As you learned in Toolbox Controls, controls are the design tools you use to build the user interface of a Visual Basic program. After you place controls on a form, they become objects that you can customize with property settings and program code. In this section, you learn about the most basic user interface controls in the Visual Basic toolbox.
Labels
Label, the simplest control in the Visual Basic toolbox, displays formatted text on a user interface form. Typical uses for the Label control include:
- Help text
- Program splash screen headings
- Formatted output, such as names, times, and dates
- Descriptive labels for other objects, including text boxes and list boxes.
A label is a control you use to display text that a user can't edit directly. We've seen, though, in
previous examples, that the text of a label box can be changed at run-time in response to events.
Label Properties:
Alignment Aligns caption within border.
Appearance Selects 3-D or flat appearance.
AutoSize If True, the label is resized to fit the text specifed by the caption property. If False, the label will remain the size defined at design time and the text may be clipped.
BorderStyle Determines type of border.
Caption String to be displayed in box.
Caption String to be displayed in box.
Font Sets font type, style, size.
WordWrap Works in conjunction with AutoSize property. If AutoSize = True, WordWrap = True, then the text will wrap and label will expand vertically to fit the Caption. If AutoSize = True, WordWrap = False, then the text will not wrap and the label expands horizontally to fit the Caption. If AutoSize = False, the text will not wrap regardless of WordWrap value.
Label Events:
- Click - Event triggered when user clicks on a label.
- DblClick - Event triggered when user double-clicks on a label.
Creating Labels on a Form
To create a label control on a form, we surely refer to the toolbox window to select the label icon, shown as capital letter “A”. When the label control is selected, the label can be placed on a form by creating a rectangle with the mouse, which is held left button clicked. Once the left button is released, the label of size as the rectangle created is placed on the form.
Creating Labels in Code
You can also set label properties with program code, as shown in the following. The program codes below, when command1 button is clicked, will set the caption of label1 as “Welcome” and label2 as “Please enter your name below:”
Private Sub Command1_Click ()
Label1.Caption = "Welcome"
Label2.Caption = "Please enter your name below:"
lblDigitalClock.Caption = Time
End Sub
Textbox
A Textbox is used to display information entered at design time, by a user at run-time, or assigned
within code. The displayed text may be edited. The Textbox control is one of the most versatile tools in the Visual Basic toolbox. This control performs two functions:
- Displaying output (such as operating instructions or the contents of a file) on a form.
- Receiving text (such as names and phone numbers) as user input.
How a text box works depends on how you set its properties and how you reference the text box
in your program code. The following popup illustration shows a text box that:
- Displays data entry instructions for the user.
- Receives input when the user types in a delivery note and clicks the Print Order button.
Text Box Properties:
Appearance Selects 3-D or flat appearance.
BorderStyle Determines type of border.
Font Sets font type, style, size.
MaxLength Limits the length of displayed text (0 value indicates unlimited length).
MultiLine Specifies whether text box displays single line or multiple lines.
PasswordChar Hides text with a single character.
ScrollBars Specifies type of displayed scroll bar(s).
SelLength Length of selected text (run-time only).
SelStart Starting position of selected text (run-time only).
SelText Selected text (run-time only).
Text Displayed text.
Text Box Events:
Change Triggered every time the Text property changes.
LostFocus Triggered when the user leaves the text box. This is a good place to examine the contents of a text box after editing.
KeyPress Triggered whenever a key is pressed. Used for key trapping, as seen in last class.
Text Box Methods:
SetFocus Places the cursor in a specified text box
The sample code below shows how to control a text box,
Command 1 is clicked,
Private Sub Command1_Click()
'The following line places text in a text box:
Text1.Text = "Enter your delivery note here."
End Sub
Command 2 is clicked,
Private Sub Command2_Click()
'This line saves input from a text box in a variable:
DeliveryNote = Text1.Text
End Sub
Command 1 is clicked,
Private Sub Command1_Click()
'The following line places text in a text box:
Text1.Text = "Enter your delivery note here."
End Sub
Command 2 is clicked,
Private Sub Command2_Click()
'This line saves input from a text box in a variable:
DeliveryNote = Text1.Text
End Sub
CommandButton
As you saw in Chapter 1, you use the CommandButton control to create buttons with a variety of uses on a form. A command button is the most basic way to get user input while a program is running. By clicking a command button, the user requests that a specific action be taken in the program. Or, in Visual Basic terms, clicking a command button creates an event, which must be processed in your program.
Here are some command buttons that you’d typically find in a program:
As you saw in Chapter 1, you use the CommandButton control to create buttons with a variety of uses on a form. A command button is the most basic way to get user input while a program is running. By clicking a command button, the user requests that a specific action be taken in the program. Or, in Visual Basic terms, clicking a command button creates an event, which must be processed in your program.
Here are some command buttons that you’d typically find in a program:
- OK - Accepts a list of options and indicates that the user is ready to proceed.
- Cancel - Discards a list of options.
- Quit - Exits an open dialog box or program.
Command Button Properties:
Appearance Selects 3-D or flat appearance.
Cancel Allows selection of button with Esc key (only one button on a form can have this property True).
Caption String to be displayed on button.
Default Allows selection of button with Enter key (only one button on a form can have this property True).
Font Sets font type, style, size.
Command Button Events:
Click Event triggered when button is selected either by clicking on it or
by pressing the access key.
Changing Command Button Properties
You can change command button properties (like those of all objects) in two ways:
- By adjusting property settings in the Properties window.
- By changing properties with program code.
DATA INPUT CONTROLS
Visual Basic provides several other controls that you can use to collect user input in a program. In this section, you learn to use four versatile toolbox controls.
This section includes the following topics:
OptionButton
To receive user input in a Visual Basic program, you can use controls that:
- Present a range of acceptable choices.
- Receive input in an acceptable format.
Creating Option Buttons
Like the other items in the Visual Basic toolbox, you create an option button on a form by clicking OptionButton in the toolbox and then drawing on the form.
Grouping Option Buttons
If you want to create a group of option buttons that work together, you must first create a frame for the buttons. (To do this, use Frame, a Visual Basic toolbox control.) Next, p lace your option buttons inside the frame so that they can be processed as a group in your program code and moved as a group along with the frame.
Checkbox
The Checkbox control is similar to the OptionButton control, except that Checkbox displays a list of choices and gives the user the option to pick multiple items (or none at all) from a list of choices . You create a check box on a form much as you would make an option button. Start by clicking the Checkbox control in the toolbox, and then draw on the form. If you want to create a group of check boxes that work together, create a frame for the buttons with Frame, a toolbox control. Then, you can place your check boxes inside the frame so that they can be processed as a group in your program code or moved as a group along with the frame.
ListBox
When you want a user to choose a single response from a long list of choices, you use the ListBox control. (Scroll bars appear if the list is longer than the list box.) Unlike option buttons, however, list boxes don’t require a default selection.
Creating List Boxes
Building a list box is simple, since it doesn’t require creating a frame or a separate object for each
list item. You just click ListBox in the Visual Basic toolbox and draw a suitably sized list box on
your form.
Setting List Box Properties
In a Visual Basic program, you can define list box characteristics in the Properties window or by
using program code, so that users can add, remove, or sort list box items while the program runs.
You add choices to a list box with the AddItem method, which is typically placed in the
Form_Load event procedure. (AddItem is a method normally used with list-oriented objects).
The sample code below shows an example of the AddItem method.
Private Sub Form_Load()
List1.AddItem “Extra hard disk”
List1.AddItem “Printer”
List1.AddItem “Satellite dish”
End Sub
Adding Default Program Statements
Each time your Visual Basic program displays a form, the Form_Load event procedure (a block of code) runs. Although Form_Load doesn’t contain default program statements, you can add statements to it. Just double-click the form to open the Form_Load event procedure in the codewindow.
ComboBox
Objects created with the ComboBox control are similar to those created with the ListBox control. Like a list box, items can be added to, removed from, or sorted in a combo (combination) box while your program runs. However, there are differences. Combo boxes take up less space on the form, show a default setting, and in their default Style property setting are only one line high. But if the user clicks the combo box while your program runs, the combo box expands to reveal a full list of choices. (If the list is too long to be displayed in the combo box, scroll bars appear).
Adding Combo Box Items
Typically, choices are added to a combo box with the AddItem method (a method normally used with list-oriented objects). You use the AddItem method by writing code in the Form_Load event procedure.
The sample code below shows an example of the Form_Load event procedure.
Private Sub Form_Load()
Combo1.AddItem “U.S. Dollars”
Combo1.AddItem “Check”
Combo1.AddItem “English Pounds”
End Sub
Source: EASTERN
MEDITERRANEAN UNIVERSITY - MECHANICAL ENGINEERING DEPARTMENT