Visual Basic Controls

Working with Visual Basic Controls:

Visual Basic offers a set of controls which are placed in the toolbox.  The additional set of components is provided in the component list. 

The property and the methods of these classes can be access through the object using dot operator

E.g Command1.caption=”Hello”

1. Text Box:The text box control is the most commonly used to get the input from the user.  The text property of the textbox can be used to access the content of the textbox control

Text Box

Properties of Text Box:

·    Enabled: Set whether the user is allowed to access the control or not.  If set to false the textbox is disabled.

 

·    Locked: If we set to true that text box will not allow the user to get the content of the text box.  Unlike the enable property if will allow to copy and paste the control of the textbox.

 

·    Maxlength:  Set the maximum length of the characters that can be entered.

 

·    Multiline:  When the text exceeds the boundaries of the control the text will be wrapping to the next line if the multiline property is set to true.

 

·    Passwordchar:  The character to be displayed should be entered here to hide the text from the user.

 

·  Text: The text entered in the textbox limited to 2048 characters.  If the multiline property is set to true then it is 32 KB.

 

·   Visible: Set whether the control is hidden or visible. Setting if false hides the control.

2. Command Button: Command button is a three dimensional rectangular button, when the user clicks the button at run time VB invokes the code given in the click event.

Most visual basic applications have command buttons that allow the user to simply click them to perform action.

Properties of Command Button:

    ·      Backcolor: Set the background color only if the style property is set to graphics (1)

 

    ·     Caption:  Set the text display on the button.

 

    ·    Cancel:  When this property is set to true then the button can be click using escape             key.

    ·    Picture:  Set the picture is display on the button if the style property of the button is set      to graphics

3. List Box:  List box control display the list of items from which the user can select one or more. If the number of item exceeds the number that can be displayed, scroll bar is automatically added to list box control.  By default the choices are displayed in the vertical columns although multiple columns can be set.

List Box

Adding Items: You can add items in two ways that is design time and runtime.

 

Design Time: At a design time by setting the list property of the property window of the list box control.

 

Run Time:  You can add the item in the list box at runtime by using following code

 

Private command1_click()

List1.Additem ”Wardha”

End Sub

 

Removing Items:

 

List1.RemoveItem 0

Remove item has one argument, index, which specifies the item to remove

 

To remove the currently selected item from the list

Privates of command1_Click()

List1.RemoveItem Lis1.ListIndex

End Sub

 Clear method

 To remove all the items from the listbox the clear method is used.

 List1. Clear

 

  Listcount property:

  List count property returns the number of item in the list box

  Privates of command1_Click()

  msgbox(“The number of Items in the List1”& List1.ListCount)

End Sub

 4. Combo Box:  A combo box control combines the features of text box and a list box.  This control allows the user to select an item either by typing text into the combo box, or by selecting it from the list.

 

Combo box presents a list of choices to the user. If the number of items exceeds what can be displayed in the combo box, the scrollbar will automatically appear on the control. The user can then scroll up and down or left to right through the list.

Combo Box

Unlike list box control, the user can select only one item at a time from the combo box.

The properties and methods of the combo box control is very much similar to list box.

 Combo Box control Vs List Box control

Although both the combo box and list box control offers the list of options there are few differences between them.

1.    In combo box control the user can type text while the text cannot be typed into the list box control

2.    User can select only one option at a time from the list of available option,  while in case of the list box control the user can select the multiple options at a time

     3.    The list of items are displayed only in single column in the combo box control,  while the items can be displayed in multiple columns in list box control.

5. Picture box: The picture box control is used to display the graphics, to act as a container for the other control, and text using print method

Picture box control is similar to image control; each can be used to display graphics in your application. Each supports the same graphics format.

 

Picture property: Picture property of the picture box control can be used to set the picture in the picture box control. The picture property of the picture box control can be set at design time as well as run time

 

Loadpicture() method : The Loadpicture()can be used to display the picture into the picture box control at the runtime.

 

The path of the image to be loaded is passed as an argument to the Loadpicture() method

Picture Box

Private Sub Command1_Click()

Picture1.Picture= Loadpicture(“C:\ uranus.jpg”)

End Sub 

Graphics methods: Picture boxes, like forms, can be used to receive the output of the graphics method such a Circle, Line and Point.

 

 To draw a line in the picture box control, the line method is used.

 

Picture1.Line(x1,y1)-(x2, y2)

 

Where x1, y1 are the coordinates of the starting point of the line and x2, y2 are the coordinates of the end point of the line.

Syntax for circle method:

 

Circle(x,y),r

 

Private Sub-Command1_Click()

Picture1.Line(10,10)-(1000, 1000)

Circle( 1200,1000),750

End Sub

6. Image Control:The image control can be used to display the images on the form. It supports the same picture format as that of picture box control.

Picture property:  The picture property of the image control is used to load the pictures at design time

Private Sub Command1_click()

Image1.Picture= Loadpicture(“C:\apple.jpg”)

End Sub 

    Stretch property: The stretch property determine whether the picture is stretch when               loaded, to the size of the image control at the design time.

    Stretching the picture can be produced the loss of the image quality 

7.   Option Button: An option button control displays an option that can be turned on or off. 

Option buttons are also called as a radio button since you can tune into only one channel at a time. Usually option button controls are used in an option group to display options from which the user can select only one.

Option button control can be grouped by drawing them inside a container such as frame control.

The value property of the option button control can be used to identify whether the option button is currently selected or not.  If the option button is currently selected then its value property is true otherwise it is false.

Option Button

Private Sub Command1_click()

If Option1.value= True then 

Msgbox “Male”

Else

Msgbox “Female”

End If 

End Sub 

8. Checkbox:  The checkbox control officer list of choices from which the user can select as many options as required.  Checkbox control displays checkmarks when it is selected.  It is commonly used to present Yes/No or True/ False selection to the user.

Value property:  The value property of the checkbox control indicates whether the checkbox is checked or unchecked.

When the checkbox is selected the value is set to 1 otherwise it is 0.

Private Sub Command1_click()

If Check1. Value=1 Then

Text1.FontBold= True

ElseIf Check1.Value=0 Then

Text1.FontBold= False

End If 

 

If Check2. Value=1 Then

Text1.FontItalic= True

ElseIf Check2.Value=0 Then

Text1.FontItalic= False

End If 

 

If Check3. Value=1 Then

Text1.FontUnderline= True

ElseIf Check3.Value=0 Then

Text1.FontUnderline= False

End If 

End Sub 

Check Box 

9. Scrollbar: Scrollbar control is a visual basic control containing a thumb, you can move the scrollbar by dragging it, clicking the mouse to either side of the scrollbar, are using the keyboard.

Scrollbar control are useful when you want to select a discrete value or for a set of only creative values in a range.

When become of the scrollbar is moved, the current value of the scrollbar is changed.

There are two type of scroll bar available in toolbox:

1. Horizontal scroll bar
2.  Vertical scroll bar

 Properties:

 

1. Max Property:  Set the maximum value of the thumb of the scrollbar reaches its extreme right
2. Min property : Set the minimum value Hindi thumb of the scrollbar reaches its extreme left
3. Smallchange property:  Set the amount of increase or decrease in the value if the user Clicks on the arrow pointing to the left or right
4. Value property:  It is the value corresponding to the position of the scroll box in the scroll bar
5. Change event:  The change event of the scrollbar is executed as the current value of the scrollbar is changed.  The scrollbar value is changed when the scroll bar thumb is more either left or right.

HScroll & VScroll

Private Sub Hscroll1_Change()

Text1.text= Hscroll1.Value

End Sub

Private Sub Vscroll1_Change()

Text2.text= Vscroll1.Value

End Sub

Array of controls:

An array is defined as a group of elements of similar type. Similarly to an array of integers, single, string an array of control can be created.

All the control in the control array will share the same name

The individual element in the control array can be referred using an index which begins with 0.

To create an array

1. Place the control on the form
2. Copy the control
3. Past control

For example to create an Array of command buttons, place a command button on the form, copy and paste it.

The first button is now referred as a command1 (0), second one as command1 (1) and so on.

The code in the click event can be specified as,

Private Sub Command1_Click (index as integer) 

End Sub

The index of the button click is passed as an argument to the procedure.

 

Setting the background color of the form using three scroll bars

 

Place a horizontal scrollbar on the form, right click on the scroll bar and select copy and click on the paste.

 It creates the control array of the scrollbar on the form.  Again paste one more scrollbar on the form

 

The first scrollbar is identified as Hscroll1(0), Second scroll bar as Hscroll1(1)  while the third as Hscroll1(2).

Array of Control

Private Sub Hscroll1_Change (Index as integer)

Form1.Backcolor= RGB(Hscroll1(0).Value,Hscroll1(1).Value,Hscroll1(2).Value)

End Sub

10. Frame: Frame control can be used to group the control in it. It is commonly used to group the radio button as only one radio button can be selected from the individual group.

 Frame control provides an identifiable grouping of controls. You can also use a frame to subdivide a form functionally- for example separate group option buttons.

 To group controls, first draw the frame control and then draw the controls inside the frame. This enables you to move the frame and the control it contains together.  If you draw the control outside the frame and then try to move It Inside, The control will be on top of the frame and you will have to move the frame and control separately.

Frame

11. File Control:

Driver list box:  Drive list box control enables a user to select a valid disc drive at runtime.  Use this control to display a list of all the valid drivers in the user system

 

Directory list box:  A directory list box control display directories and path at runtime.  Use this control to display the hierarchical list of directories

 

File list box:  If file list box control locates and list file in the directory specified by the path property at runtime.  Use this control to display a list of files selected by file type 

Private Sub Form_Load()

Drive1.Drive=”C:\”

End Sub

Private Sub Drive1_Change()

Dir1.Path=Drive1.Drive

End Sub

Private Sub Dir1_Change()

File1.Path= Dir1.Path

End Sub

Drive List Box

Directory List

File List