Lecture 1 -responding To Events (vb 2008)

Application Programming 

Instructor Contact Information: 

John A. Rose, PhD (Assoc. Prof., APU ICT Institute)   

APU Office: Building BII, Fourth Floor E-mail: [email protected] Web-site: http://www.apu.ac.jp/~jarose/

Texts and Materials 

Primary Text: ‘Beginning VB.NET 2008’, Ch. 6 +  



Authors: Willis and Newsome Publisher: Wiley (2008)

Course Slides

Course Syllabus (tentative) 

Introduction: Building Windows Applications  



Dialog Boxes  



Lecture 1 – Responding to Events Lectures 2 – Creating Complex Applications Lecture 3 – Dialog Boxes (1) Lecture 4 – Dialog Boxes (2)

Creating Menus, Debugging, and Error Handling   

Lecture 5 – Creating Menus (1) Lecture 6 – Creating Menus (2) Lecture 7-8 – Debugging and Error Handling 



Midterm Examination

Object Oriented Programming     

Lecture 9 – Introduction to Objects Lecture 10 – Inheritance Lectures 11 – Polymorphism Lecture 12 – Shared Class Resources Lectures 12 – The .Net Classes 

Final Examination or Submission of Final Project

Course Methodology 

Lecture materials will be distributed at the beginning of each class…  



Followed by the Lecture. Where possible, examples will be presented with figures.

Each class is 95 minutes. After each lecture-period: 

students will then be provided time for practice (as time permits). 





For a total of 95 minutes (lecture + practice)

Teaching Assistants (TAs) will be available to answer questions during the practice period.

Note: substantial practice and work beyond the class period will be required.

Course Evaluation (Grading) 

The final grade (100%) will be awarded using the following criteria for evaluation (tentative): 

Attendance: 20%  



Mid-term Exam/Projects: 35%  





Students should come to each class. Note: points will be deducted for lateness or inappropriate behavior. Midterm: An In-class test After Lecture 7

Final Examination (comprehensive test): 45%

Important Notes about grading: 

Do all homework and In class programs (VB .NET Projects). 



As done in class / assigned.

Note carefully that the above is tentative. 

The above weights/items are subject to change.

Miscellaneous Instructions 

Students should bring their own data storage devices: 

Necessary for storing work: 

USB 2.0 Flash Memory (preferred)  



CD-RW 



650 or 700 MB

Floppy Disk 



64 MB or higher Windows XP Compatible

3.5’, 1.4 MB

These can be purchased in the APU Book Store.

Lecture 1: Responding to Events

Outline 

Introduction:  



Event Example: Multiple Button Events  



WinForms Responding to Events

Using the Class Name and Member Name combo boxes. Adding multiple button events.

Building a Simple Application: Char/Word Counter  

Using the controls we have… And a new control, the Radio Button.

Windows Forms 

The basic element of Applications are Windows: 

As we have seen, Windows support placement of controls…  



Windows support Rapid Application Development (RAD): 

Developers simply draw controls on the screen…  



The ‘Visual’ approach (e.g., VB .NET) We have used a blank window called the Design Window (Form1).

Non-visual: Need to code each Window / Control ‘from scratch’. 



Buttons to handle user requests Labels, TextBoxes, ListBoxes, etc for GUI-based Input/Output

Usually, 1000’s of lines of code required (e.g., Java)

In Visual Basic, windows are called ‘Forms’  

Sometimes also called ‘WinForms’ We have already been using Forms in our simple applications… 

Now, we will take a closer look at Forms and Form use. 



Including the use of multiple forms.

Our Goal: making fully-featured Windows applications.

Event-Driven Programming 

In GUI-based Programming: 

We build a user interface (GUI) to ease user communication... 



By painting controls on the Design Window.

Each control can recognize certain user actions  

Example: a click. In VB .NET, such recognizable actions are called events… 



We use this Event recognition capability to drive program behavior: 

By coding subroutines called event handlers: 

Sometimes called ‘action listeners’ (Java)… 





Which wait for a specific event, at a specific control.

These are identified by the ‘Handles’ keyword… 

which registers the event, for us.

Given occurrence of the registered event (Control, Event). 



In other languages (Java), the word ‘action’ is also used.

The Subroutine’s lines of code are then executed .

This model of programming is called ‘Event-Driven Programming’ 

Let’s take a closer look at the ‘event philosophy’… 

by setting up a button event.

Button Events: A Second Look 

Open up VB Studio .NET and make a new project… 

With a single ‘Welcome’ button:

The Class Name Combo Box 

Next, drop down the list in the Class Name combo box: 



The combo box options will appear, as shown above. 



At the top of the Code Window…

It mainly lists the Classes and Members added to the current project.

Here: 1. Form 1 is a Class (an Object definition) 

As denoted by its icon (three connected boxes: purple/blue/yellow)

2. The last two items are slightly indented… 

This means they are all related to Form1.

3. (Form1 Events) are a Events of Form1. 

This is denoted by its icon (a lightning bolt).

4. btnWelcome is a Member of Form1. 

This is denoted by its icon (a small blue box).

The Method Name Combo Box 

Next, drop down the list in the Method Name combo box: 



At the top right of the Code Window…

The items that appear depend on the Class Name combo box selection: 

Here, Form1 is selected at left… 



So, names of the Libraries, Classes, etc in the current project are listed at right.

Note that: 1. Selecting the (Declarations) entry takes you to the Class top… 

Where you can change the Class definition, and add members.

2. Items appear either bold (existing) or faint (not yet created). 

Here, the Finalize method can automatically be created by selecting it. 

We will not discuss Finalize until later...

3. Methods are denoted by a small purple square icon. 4. Libraries are denoted by an icon with 4 stacked books.

Adding more Event Handlers 

Next, select btnWelcome in the Class Name combo box: 

Only items related to btnWelcome now appear in the Method Name combo box:  Specifically, events are shown (icon: lightning bolt)... 



Note that existing events are shown in bold (Click)

Let’s use this combo box to add 2 more event handlers to btnWelcome… 



By selecting the events, MouseEnter and MouseLeave…  This creates two new, empty event handlers. Now, add the code below to the two new event handlers:

Adding Event Handlers (Test Function) 

Let’s test the function of our simple, 3-event button…

Program 2 – Char/Word Counting Tool 

Let’s practice by making a second application… 



A simple counting utility (tool)

Goal: Design a tool with the ability to accept input text, and: 

Ability 1: Count the characters in the input Text  





Using the property String.Length And the TextBox event handler TextChanged

Ability 2: Count the words in the input Text

To allow selection of these actions/abilities by the user: 

We use a new type of control, the Radio Button (rad) 

A user selecting a particular Radio Button sets its Checked property: 



Only 1 Radio Button can be checked, at one time, in a single group…  



RadioButton.Checked  True

In our case, our group is the entire Container called Form1 Note: We could also make ‘internal’ groups with Group Boxes.

First, lets make the GUI and program the Char. Counting ability:

Char/Word Counting Tool (Ability 1) 

First, construct the GUI and program the Character Counting ability: 

We need 3 Labels (lbl), 1 TextBox (txt), 2 Radio Buttons (rad), and 1 button (btn):

Char/Word Counting Tool (Ability 2) 

Again, our goal is to make a tool with two abilities: 

Ability 1: Count the characters in the input Text  





Using the property String.length And the TextBox event listener TextChanged

Ability 2: Count the words in the input Text

Now, let’s modify our tool to perform its second ability…

Counting Words (Step 1) 

First, let’s add a Function which counts the ‘words’ in an input string…

Counting Words (Step 2) 

Next, add a Function to UPDATE the GUI, for ALL counting activities…

Counting Words (Test Function)