原文： http://zetcode.com/gui/vbgtk/widgets/

在 Visual Basic GTK# 编程教程的这一部分中，我们将介绍一些小部件。

小部件是 GUI 应用的基本构建块。 多年来，几个小部件已成为所有 OS 平台上所有工具包中的标准。 例如，按钮，复选框或滚动条。 GTK# 工具箱的理念是将小部件的数量保持在最低水平。 将创建更多专门的小部件作为自定义 GTK# 小部件。

CheckButton

CheckButton是具有两种状态的窗口小部件：打开和关闭。 接通状态通过复选标记显示。 它用来表示一些布尔属性。

  1. ' ZetCode Mono Visual Basic GTK# tutorial
  2. '
  3. ' This program toggles the title of the
  4. ' window with the CheckButton widget
  5. '
  6. ' author jan bodnar
  7. ' last modified May 2009
  8. ' website www.zetcode.com
  10. Imports Gtk
  12. Public Class GtkVBApp
  13.     Inherits Window
  15.     Public Sub New
  17.         MyBase.New("CheckButton")
  19.         Me.InitUI
  21.         Me.SetDefaultSize(250, 150)
  22.         Me.SetPosition(WindowPosition.Center)
  23.         AddHandler Me.DeleteEvent, AddressOf Me.OnDelete
  25.         Me.ShowAll
  27.     End Sub
  29.     Private Sub InitUI
  31.         Dim cb As New CheckButton("Show title")
  32.         cb.Active = True
  34.         AddHandler cb.Toggled, AddressOf Me.OnToggle
  36.         Dim fix As New Fixed
  37.         fix.Put(cb, 50, 50)
  39.         Me.Add(fix)
  41.     End Sub
  43.     Sub OnToggle(ByVal sender As Object, ByVal args As EventArgs)
  45.         If sender.Active
  46.             Me.Title = "CheckButton"
  47.         Else
  48.             Title = " "
  49.         End If
  51.     End Sub
  53.     Sub OnDelete(ByVal sender As Object, _
  54.             ByVal args As DeleteEventArgs)
  55.         Application.Quit
  56.     End Sub
  58.     Public Shared Sub Main
  60.         Application.Init
  61.         Dim app As New GtkVBApp
  62.         Application.Run
  64.     End Sub
  66. End Class

根据CheckButton的状态，我们将在窗口的标题栏中显示标题。

  1. Dim cb As New CheckButton("Show title")

CheckButton小部件已创建。

  1. cb.Active = True

默认情况下标题是可见的，因此我们默认情况下选中复选按钮。

  1. If sender.Active
  2.     Me.Title = "CheckButton" 
  3. Else
  4.     Title = " "
  5. End If

根据CheckButton的Active属性，我们显示或隐藏窗口的标题。

小部件 - 图1

图：CheckButton

Label

Label小部件显示文本。

  1. ' ZetCode Mono Visual Basic GTK# tutorial
  3. ' This program shows lyrics on 
  4. ' the window in a label widget
  5. '
  6. ' author jan bodnar
  7. ' last modified May 2009
  8. ' website www.zetcode.com
  10. Imports Gtk
  12. Public Class GtkVBApp
  13.     Inherits Window
  15.     Dim text As String = "Meet you downstairs in the bar and heard" & vbNewLine & _
  16. "your rolled up sleeves and your skull t-shirt" & vbNewLine & _
  17. "You say why did you do it with him today?" & vbNewLine & _
  18. "and sniff me out like I was Tanqueray" & vbNewLine & _
  19. "" & vbNewLine & _
  20. "cause you're my fella, my guy" & vbNewLine & _
  21. "hand me your stella and fly" & vbNewLine & _
  22. "by the time I'm out the door" & vbNewLine & _
  23. "you tear men down like Roger Moore" & vbNewLine & _
  24. "" & vbNewLine & _
  25. "I cheated myself" & vbNewLine & _
  26. "like I knew I would" & vbNewLine & _
  27. "I told ya, I was trouble" & vbNewLine & _
  28. "you know that I'm no good"
  30.     Public Sub New
  32.         MyBase.New("You know I'm No Good")
  34.         Me.InitUI
  36.         Me.SetPosition(WindowPosition.Center)
  37.         Me.BorderWidth = 10
  38.         AddHandler Me.DeleteEvent, AddressOf Me.OnDelete
  40.         Me.ShowAll
  42.     End Sub
  44.     Private Sub InitUI
  46.         Dim lyrics As New Label(text)
  47.         Me.Add(lyrics)
  49.     End Sub
  51.     Sub OnDelete(ByVal sender As Object, ByVal args As DeleteEventArgs)
  52.         Application.Quit
  53.     End Sub
  55.     Public Shared Sub Main
  57.         Application.Init
  58.         Dim app As New GtkVBApp
  59.         Application.Run
  61.     End Sub
  63. End Class

该代码示例在窗口上显示了一些歌词。

  1.     Dim text As String = "Meet you downstairs in the bar and heard" & vbNewLine & _
  2. "your rolled up sleeves and your skull t-shirt" & vbNewLine & _
  3. ...

我们定义了多行文字。 与 C# ，Python 或 Ruby 不同，没有简单的结构可以用 Visual Basic 语言创建多行文本。 若要在 Visual Basic 中创建多行文本，我们使用vbNewLine打印常量，+连接字符和_行终止字符。

  1. Me.BorderWidth = 10

Label周围有一些空白。

  1. Dim lyrics As New Label(text)
  2. Me.Add(lyrics)

Label小部件已创建并添加到窗口。

小部件 - 图2

图：Label小部件

Entry

Entry是单行文本输入字段。 该小部件用于输入文本数据。

  1. ' ZetCode Mono Visual Basic GTK# tutorial
  2. '
  3. ' This program demonstrates the 
  4. ' Entry widget. Text entered in the Entry
  5. ' widget is shown in a Label widget.
  6. '
  7. ' author jan bodnar
  8. ' last modified May 2009
  9. ' website www.zetcode.com
  11. Imports Gtk
  13. Public Class GtkVBApp
  14.     Inherits Window
  16.     Dim label As Label
  18.     Public Sub New
  20.         MyBase.New("Entry")
  22.         Me.InitUI
  24.         Me.SetDefaultSize(250, 150)
  25.         Me.SetPosition(WindowPosition.Center)
  26.         AddHandler Me.DeleteEvent, AddressOf Me.OnDelete
  28.         Me.ShowAll
  30.     End Sub
  32.     Private Sub InitUI
  34.         Dim fixed As New Fixed
  36.         label = New Label("...")
  37.         fixed.put(label, 60, 40)
  39.         Dim entry As New Entry
  40.         fixed.put(entry, 60, 100)
  42.         AddHandler entry.Changed, AddressOf Me.OnTextChanged
  44.         Me.Add(fixed)
  46.     End Sub
  48.     Sub OnTextChanged(ByVal sender As Object, _
  49.             ByVal args As EventArgs)
  50.         label.Text = sender.Text
  51.     End Sub
  53.     Sub OnDelete(ByVal sender As Object, _
  54.             ByVal args As DeleteEventArgs)
  55.         Application.Quit
  56.     End Sub
  58.     Public Shared Sub Main
  60.         Application.Init
  61.         Dim app As New GtkVBApp
  62.         Application.Run
  64.     End Sub
  66. End Class

此示例显示了条目小部件和标签。 我们输入的文本将立即显示在标签小部件中。

  1. Dim entry As New Entry

Entry小部件已创建。

  1. AddHandler entry.Changed, AddressOf Me.OnTextChanged

如果Entry小部件中的文本被更改，我们将调用OnTextChanged方法。

  1. Sub OnTextChanged(ByVal sender As Object, _
  2.         ByVal args As EventArgs)
  3.     label.Text = sender.Text
  4. End Sub

我们从Entry小部件获取文本并将其设置为标签。

小部件 - 图3

图：Entry小部件

ToggleButton

ToggleButton是具有两种状态的按钮。 已按下但未按下。 通过单击可以在这两种状态之间切换。 在某些情况下此功能非常合适。

  1. ' ZetCode Mono Visual Basic GTK# tutorial
  2. '
  3. ' This program uses toggle buttons to
  4. ' change the background color of
  5. ' a widget.
  6. '
  7. ' author jan bodnar
  8. ' last modified May 2009
  9. ' website www.zetcode.com
  11. Imports Gtk
  13. Public Class GtkVBApp
  14.     Inherits Window
  16.     Dim darea As DrawingArea
  17.     Dim color As Gdk.Color
  19.     Public Sub New
  21.         MyBase.New("Togggle buttons")
  23.         Me.InitUI
  25.         Me.SetDefaultSize(350, 240)
  26.         Me.SetPosition(WindowPosition.Center)
  27.         AddHandler Me.DeleteEvent, AddressOf Me.OnDelete
  29.         Me.ShowAll 
  31.     End Sub
  33.     Private Sub InitUI
  35.         color = New Gdk.Color(0, 0, 0)
  37.         Dim redb As New ToggleButton("Red")
  38.         redb.SetSizeRequest(80, 35)
  39.         AddHandler redb.Toggled, AddressOf Me.OnToggled
  41.         Dim greenb As New ToggleButton("Green")
  42.         greenb.SetSizeRequest(80, 35)
  43.         AddHandler greenb.Toggled, AddressOf Me.OnToggled
  45.         Dim blueb As New ToggleButton("Blue")
  46.         blueb.SetSizeRequest(80, 35)
  47.         AddHandler blueb.Toggled, AddressOf Me.OnToggled
  49.         darea = New DrawingArea
  50.         darea.SetSizeRequest(150, 150)
  51.         darea.ModifyBg(StateType.Normal, color)
  53.         Dim fixed As New Fixed
  54.         fixed.Put(redb, 30, 30)
  55.         fixed.Put(greenb, 30, 80)
  56.         fixed.Put(blueb, 30, 130)
  57.         fixed.Put(darea, 150, 30)
  59.         Me.Add(fixed)
  61.     End Sub
  63.     Private Sub OnToggled(ByVal sender As Object, _
  64.             ByVal args As EventArgs)
  66.         Dim red As Integer = color.Red
  67.         Dim green As Integer = color.Green
  68.         Dim blue As Integer = color.Blue
  70.         If sender.Label.Equals("Red") 
  71.             If sender.Active 
  72.                 color.Red = 65535
  73.             Else 
  74.                 color.Red = 0
  75.             End If
  76.         End If
  78.         If sender.Label.Equals("Green")
  79.             If sender.Active 
  80.                 color.Green = 65535
  81.             Else 
  82.                 color.Green = 0
  83.             End If 
  84.         End If
  86.         If sender.Label.Equals("Blue") 
  87.             If sender.Active 
  88.                 color.Blue = 65535
  89.             Else 
  90.                 color.Blue = 0
  91.             End If
  92.         End If     
  94.         darea.ModifyBg(StateType.Normal, color)
  96.     End Sub
  98.     Sub OnDelete(ByVal sender As Object, _
  99.             ByVal args As DeleteEventArgs)
  100.         Application.Quit
  101.     End Sub
  103.     Public Shared Sub Main
  105.         Application.Init
  106.         Dim app As New GtkVBApp
  107.         Application.Run
  109.     End Sub
  111. End Class

在我们的示例中，我们显示了三个切换按钮和一个DrawingArea。 我们将区域的背景色设置为黑色。 切换按钮将切换颜色值的红色，绿色和蓝色部分。 背景颜色取决于我们按下的切换按钮。

  1. color = New Gdk.Color(0, 0, 0)

这是将使用切换按钮更新的颜色值。

  1. Dim redb As New ToggleButton("Red")
  2. redb.SetSizeRequest(80, 35)
  3. AddHandler redb.Toggled, AddressOf Me.OnToggled

ToggleButton小部件已创建。 我们将其大小设置为80x35像素。 每个切换按钮具有相同的处理器方法。

  1. darea = New DrawingArea
  2. darea.SetSizeRequest(150, 150)
  3. darea.ModifyBg(StateType.Normal, color)

DrawingArea小部件是显示颜色的小部件，由切换按钮混合。 开始时，它显示为黑色。

  1. If sender.Label.Equals("Red") 
  2.     If sender.Active 
  3.         color.Red = 65535
  4.     Else 
  5.         color.Red = 0
  6.     End If
  7. End If

我们根据Active属性的值更新颜色的红色部分。

  1. darea.ModifyBg(StateType.Normal, color)

我们更新DrawingArea小部件的颜色。

小部件 - 图4

图：ToggleButton widget

ComboBox

ComboBox是一个小部件，允许用户从选项列表中进行选择。

  1. ' ZetCode Mono Visual Basic GTK# tutorial
  2. '
  3. ' In this program, we use the ComboBox
  4. ' widget to select an option. 
  5. ' The selected option is shown in the
  6. ' Label widget
  7. '
  8. ' author jan bodnar
  9. ' last modified May 2009
  10. ' website www.zetcode.com
  12. Imports Gtk
  14. Public Class GtkVBApp
  15.     Inherits Window
  17.     Dim lbl As Label
  19.     Public Sub New
  21.         MyBase.New("ComboBox")
  23.         Me.InitUI
  25.         Me.SetDefaultSize(350, 240)
  26.         Me.SetPosition(WindowPosition.Center)
  27.         AddHandler Me.DeleteEvent, AddressOf Me.OnDelete
  29.         Me.ShowAll
  31.     End Sub
  33.     Private Sub InitUI
  35.        Dim distros() As String = New String() { _
  36.             "Ubuntu", _
  37.             "Mandriva", _
  38.             "Red Hat", _
  39.             "Fedora", _
  40.             "Gentoo" _
  41.        } 
  43.         Dim fixed As New Fixed
  45.         Dim cb As New ComboBox(distros)
  46.         AddHandler cb.Changed, AddressOf Me.OnChanged
  47.         lbl = New Label("...")
  49.         fixed.Put(cb, 50, 40)
  50.         fixed.Put(lbl, 50, 140)
  52.         Me.Add(fixed)
  54.     End Sub
  56.     Private Sub OnChanged(ByVal sender As Object, _
  57.            ByVal args As EventArgs)
  58.        lbl.Text = sender.ActiveText
  59.     End Sub
  61.     Sub OnDelete(ByVal sender As Object, _
  62.             ByVal args As DeleteEventArgs)
  63.         Application.Quit
  64.     End Sub
  66.     Public Shared Sub Main
  68.         Application.Init
  69.         Dim app As New GtkVBApp
  70.         Application.Run
  72.     End Sub
  74. End Class

该示例显示了一个组合框和一个标签。 组合框具有六个选项的列表。 这些是 Linux Distros 的名称。 标签窗口小部件显示了从组合框中选择的选项。

  1. Dim distros() As String = New String() { _
  2.     "Ubuntu", _
  3.     "Mandriva", _
  4.     "Red Hat", _
  5.     "Fedora", _
  6.     "Gentoo" _
  7. }

这是一个字符串数组，将显示在ComboBox小部件中。

  1. Dim cb As New ComboBox(distros)

ComboBox小部件已创建。 构造器将字符串数组作为参数。

  1. Private Sub OnChanged(ByVal sender As Object, _
  2.         ByVal args As EventArgs)
  3.     lbl.Text = sender.ActiveText
  4. End Sub

在OnChanged方法内部，我们从组合框中获取选定的文本并将其设置为标签。

小部件 - 图5

图：ComboBox

在本章中，我们使用 Visual Basic 语言展示了 GTK# 编程库的一些基本小部件。