Visual Basic 3

1
Visual Basic 3

• Some new components
• Some new capabilities
• OOD/OOP

2
Index of projects covered in this ppt

• Date time display
• Format currency
• Form with picture box, group boxes, radiobuttons
• Flags of the world (more picture boxes, images)
• Another picturebox/radiobutton example
• Images from file example with combobox
• Changing fonts using current property settings or
  font literal values

3
Some points about class programming practices

• Try to use conventional names in your projects.
  It will make them easier to edit and code
• Some of you need more practice with arithmetic
  and with using data supplied in a textbox. You
  may need to take time outside of class to work on
  optional exercises or class projects.
• Note If you dont show me your labs or projects,
  I do not mark them as complete. It is your
  responsibility to make sure I see your completed
  work. If I havent seen your project during the
  class period, show me after class I have office
  hour then. If you are not sure if I marked you
  come see me (F239) during office hour or email me
  which lab or project you want to know about.

4
Some points about class programming practices

• Your text, section 3.3 goes over how to perform
  calculations with numbers.
• Read this section of the text and do the
  exercises.
• Complete the operator practice form from the last
  slideshow.

5
An aside Foreground and background colors

• Users do best with grayscale coloring. But you
  can modify foreground and background color
  settings. In the forms properties select
  backcolor.

6
Select custom, web or system
7
Select a color from the palette
8
Declaring/initializing variables

• Variables are declared using dim in VB
• Dim name as String
• Dim value as Integer
• Dim val,num,x,y,z as Double
• You can initialize variable values when you
  declare them, as in
• Dim value as integer 100
• Dim name as String Bob

9
You can declare constants

• Const pi as double3.1412
• Const ourbusiness as StringVB Inc
• Const basehours as single40.0
• Constants may not be altered by assigning them a
  new value later in your program. Typically,
  they would be declared at the class level (not
  discussed yet), just below the line at the top of
  your code view
• Public class
• put Global vars and consts here

10
A date literal

• Date literals must appear within symbols.
• They may contain date, time or both
• Example formats
• 12/10/2006
• 313 PM
• 211502 military
• 12/10/2006 313 PM

11
Conversions for date

• You can convert date format values or strings to
  date type as in
• Dim startdate, thedate as date
• Dim stringval as string 12/3/2005
• Startdate 12/3/2005 10000 AM
• thedateSystem.convert.todatetime(stringval)

12
Formatting dates as Strings for display

• Dateformat.generaldate() will return dd/mm/yyyy
  if the date is just a date, otherwise see below
  for longtime
• Dateformat.longdate gives day of week, month and
  day, no time returned as in Saturday, August 10,
  2005
• Dateformat.shortdate formats as in general date
  above, no time is reported.
• Dateformat.longtime does not report date part,
  but gives time in long format as in 032218 PM
• Dateformat.shorttime returns military time in
  format HHMM
• Access functions as
• lblDateInfo.textFormatDateTime(someDate,DateForma
  t.shorttime)

13
Form to display current date/time on load
14
Date literals

• Now returns the current day and time
• Today returns the current day (no time)
• TimeOfDay returns the current time, no date.

15
Onload code for previous form

• Private Sub frmDayTime_Load(ByVal sender As
  System.Object, ByVal e As System.EventArgs)
  Handles MyBase.Load
• Dim thedate As Date
• thedate Today
• lbldate.Text FormatDateTime(thedate,
  DateFormat.LongDate)
• lbltime.Text FormatDateTime(thedate,
  DateFormat.LongTime)
• End Sub

16
Percent formatting

• You can format reals (single, double, decimal or
  literal values) as strings with percent format
  using the formatpercent() function
• FormatPercent(.789) will return 78.9
• FormatPercent(.48129) will return 48.13
• FormatPercent(8.2) will return 820.00
• FormatPercent(.3876,1) will return 38.7
• Note the following it multiplies parameter by
  100 and then does a toString(). The default
  number of percentage places is 2.

17
Currency formatting

• Real values can be formatted as currency using
  toString(C) or FormatCurrency

18
Button click code

• Private Sub btndisplay_Click(ByVal sender As
  System.Object, ByVal e As System.EventArgs)
  Handles btndisplay.Click
• Dim value As Single Single.Parse(txtvalu
  e.Text)
• lbldisplay1.Text lbldisplay1.Text ""
  value.ToString("C")
• lbldisplay2.Text lbldisplay2.Text ""
  FormatCurrency(value.ToString())
• End Sub

19
Lets build a new form
20
After clicking the image, typing new text and
selecting a radiobutton
21
New components are groupbox, radiobutton and
picturebox

• Youll find these new components are pretty easy
  to use. From the toolbox
• Select a groupbox and drop it on your form.
• Now drop 3 radiobuttons into the groupbox.
• Drop a picturebox on your form.
• And another, right on top of the first.
• Add two labels and a textbox.

22
Set properties

• Our text uses radXXX to name radioButtons. I
  noticed another text used names like
  greenRadioButton and inputTextBox. I will allow
  you to follow that convention if you wish.
• I also noticed our text leaves default names for
  controls which are not accessed in subroutines,
  though youll have to be careful. I will also
  allow you to follow this example.
• You should not generally need to reference
  groupboxes, or even labels, unless the text on
  them is used for result-display purposes.
• I left my groupbox and pictureboxes with their
  default names.
• Name your labels and textbox and set their text
  properties.

23
properties

• I set the font of my lblMessage to be symbol
  (greek).
• For each picturebox, I selected the image
  property and then clicked the () to open a
  Select Resource Dialog Box and browsed my system
  to find some images.

24
Setting the image
25
What functionality do we want?

• Radiobuttons should change the color of the
  displayed text (in lblMessage).
• Since these are in a groupbox, VB will handle the
  exclusionary aspect of the functionality.
• When one image is clicked, I want it to go away
  and the other to be displayed.

26
Tab ordering when using group boxes

• Group boxes get tab ordering relative to other
  controls on your form, then controls inside a
  group box are ordered relative to each other.

27
Subroutines needed

• Click on a radiobutton and provide code like
  messageLabel.ForeColor Color.Green
• to the stubbed subroutine. Heres a complete
  example
• Private Sub greenRadioButton_CheckedChanged(ByVal
  sender As System.Object, ByVal e As
  System.EventArgs) Handles greenRadioButton.Checked
  Changed
• messageLabel.ForeColor Color.Green
• End Sub

28
Coming attractions a problem with the code in
the previous slide

• Green radio button checked changed event is
  fired when green radiobutton is selected or
  unselected. The code in the previous slide works
  because, when blue (for example) is selected,
  first green rb checked changed event is fired,
  then blue rb checked changed is fired, so the
  users current choice is updated properly. Well
  learn in a couple of weeks how to improve the
  event handler code to check whether the rb is
  CURRENTLY checked with a control structure called
  if then
• If greenradiobutton.checked then
• messageLabel.ForeColor Color.Green
• End if

29
Subroutines needed

• Click a picturebox. Add code like this to one
  stubbed method (and the opposite code to the
  other)
• PictureBox2.Visible False
• PictureBox1.Visible True
• Heres one of the two complete subroutines
• Private Sub PictureBox2_Click(ByVal sender As
  System.Object, ByVal e As System.EventArgs)
  Handles PictureBox2.Click
• PictureBox2.Visible False
• PictureBox1.Visible True
• End Sub

30
OOP Classes and variable scope

• Classes consist of fields, constructors and
  methods.
• In VB, methods are called subs.
• Fields are variables declared at the top of the
  class, visible to all the subs and functions in
  the class. Such variables should not be redefined
  in a sub they are already available.
• We have already been using class fields, like
  txtinput.text and methods, like txtinput.clear()
  or me.close() in our examples.

31
variable scope

• Parameters to functions and subs have local
  scope. They live only within the sub or function
  and are not available elsewhere.
• VB defines your controls for you (in hidden
  code). They are fields of the class and have
  global scope.
• Variables dimensioned inside subs and functions
  also have local scope and cant be referenced
  outside the sub or function containing the
  definition.

32
variable scope

• A variable which needs to be accessed in many
  subs will need to be passed to each, or declared
  as a class field.

33
Illustrating OOP Flags of the world
34
About this app

• The Flags project contains checkboxes,
  radiobuttons, one picturebox and groupboxes.
• Only checkboxes are new for us.
• But updating the display involves putting a new
  image on the picture box, and changing the text
  in the country label.

35
About this app

• Well need to be able to get images from files.
• Well need to keep track of the current country.
• Since multiple subs need to update the display we
  will create our own sub called updateDisplay.
• What parameters does updateDisplay need?

36
What parameters does updateDisplay need?

• There are as usual- many ways of doing it.
• The simplest might be to have a (class) field
  value (String) which holds the current country
  name. Well call it country. The code
• Dim country as String goes near the top of our
  code, but after the start of the class definition

37
Controls and their properties

• Not following VB convention, I named radiobuttons
  USARadioButton (etc)
• In their properties, I set initial visibility of
  my two labels to false.
• I initialized country string and flaglabel text
  to USA.
• Flaglabel text is initialized in properties.
• Country is initialized in the class constructor
  after the call to super.

38
the constructor

• Public Sub New()
• MyBase.New()
• country "usa must go here since it
  is displayed
• 'This call is required by the Windows
  Form Designer.
• InitializeComponent()
• 'Add any initialization after
  InitializeComponent() call
• End Sub

39
More about this app

• Well need to get images from files. To do this
  we need to import some capability we havent used
  yet System.io. The code
• Import system.io goes right at the top of our
  code.
• Each radiobutton event handler just changes the
  name of the current country and calls the sub
  updateDisplay() passing it the country name.
• The checkbox event handlers simply set labels to
  visible or invisible based on whether they
  themselves are checked.

40
Code for one of the radiobuttons

• Private Sub SwedenRadioButton_CheckedChanged(ByVal
  sender As System.Object, ByVal e As
  System.EventArgs) Handles SwedenRadioButton.Checke
  dChanged
• updateDisplay("Sweden") that is all we
  need to do
• End Sub

41
Code for updateDisplay

• Private Sub updateDisplay(ByVal countryname As
  String)
• country countryname update field value
• flagLabel.Text country
• need to get another imageglue on country name
• MyPictureBox.Image Image.FromFile(Direct
  ory.GetCurrentDirectory country ".gif")
• End Sub

42
Code for one of the checkbox clicked event
handlers

• Private Sub countryCheckBox_CheckedChanged(ByVal
  sender As System.Object, ByVal e As
  System.EventArgs) Handles countryCheckBox.CheckedC
  hanged
• set flaglabel visibility to true or false
  depending on the checkbox setting
• flagLabel.Visible countryCheckBox.Checke
  d
• End Sub

43
Image files

• Youll need to copy whatever flag images you want
  into the current project directory.
• Youll need to give them names like binUSA.gif
• VB attaches the bin to the front of the file
  name when you get the directory in the debugger,
  but not when it is run as an exe file.
• To deploy the app as an executable youll have to
  fix the path name for the flag gif files and
  possibly copy the gif files to wherever the
  application is supposed to run from.

44
Exercise Digit extraction

• Allow the user to enter a five-digit number.
• Display the digits, each in its own read-only
  textbox.
• Provide Enter and Clear buttons.

45
GUI
46
Notes

• Make the output textboxes read only.
• Set the maximum length property of the input
  textbox to 5.
• Use layout managers to get the alignments and
  sizes right.
• Use the mod operation to get the ones place
  value. Then use the \ operation to go on to the
  next digit.

47
Notes

• You could provide this functionality many ways.
• Later in the semester well learn to do it by
  chopping the input string up into pieces 1
  character long each.

48
Another exercise Message formatter
49
Radio buttons control color

• Private Sub rbRed_CheckedChanged(ByVal sender As
  System.Object, ByVal e As System.EventArgs)
  Handles rbRed.CheckedChanged
• Me.lblMessage.ForeColor Color.Red
• End Sub

50
Checkbox determines if message should be displayed

• Private Sub cbMessage_CheckedChanged(ByVal
  sender As System.Object, ByVal e As
  System.EventArgs) Handles cbMessage.CheckedChanged
  
• Me.lblMessage.Visible cbMessage.Checked
• End Sub

51
Button click may display message

• Private Sub btnClear_Click(ByVal sender As
  System.Object, ByVal e As System.EventArgs)
  Handles btnClear.Click
• With Me
• With .txtName
• .Clear()
• .Focus()
• End With
• .txtMessage.Clear()
• .lblMessage.Text ""
• End With
• End Sub

52
Click on picturebox to toggle picure box display
53
Pictureboxes event code

• Private Sub pbBig_Click(ByVal sender As
  System.Object, ByVal e As System.EventArgs)
  Handles pbBig.Click
• pbBig.Visible False
• pbLittle.Visible True
• End Sub
• Private Sub pbLittle_Click(ByVal sender As
  System.Object, ByVal e As System.EventArgs)
  Handles pbLittle.Click
• pbLittle.Visible False
• pbBig.Visible True
• End Sub

54
Getting images
55
More on images and fonts
56
Combobox image.fromFile
57
Combo box

• Select the collection property to populate the
  combo box
• I used
• Picturebox.imageimage.fromfile(C\penguin.gif)
  
• My combobox selected index changed sub code is
  below
• If cbbchoose.Text "dog" Then
• pb.Image Image.FromFile("c\dog.gif"
  )
• ElseIf cbbchoose.Text "bear" Then
• pb.Image Image.FromFile("c\bear.gif
  ")
• Else
• pb.Image Image.FromFile("c\penguin.
  gif")
• 'pb.Refresh()
• End If
• Note I didnt take time to figure out how to get
  it to look in the application directory

58
Changing fonts via button press
59
I didnt figure out how to get a font literal in
this application
60
code

• Private Sub btnfont3_Click(ByVal sender As
  System.Object, ByVal e As System.EventArgs)
  Handles btnfont3.Click
• lbldisplay.Font btnfont3.Font()
• End Sub
• Private Sub btnfont1_Click(ByVal sender As
  System.Object, ByVal e As System.EventArgs)
  Handles btnfont1.Click
• lbldisplay.Font btnfont1.Font()
• End Sub
• Private Sub btnfont2_Click(ByVal sender As
  System.Object, ByVal e As System.EventArgs)
  Handles btnfont2.Click
• lbldisplay.Font btnfont2.Font()
• End Sub

61
Literal font names
62
Press button to change font
63
code

• Private Sub btn3_Click(ByVal sender As
  System.Object, ByVal e As System.EventArgs)
  Handles btn3.Click
• Dim f As New System.Drawing.Font("Arial",
  10)
• ' Assign the font to the control
• lbl1.Font f
• ' To set additional properties, you must
  create a new Font object.
• lbl1.Font f
• 'lbl1.Font New System.Drawing.Font(lbl1.
  Font, FontStyle.Bold Or FontStyle.Italic)
• End Sub
• Private Sub Btn2_Click(ByVal sender As
  System.Object, ByVal e As System.EventArgs)
  Handles Btn2.Click
• Dim f As New System.Drawing.Font("Symbol",
  12)
• lbl1.Font f
• ' or use...
• 'lbl1.Font New System.Drawing.Font(f,
  FontStyle.Bold)
• End Sub
• Private Sub btn1_Click(ByVal sender As
  System.Object, ByVal e As System.EventArgs)
  Handles btn1.Click
• Dim f As New System.Drawing.Font("SansSeri
  f", 12)
• lbl1.Font f
• lbl1.Font New System.Drawing.Font(lbl1.F
  ont, FontStyle.Underline)
• End Sub

64
Image.fromfile(P\...) does work in F306 lab a
screenshot
65
Code for previous slide

• Private Sub Form1_Load(ByVal sender As
  System.Object, ByVal e As System.EventArgs)
  Handles MyBase.Load
• PictureBox1.Image Image.FromFile("p\afr
  ica1.jpg")
• End Sub