More Advanced Windows Forms Controls and Coding

1
More Advanced Windows Forms Controls and Coding

• Tutorial 6

2
Lesson A

• Advanced Windows Controls, and Inheritance and
  Polymorphism in OOP

3
Objectives

• Understand the MonthCalendar, DateTimePicker,
  NumericUpDown, and TrackBar Windows Forms
  controls
• Discover and apply additional Windows Forms
  controls, including the ProgressBar,
  DomainUpDown, StatusBar, ToolTip, RichTextBox,
  and ContextMenu controls
• Understand the concepts behind inheritance and
  polymorphism in Visual Basic .NET, including
  abstract classes, sealed classes, and the related
  notions of overloads and shadows
• Sort tiny arrays (that is, arrays with fewer than
  10 elements)
• Design workarounds for control arrays (no longer
  supported in Visual Basic .NET)

4
Understanding Advanced Windows Forms Controls

• Understanding the MonthCalendar Control
• Useful alternative to the DateTimePicker control
  when you need to display a schedule showing
  multiple dates or months
• Can only display dates that fall between the
  MinDate and MaxDate properties
• Scoring application
• Needs to display a two-month calendar

5
Understanding the Formatting of the
DateTimePicker Control

• DateTimePicker control
• Used in the Scoring application to select a time
  of day
• Format property can be used to set the format of
  the DateTimePicker
• ShowUpDown property
• When False (the default), clicking the down arrow
  displays a month calendar
• When True, the control contains an up-down arrow
  rather than a down arrow
• Enables you to restrict user to changing only
  those elements of the date/time value that you
  have chosen to display
• Prevents the month calendar display when that
  would be inappropriate

6
Important Properties of the DateTimePicker control
7
Advanced Windows Forms Controls

• Understanding the NumericUpDown Control
• NumericUpDown control
• Provides a convenient display for a numeric value
  that the user may need to increase or decrease at
  runtime
• Understanding the TrackBar Control
• TrackBar control
• Provides a visual display and functionality
  similar to a HorizontalScrollBar control

8
Properties of the NumericUpDown Control
9
Important Properties of the TrackBar Control
10
Discovering Additional Windows Forms Controls

• Progress bar
• Can be used in much the same manner as a scroll
  bar or track bar
• Traditionally applied to tracking the progress of
  lengthy background computer operations
• Provides a continually updated indicator that an
  operation is proceeding
• DomainUpDown control
• Contains a collection of strings, one of which is
  displayed in the control
• A different set of properties and methods is
  needed to load and manipulate the strings
• Sorted property
• Determines whether the items in the control are
  displayed alphabetically
• Wrap property
• Determines what happens when you click after the
  last item or before the first item in the list

11
Important Properties of the ProgressBar Control
12
Important Properties of the DomainUpDown Control
13
Discovering Additional Windows Forms Controls
(Continued)

• Understanding the StatusBar Control
• A potentially complex control that is used to
  display the status of an application
• Can contain any number of StatusBarPanel objects,
  each of which can display text, an image, or
  programmer-drawn controls
• Understanding the ToolTip Control
• ToolTips
• Small pop-up windows that display text when the
  user moves the insertion point over a control
• Component can be added to any container, such as
  a form, Panel control, ToolBar, or StatusBar
• Understanding the RichTextBox Control
• Provides for the display of formatted text using
  Rich Text Format (RTF) style and formatting
  commands
• Allows formatting to be applied to any portion of
  text selected within the control

14
Properties of the ToolTip Control
15
Discovering Additional Windows Forms Controls
(Continued)

• Understanding the ContextMenu Component
• A short pop-up menu that appears when the user
  right-clicks while the cursor hovers over a form
  or control
• Items normally duplicate those that appear in the
  forms main menu
• Understanding Add-ins Customizing the Toolbox
• Possible to build your own controls and add them
  to the Toolbox
• To see the built-in controls that you can add to
  the Toolbox
• Right-click the Toolbox and choose Customize
  Toolbox

16
Understanding Inheritance and Polymorphism

• Inheritance
• Ability of a derived class or an instantiated
  object to inherit the properties, methods, and
  events of a base class
• Single inheritance only supported in Visual Basic
  .NET
• Polymorphism
• Ability of a derived class or instantiated object
  to provide its own unique implementation of a
  method declared or defined in the base class

17
Understanding Inheritance and Polymorphism
(Continued)

• Abstract class
• A class that cannot be instantiated and must be
  inherited
• Inherited class must implement those portions of
  the abstract class that have been declared, but
  not yet defined
• Usually contains
• Elements that are designed to be inherited
  without modification
• Public or Protected methods that are modified or
  implemented in the inherited class
• Definition of a derived class begins with the
  Inherits keyword

18
Model for the Definition of a Class Derived from
an Abstract Class
19
Understanding Inheritance and Polymorphism
(Continued)

• Sealed class
• Exact opposite of an abstract class
• Cannot be inherited
• Declared in Visual Basic .NET with the keyword
  NotInheritable in the declaration header
• Overloading
• Overloads keyword declares a method that matches
  the name of an existing member, but contains a
  different argument list
• Shadowing
• Related to the notions of overriding and
  overloading a program element
• Overriding
• Requires that
• The overridden element be declared Overridable
• The overriding element be declared with the
  Overrides keyword

20
Sample of Overloaded Methods
21
Sample of a Shadowed Program Element
22
Sorting a Tiny Array

• Computers
• Spend a significant amount of time sorting and
  comparing items in lists
• Short list
• Requires sorting only a handful of items
• Algorithm
• Computer compares two items at a time, and if
  they are in the wrong order, swaps their
  positions
• More sophisticated sorting routines
• Gain their efficiency through strategies for
  comparing the correct two items each time

23
Hildas Simple Sort
24
Understanding Workarounds for Control Arrays

• Three workarounds for the absence of control
  arrays in Visual Basic .NET
• Use the Tag property or TagIndex to identify an
  individual control or a group of controls
• Write a single procedure that handles multiple
  events, often combined with a Select Case
  statement that examines the Name property of
  sender
• Create an array of strings (or of structures)
  with values that correspond to the Name or Text
  (or perhaps other) property of each control in
  the collection

25
Lesson B

• Implementing an Outlook-style Application

26
Objectives

• Convert the Scoring application to an
  Outlook-style interface
• Incorporate the MonthCalendar, DateTimePicker,
  NumericUpDown, and TrackBar Windows Forms
  controls into the Scheduling pane of the Scoring
  application
• Modify the layout of Events.txt and structEvent
  to incorporate an EventID as an identifier or key
  for each event, change the scheduled start time
  for each event, and include country codes for
  scoring events involving national teams
• Provide the functionality to change the starting
  dates for the Friendsville International Games
• Allow the user to change the date and the start
  time of any specific event

27
Converting the Scoring Application to an
Outlook-style Interface

• To convert Scoring to a Microsoft Outlook-style
  interface
• Copy your completed Scoring application from
  Tutorial 5 into the VB.NET\Student\Tut06 folder.
  Rename the solution folder (but not the solution
  file) FinalScoring. Start Visual Basic .NET, and
  open the Scoring solution from the new
  FinalScoring folder
• Open frmScoreMain in the Windows Form Designer,
  if necessary. Click the ListView1 control, and
  change its Dock property from Fill to Top
• Click the form, and make the form taller, opening
  a space underneath the ListView control
• Click the ListView control and then make it
  shorter, dividing the right side of the form into
  two roughly equal halves, with the ListView in
  the top-right pane and an empty pane at the
  bottom right. With the ListView still selected,
  click Edit Cut to remove the ListView control
  and save it on the Windows Clipboard
• Draw a Panel control in the empty pane on the
  right, and set its Dock property to Fill

28
Converting the Scoring Application to an
Outlook-style Interface (Continued)

• With the Panel control still selected, click Edit
  Paste to put the ListView control on the form,
  above Panel1
• With the ListView control still selected,
  double-click the Splitter control in the Toolbox,
  and set its Dock property to Top
• Draw another Panel control in the empty space
  below the ListView control, and set its Dock
  property to Fill Open the Code Editor for
  frmScoreMain. At the end of the header statement
  for the Sub ListView1_DoubleClick() procedure,
  add the phrase Handles ListView1.DoubleClick
• Open the Code Editor for frmScoreMain. At the end
  of the header statement for the Sub
  ListView1_DoubleClick() procedure, add the phrase
  Handles ListView1.DoubleClick
• Run the Scoring application to ensure that
  everything still works as it did at the end of
  Tutorial 5, and to see that you can resize the
  two right panes on frmScoreMain

29
Adding Controls to frmScoreMain

• Task
• Add the appropriate controls to the Scheduling
  pane of frmScoreMain
• MonthCalendar control has two purposes
• Displays the calendar dates for the Friendsville
  International Games
• Displays the calendar date for an individual
  event
• TrackBar control
• Provides a visual representation of the Event Day

30
Incorporating an Identifier or Key for Each Event

• To use the revised Events.txt file and make the
  necessary coding changes in Scoring
• Replace the code in Module1 structEvent with the
  code in Figure 6-36
• Copy the Events.txt file from the
  VB.NET\Student\Tut06 folder to the
  VB.NET\Student\Tut06\FinalScoring\bin folder
• The coding that loads the Events.txt file into an
  internal array must also be modified. This occurs
  in the frmScoreMain.vb file in the
  frmScoreMain_Load() procedure. Substitute the
  code shown in Figure 6-37 for the corresponding
  code in the original frmScoreMain_Load()
  procedure. This code adds the statements that
  input the four new elements in Events.txt,
  namely, the EventID, Country1, Country2, and
  StartTime
• The EventID also needs to appear in the ListView
  control. Therefore, modify the AddListViewItem()
  procedure in frmScoreMain.vb, as shown in Figure
  6-38

31
Revised Layout of Events.txt
32
Loading Events.txt into an Array
33
AddListViewItem() Procedure
34
Providing Functionality to Change the Start Date
for the Games

• To incorporate the variable StartDate for the
  Games
• Copy the file StartDate.txt from the
  VB.NET\Student\Tut06 folder to the
  VB.NET\Student\Tut06\FinalScoring\bin folder
• Add the following public variable to the
  declaration of public variables in Module1 for
  the StartDate Public pStartDate As Date. Insert
  the code in Figure 6-39 into frmScoreMain_Load()
• Place a bright red Done button on the form on top
  of the upper middle of the MonthCalendar control.
  Name the button btnDone, and open the Properties
  list. Set the Visible property to False
• Program the mnuToolsChangeStartDate_Click()
  procedure to ask the user whether the user wants
  to change the start date for the Friendsville
  International Games
• When the user clicks the Done button, the new
  start date is written to the file, and the
  MonthCalendar control is updated with the new
  time frame

35
Loading the Start Date for the Games
36
Displaying and Altering Schedule Data for a
Specific Event

• To display and alter the event day and time
• Open the ListView1_Click() procedure and code it,
  as shown in Figure 6-42
• The TrackBar control should always mirror the
  value of the NumericUpDown control (nudDay). In
  the Code editor, open the ValueChanged() event
  procedure for nudDay, and insert the code shown
  in Figure 6-44
• To change its scheduled day or time, the user
  selects a list view item and then clicks Tools
  Change Event Date. To achieve this functionality,
  program the mnuToolsChangeEventDate() procedure
  to ask the user if he or she wants to change the
  day or time for this event
• Clicking the Done button in this case should
  trigger the code shown in Figure 6-45
• You have now been given two sets of code for the
  btnDone_Click() procedure. Your code must
  determine which code segment to execute based on
  the value of lblEventID, as explained earlier

37
Final Coding Elements

• To complete the Scoring application
• Program the About menu selection to display a
  simple About Scoring form, and program the Exit
  menu selection to end the application
• Whenever a tree view item is selected,
  frmScoreMain_Load() should be invoked again,
  because the same basic actions are called for.
  Therefore, insert the call that follows as the
  first statement in Sub TreeView1_AfterSelect()
  frmScoreMain_Load(sender, e)
• Run the Scoring application, try every option,
  and clean up any odds and ends that you may have
  overlooked up to this point

38
Lesson C

• Implementing an Abstract Class

39
Objectives

• Plan for the remaining tasks in the Scoring
  application
• Automatically search through and select an item
  from a combo box based on data selected from an
  array
• Determine when to use Public (Global) variables
• Build an abstract class and use it in an
  application
• Create classes that use inheritance and
  polymorphism

40
Planning the Remaining Tasks in the Scoring
Application

• Application needs the following features
• For events in team sports, the nationality and
  flag icon (in the ctrlNation controls) should be
  automatically selected
• Standardized information about athletes needs to
  be stored in a file, and the file needs to be
  loaded into an array at startup
• A new frmCompetition must be created
• In all the individual scoring modules
• User should be able to select competitors from a
  list of eligible athletes
• ctrlNation control corresponding to each
  competitor should be automatically selected
• In all the individual scoring modules
• Results should indicate first, second, and third
  place finishers
• FigWelcome and Logon class libraries should be
  called

41
Automatically Searching and Selecting from a
Combo Box

• Internal properties and methods of a user-defined
  control
• Not programmatically accessible to projects that
  use them
• ctrlNation
• Must be modified to search through its list of
  nations and display the correct country name and
  flag
• Class frmTeam includes ctrlTeamScore
• Two country codes
• Must be passed from frmScoreMain to frmTeam, then
  from frmTeam to ctrlTeamScore and then from
  ctrlTeamScore individually to ctrlNation1 and
  ctrlNation2
• In ctrlNation
• Create a method that searches through the
  available nation codes
• If it finds the right one, assign the correct
  country name and flag icon to the constituent
  controls in ctrlNation

42
Revisiting Public (Global) Variables Adding
Athletes to Module1

• Public variables and constants can present
  problems due to
• Naming collisions
• Misinterpretation
• Scoping problems
• Difficulties related to the reuse of software
  components
• Principles
• Variable needed in only one place should be
  defined in only that one place, with the most
  restricted scope possible
• When a variable is needed in very few places or
  when it is needed in a class that could be
  reused, it should be passed as a parameter to the
  components that need it
• Only when a variable is useful and necessary
  throughout an application should it be declared
  as a public variable

43
Building an Abstract Class frmCompetition

• To create frmCompetition
• Open frmSpeed in the Windows Form Designer. In
  the Properties window, change its name from
  frmSpeed to frmCompetition. Right-click the name
  frmSpeed.vb in Solution Explorer, select Rename,
  and type the new filename frmCompetition.vb
• Delete the eight labels (lblName1, lblName2, and
  so on) and replace them with ComboBox controls
  named cboName1, cboName2, ..., cboName8. Set the
  Tag property of each ComboBox to 1, 2, ..., 8,
  respectively, and set the Visible property for
  each to False. Set the Text property for each to
  Select a competitor
• Make minor modifications to the GUI change the
  Name property of btnEnterTimes to
  btnEnterResults, and change the Buttons Text
  property to Enter Results. Within the Competitors
  group box, the name of the label that serves as a
  column header for Times should be set to
  lblResultsColumnHeader, and its Text property
  should be Results
• Replace the original btnEnterCompetitors_Click()
  procedure with the procedure shown in Figure 6-55
  for loading the names of potential competitors
  into each combo box
• When a competitors name is selected, the program
  should automatically select the name and flag of
  the country that competitor represents

44
Building an Abstract Class frmCompetition
(Continued)

• The logic for entering results has not changed,
  but you just changed the name of the button from
  btnEnterTimes to btnEnterResults, and therefore
  you must also change the name of the procedure to
  btnEnterResults_Click(). Further, your code
  should reflect the generalized nature of the
  class. Generalize the InputBox prompt in the
  btnEnterResults_Click() procedure by entering
  Enter the result for competitor i
• The previous btnCompetitionOver_Click() procedure
  needs to be replaced completely, because it was
  designed to select only the winner. The new
  procedure determines the order of finish, from
  first to last place. Replace the existing
  btnCompetitionOver_Click() procedure with the
  code in Figure 6-57
• Insert the AssignWinners() procedure, called from
  frmCompetition into Module1, as shown in Figure
  6-58
• You should test the program at this point
• Lastly, some elements of frmCompetition must be
  customized for each type of scoring. To implement
  this idea, you need to convert frmCompetition to
  an abstract class, and you must require each
  derived class to override a procedure that
  provides the requisite settings

45
Using Inheritance and Polymorphism frmSpeed,
frmDistance, and frmJudge

• Abstract class
• Graphical interface (if any) of a class derived
  from an abstract class cannot be viewed in the
  Windows Form Designer
• Reason
• Designer must instantiate the object to
  materialize the view, and by its nature, an
  abstract class cannot be instantiated
• To add or manipulate graphical objects in a class
  derived from an abstract class
• Enter the statements in code
• Assign any nondefault property settings in code

46
Code for frmSpeed
47
Adding FigWelcome and Logon

• To add FigWelcome and Logon to the Scoring
  application
• Add the necessary references to the class
  libraries in the References list for the
  application
• Use the Imports statement to import each library
  before the class declaration for frmScoreMain
• To incorporate FigWelcome and Logon into
  frmScoreMain, insert the code shown in Figure
  6-62 at the top of frmScoreMain_Load()
• Test the completed Scoring application to ensure
  that everything works as intended

48
Incorporating FigWelcome and Logon
49
Summary

• MonthCalendar control
• Useful for picking a range of dates or a list of
  separate dates spanning one or more months
• ProgressBar control
• Provides a visual measure of progress toward the
  accomplishment of some task, such as downloading
  a file
• Customizing the toolbox
• Allows many other Visual Basic .NET controls to
  be available as add-ins or built-ins
• Abstract classes
• Must be inherited they cannot be instantiated
• Simplest sort routine
• Appropriate for sorting an array of up to 10
  elements
• Common techniques for manipulating groups of
  related controls
• Using the Tab or TabIndex property to identify
  each control or group of controls
• Inserting an event handler that handles multiple
  events
• Creating a parallel array that corresponds to the
  group of controls

50
Summary

• Conversion of an existing application from a
  Windows Explorer-style GUI to an Outlook-style
  GUI is relatively straightforward
• Graphical controls (MonthCalendar,
  DateTimePicker, NumericUpDown, and TrackBar)
• Can be intertwined to support date and time
  scheduling and manipulation
• Can interact with the user and with each other to
  provide robust functionality
• DateTimePicker control
• Preferred for selecting an individual date or
  time of day

51
Summary

• Inheritance and polymorphism
• Can greatly simplify complex coding tasks
• From an existing control library
• Possible to modify the source, or
• You can derive from the source and modify the
  derived class
• As coding tasks become more complex
• Scoping rules and encapsulation become more
  important
• Simple sorting algorithm
• Also applicable to multidimensional lists,
  provided they are short lists