[RESOLVED] list.remove method

[bodylojohn]

Hello,

I use the following code to add multiple lines on a picturebox.
Each time I press the button next a line gets added to the list of lines.
Everything works fine (Thanks to the help of you guys).

Here comes my problem: When i press the cancel button I want to delete a line from the list.
So suppose I have 3 lines on my picturebox, the first time I press the cancel button the LAST line I added should be removed from the picturebox.
The second time I press the cancel button, the second line should be deleted and so on...

Also I would appreceate it if you could check my code if it is well programmed.

Thanks in advance.

Public Class frmCutSelectedSheet
 
    Dim GraphicsFun As System.Drawing.Graphics
    Dim PenColor As New System.Drawing.Pen(Color.Red)
    Private lines As New List(Of Line)
    Dim start As Point
    Dim [end] As Point
    Dim counter As Integer = 0
    Dim Coordinates As String
    Dim NumberOfCuts As Integer
 
 
    Private Sub frmCutSelectedSheet_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        'Place a blank image in the PictureBox control.
        Me.pctPaintBox.Image = New Bitmap(Me.pctPaintBox.Width, Me.pctPaintBox.Height)
        lblStartingX.Text = "<= " & Me.pctPaintBox.Width - 1
        lblStartingY.Text = "<= " & Me.pctPaintBox.Height - 1
        lblEndingX.Text = "<= " & Me.pctPaintBox.Width - 1
        lblEndingY.Text = "<= " & Me.pctPaintBox.Height - 1
        Me.txtStartingX.Enabled = False
        Me.txtStartingY.Enabled = False
        Me.txtEndingX.Enabled = False
        Me.txtEndingY.Enabled = False
    End Sub
 
    Private Sub pctPaintBox_Paint(ByVal sender As Object, ByVal e As System.Windows.Forms.PaintEventArgs) Handles pctPaintBox.Paint
        'Draw each line on the control.
        For Each line As Line In Me.lines
            e.Graphics.DrawLine(Pens.Black, line.Start, line.End)
        Next line
    End Sub
 
    Private Sub Save()
        'Create a Graphics object from the Image in the PictureBox.
        Dim g As Graphics = Graphics.FromImage(Me.pctPaintBox.Image)
 
        'Draw each line on the image to make them permanent.
        For Each line As Line In Me.lines
            g.DrawLine(Pens.Black, line.Start, line.End)
        Next line
 
        'Clear the temporary lines that were just saved.
        Me.Clear()
    End Sub
 
    Private Sub Clear()
        'Clear all unsaved lines.
        Me.lines.Clear()
 
        'Force the control to repaint so the lines are removed.
        Me.pctPaintBox.Refresh()
    End Sub
 
    Private Sub btnNextCut_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnNextCut.Click
        If counter = 0 Then
            Me.txtStartingX.Enabled = True
            Me.txtStartingY.Enabled = True
            Me.txtEndingX.Enabled = True
            Me.txtEndingY.Enabled = True
            counter += 1
        Else
            Call Me.Clear()
            With Me.pctPaintBox
                If txtStartingX.Text >= .Width Then
                    MsgBox("X coordinate startpoint is invalid")
                    Exit Sub
                ElseIf txtStartingY.Text >= .Height Then
                    MsgBox("Y coordinate startpoint is invalid")
                    Exit Sub
                ElseIf txtEndingX.Text >= .Width Then
                    MsgBox("X coordinate endingpoint is invalid")
                    Exit Sub
                ElseIf txtEndingY.Text >= .Height Then
                    MsgBox("Y coordinate endingpoint is invalid")
                    Exit Sub
                Else
 
                    [end] = New Point(txtEndingX.Text, txtEndingY.Text)
                    start = New Point(txtStartingX.Text, txtStartingY.Text)
 
                    'Add the new line to the list.
                    Me.lines.Add(New Line(Me.start, [end]))
 
                    'Force the control to repaint so the new line is drawn.
                    Me.pctPaintBox.Invalidate(New Rectangle(Math.Min(Me.start.X, [end].X), _
                                                           Math.Min(Me.start.Y, [end].Y), _
                                                          Math.Abs(Me.start.X - [end].X), _
                                                         Math.Abs(Me.start.Y - [end].Y)))
                    'Me.Refresh()
                    Call Me.Save()
 
                    If Coordinates = "" Then
                        Coordinates = "(" & txtStartingX.Text & "," & txtStartingY.Text & "," & txtEndingX.Text & "," & txtEndingY.Text & ")"
                    Else
                        Coordinates = Coordinates & "#" & "(" & txtStartingX.Text & "," & txtStartingY.Text & "," & txtEndingX.Text & "," & txtEndingY.Text & ")"
                    End If
 
                    txtStartingX.Text = ""
                    txtStartingY.Text = ""
                    txtEndingX.Text = ""
                    txtEndingY.Text = ""
                    lblCuts.Text = "Cuts : " & Me.lines.Count
                    counter += 1
                End If
            End With
        End If
 
    End Sub
 
    Private Sub btnCancel_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnCancel.Click
 
    End Sub
End Class
 
Public Class Line
    'The line's start point.
    Private _start As Point
 
    'The line's end point.
    Private _end As Point
 
    'The line's start point.
    Public Property Start() As Point
        Get
            Return Me._start
        End Get
        Set(ByVal value As Point)
            Me._start = value
        End Set
    End Property
 
    'The line's end point.
    Public Property [End]() As Point
        Get
            Return Me._end
        End Get
        Set(ByVal value As Point)
            Me._end = value
        End Set
    End Property
 
    Public Sub New()
        Me.New(Point.Empty, Point.Empty)
    End Sub
 
    Public Sub New(ByVal start As Point, ByVal [end] As Point)
        Me._start = start
        Me._end = [end]
    End Sub
End Class

[jmcilhinney]

In the Click event handler of the button you simply need to remove the last Line from the collection and repaint the control.

Dim removedLine As Line = Me.lines(Me.lines.Count - 1)
 
Me.lines.Remove(removedLine)
Me.pctPaintBox.Invalidate(New Rectangle(Math.Min(removedLine.Start.X, removedLine.End.X), _
                                        Math.Min(removedLine.Start.Y, removedLine.End.Y), _
                                        Math.Abs(removedLine.Start.X - removedLine.End.X), _
                                        Math.Abs(removedLine.Start.Y - removedLine.End.Y)))

[bodylojohn]

Hello,

thanks for the reply.
But when I add 2 lines and I press the cancel button I get the following message:

"Index was out of range. Must be non-negative and less than the size of the collection.
Parameter name: index"

[jmcilhinney]

Your original code is copied from my CodeBank submission so I'm fairly familiar with it. If you've added Line objects to that List then the code in post #2 will work exactly as you've asked. The ONLY reason that you might have an issue is if you continue to press your button after you've removed all the Lines. It's your responsibility to prevent that happening by disabling the button when you remove the last line and/or testing the Count property of the List before attempting to remove a Line.

[jmcilhinney]

One more thing. You may need to expand the invalidated rectangle very slightly. In my testing it seemed to leave the odd pixel behind, so maybe just expand it by 1 in each direction to be safe.

[bodylojohn]

Hello,

I have tried to add 3 lines (works perfect).
Then I press 1 time and I get the errormessage


"Index was out of range. Must be non-negative and less than the size of the collection.
Parameter name: index"

The rectangle isn't even reached in the procedure.
Because I get the error message on the:

Dim removedLine As Line = Me.lines(Me.lines.Count - 1)

Statement

[bodylojohn]

I did a little more research in the code and it seems that me.lines.count stays 0.
So when I add 3 lines the value of me.lines.count should be 3.
Right???

But how do I solve this??

[bodylojohn]

I have thrown out the clear method in the btnnext sub.
Now it count but the code still doesnt work.

I hope you guys can help me.
I got the feelin' this problem is about to be solved.

[bodylojohn]

Right now I got the code so far that when I press the cancel button I dont get the error message...
BUT...
I I have 3 lines and I press the cancel button I still see 3 lines.
Do I press the button again I get the error message.

I tried a refresh but that didn't work

[jmcilhinney]

OK, the whole idea of the List is so that it stores the Lines temporarily until you call Save, at which point the lines are drawn permanently on an Image object. The comments in the Save method specifically state that the lines are made permanent and removed from the List. Your code calls Save every time it creates a new Line, so it is immediately made permanent and removed from the List. If you want the ability to undo then don't call Save. That was the whole point of including that Save method in the first place.

[bodylojohn]

jmcilhinney you are SUPERMAN!!!

It works now...

Everybody THANK you very very much.