# 对话框 > 原文： [http://zetcode.com/gui/vbwinforms/dialogs/](http://zetcode.com/gui/vbwinforms/dialogs/) 在 Visual Basic Winforms 教程的这一部分中，我们将讨论对话框。 对话框窗口或对话框是大多数现代 GUI 应用必不可少的部分。 对话被定义为两个或更多人之间的对话。 在计算机应用中，对话框是一个窗口，用于与应用“对话”。 对话框用于输入数据，修改数据，更改应用设置等。对话框是用户与计算机程序之间进行通信的重要手段。 基本上有两种类型的对话框。 预定义对话框和自定义对话框。 ## `FolderBrowserDialog` 此对话框提示用户选择一个文件夹。 ```vb ' ZetCode Mono Visual Basic Winforms tutorial ' ' In this program we select a directory with a ' FolderBrowser dialog. The selected directory's ' name is shown in the statusbar. ' ' author jan bodnar ' last modified May 2009 ' website www.zetcode.com Imports System.Windows.Forms Imports System.Drawing Public Class WinVBApp Inherits Form Dim statusbar As StatusBar Public Sub New Me.Text = "FolderBrowserDialog" Me.Size = New Size(300, 250) Me.InitUI Me.CenterToScreen End Sub Private Sub InitUI Dim toolbar As New ToolBar Dim open As New ToolBarButton statusbar = New StatusBar statusbar.Parent = Me toolbar.Buttons.Add(open) Me.Controls.Add(toolbar) AddHandler toolbar.ButtonClick, AddressOf Me.OnClicked End Sub Private Sub OnClicked(ByVal sender As Object, _ ByVal e As ToolBarButtonClickEventArgs) Dim dialog As New FolderBrowserDialog If dialog.ShowDialog(Me) = DialogResult.OK statusbar.Text = dialog.SelectedPath End If End Sub Public Shared Sub Main Application.Run(New WinVBApp) End Sub End Class ``` 我们有一个工具栏和一个工具栏按钮。 点击按钮，`FolderBrowserDialog`出现在屏幕上。 所选文件夹的名称显示在状态栏中。 ```vb Dim dialog As New FolderBrowserDialog ``` `FolderBrowserDialog`已创建。 ```vb If dialog.ShowDialog(Me) = DialogResult.OK statusbar.Text = dialog.SelectedPath End If ``` `ShowDialog`方法在屏幕上显示对话框。 如果单击对话框的“确定”按钮，则所选的目录路径将显示在状态栏上。  图：`FolderBrowserDialog` ## `ColorDialog` 此对话框显示可用的颜色以及使用户能够定义自定义颜色的控件。 ```vb ' ZetCode Mono Visual Basic Winforms tutorial ' ' In this program we use the ColorDialog ' to change a color of a rectangle ' ' author jan bodnar ' last modified May 2009 ' website www.zetcode.com Imports System.Windows.Forms Imports System.Drawing Public Class WinVBApp Inherits Form Private col As Color Private Const rectWidth As Integer = 100 Private Const rectHeight As Integer = 100 Private Dim r As Rectangle Public Sub New Me.Text = "ColorDialog" Me.Size = New Size(300, 250) Me.InitUI Me.CenterToScreen End Sub Private Sub InitUI Dim tbar As New ToolBar Dim open As New ToolBarButton col = Color.Blue tbar.Buttons.Add(open) Me.LocateRect Me.SetStyle(ControlStyles.ResizeRedraw, True) Controls.Add(tbar) AddHandler Me.Paint, AddressOf Me.OnPaint AddHandler tbar.ButtonClick, AddressOf Me.OnClicked End Sub Private Sub OnPaint(ByVal sender As Object, ByVal e As PaintEventArgs) Dim g As Graphics = e.Graphics Me.LocateRect Dim brsh As New SolidBrush(col) g.FillRectangle(brsh, r) End Sub Private Sub OnClicked(ByVal sender As Object, _ ByVal e As ToolBarButtonClickEventArgs) Dim dialog As New ColorDialog If dialog.ShowDialog(Me) = DialogResult.OK col = dialog.Color Me.Invalidate End If End Sub Private Sub LocateRect Dim x As Integer = (Me.ClientSize.Width - rectWidth) / 2 Dim y As Integer = (Me.ClientSize.Height - rectHeight) / 2 r = New Rectangle(x, y, rectWidth, rectHeight) End Sub Public Shared Sub Main Application.Run(New WinVBApp) End Sub End Class ``` 在此代码示例中，我们使用`ColorDialog`为位于窗体控件中间的矩形选择颜色。 ```vb col = Color.Blue ``` 开始时，矩形的颜色是蓝色。 我们使用`col`变量来确定矩形的颜色。 ```vb Dim dialog As New ColorDialog ``` `ColorDialog`已创建。 ```vb If dialog.ShowDialog(Me) = DialogResult.OK col = dialog.Color Me.Invalidate End If ``` 该代码显示颜色对话框。 如果单击“确定”按钮，则将获得选定的颜色并调用`Invalidate`方法。 该方法会使控件的整个表面无效，并使控件重画。 结果是用新的颜色值绘制了矩形。  图：`ColorDialog` ## `FontDialog` `FontDialog`用于选择字体。 ```vb ' ZetCode Mono Visual Basic Winforms tutorial ' ' In this program we use the FontDialog ' to change a font of a label ' ' author jan bodnar ' last modified May 2009 ' website www.zetcode.com Imports System.Windows.Forms Imports System.Drawing Public Class WinVBApp Inherits Form Private Dim txt As Label Public Sub New Me.Text = "FontDialog" Me.Size = New Size(300, 250) Me.InitUI Me.CenterToScreen End Sub Private Sub InitUI Dim tbar As New ToolBar tbar.Parent = Me Dim open As New ToolBarButton tbar.Buttons.Add(open) txt = New Label txt.Parent = Me txt.Text = "Winforms tutorial" Me.LocateText txt.AutoSize = True AddHandler Me.Resize, AddressOf Me.OnResize AddHandler tbar.ButtonClick, AddressOf Me.OnClicked End Sub Private Sub OnClicked(ByVal sender As Object, _ ByVal e As ToolBarButtonClickEventArgs) Dim dialog As New FontDialog If dialog.ShowDialog(Me) = DialogResult.OK txt.Font = dialog.Font Me.LocateText End If End Sub Private Sub LocateText txt.Top = (Me.ClientSize.Height - txt.Height) / 2 txt.Left = (Me.ClientSize.Width - txt.Width) / 2 End Sub Private Sub OnResize(ByVal sender As Object, ByVal e As EventArgs) Me.LocateText End Sub Public Shared Sub Main Application.Run(New WinVBApp) End Sub End Class ``` 我们在表单控件的中间绘制一些文本。 我们使用字体对话框更改此文本的字体。 ```vb Dim dialog As New FontDialog ``` `FontDialog`已创建。 ```vb If dialog.ShowDialog(Me) = DialogResult.OK txt.Font = dialog.Font Me.LocateText End If ``` 单击“确定”按钮时，将为`Label`控件设置新选择的字体。 由于文本的大小会随着字体的变化而变化，因此我们必须调用`LocateText`方法，该方法将文本定位在表单控件的中间。  图：`FontDialog` ## `OpenDialog` 此对话框用于打开文件。 ```vb ' ZetCode Mono Visual Basic Winforms tutorial ' ' In this program we use the OpenDialog to ' open a file and show its contents in ' a TextBox control ' ' author jan bodnar ' last modified May 2009 ' website www.zetcode.com Imports System.Windows.Forms Imports System.Drawing Imports System.IO Public Class WinVBApp Inherits Form Private txtBox As TextBox Public Sub New Me.Text = "OpenDialog" Me.Size = New Size(300, 250) Me.InitUI Me.CenterToScreen End Sub Private Sub InitUI Dim tbar As New ToolBar tbar.Parent = Me Dim open As New ToolBarButton tbar.Buttons.Add(open) txtBox = New TextBox txtBox.Parent = Me txtBox.Multiline = True txtBox.ScrollBars = ScrollBars.Both txtBox.WordWrap = False txtBox.Parent = Me txtBox.Dock = DockStyle.Fill AddHandler tbar.ButtonClick, AddressOf Me.OnClicked End Sub Private Sub OnClicked(ByVal sender As Object, _ ByVal e As ToolBarButtonClickEventArgs) Dim dia As New OpenFileDialog dia.Filter = "VB files (*.vb)|*.vb" If dia.ShowDialog(Me) = DialogResult.OK Dim reader As New StreamReader(dia.FileName) Dim data As String = reader.ReadToEnd reader.Close txtBox.Text = data End If End Sub Public Shared Sub Main Application.Run(New WinVBApp) End Sub End Class ``` 我们使用`OpenDialog`控件打开 VB 源文件。 我们有一个`TextBox`控件，用于显示文件。 ```vb Dim dia As New OpenFileDialog ``` `OpenDialog`已创建。 ```vb dia.Filter = "VB files (*.vb)|*.vb" ``` 我们将`Filter`属性设置为 VB 源文件。 此对话框实例只能选择 VB 文件。 ```vb If dia.ShowDialog(Me) = DialogResult.OK Dim reader As New StreamReader(dia.FileName) Dim data As String = reader.ReadToEnd reader.Close txtBox.Text = data End If ``` 单击确定后，我们读取所选文件的内容并将其放入`TextBox`控件。  图：`OpenDialog` 在 Visual Basic Winforms 教程的这一部分中，我们显示了各种对话框。