficiale dell'oggetto Object corrente.Creates a shallow copy of the current Object.

(Ereditato da Object)
ToString()

Restituisce una stringa che rappresenta l'oggetto corrente.Returns a string that represents the current object.

(Ereditato da Object)

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