ListView.OwnerDraw Propriedade
Definição
Importante
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Obtém ou define um valor que indica se o controle ListView é desenhado pelo sistema operacional ou pelo código que você fornece.
public:
property bool OwnerDraw { bool get(); void set(bool value); };public bool OwnerDraw { get; set; }member this.OwnerDraw : bool with get, setPublic Property OwnerDraw As BooleanValor da propriedade
true se o controle ListView for desenhado pelo código que você fornecer; false se o controle ListView for desenhado pelo sistema operacional. O padrão é false.
Exemplos
O exemplo de código a seguir demonstra como fornecer desenho personalizado para um ListView controle. O ListView controle no exemplo tem uma tela de fundo de gradiente. Subitems com valores negativos têm um primeiro plano vermelho e uma tela de fundo preta.
Um manipulador para o DrawItem evento desenha a tela de fundo para itens inteiros. Um manipulador para o DrawSubItem evento desenha os valores de texto e o texto e a tela de fundo para subitens que têm valores negativos. Um manipulador para o DrawColumnHeader evento desenha cada cabeçalho de coluna.
Um ContextMenu componente fornece uma maneira de alternar entre a exibição de detalhes e a exibição de lista. No modo de exibição de lista, somente o DrawItem evento é gerado. Nesse caso, o texto e a tela de fundo são desenhados no DrawItem manipulador de eventos.
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
Comentários
Normalmente ListView , um controle é desenhado pelo sistema operacional. Para personalizar a aparência de ListView itens, subitens e cabeçalhos de coluna, defina a OwnerDraw propriedade como true e forneça um manipulador para um ou mais dos seguintes eventos: DrawItem, DrawSubItem, DrawColumnHeader. Isso é chamado de desenho de proprietário. Quando a View propriedade é definida como View.Details, todos os três eventos ocorrem; caso contrário, apenas o DrawItem evento ocorre.
Observação
Normalmente, as informações de subitem aparecem no modo de exibição de bloco, bem como na exibição de detalhes, mas no modo de exibição de bloco, elas devem ser desenhadas em um manipulador para o DrawItem evento. O DrawSubItem evento não ocorre para subitens para os quais nenhum ColumnHeader objeto foi adicionado à Columns coleção. Observe também que o primeiro subitem de cada ListViewItem objeto representa o próprio item pai e é exibido na primeira coluna.
Na exibição de detalhes, você pode manipular o DrawItem evento para desenhar elementos comuns a todos os subitens, como a tela de fundo, e manipular o DrawSubItem evento para desenhar elementos para subitens individuais, como valores de texto. Você também pode desenhar todos os itens no ListView controle usando apenas um dos dois eventos, embora isso possa ser menos conveniente. Para desenhar cabeçalhos de coluna na exibição de detalhes, você deve manipular o DrawColumnHeader evento.
Observação
Para evitar problemas com a cintilação de elementos gráficos ao desenhar o proprietário, substitua o ListView controle e defina a DoubleBuffered propriedade como true.
Para obter mais informações sobre como lidar com eventos, consulte Manipulando e levantando eventos.
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