Transcript CS 102
Graphical/Event-Driven Programs
Event loop/architecture
Form_Load method
Basic controls
Example simple program
Input boxes
List boxes
Created by Visual Studio
Project should be of type: Windows Form
Application
VS creates several key files for you:
<project>.sln – Solution file. Contains names and types of
all files in the project
<project> - Directory containing all files in the project
<project>\Form1.Designer.vb – GUI form details
<project>\Form1.vb – Code for the form
Other files you don’t need to worry about
Don’t change these files manually. Do it all through VS.
Everything you need for a working program is
already created
You can just execute the program
Won’t do anything, but the form will display!
Just add controls as needed, and event
handlers as desired
Critical event procedure
Exists for EVERY form in your program
It is 100% optional – you do not have to use it
Any code in the form is executed when the
form is first loaded and drawn on the screen
To edit the method, just double click anywhere
in the background of the form
If you decide you don’t want it, just delete the
code for the method
The following is the code module that results
after you double click on the empty form for a
new project, and add one line of code to it
Public Class Form1
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles MyBase.Load
MsgBox("Form load is being executed!")
End Sub
End Class
First and last lines are standard for all forms
Form load header is standard and created by
VS
Form Load methods are very common, and are
used for tasks such as:
Initializing data in fields on the form
List boxes
Text boxes
Others
Setting the focus (field that is currently active)
Reading data from a database for use on the form
Anything else you want initially performed on the
form
Visual Studio provides an incredible number of
out-of-the-box controls for your use
You can obtain a huge number of controls
written by others for virtually any task, for
example:
Just drop them on the form, and write code for their
events
Twitter controls
Controls for writing OnStar applications
It is pretty easy to create your own new
controls, and to add custom events to them
The following is a brief list of controls available
to you in VB:
Label – A static text label on a form
Button – A push button
Text box – A box for users to type/enter data
Radio button – A set of radio buttons to select one
choice (of many)
Check box – A box that can be checked, or not
Combo box – A dropdown list box that you can type
data into
Picture box – A control that is used to display an
image
List box – A control with multiple entries. You
can select one, or multiple items
Date/time picker – A control that allows you to
pick date and/or time
Link label – A static text label that is also a
hyperlink
Progress bar – A bar to show completion of a
process
MonthCalendar – A control that displays a
calendar
Timer – A control that calls an event every so
often, based on the property in the timer
Web browser – Handles all facets of a web
browser
Data grid controls – Interacts, displays, enters,
modify database data
Horizontal/vertical scroll bars – Allows you to
select from a range
Numeric Up/Down – Allows you to set a
number by clicking up/down
Masked Text Box – A text box that the user can
supply a mask, to enforce data entry rules
Menu strip – Add menus to your application
Rich Text Box – A multi-line text box that
allows Rich Text Format (RTF) to be entered
Open/Save File dialog controls
Print File dialogs
Method for user to enter data
You can specify:
Dialog title
Prompt
Default value
You can create a validation routine for the data
when it is entered
Button click method
You can mask the data as entered for security
Ex: Password field
Control to list a series of items
Can select among them
Can select multiple items from the list
Can have scroll bars on the listbox
Can add items to the list
Can remove items from the list
Can retrieve selected items
Can have multi-column list boxes
Can have checked list boxes
Often, when you are writing event methods
you will want to stop the entire VB program
Use ‘End’ method
Private Sub Button1_Click(ByVal sender As System.Object, _
ByVal e As System.EventArgs) Handles Button1.Click
End
End Sub
Every control that is created has pre-defined
properties
Properties allow you to easily/quickly change
many attributes of the control
Properties are changed in the properties
window (by default, bottom right of page)
Users can create new properties for controls
(you will not do this for this course)
Many properties are common among many
control types – some are specific for that
control
Some common properties are:
Name – The unique name of the control. VB auto-names
them for you. You should ALWAYS change the name of
the control
Backcolor – Background color
Forecolor – Foreground color
Enabled – Is the control active (can you use it)
Visible – Is the control visible, or not seen
Location – Where is the control on the form
This is almost always set by drag/drop
Tab Index – Which control number is this (tab order)
Text – What text is displayed in the control when the
form is displayed