An array of controls

1
An array of controls

• Not particularly convenient in VB
• Examples array of pictureboxes
• Array of textboxes
• Notes on Concentration game (a possible final
  project)

2
Recall the microwave oven? (Proj12)
3
Digit-button handlers

• We built a subroutine for every button which
  looked like this
• Private Sub Btn1_Click(ByVal sender As
  System.Object, ByVal e As System.EventArgs)
  Handles Btn1.Click
• Beep()
• strtime "1"
• displayTime()
• End Sub

4
Simplifying the code

• Make one sub handle all the digit buttons
• Private Sub Digit_Button(ByVal sender As
  System.Object, ByVal e As System.EventArgs)
  Handles Btn1.Click,Btn2.Click,
• Delete the old subs and edit the code inside this
  one strtime "1 wont work anymore.
• Use
• Dim a as String sender.tostring()
• strtime a.substring(a.length-1,1)

5
An array of textboxes
6
The entire code so far

• Public Class Form1
• Dim txt As TextBox() field value at top so
  txt(i) can be recognized
• Private Sub Form1_Load(ByVal sender As
  System.Object, ByVal e As System.EventArgs)
  Handles MyBase.Load
• txt New TextBox() TextBox1, TextBox2,
  TextBox3
• assign actual names to elements of txtbox array
• Dim i As Integer
• For i 0 To txt.Length - 1
• txt(i).Text "I am txtbox" I
  display something
• Next
• End Sub
• End Class

7
When text is changed in any textbox, the 4th
textbox gets the new text
8
Code for one of the textchanged events

• Private Sub TextBox1_TextChanged(ByVal sender As
  System.Object, ByVal e As System.EventArgs)
  Handles TextBox1.TextChanged
• TextBox4.Text txt(0).Text
• End Sub
• This code has an event handler sub for each
  control in the array. A lot of unnecessary
  code!!!!
• It is possible to get one event handler (sub) to
  handle all the textbox changed events, and thus
  to save a lot of code. See third example in this
  slideshow.

9
About the next example

• This short ppt shows how to declare an array of
  controls (in this case pictureboxes)
• And then to coordinate action on those array
  elements based on the actual pictureboxes placed
  on the form during design.
• You will need to be concerned somewhat with the
  size of the image file too big wont
  fit/display properly, so choose small files.
• Youll also need to make sure your form is big
  enough to hold a bunch of pictureboxes
• The example shown here has just 3.

10
Three pictureboxes (backs)
11
Clicking a picturebox flips it over
12
And clicking again shows the back
13
Field declarations and formload

• fields
• Dim cntr(3) As Integer
• Dim names As String() "c\icecream.jpg",
  "c\gfruit.jpg", "c\fatlady.jpg" the pictures
  Ill use
• Dim pics As PictureBox() must go at top so
  different subs can access
• Formload method
• Need to assign array elements to actual allocated
  controls
• pics New PictureBox() PictureBox1,
  PictureBox2, PictureBox3
• these are the actual pic box names I used in
  design
• Load initial pictures
• Dim i As Integer
• For i 0 To names.Length - 1
• cntr(i) 0 zero counters
• pics(i).Image Image.FromFile(names(i)) put
  on a picture
• Next

14
Clicking a picturebox

• Clicking a picturebox toggles the displayed
  image
• we keep track by counting mod 2
• Increment the counter and mod by 2 each time
  picturebox is clicked
• Set the image based on odd/even count value

15
PictureBox1_Click code (similar for others)

• Private Sub PictureBox1_Click(ByVal sender As
  System.Object, ByVal e As System.EventArgs)
  Handles PictureBox1.Click
• cntr(0) (cntr(0) 1) Mod 2 count mod
  2
• If cntr(0) 0 Then if even show back
• pics(0).image Image.FromFile("c\jra
  ff.jpg")
• Else if odd show front
• pics(0).Image Image.FromFile(names(0
  ))
• End If
• End Sub

16
Cutting down on the necessary code- V1.2 of
textbox array example
17
The entire code for this example

• Public Class Form1
• Dim txt As TextBox()
• Private Sub Form1_Load(ByVal sender As
  System.Object, ByVal e As System.EventArgs)
  Handles MyBase.Load
• txt New TextBox() TextBox1, TextBox2,
  TextBox3
• Dim i As Integer
• For i 0 To txt.Length - 1
• txt(i).Text "I am txtbox" i
• Next
• End Sub
• a single sub is called if any textbox is
  changed
• Private Sub TextisChanged(ByVal sender As
  System.Object, ByVal e As System.EventArgs)
  Handles TextBox1.TextChanged, TextBox2.TextChanged
  , TextBox3.TextChanged
• Dim i As Integer
• For i 0 To txt.Length - 1
• If sender.Equals(txt(i)) Then see
  which one was changed
• TextBox4.Text txt(i).Text
  then change txtbox4 appropriately
• End If
• Next
• End Sub

18
shuffling

• Need to mark all cards as not shuffled.
• I used an array of ints set to -1 to mean not
  shuffled
• Need to pick 2 random values.
• I picked one random value a position in the
  array that was still not shuffled and then
  picked the 2nd one by adding an amount mod
  picnums to the first.
• Mark these positions with their picnum
• Keep going until all positions have been
  shuffled.
• For ten cards, you need 5 pictures, and you need
  to go around successfully picking pairs 5 times.
• Not shown after shuffling, display the pictures
  using the numbers stored in the array.

19
Shuffling set all cards to not shuffled

• Dim i As Integer
• For i 0 To 5
• cntr(i) -1 'empty counters
• pics(i).Image Image.FromFile("c\jraff.
  jpg")
• 'put on back picture
• Next

20
shuffling

• pos1 0
• pos2 0
• picnum 0
• Do While picnum lt 3 I used 6 pictures so I need
  3 pairs
• pos1 r.Next(6) I used 6 pictures
  so get a random 0..5
• Do While cntr(pos1) ltgt -1 while a
  shuffled card picked
• pos1 r.Next(6) pick another
• Loop
• pos2 (pos1 5) Mod 6 arbitrarily
  pick his pair card
• cntr(pos1) picnum set these two
  cards with their picnum
• cntr(pos2) picnum
• picnum picnum 1 success so count
  one more
• Loop

21
Using a listbox to display successful shuffling
22
Remarks on prev slide

• I put a listbox on just to see what pairs I got.
• Next step after testing shuffling would be to
  begin coding the actual concentration game.

23
Concentration game

• Form load should shuffle integers and display
  card backs.
• You might want a button called play again.
• Not shown in this ppt you might set background
  color of pictureboxes to black to indicated a
  pair has been chosen.
• You can disable pictureboxes when they are
  successfully picked so that clicking doesnt do
  anything.
• Youll need to re-enable pictureboxes, set backs
  to back-of-card image, and do all the reshuffling
  code for the play again button.

24
Concentration game..how to play

• Not shown in ppt. When a game starts, you need
  to set a click counter to zero. You also need a
  pair counter set to 0 to count the number of
  matched pairs.
• When a picturebox is clicked, increment your
  click count, flip it over (the integer in my cntr
  array tells which picture to draw on it.) Maybe
  youll want to save his picnum somewhere.
• When a 2nd picturebox is clicked, click count
  again. If click count is 2, Get the picnum of the
  2nd picture. Check the picnumbers on the clicked
  pictures. If they are the same, disable these
  pictureboxes, put backgrounds to black, count the
  pair match, set click counter back to zero.

25
Checking to see if I can flip over cards
26
Flipping over cards when clicked

• Private Sub PicClick(ByVal sender As
  System.Object, ByVal e As System.EventArgs)
  Handles PictureBox1.Click, PictureBox2.Click,
  PictureBox3.Click, PictureBox4.Click,
  PictureBox5.Click, PictureBox6.Click
• Dim i As Integer
• For i 0 To 5
• If sender.Equals(pics(i)) Then
• 'see which one was changed
• pics(i).Image
  Image.FromFile(names(cntr(i))) 'then change
  picbox appropriately
• End If
• Next
• End Sub

27
Beginning the game

• In formload, disable all the pictureboxes. (next
  slide)
• Add a start button and put the code to shuffle
  the cards and enable the pictureboxes in the
  event sub for that button. (not shown)

28
formload

• Private Sub Form1_Load(ByVal sender As
  System.Object, ByVal e As System.EventArgs)
  Handles MyBase.Load
• pics New PictureBox() PictureBox1,
  PictureBox2, PictureBox3, PictureBox4,
  PictureBox5, PictureBox6
• 'these are the pic box names I used in
  design
• Dim i As Integer
• For i 0 To 5
• pics(i).Enabled False
• Next
• End Sub

29
More remarks

• You may want a boolean named match to keep track
  of whether there was a match
• Youll need another image to put on pictures
  which have been matched (plus disable them)
• Make sure that the player clicks two different
  pictures (not the same one twice)