Basic Controls & Properties

Basic Controls & Properties

Chapter 2

Overview

VB-IDE Basic Controls

Command Button Label Text Box Picture Box

Program Editor Setting Properties with Code

The Visual Basic IDE

The Workspace & Toolbox

Selecting Tools

Using the toolbox and the Workspace Window you can build a form that has nearly any desired appearance Double click on an icon in the toolbox to create a new

instance of that type of object in your workspace These objects are called controls

Using the mouse, a control can be resized or moved

The Project Window

This window allows you to select and open one or more forms that are used in a given project.

You may use this window to adjust the position of the form on the CRT screen.

Clicking on the “X” will close this window and leave room for other things.

The Form Layout Window

This window allows you to examine and modify the various properties of control objects in a program Properties govern the

appearance and behavior of a control object

They may be modified using the properties window, or by VB code

The Properties Window

The Command Control The command control

is one of the most important tools in the toolbox

Double clicking on the command button icon will install a command button on the working form

Command Button

Adding a Command Button

The command buttons are named, by default Command1, Command2, etc.

They may be moved or changed in size using the mouse

Properties of Command Buttons

Each command button has several properties. govern the button’s appearance and behavior

The most important are the (name) and the caption (name) is how a programmer can

refer to the button in VB code caption is the text a user will see

displayed inside the button

Highlighting a Property

When you highlight a property, its definition appears below the properties window

Names and Captions

Clicking on the (name) property lets us name it “cmdstop”, (note the name starts with “cmd”)

Changing the caption to “Stop” gives the user an idea as to the button’s function

Naming Convention

Good practice in Visual Basic suggests that we should name all objects in a program with names that indicate their function These names are invariant during a program’s execution and are

seen only by programmers Command buttons names should begin with the prefix “cmd” Names should begin with the prefix for the given object type, and

should contain only letters and numbers

Captions are used to convey information to the user They can change as the program runs They may contain any letters, numbers, spaces, etc.

Command Buttons & The Program Editor

Visual Basic (VB) supports a text editor (not a word processor) that permits the writing and modification of program code

The program editor is one of two sub-windows that appears in the Workspace The other is the Forms window

Many of the commands used in the program editor are like those used in word processors, but there are differences

Entering the Editor

The editor is normally entered by “double clicking” on an “Event Producing Object” in the workspace.

The result is a code window which opens with the “subroutine” describing that event as the focus.

Entering Event Code

Double clicking on the “cmdStop” button itself, causes the Code window to open The VB commands that

define the button’s function go here

The “End” command terminates the VB program

The Label Control The label control is an

object with 37 named Properties

You can adjust its size and position with the mouse

You can change its (name) its caption and visibility using the Properties window

Label Control Properties

Using Labels

The label control is usable only for output It cannot accept input from the user

Its size, shape, color, visibility and the form of the information presented can be controlled By editing its properties By writing VB code to change its properties

Labels can be sized and moved using the mouse.

A Program Using a Label

Using a Label

When program execution begins, the system starts as in “A”, when the cmdby button is pressed the system goes to “B”

Repeated pressing of the cmdby button bounces the system between the two states

Naming Convention

Labels should be given a (name) that begins with “lbl”.

The Caption property of a label may be anything that makes sense; one or more words or symbols. Caption is displayed for the user (name) is only accessible to the programmer

The Visible property may be either True or False If false, the label is not displayed

3. The Text Box Control

Labels are designed to be used for output Command buttons can accept input from

the user, but only of a limited nature The text box control allows the user

input data

Text Box Properties

The text property contains the string of text displayed by the text box

Unlike labels, by default this text can be edited by the user at runtime

The proper prefix for text box names is txt

Text boxes do not have Caption property!

4. The Picture Box The Picture box control can be

used to display a picture on the form

The proper prefix for picture box names is pct

Click on its Picture property A command button with an ellipsis

(…) will be displayed By clicking on the button, a dialog

box will appear to select the graphic file to display within the picture box control