Before writing an event procedure for control to response to a user's input, you have to set certain properties for the control to determine its appearance and how it will work with the event procedure and you can also set the properties of the controls in the properties window or at runtime.
Above figure is a typical properties window for a form. You can rename the form caption to any name that you like best and in the properties window, the item appears at the top part is the object currently selected (in the figure above, the object selected is Form1). At the bottom part, the items listed in the left column represent the names of various properties associated with the selected object while the items listed in the right column represent the states of the properties and properties can be set by highlighting the items in the right column then change them by typing or selecting the options available. For example, in order to change the caption, just highlight Form1 under the name Caption and change it to the other names. You may also try to alter the appearance of the form by setting it to flat or 3D. Other things you can do are to change its background and foreground color, change the font type and font size, enable or disable minimize and maximize buttons and etc.
You can also change the properties at runtime to give special effects such as change of color, animation effect and shape and so on. For example the following code will change the form color to red every time the form is loaded and VB uses hexadecimal system to represent the color. You can check the color codes in the properties windows which are showed up under BackColor and ForeColor.
Private Sub Form_Load()
Form1.Show
Form1.BackColor = &H000000FF&
End Sub
Handling some of the common controls
1.The Text Box
The text box is the standard control that is used to receive input from the user and also to display the output. It can handle string (text) and numeric data but not pictures or images.
String in a text box can be converted to a numeric data by using the function Val(text) and the following example illustrates a simple program that processes the inputs from the user.
In this program, two text boxes are inserted into the form together with a few labels and the two text boxes are used to accept inputs from the user and one of the labels will be used to display the sum of two numbers that are entered into the two text boxes. Besides,using the plus operator a command button is also programmed to calculate the sum of the two numbers.
Private Sub Command1_Click()
‘To add the values in text box 1 and text box 2
Sum = Val(Text1.Text) + Val(Text2.Text)
‘To display the answer on label 1
Label1.Caption = Sum
End Sub
2.The Label
The label is a very useful control for Visual Basic, as it is not only used to provide instructions and guides to the users, it can also be used to display outputs and one of its most important properties is Caption. Using the syntax label.Caption, it can display numeric and text data .
You can change its caption in the properties window and also at the runtime.
3.The Command Button
The command button is a very important control as it is used to execute commands and it displays an illusion that the button is pressed when the user click on it.
The most common event associated with the command button is the Click event, and the syntax for the procedure is as follows:
Private Sub Command1_Click ()
Statements
End Sub
4.The Picture Box
The Picture Box is one of the controls that used to handle graphics and you can load a picture at design phase by clicking on the picture item in the properties window and select the picture from the selected folder. You can also load the picture at runtime using the LoadPicture method and for example,the statement will load the picture grape.gif into the picture box.
The Image Box is another control that handles images and pictures and it functions almost identically to the picture box. However, there is one major difference, the image in an Image Box is stretchable, which means it can be resized and this feature is not available in the Picture Box. Similar to the Picture Box,to load the picture it can also use the LoadPicture method.
For example, the statement loads the picture grape.gif into image box.
The function of the List Box is to present a list of items where the user can select and click the items from the list.
In order to add items to the list, we can use the AddItem method and for example, if you wish to add a number of items to list box 1, you can key in the following statements
Private Sub Form_Load ( )
List1.AddItem “Lesson1”
List1.AddItem “Lesson2”
List1.AddItem “Lesson3”
List1.AddItem “Lesson4”
End Sub
Note:The items in the list box can be identified by the ListIndex property and the value of the ListIndex for the first item is 0, the second item has a ListIndex 1, and the second item has a ListIndex 2 and so on
7.The Combo Box
The function of the Combo Box is also to present a list of items where the user can select and click the items from the list. However, the user needs to click on the small arrowhead on the right of the combo box to see the items which are presented in a drop-down list and in order to add items to the list, you can also use the AddItem method.
For example, if you wish to add a number of items to Combo box 1, you can key statements as follows
The Check Box control lets the user to unselect or select an option. When the Check Box is checked, its value is set to 1 and when it is unchecked, the value is set to 0 and you can include the statements Check1.Value=1 to mark the Check Box and Check1.Value=0 unmark the Check Box, and use them to initiate certain actions. For example, the program will change the background color of the form to red when the check box is unchecked and when the check box is checked it will change to blue.
You will learn about the conditional statement If….Then….Elesif in later lesson and vbBlue and VbRed are color constants and BackColor is the background color property of the form.
Private Sub Check1_Click ()
If Check1.Value = 0 Then
Form1.BackColor = vbRed
ElseIf Check1.Value = 1 Then
Form1.BackColor = vbBlue
End If
End Sub
9.The Option Box
The Option Box control also lets the user select one of the choices.
However, two or more Option Boxes must work together because as one of the Option Boxes is selected and the other Option Boxes will be unselected. In fact, only one Option Box can be selected at one time. When an option box is selected, its value is set to “True” and its value is set to “False” when it is unselected. In the following example, the shape control is placed in the form together with six Option Boxes and when the user clicks on different option boxes, different shapes will appear.
The values of the shape control are 0, 1, and 2,3,4,5 which will make it appear as a rectangle,an oval shape, a square , a rounded rectangle and a rounded square respectively.
Private Sub Option1_Click ( )
Shape1.Shape = 0
End Sub
Private Sub Option2_Click()
Shape1.Shape = 1
End Sub
Private Sub Option3_Click()
Shape1.Shape = 2
End Sub
Private Sub Option4_Click()
Shape1.Shape = 3
End Sub
Private Sub Option5_Click()
Shape1.Shape = 4
End Sub
Private Sub Option6_Click()
Shape1.Shape = 5
End Sub
10.The Drive List Box
The Drive ListBox is used to display a list of drives available in your computer and when you place this control into the form and run the program, you will be able to select different drives from your computer as shown in the following figure.
11.The Directory List Box
The Directory List Box is used to display the list of folders or directories in a selected drive. You will be able to select different directories from a selected drive in your computer as shown in Figure below,when you place this control into the form and run the program,
12.The File List Box
The File List Box is used to display the list of files in a selected directory or folder and when you place this control into the form and run the program, you will be able to a list of files in a selected directory as shown in Figurebelow
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