# 贪食蛇 > 原文： [http://zetcode.com/gui/vbgtk/nibbles/](http://zetcode.com/gui/vbgtk/nibbles/) 在 Visual Basic GTK# 编程教程的这一部分中，我们将创建贪食蛇游戏克隆。 贪食蛇是较旧的经典视频游戏。 它最初是在 70 年代后期创建的。 后来它被带到 PC 上。 在这个游戏中，玩家控制蛇。 目的是尽可能多地吃苹果。 蛇每次吃一个苹果，它的身体就会长大。 蛇必须避开墙壁和自己的身体。 ## 开发 蛇的每个关节的大小为 10px。 蛇由光标键控制。 最初，蛇具有三个关节。 游戏立即开始。 游戏结束后，我们在窗口中心显示`"Game Over"`消息。 `board.vb` ```vb Imports Gtk Imports Cairo NameSpace BoardSpace Public Class Board Inherits DrawingArea Const WIDTH As Integer = 300 Const HEIGHT As Integer = 300 Const DOT_SIZE As Integer = 10 Const ALL_DOTS As Integer = 900 Const RAND_POS As Integer = 30 Const DELAY As Integer = 140 Dim x(ALL_DOTS) As Integer Dim y(ALL_DOTS) As Integer Dim dots As Integer Dim apple_x As Integer Dim apple_y As Integer Dim left As Boolean = False Dim right As Boolean = True Dim up As Boolean = False Dim down As Boolean = False Dim inGame As Boolean = True Dim dot As ImageSurface Dim apple As ImageSurface Dim head As ImageSurface Public Sub New MyBase.New ModifyBg(StateType.Normal, New Gdk.Color(0, 0, 0)) Me.InitGame End Sub Private Sub InitGame dots = 3 For z As Integer = 0 To dots-1 x(z) = 50 - z*10 y(z) = 50 Next Try dot = New ImageSurface("dot.png") head = New ImageSurface("head.png") apple = New ImageSurface("apple.png") Catch Console.WriteLine("Images not found") Environment.Exit(1) End Try Me.LocateApple Dim timer As New GLib.TimeoutHandler(AddressOf Me.OnTimer) GLib.Timeout.Add(100, timer) AddHandler Me.ExposeEvent, AddressOf Me.OnExpose End Sub Protected Sub OnExpose(ByVal sender As Object, ByVal e As ExposeEventArgs) Dim cc As Cairo.Context = Gdk.CairoHelper.Create(sender.GdkWindow) If inGame Me.DrawObjects(cc) Else Me.GameOver(cc) End If Dim disposeTarget As IDisposable = CType(cc.Target, IDisposable) disposeTarget.Dispose Dim disposeContext As IDisposable = CType(cc, IDisposable) disposeContext.Dispose End Sub Private Sub DrawObjects(ByVal cc As Cairo.Context) cc.SetSourceSurface(apple, apple_x, apple_y) cc.Paint For z As Integer = 0 to dots - 1 If z = 0 cc.SetSourceSurface(head, x(z), y(z)) cc.Paint Else cc.SetSourceSurface(dot, x(z), y(z)) cc.Paint End If Next End Sub Private Sub GameOver(ByVal cc As Cairo.Context) Dim message As String = "Game Over" Dim x As Integer = Allocation.Width / 2 Dim y As Integer = Allocation.Height / 2 cc.SetSourceRGB(1, 1, 1) cc.SetFontSize(18) Dim extents As TextExtents = cc.TextExtents(message) cc.MoveTo(x - extents.Width/2, y) cc.ShowText(message) inGame = False End Sub Private Sub CheckApple If x(0) = apple_x And y(0) = apple_y dots += 1 Me.LocateApple End If End Sub Private Sub Move For z As Integer = dots To 1 Step -1 x(z) = x(z - 1) y(z) = y(z - 1) Next If left x(0) -= DOT_SIZE End If If right x(0) += DOT_SIZE End If If up y(0) -= DOT_SIZE End If If down y(0) += DOT_SIZE End If End Sub Private Sub CheckCollision For z As Integer = dots To 1 Step -1 If z > 4 And x(0) = x(z) And y(0) = y(z) inGame = False End If Next If y(0) > HEIGHT inGame = False End If If y(0) < 0 inGame = False End If If x(0) > WIDTH inGame = False End If If x(0) < 0 inGame = False End If End Sub Private Sub LocateApple Dim rand As New Random Dim r As Integer = rand.Next(RAND_POS) apple_x = r * DOT_SIZE r = rand.Next(RAND_POS) apple_y = r * DOT_SIZE End Sub Private Function OnTimer As Boolean If inGame Me.CheckApple Me.CheckCollision Me.Move Me.QueueDraw Return True Else Return False End If End Function Public Sub OnKeyDown(ByVal e As Gdk.EventKey) Dim key As Integer = e.KeyValue If key = Gdk.Key.Left AndAlso Not right left = True up = False down = False End If If key = Gdk.Key.Right AndAlso Not left right = True up = False down = False End If If key = Gdk.Key.Up AndAlso Not down up = True right = False left = False End If If key = Gdk.Key.Down AndAlso Not up down = True right = False left = False End If End Sub End Class End Namespace ``` 首先，我们将定义一些在游戏中使用的全局变量。 `WIDTH`和`HEIGHT`常数确定电路板的大小。 `DOT_SIZE`是苹果的大小和蛇的点。 `ALL_DOTS`常数定义了板上可能的最大点数。 `RAND_POS`常数用于计算苹果的随机位置。 `DELAY`常数确定游戏的速度。 ```vb Dim x(ALL_DOTS) As Integer Dim y(ALL_DOTS) As Integer ``` 这两个数组存储蛇的所有可能关节的 x，y 坐标。 `InitGame`方法初始化变量，加载图像并启动超时功能。 ```vb If inGame Me.DrawObjects(cc) Else Me.GameOver(cc) End If ``` 在`OnExpose`方法内部，我们检查`inGame`变量。 如果为真，则绘制对象。 苹果和蛇的关节。 否则，我们显示`"Game Over"`文本。 ```vb Private Sub DrawObjects(ByVal cc As Cairo.Context) cc.SetSourceSurface(apple, apple_x, apple_y) cc.Paint For z As Integer = 0 to dots - 1 If z = 0 cc.SetSourceSurface(head, x(z), y(z)) cc.Paint Else cc.SetSourceSurface(dot, x(z), y(z)) cc.Paint End If Next End Sub ``` `DrawObjects`方法绘制苹果和蛇的关节。 蛇的第一个关节是其头部，用红色圆圈表示。 ```vb Private Sub CheckApple If x(0) = apple_x And y(0) = apple_y dots += 1 Me.LocateApple End If End Sub ``` `CheckApple`方法检查蛇是否击中了苹果对象。 如果是这样，我们添加另一个蛇形关节并调用`LocateApple`方法，该方法将随机放置一个新的 Apple 对象。 在`Move`方法中，我们有游戏的关键算法。 要了解它，请看一下蛇是如何运动的。 您控制蛇的头。 您可以使用光标键更改其方向。 其余关节在链上向上移动一个位置。 第二关节移动到第一个关节的位置，第三关节移动到第二个关节的位置，依此类推。 ```vb For z As Integer = dots To 1 Step -1 x(z) = x(z - 1) y(z) = y(z - 1) Next ``` 该代码将关节向上移动。 ```vb If left x(0) -= DOT_SIZE End If ``` 将头向左移动。 在`CheckCollision`方法中，我们确定蛇是否击中了自己或撞墙之一。 ```vb For z As Integer = dots To 1 Step -1 If z > 4 And x(0) = x(z) And y(0) = y(z) inGame = False End If Next ``` 如果蛇用头撞到关节之一，我们就结束游戏。 ```vb If y(0) > HEIGHT inGame = False End If ``` 如果蛇击中了棋盘的底部，我们就结束了游戏。 `LocateApple`方法在板上随机放置一个苹果。 ```vb Dim rand As New Random Dim r As Integer = rand.Next(RAND_POS) ``` 我们得到一个从 0 到`RAND_POS-1`的随机数。 ```vb apple_x = r * DOT_SIZE ... apple_y = r * DOT_SIZE ``` 这些行设置了`apple`对象的 x，y 坐标。 ```vb If inGame Me.CheckApple Me.CheckCollision Me.Move Me.QueueDraw Return True Else Return False End If ``` 每 140 毫秒，将调用`OnTimer`方法。 如果我们参与了游戏，我们将调用三种构建游戏逻辑的方法。 否则，我们返回`False`，它将停止计时器事件。 在`Board`类的`OnKeyDown`方法中，我们确定按下的键。 ```vb If key = Gdk.Key.Left AndAlso Not right left = True up = False down = False End If ``` 如果单击左光标键，则将`left`变量设置为`true`。 在`Move`方法中使用此变量来更改蛇对象的坐标。 还要注意，当蛇向右行驶时，我们不能立即向左转。 `nibbles.vb` ```vb ' ZetCode Mono Visual Basic GTK# tutorial ' ' In this program, we create ' a Nibbles game clone ' ' author jan bodnar ' last modified May 2009 ' website www.zetcode.com Imports Gtk Public Class GtkVBApp Inherits Window Dim WIDTH As Integer = 250 Dim HEIGHT As Integer = 150 Dim board As BoardSpace.Board Public Sub New MyBase.New("Nibbles") board = New BoardSpace.Board Me.Add(board) AddHandler Me.DeleteEvent, AddressOf Me.OnDelete Me.Resize(310, 310) Me.Move(300, 300) Me.ShowAll End Sub Private Sub OnDelete(ByVal sender As Object, _ ByVal args As DeleteEventArgs) Application.Quit End Sub Protected Overrides Function OnKeyPressEvent(ByVal e As Gdk.EventKey) As Boolean board.OnKeyDown(e) Return True End Function Public Shared Sub Main Application.Init Dim app As New GtkVBApp Application.Run End Sub End Class ``` 在这个类中，我们设置了贪食蛇游戏。 ```vb Protected Overrides Function OnKeyPressEvent(ByVal e As Gdk.EventKey) As Boolean board.OnKeyDown(e) Return True End Function ``` 在这个类中，我们捕获按键事件。 并将处理委托给板类的`OnKeyDown`方法。  图：贪食蛇 以下命令编译游戏。 ```vb vbnc -r:/usr/lib/mono/gtk-sharp-2.0/gtk-sharp.dll -r:/usr/lib/mono/gtk-sharp-2.0/gdk-sharp.dll -r:/usr/lib/mono/2.0/Mono.Cairo.dll -r:/usr/lib/mono/gtk-sharp-2.0/glib-sharp.dll nibbles.vb board.vb ``` 这是使用 GTK# 库和 Visual Basic 编程语言编写的贪食蛇电脑游戏。