Visual Basic电影程序

Question

I'm having a weird issue with this VB program I'm working on for class. I'm honestly not entirely sure why I'm running into the problem, because I've done other assignments with ease that were relatively similar to this. The program is designed to allow me to add certain movies from the store (left list box) to the cart (the right list box.) You can see that I added Spider-Man two times (because who doesn't like Spider-Man?) and it did correctly show the name and the $2 each time. However the first label box in the bottom should be accumulating each time I add the movie to the box, but it stays firm at the first movie I pick. If I were to pick any of the other movies, which are all more expensive, it will still stay at the first movie I picked.

EDIT: I should add, I was having the same issue before I moved some parts of the code into their respective functions.

Public Class mainForm

Public strMovies() As String =
        {"Spider-Man", "Daredevil", "Hulk", "The Punisher", "Spider-Man 2",
         "Fantastic Four", "Spider-Man 3", "Iron Man", "The Amazing Spider-Man", "The Wolverine"}
Public intMoviePrices() As Integer =
    {2, 4, 6, 8, 10, 12, 14, 16, 18, 20}

Dim X As Integer
Dim Y As Integer
Dim moviecost As Integer
Dim movietax As Double
Dim numberdvds As Integer
Dim shippingcharge As Double
Dim netcost As Double
Dim movieChoice As String


Private Sub ListBox1_SelectedIndexChanged(sender As Object, e As EventArgs) Handles lstCom.SelectedIndexChanged

End Sub


Public Function calculateTotals(movieChoice) As Integer



    moviecost = moviecost + intMoviePrices(movieChoice)
    movietax = (moviecost * 1.04) - moviecost
    If numberdvds >= 5 Then
        shippingcharge = 5
    Else
        shippingcharge = numberdvds
    End If
    netcost = movietax + moviecost + shippingcharge

    lblgrosscost.Text = moviecost
    lblsalestax.Text = FormatNumber(movietax, 2)
    lblshipping.Text = shippingcharge
    lblnetcost.Text = netcost

    Return moviecost
    Return movietax

End Function

Public Function addMovie() As String




    movieChoice = lstCom.SelectedIndex

    For X = LBound(strMovies) To UBound(strMovies)
        If lstCom.SelectedIndex = X Then
            lstCom2.Items.Add(strMovies(X) & " $" + intMoviePrices(movieChoice).ToString)
            numberdvds += 1
            Call calculateTotals(movieChoice)

        End If
    Next

End Function

Public Function removeMovie() As String



    For X = LBound(strMovies) To UBound(strMovies)
        If lstCom2.SelectedIndex = X Then
            lstCom2.Items.Remove(lstCom2.SelectedItem)
            numberdvds -= 1
            Call calculateTotals(movieChoice)

        End If
    Next





End Function

Private Sub mainForm_Load(sender As Object, e As EventArgs) Handles MyBase.Load




    lstCom.Items.Add("Spider-Man")
    lstCom.Items.Add("Daredevil")
    lstCom.Items.Add("Hulk")
    lstCom.Items.Add("The Punisher")
    lstCom.Items.Add("Spider-Man 2")
    lstCom.Items.Add("Fantastic Four")
    lstCom.Items.Add("Spider-Man 3")
    lstCom.Items.Add("Iron Man")
    lstCom.Items.Add("The Amazing Spider-Man")
    lstCom.Items.Add("The Wolverine")
    lstCom.SelectedIndex = 0


End Sub

Private Sub btnAdd_Click(sender As Object, e As EventArgs) Handles btnAdd.Click

    Call addMovie()

End Sub

Private Sub btnExit_Click(sender As Object, e As EventArgs) Handles btnExit.Click

    Me.Close()

End Sub

Private Sub btnRemove_Click(sender As Object, e As EventArgs) Handles btnRemove.Click

    Call removeMovie()
End Sub

End Class

Answer 1

You are resetting movie cost each time you calculate as it is relative to that function only.

Move this:

Dim moviecost As Integer

Outside of the function for a quick fix but to do it properly I would leave it in there and calculate from the basket every time, the reason I would do this is because if you remove something from the cart you don't remove the price. Best to dynamically calculate based on the cart contents every time a change is made.

Also you can replace ALL of this:

If lstCom.SelectedIndex = 0 Then
    lstCom2.Items.Add ("Spider-Man " + "$" + intMoviePrices(movieChoice).ToString)
    Call calculateTotals(movieChoice)
ElseIf lstCom.SelectedIndex = 1 Then
    lstCom2.Items.Add ("Daredevil " + "$" + intMoviePrices(movieChoice).ToString)
ElseIf lstCom.SelectedIndex = 2 Then
    lstCom2.Items.Add ("Hulk " + "$" + intMoviePrices(movieChoice).ToString)
ElseIf lstCom.SelectedIndex = 3 Then
    lstCom2.Items.Add ("The Punisher " + "$" + intMoviePrices(movieChoice).ToString)
ElseIf lstCom.SelectedIndex = 4 Then
    lstCom2.Items.Add ("Spider-Man 2 " + "$" + intMoviePrices(movieChoice).ToString)
ElseIf lstCom.SelectedIndex = 5 Then
    lstCom2.Items.Add ("Fantastic Four " + "$" + intMoviePrices(movieChoice).ToString)
ElseIf lstCom.SelectedIndex = 6 Then
    lstCom2.Items.Add ("Spider-Man 3 " + "$" + intMoviePrices(movieChoice).ToString)
ElseIf lstCom.SelectedIndex = 7 Then
    lstCom2.Items.Add ("Iron Man " + "$" + intMoviePrices(movieChoice).ToString)
ElseIf lstCom.SelectedIndex = 8 Then
    lstCom2.Items.Add ("The Amazing Spider-Man " + "$" + intMoviePrices(movieChoice).ToString)
ElseIf lstCom.SelectedIndex = 9 Then
    lstCom2.Items.Add ("The Wolverine " + "$" + intMoviePrices(movieChoice).ToString)
End If

With this:

For X = LBound(strMovies) To UBound(strMovies)
    If lstCom.SelectedIndex = X Then
        lstCom2.Items.Add (strMovies(X) & " $" + intMoviePrices(movieChoice).ToString)
        Call calculateTotals(movieChoice)
    End If
Next

Then put this at the top of that function:

Dim X As Integer

Answer 2

Adding another answer as this is the second question. I have modified your code but can't test as I don't have the project.

Please check it out and report back. Note you need to put some smarts into the removeMovie routine to work out the cost and tax, refer to what I did to the addMovie function to get an idea.

The calculate totals routine basically just formats and posts the data, the actual numbers are worked out when things are added / remove. I have removed the MovieChoice variable being passed into it as it is no longer relevant.

Public strMovies() As String =
        {"Spider-Man", "Daredevil", "Hulk", "The Punisher", "Spider-Man 2",
         "Fantastic Four", "Spider-Man 3", "Iron Man", "The Amazing Spider-Man", "The Wolverine"}
Public intMoviePrices() As Integer =
    {2, 4, 6, 8, 10, 12, 14, 16, 18, 20}

Dim X As Integer
Dim Y As Integer
Dim moviecost As Integer
Dim movietax As Double
Dim numberdvds As Integer
Dim shippingcharge As Double
Dim netcost As Double
Dim movieChoice As String


Private Sub ListBox1_SelectedIndexChanged(sender As Object, e As EventArgs) Handles lstCom.SelectedIndexChanged

End Sub


Public Function calculateTotals() As Integer
    If numberdvds > 4 Then
        shippingcharge = 5
    Else
        shippingcharge = numberdvds
    End If
    netcost = movietax + moviecost + shippingcharge
    lblgrosscost.Text = moviecost
    lblsalestax.Text = FormatNumber(movietax, 2)
    lblshipping.Text = shippingcharge
    lblnetcost.Text = netcost
End Function

Public Function addMovie() As String
    movieChoice = lstCom.SelectedIndex
    moviecost = moviecost + intMoviePrices(movieChoice)
    movietax = movietax + (intMoviePrices(movieChoice) * 0.04)
    For X = LBound(strMovies) To UBound(strMovies)
        If lstCom.SelectedIndex = X Then
            lstCom2.Items.Add (strMovies(X) & " $" + intMoviePrices(movieChoice).ToString)
            numberdvds = numberdvds + 1
            Call calculateTotals()
        End If
    Next
End Function

Public Function removeMovie() As String
    'Need to add code to remove cost and tax here
    For X = LBound(strMovies) To UBound(strMovies)
        If lstCom2.SelectedIndex = X Then
            lstCom2.Items.Remove (lstCom2.SelectedItem)
            numberdvds = numberdvds - 1
            Call calculateTotals()
        End If
    Next
End Function

Private Sub mainForm_Load(sender As Object, e As EventArgs) Handles MyBase.Load
    For X = LBound(strMovies) To UBound(strMovies)
        lstCom.Items.Add (strMovies(X))
    Next
End Function

Private Sub btnAdd_Click(sender As Object, e As EventArgs) Handles btnAdd.Click
    Call addMovie
End Function

Private Sub btnExit_Click(sender As Object, e As EventArgs) Handles btnExit.Click
    Me.Close()
End Function

Private Sub btnRemove_Click(sender As Object, e As EventArgs) Handles btnRemove.Click
    Call removeMovie
End Function