# 贪食蛇 > 原文： [http://zetcode.com/gui/vbqyoto/nibbles/](http://zetcode.com/gui/vbqyoto/nibbles/) 在 Visual Basic Qyoto 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 Qyoto NameSpace BoardSpace public class Board Inherits QFrame 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 timer As QBasicTimer Dim ball As QImage Dim apple As QImage Dim head As QImage Public Sub New() Me.SetStyleSheet("QWidget { background-color: black }") Me.FocusPolicy = Qt.FocusPolicy.StrongFocus Try ball = New QImage("dot.png") apple = New QImage("apple.png") head = New QImage("head.png") Catch e As Exception Console.WriteLine("Cannot read images") Console.WriteLine(e.Message) Environment.Exit(1) End Try 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 Me.LocateApple() timer = New QBasicTimer() timer.Start(DELAY, Me) End Sub Protected Overrides Sub PaintEvent(ByVal e As QPaintEvent) Dim painter As New QPainter() painter.Begin(Me) If inGame Me.DrawObjects(painter) Else Me.GameOver(painter) End If painter.End() End Sub Private Sub DrawObjects(ByVal painter As QPainter) painter.DrawImage(apple_x, apple_y, apple) For z As Integer = 0 to dots - 1 If z = 0 painter.DrawImage(x(z), y(z), head) Else painter.DrawImage(x(z), y(z), ball) End If Next End Sub Private Sub GameOver(ByVal painter As QPainter) Dim msg As String = "Game Over" Dim small As New QFont("Helvetica", 12) small.SetBold(True) Dim metr As New QFontMetrics(small) Dim textWidth As Integer = metr.Width(msg) Dim h As Integer = Me.Height Dim w As Integer = Me.Width painter.SetPen(New QPen(New QBrush(Qt.GlobalColor.white), 1)) painter.SetFont(small) painter.Translate(New QPoint(w/2, h/2)) Dim text_x As Integer = -textWidth / 2 Dim text_y As Integer = 0 painter.DrawText(text_x, text_y, msg) 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 Protected Overrides Sub TimerEvent(ByVal e As QTimerEvent) If inGame Me.CheckApple() Me.CheckCollision() Me.Move() Else timer.Stop() End If Me.Repaint() End Sub Protected Overrides Sub KeyPressEvent(ByVal e As QKeyEvent) Dim key As Integer = e.Key() If key = Qt.Key.Key_Left And Not right left = True up = False down = False End If If key = Qt.Key.Key_Right And Not left right = True up = False down = False End If If key = Qt.Key.Key_Up And Not down up = True right = False left = False End If If key = Qt.Key.Key_Down And 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(painter) Else Me.GameOver(painter) End If ``` 在`PaintEvent()`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 painter As QPainter) painter.DrawImage(apple_x, apple_y, apple) For z As Integer = 0 to dots - 1 If z = 0 painter.DrawImage(x(z), y(z), head) Else painter.DrawImage(x(z), y(z), ball) 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() Else timer.Stop() End If ``` 每 140 毫秒，将调用`TimerEvent()`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，我们将停止计时器。 在`Board`类的`KeyPressEvent()`方法中，我们确定按下的键。 ```vb If key = Qt.Key.Key_Left And 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 Qt tutorial ' ' In this program, we create ' a Nibbles game clone ' ' author jan bodnar ' last modified May 2009 ' website www.zetcode.com Imports Qyoto Imports BoardSpace Public Class VBQApp Inherits QMainWindow Dim WIDTH As Integer = 250 Dim HEIGHT As Integer = 150 Public Sub New() Me.SetWindowTitle("Nibbles") Dim board As New BoardSpace.Board() Me.SetCentralWidget(board) Me.Resize(310, 310) Me.Move(300, 300) Me.Show() End Sub Public Shared Sub Main(ByVal args() As String) Dim qapp As New QApplication(args) Dim app As New VBQApp QApplication.Exec() End Sub End Class ``` 在这个类中，我们设置了贪食蛇游戏。  图：贪食蛇 这是用 Qyo​​to 库和 Visual Basic 编程语言编写的贪食蛇电脑游戏。