A-level Computing/AQA/The Computing Practical Project/Advanced VB.NET

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All the programming you have done so far has been with the command line. This is great if all you want is text on a screen, but you probably want to display some graphics. There are several places you can get started:


Here we are going to look how we can very quickly display graphics in VB.NET and make some simple games. To display graphics we are going to use the GDI+ library of tools. DirectX is much more powerful, but for our needs GDI+ is a simple way to get started. GDI+ allows you to draw both vector and bitmap graphics to the screen. There are a couple of functions that you need to be familiar with:

frmGame_Load[edit]

This code runs when the form is first loaded

frmGame_KeyDown[edit]

This code runs on the event of clicking a key on your keyboard

tmrBall_Tick[edit]

You need to have added a timer to your project and named it tmrBall. This code runs on each tick of the timer.

Paint[edit]

This code draws the items on to the screen

Public Class frmGame
    Dim x1, y1, w1, h1 As Integer
    Dim x2, y2, w2, h2 As Integer
    Dim bx, by, bw, bh, bdirx, bdiry As Integer
 
    'As soon as the game starts the paddles are set up and the ball started
    Private Sub frmGame_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        x1 = 5
        y1 = Me.Height / 2
        w1 = 5
        h1 = 20
 
        x2 = Me.Width - 15
        y2 = Me.Height / 2
        w2 = 5
        h2 = 20
 
        bx = Me.Width / 2
        by = Me.Height / 2
        bw = 10
        bh = 10
 
        bdirx = 2
        bdiry = -2
 
    End Sub
 
    'On the event of pressing a key, this code finds which key has been pressed and moves the paddles
    Private Sub frmGame_KeyDown(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyEventArgs) Handles Me.KeyDown
        If e.KeyCode = Keys.Up Then
            If y2 - 3 > 12 Then
                y2 = y2 - 3
            End If
        End If
 
        If e.KeyCode = Keys.Down Then
            If y2 + 3 < Me.Height - 40 Then
                y2 = y2 + 3
            End If
        End If
        Invalidate()
    End Sub
 
    'On each tick of the timer, the ball moves around the screen
    Private Sub tmrBall_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles tmrBall.Tick
        bx = bx + bdirx
        by = by + bdiry
 
        If by + bdiry < 12 Then
            bdiry = bdiry * -1
        End If
        If by + bdiry > Me.Height - 40 Then
            bdiry = bdiry * -1
        End If
 
        'collides with paddle 1
        If bx < x1 And by > y1 And by < y1 + h1 Then
            bdirx = bdirx * -1
        End If
 
        If bx > x2 And by > y2 And by < y2 + h2 Then
            bdirx = bdirx * -1
        End If
        Invalidate()
    End Sub
 
    'This code runs each time the invalidate() procedure is called
    Private Sub frmGame_Paint(ByVal sender As Object, ByVal e As System.Windows.Forms.PaintEventArgs) Handles Me.Paint
        Dim pallete As Drawing.Graphics = Me.CreateGraphics
        Dim brush_black As New SolidBrush(Color.Black)
 
        pallete.FillRectangle(brush_black, New Rectangle(bx, by, bw, bh))
 
        pallete.FillRectangle(brush_black, New Rectangle(x1, y1, w1, h1))
        pallete.FillRectangle(brush_black, New Rectangle(x2, y2, w2, h2))
 
        pallete.FillRectangle(Brushes.DarkGreen, New Rectangle(2, 2, Me.Width - 2, 10))
        pallete.FillRectangle(Brushes.DarkGreen, New Rectangle(2, Me.Height - 40, Me.Width - 2, 10))
 
    End Sub
End Class