# 對話框 > 原文： [http://zetcode.com/gui/vbwinforms/dialogs/](http://zetcode.com/gui/vbwinforms/dialogs/) 在 Visual Basic Winforms 教程的這一部分中，我們將討論對話框。 對話框窗口或對話框是大多數現代 GUI 應用必不可少的部分。 對話被定義為兩個或更多人之間的對話。 在計算機應用中，對話框是一個窗口，用于與應用“對話”。 對話框用于輸入數據，修改數據，更改應用設置等。對話框是用戶與計算機程序之間進行通信的重要手段。 基本上有兩種類型的對話框。 預定義對話框和自定義對話框。 ## `FolderBrowserDialog` 此對話框提示用戶選擇一個文件夾。 ```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 ``` 我們有一個工具欄和一個工具欄按鈕。 點擊按鈕，`FolderBrowserDialog`出現在屏幕上。 所選文件夾的名稱顯示在狀態欄中。 ```vb Dim dialog As New FolderBrowserDialog ``` `FolderBrowserDialog`已創建。 ```vb If dialog.ShowDialog(Me) = DialogResult.OK statusbar.Text = dialog.SelectedPath End If ``` `ShowDialog`方法在屏幕上顯示對話框。 如果單擊對話框的“確定”按鈕，則所選的目錄路徑將顯示在狀態欄上。  圖：`FolderBrowserDialog` ## `ColorDialog` 此對話框顯示可用的顏色以及使用戶能夠定義自定義顏色的控件。 ```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 ``` 在此代碼示例中，我們使用`ColorDialog`為位于窗體控件中間的矩形選擇顏色。 ```vb col = Color.Blue ``` 開始時，矩形的顏色是藍色。 我們使用`col`變量來確定矩形的顏色。 ```vb Dim dialog As New ColorDialog ``` `ColorDialog`已創建。 ```vb If dialog.ShowDialog(Me) = DialogResult.OK col = dialog.Color Me.Invalidate End If ``` 該代碼顯示顏色對話框。 如果單擊“確定”按鈕，則將獲得選定的顏色并調用`Invalidate`方法。 該方法會使控件的整個表面無效，并使控件重畫。 結果是用新的顏色值繪制了矩形。  圖：`ColorDialog` ## `FontDialog` `FontDialog`用于選擇字體。 ```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 ``` 我們在表單控件的中間繪制一些文本。 我們使用字體對話框更改此文本的字體。 ```vb Dim dialog As New FontDialog ``` `FontDialog`已創建。 ```vb If dialog.ShowDialog(Me) = DialogResult.OK txt.Font = dialog.Font Me.LocateText End If ``` 單擊“確定”按鈕時，將為`Label`控件設置新選擇的字體。 由于文本的大小會隨著字體的變化而變化，因此我們必須調用`LocateText`方法，該方法將文本定位在表單控件的中間。  圖：`FontDialog` ## `OpenDialog` 此對話框用于打開文件。 ```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 ``` 我們使用`OpenDialog`控件打開 VB 源文件。 我們有一個`TextBox`控件，用于顯示文件。 ```vb Dim dia As New OpenFileDialog ``` `OpenDialog`已創建。 ```vb dia.Filter = "VB files (*.vb)|*.vb" ``` 我們將`Filter`屬性設置為 VB 源文件。 此對話框實例只能選擇 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 ``` 單擊確定后，我們讀取所選文件的內容并將其放入`TextBox`控件。  圖：`OpenDialog` 在 Visual Basic Winforms 教程的這一部分中，我們顯示了各種對話框。