Lecture 10 Additional Controls and Objects

1
Lecture 10 Additional Controls and Objects

2
List Boxes and Combo Boxes

• See Figure 11.1, p. 498
• Combo boxes list box text box

3
List Box Control

• List box will display a single column of strings,
  referred to as items.
• The items appear initially can be specified
• either at design time with the List property
• Sorted property
• When it is set to True, the items will
  automatically be displayed in alphabetical order.
• The default value is False
• or set with code in the Form_Load event
  procedure
• code is used to access, add, or delete items from
  the list
• The prefix for the name of a list box is lst.

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Set Items with Code

• lstBox.AddItem str Add str to the list box
  lstBox.
• If Sorted property is True, str is added at the
  proper sorted position
• Otherwise, at the end of list
• lstBox.ListCount The number of items in the list
  box lstBox.
• Each item in the lstBox is identified by an index
  number ranging from 0 through lstBox.ListCount-1
• lstBox.NewIndex the index number of the item
  most recently added to lstBox by the AddItem
  method.
• lstBox.ListIndex the index number of the item
  currently highlighted in lstBox
• If no item is highlighted, the value of ListIndex
  is -1.

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Set Items with Code (contd)

• lstBox.List(n) the item of lstBox having index
  n.
• The string array lstBox.List() holds the list of
  items stored in the list box.
• E.g., Print lstBox.List(0) displays the first
  item of lstBox.
• lstBox.List(lstBox.ListIndex) or List1.Text the
  item (string) currently highlighted in list box
  List1.
• lstBox.RemoveItem n deletes the item of index n
  from lstBox.
• lstBox.RemoveItem lstBox.ListIndex deletes the
  item currently highlighted in lstBox.
• lstBox.Clear deletes every item of lstBox.

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Examples

• See Example 1 and 2, p. 499--502
• Note The index associated with an item will
  change when a lesser item is added to or
  removed from the list.
• lstBox.ItemData(n) m associates the number m
  with the item of index n
• lstBox.ItemData(lstBox.NewIndex) m associates
  the number m with the item most recently added to
  the list box.
• lstBox can be thought of as consisting of two
  arrays, lstBox() and lstBox.ItemData().

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Combo Box Control

• Combo box a text box with a help list attached.
• Either typing in information into the box
• or selecting the appropriate piece of information
  from a list.
• Two most useful types of combo box (see fig.
  11.2)
• style 0 the list drops down when the user clicks
  on the arrow, and then disappears after a
  selection is made.
• Style 1 the list is always visible.
• In either case, when an item from the list is
  highlighted, the item appears in the text box at
  the top and its value is assigned to the Text
  property of the combo box.

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Combo Box Control

• Combo boxes have essentially the same properties,
  events, and methods as list box.
• All statements discussed for list boxes also hold
  for combo boxes.
• The Style property of a combo box must be
  specified at design time.

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Example

• See EXAMPLE 3, p.503

10
File-related List Boxes

• VB provides the appropriate lists for the three
  boxes.
• Drive box
• Directory box
• File box
• The selected items for three controls are
  identified by the Drive, Path, and FileName
  properties, respectively.

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EXAMPLE

• See EXAMPLE 4, p. 504

12
Homework

• EXERCISES 11.1, 32 and 34.

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Nine Elementary Controls

• Frame control
• Used to group related sets of controls for visual
  effect.
• Important when working with groups of option
  button controls.
• Check box control consists of a small square and
  a caption, presents the user with a yes/no
  choice. (see EXAMPLE 1)
• Value property of a check box is 0 when the
  square is empty and is 1 otherwise.

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Nine Elementary Controls (contd)

• Option button control
• Used to give the user a single choice from
  several options.
• A group of several option buttons is attached to
  a frame or a picture box.
• Value property of an option button tells if the
  button is on or off. (True or False)

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Nine Elementary Controls (contd)

• Horizontal and Vertical scroll bar controls
• The main properties of a scroll bar control are
  Min, Max, Value, SmallChange, and LargeChange.
• See EXAMPLE 5, p. 516
• Timer control
• Shape control
• Line control
• Image control

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Homework

• EXERCISES 11.2, 40, p.523

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Five Additional Objects

• The Menu control
• Lab create Figure 11.17
• Clipboard object used to copy or move text from
  one location to another
• Clipboard.SetText str replaces any text
  currently in the clopboard with str.
• str Clipboard.GetText() assign the text in the
  clopboard to the string variable str.
• Clipboard.Clear deletes the contents of the
  clipboard

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Five Additional Objects

• Multiple forms A VB program can contain more
  than one form.
• Additional forms are created from the Project
  menu with AddForm
• Forms are hidden or activated with the statement
  Form1.Hide or Form2.Show
• Two or more forms can be visible at the same time
• formName.Show 1 Form formName is said to be
  modal. The user will not be allowed to shift the
  focus to any other form until formName is hidden.