Question

I’m building a maze application in visual basic. The game relies on two variables, X and Y which are integers. There’s a timer which basically invalidates the whole form for a redraw. Now my question is, that there are various squares and rectangles dotted around the form. How would I create a handler, or something as such to detect if the square that the form draws is touching these objects?

Code:

Public Class Form1
    Const W As Integer = 35 'Width
    Const H As Integer = 35 'Height

    Dim X As Integer
    Dim Y As Integer

    Private Sub Form1_KeyDown(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyEventArgs) Handles Me.KeyDown
        'Handles if a key is pressed
        Select Case e.KeyCode
            Case Keys.Up
                Y -= 2
            Case Keys.Down
                Y += 2
            Case Keys.Left
                X -= 2
            Case Keys.Right
                X += 2

            Case Keys.Escape
                Me.Close()
        End Select
    End Sub

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Me.Text = "Maze"
        TmrRedraw.Start()
        MsgBox("Press ESC to quit")
        Cursor.Position = Me.Location
    End Sub

    Private Sub TmrRedraw_Tick(ByVal sender As Object, ByVal e As System.EventArgs) Handles TmrRedraw.Tick
        If CollisionDetect() = False Then
            Me.Invalidate()
            CheckForWin()
        End If
    End Sub

    Private Function CollisionDetect()
        Dim Collision As Boolean = False

        'Here is where the problem lies 


        Return Collision
    End Function

    Private Sub Form1_Paint(ByVal sender As Object, ByVal e As System.Windows.Forms.PaintEventArgs) Handles Me.Paint
        e.Graphics.FillRectangle(Brushes.Blue, X, Y, W, H)

    End Sub

    Private Sub CheckForWin()
        Dim WinSqX As Integer = WinSquare.Location.X
        Dim WinSqY As Integer = WinSquare.Location.Y

        If X = WinSqX And Y = WinSqY Then

            TmrRedraw.Stop()
            MsgBox("Congratulations! You won!")
            Me.Close()
        End If


    End Sub
End Class

Oh yes – the player must use the arrow keys to change the X and Y, and when it redraws, it will move.

Thanks

Answer 1

I don’t see the need for the timer in your example since you just need to invalidate whenever the user is pressing the keyboard.

For object collision, you would need a list of objects that have their rectangle coordinates, and then just test for an intersection:

Public Class Form1
  Dim block As New Rectangle(0, 0, 35, 35)  
  Dim listOfThings As New List(Of Rectangle)

  Public Sub New()
    InitializeComponent()
    Me.DoubleBuffered = True

    listOfThings.Add(New Rectangle(40, 40, 35, 35))
  End Sub

  Private Sub Form1_KeyDown(ByVal sender As Object, ByVal e As KeyEventArgs) Handles MyBase.KeyDown
    Select Case e.KeyCode
      Case Keys.Up
        MoveBlock(0, -2)
      Case Keys.Down
        MoveBlock(0, 2)
      Case Keys.Left
        MoveBlock(-2, 0)
      Case Keys.Right
        MoveBlock(2, 0)
      Case Keys.Escape
        Me.Close()
    End Select
  End Sub

  Private Sub MoveBlock(ByVal moveX As Integer, ByVal moveY As Integer)
    block.X += moveX
    block.Y += moveY

    For Each r As Rectangle In listOfThings
      If r.IntersectsWith(block) Then
        MessageBox.Show("Game Over")
      End If
    Next

    Me.Invalidate()
  End Sub

  Private Sub Form1_Paint(ByVal sender As Object, ByVal e As PaintEventArgs) Handles Me.Paint
    e.Graphics.Clear(Color.White)

    For Each r As Rectangle In listOfThings
      e.Graphics.DrawRectangle(Pens.Red, r)
    Next

    e.Graphics.FillRectangle(Brushes.Blue, block)
  End Sub
End Class