Wyo VB Lecture Notes

Objective #1: Be able to use various Mouse events.

• A MouseClick event occurs when the user clicks the mouse. The following method displays the coordinates of where the mouse was clicked
  
  Private Sub Form1_MouseClick(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles Me.MouseClick
  
     If (e.Button = Windows.Forms.MouseButtons.Left) Then
        MessageBox.Show("The mouse was clicked at (" + e.X.ToString + ", " + e.Y.ToString + ")")
     End If
  
  End Sub
  
  
• A MouseMove event occurs when the mouse's position changes. The following method displays the coordinates of the mouse in two labels
  
  Private Sub Form1_MouseMove(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles MyBase.MouseMove
     lblX.Text = e.X
     lblY.Text = e.Y
  End Sub
  
  The following code segment goes even further to allow the user to drag a picture box around the screen and detects a collision with a line segment:
  
  

    ' move player around screen with mouse
    Private Sub Form1_MouseMove(sender As Object, e As System.Windows.Forms.MouseEventArgs) Handles Me.MouseMove
        picPlayer.Left = e.X - picPlayer.Width / 2
        picPlayer.Top = e.Y - picPlayer.Height / 2
        ' Can you explain why the statement above is 
        ' better than the shorter statement:         picPlayer.Top = e.Y

       
        If (picPlayer.Left < 200 And picPlayer.Right > 200 And picPlayer.Top < 150 And picPlayer.Bottom > 100) Then
            MessageBox.Show("collision")
        End If

    End Sub
    
    ' draw maze
    Private Sub Form1_Paint(sender As Object, e As System.Windows.Forms.PaintEventArgs) Handles Me.Paint
        e.Graphics.DrawLine(Pens.Black, 200, 100, 200, 150)
    End Sub

  

• A MouseDown event occurs when the user presses the mouse button somewhere on the form. The following method displays the coordinates of where the mouse was clicked
  
  Private Sub Form1_MouseDown(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles MyBase.MouseDown
  
     If (e.Button = Windows.Forms.MouseButtons.Left) Then
        MessageBox.Show("The mouse was clicked at (" + e.X.ToString + ", " + e.Y.ToString + ")")
     End If
  
  End Sub
  
  
• A MouseUp event occurs when the user releases the mouse button. Note that the MouseUp event may occur in the very next instant after its corresponding MouseDown event if the user clicked the mouse quickly. Or, if the user decides to hold down the mouse button for a long time or he/she drags the mouse across the screen, the MouseUp event will occur much later than its corresponding MouseDown event.