MDI Programming

1
Chapter 13

• MDI Programming

2
Objectives (1)

• Understand the characteristics of MDI
  applications
• Organize the procedures between forms in MDI
  applications
• Understand the role of standard forms in an MDI
  application
• Integrate menus in an MDI application and create
  context menus
• Understand the relationships between events in an
  MDI application

3
Objectives (2)

• Manage and organize the forms that make up an MDI
  application
• Configure the RichTextBox control to display
  custom fonts and colors
• Read and write files with the RichTextBox control
• Format a RichTextBox control instance
• Use zooming
• Detect links to Web pages

4
Solution Organization
5
Characteristics of MDI Programs

• Single-document interface applications
• Create one instance of a particular form
• Multiple-document interface (MDI) applications
• Create multiple instances of the same form
• Display those multiple form instances such that
  they appear inside the region of another form
• Excel is an MDI application, for example

6
MDI Applications

• You can use three different types of forms in an
  MDI application
• An MDI parent form acts as the container for the
  MDI child forms in the solution
• An MDI child form always appears inside the
  visible region of its MDI parent form
• A project may have one or more MDI child forms
• Standard forms can be displayed anywhere on the
  screen and are not contained by the MDI parent
  form
• Standard forms are typically displayed as dialog
  boxes

7
Characteristics of MDI Applications

• MDI child forms can not be extended beyond the
  visible region of the containing MDI parent form
• Iconified MDI child forms do not appear on the
  task bar
• The user positions the icon inside the visible
  region of the MDI parent form
• Menus of MDI parent and MDI child forms are
  integrated

8
Displaying an MDI Child Form

• Code to create MDI child form appears in MDI
  parent form
• Create the child form instance
• Dim frmCurrentChild As New frmMdiChild()
• Designate the form as a child form
• frmCurrentChild.MdiParent Me
• Display the child form
• frmCurrentChild.Show()

9
Organizing Proceduresin MDI Applications (1)

• The following list describes the problems shared
  by nearly all MDI applications
• Procedures and data must often be shared by both
  MDI parent forms and MDI child forms
• An MDI parent form often needs to know which MDI
  child form instance is active
• From the MDI child form, you must often reference
  members of the MDI parent form or the MDI parent
  form itself

10
Organizing Proceduresin MDI Applications (2)

• When organizing the procedures and variables in
  an MDI application, consider the following rules
• Locate the procedures that create instances of
  the MDI child forms in the MDI parent form
• In the MDI child form(s), create the procedures
  responsible for managing each instance of the MDI
  child form
• To share a global reference to the MDI parent
  form, declare a Friend or global variable in a
  module file
• When the MDI parent form loads, store a reference
  to the MDI parent form in the Friend or global
  variable

11
Standard Forms in MDI Applications

• MDI applications can have standard forms
• Characteristics
• Standard forms typically do not have menus
• Standard forms are typically displayed as modal
  dialog boxes

12
Menus and MDI Applications

• Each MDI parent form and any MDI child form in a
  solution can have its own menu system
• MDI application menus have unique characteristics
• One menu bar appears below the title bar of the
  MDI parent form
• An MDI parent forms menu appears when no MDI
  child forms are loaded
• When an instance of an MDI child form is loaded
  or has focus, the menu of the MDI parent form is
  merged with the menu of the MDI child form
• Standard forms in an MDI application can have an
  associated menu but typically they do not

13
Merging Menus

• Menus of MDI parent and MDI child forms are
  merged based on the following property values
• MergeOrder property
• Applies to a MenuItem and contains an Integer
  value
• Indicates the relative order in which two menus
  or menu items will be merged
• MergeType property
• Works in conjunction with the MergeOrder property
  
• Defines whether one menu will replace another
  menu, whether one menu will be added to another
  menu, or whether menu items will be merged
  together

14
The MergeType Property

• The MergeType property has a data type of
  MenuMerge
• Possible enumeration values
• Add - menu on the MDI child form will be added to
  the menu of the MDI parent form
• MergeItems - menu items on the MDI child form
  menu will be merged with the menu items on the
  MDI parent form menu
• Remove - MDI parent form menu or menu item will
  not appear in the merged menu
• Replace - causes the menu of the MDI child form
  to replace the menu appearing on the MDI parent
  form

15
Merging Menus (1)
16
Merging Menus (2)
17
Merging Menus (3)
18
Using Menus to Select MDI Child Forms

• To select and display an MDI child form from a
  menu
• Set the MdiList property of a menu item to True
• This setting causes the menu item to display a
  list of MDI child form instances
• The caption appearing in the menu is the same as
  the caption appearing in the title bar of the MDI
  child form
• The process is automatic - you need not write any
  statements to display the MDI child forms

19
Arranging MDI Child Forms

• The LayoutMdi method applies to the MDI parent
  form
• Use to configure display of child forms
• Four valid enumeration values
• ArrangeIcons - iconified MDI child windows are
  arranged along the bottom of the MDI parent form
• Cascade - visible MDI child windows are arranged
  such that each MDI child window appears below
  another MDI child window and is indented
• TileHorizontal - divides the MDI child forms
  horizontally to fill the visible region of the
  MDI parent form
• TileVertical - divides the MDI child forms
  vertically to fill the visible region of the MDI
  parent form

20
Context Menus

• Context menus typically appear when the user
  right-clicks on a control instance or the form
  itself
• To create a context menu
• Create an instance of the ContextMenu control
• Create the menu items in-place
• Associate the context menu with a form or control
  instance by setting the ContextMenu property of
  the desired form or control instance to the
  context menu

21
Context Menus (Illustration)
Context menu title cannot be changed
Menu items
22
MDI Event Relationships

• Windows fires various events as the user
  navigates from form to form in an MDI application
• Events
• The Closing event fires for both the MDI parent
  and MDI child forms
• Fires first for all children and then the parent
• Event can be cancelled
• The Enter event fires for the MDI child form
  getting focus
• Use to update status information
• The Leave event fires just before an instance of
  the MDI child form loses focus

23
Order of Closing Events
24
Managing MDI Child Forms

• There is no Forms collection to manage the loaded
  MDI forms of an application
• Create a class to enable the developer to add and
  remove forms from the collection, and enumerate
  the collection with a For Each loop

25
Rich Text Files and the RichTextBox Control

• The RichTextBox control allows the user to edit
  files having a standardized file format called
  Rich Text Format (RTF)
• Embedded inside RTF files are formatting
  directives
• The control instance interprets the directives to
  perform a desired formatting task

26
Rich Text File
27
Formatted Text
28
RichTextBox Control (Properties)

• The Boolean AcceptsTab property defines what
  happens when the user presses the Tab key
• If set to True, a tab character is inserted into
  the control instance
• The DetectUrls property causes the RichTextBox
  control to recognize URLs
• The Lines property returns an array of strings
• Array of strings contains one element for each
  line appearing in the control instance
• The MultiLine property has the same purpose as
  the MultiLine property of the TextBox control
• If set to True, the control instance will display
  text on multiple lines

29
RichTextBox Control (Properties)

• The RightMargin property sets the rightmost limit
  for the text that appears on a line
• The ScrollBars property defines whether scroll
  bars appear in the region of the control instance
• Property can be configured to display scroll bars
  only when necessary or always
• The SelectedRTF property contains the selected
  text, including all rich text formatting
  directives

30
RichTextBox Control (Properties)

• The SelectedText property contains the selected
  text
• The SelectionColor property defines the color of
  the selected text or insertion point
• The SelectionFont property defines the font of
  the selected text or insertion point
• The SelectionStart property contains an Integer
  and defines the position of the starting
  character of the selection
• The SelectionLength property contains the number
  of characters in the selection

31
RichTextBox Control (Methods)

• The Clear method removes all the text from the
  control instance
• The Copy method copies the selected text to the
  Windows clipboard
• The Cut method removes the selected text and
  places it in the Windows clipboard
• The Paste method copies the contents of the
  Windows clipboard into an instance of the
  RichTextBox control
• The LoadFile method reads a file into the
  RichTextBox control instance
• The SaveFile method saves the contents of a
  RichTextBox control instance to a file

32
RichTextBox Control (Events)

• The LinkClicked event only fires when the
  DetectUrls property is set to True
• The event fires when the user clicks a link
• The TextChanged event fires when the user
  modifies the contents of a RichTextBox control
  instance
• The SelectionChanged event fires when the user
  selects different text or moves the insertion
  point

33
LoadFile and SaveFile Methods

• LoadFile and SaveFile methods read and write a
  text file or rich text file, respectively
• Overloads Public Sub LoadFile(path As String,
  filetype As
• RichTextBoxStreamType)
• Overloads Public Sub SaveFile(path As String,
  filetype As
• RichTextBoxStreamType)
• The path argument contains the folder and file
  name of the file to open or save
• The filetype enumeration defines how the LoadFile
  or SaveFile methods will interpret the file
  contents

34
LoadFile and SaveFile (Example)

• Read and write the text file named Demo.rtf as a
  rich text file
• rtfText.LoadFile("C\Demo.rtf", _
• RichTextBoxStreamType.RichText)
• rtfText.SaveFile("C\Demo.rtf",_
• RichTextBoxStreamType.RichText)

35
Formatting a Rich Text Box

• When formatting the contents of the rich text
  box, two concepts are important
• When no text is selected in the control instance,
  the cursor position is referred to as the
  insertion point
• If the user applies formatting attributes such as
  boldface, the characters typed by the user at the
  insertion point will appear in boldface and have
  that selected font
• Selected text is called the selection
• Any formatting attributes chosen by the user will
  be applied to the selection

36
Working with the Selection

• The SelectionFont property returns the font of
  the insertion point or selection
• The SelectionFont property, in turn, has
  properties named Bold, Italic, and Underline
• These three properties can store the following
  values
• Nothing - the selected text contains characters
  having different fonts
• True - characters in the selection or the
  character following the insertion point have the
  selected font style applied
• False - (default) neither the characters in the
  selection nor the character following the
  insertion point have the selected font style
  applied

37
The ColorDialog Control

• The ColorDialog control allows the user to select
  a color from a standard dialog box
• The ColorDialog control does not set the color of
  an object, it merely returns a color
• The ColorDialog control contains two sections
• The first section displays basic colors
• The second section allows the user to define
  custom colors
• Set properties to allow custom color selection
  and creation

38
The ColorDialog Control (Properties)

• Selected color is returned in the Color property
• The Boolean AllowFullOpen property allows the
  user to select custom colors
• The Boolean FullOpen property displays custom
  colors section

39
ColorDialog (Illustration)
Basic colors
Custom colors
40
Setting Fonts

• The FontDialog control allows the user to select
  fonts
• To use the FontDialog control
• First set properties to define the options that
  will appear to the user on the dialog box
• Then display the control instance
• Selected font is returned in the Font property

41
FontDialog Control (Properties)

• The Color property defines the font color
• The Font property defines the selected font
• The MinSize and MaxSize properties allow you to
  specify the minimum and maximum user selectable
  font sizes
• The ShowApply property, if set to True, causes
  the Font dialog box to display an Apply button
• The ShowColor property (Boolean), if set to True,
  allows the user to select colors in the Font
  dialog box
• The ShowEffects property (Boolean) defines
  whether or not the user can select font effects,
  such as boldface and underlining

42
FontDialog Control (Events and Methods)

• Events
• The Apply event fires when the user clicks the
  Apply button
• The Apply button only appears if the ShowApply
  property is set to True
• Methods
• The ShowDialog method displays the dialog box

43
FontDialog Control (Illustration)
44
Setting Individual Font Attributes

• Setting individual font attributes requires a bit
  flag
• Determine whether the attribute is set and add
  the value to the bit flag
• Convert bit flag to FontStyle using CType

45
Setting Font Attributes (Illustration)
46
Zooming

• The RichTextBox control supports capabilities to
  zoom in and out of a documents contents
• The ZoomFactor property allows you to change the
  magnification of the text displayed in a
  RichTextBox control instance
• A ZoomFactor of 1 displays the text in normal
  magnification
• A setting of 1.5 displays the text as 150 of
  normal

47
Detecting Links to Web Pages

• By setting the DetectUrls property to True, VB
  .NET will automatically detect when the user
  types a URL into the RichTextBox control instance
• You must also create a LinkClicked event handler
  that will execute when the user clicks on the URL
• To start another program, such as Internet
  Explorer, you call the Start method of the
  Process class of the System.Diagnostics namespace

48
Start Method of the Process Class

• The overloaded Start method starts a new process,
  such as Internet Explorer
• Overloads Public Shared Function Start(filename
  As String) As Process
• Overloads Public Shared Function Start(filename
  As String, arguments As String) As Process
• The filename argument contains the path and the
  file name of the program to start
• The arguments argument contains any command-line
  arguments that should be passed to the program

49
Start Method Example

• Start Internet Explorer
• System.Diagnostics.Process.Start("Iexplore", _
• "www.course.com")