Teaching Object-Oriented Concepts Through GUI Programming

Jesse M. Heines Martin J. Schedlbauer

Dept. of Computer ScienceUniv. of Massachusetts Lowell

Eleventh Workshop on Pedagogies and Tools for the Teaching and Learning of Object Oriented Concepts

ECOOP, Berlin, Germany, 30 July 2007

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The OOP Teaching Field The Starting Line

Introducing OO concepts

Working OO examples

CS 1 and CS 2

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The OOP Teaching Field The Starting Line

Introducing OO concepts

Working OO examples

CS 1 and CS 2

The Finish Line Applying OO concepts Solving programming

problems Advanced courses

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The OOP Workshop Field 3 papers dealing with “Beginners,”

“CS1& 2,” and “Novice Programmers” Schmolitzky Späh and Schmolitzky Ma, Ferguson, Roper, and Wood

2 papers on “Objects First” Ehlert and Schulte Shümmer and Kösters

2 papers on applying OO concepts Hadar and Hadar Heines and Schedlbauer

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The OOP Cognitive Field Our experience is that regardless of

how and when OO concepts are introduced, students have trouble applying those concepts in project-based courses

Why? Lack of experience with large programs

The real benefits of OO are difficult to see in the small programs typically used as examples

Consequently, OO concepts do become part of the student’s cognitive field and programming style

“I need an object” instead of “I need a routine”

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OOP in Class vs. at Work Small programs Large programs

100s of lines 1000s of lines Standalone Hierarchies built

programs using previous code Single files Linked modules

Coded solo Coded in teams Code is never Documentation is

documented absolutely required

Never reused Reused repeatedly By self or others By self and others

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OOP and GUI Programming Excellent examples of class

hierarchies Java Swing and .NET Students learn just by browsing

Excellent tools for large programs NetBeans, Eclipse, Visual Studio, BlueJ Form designers and code generators

(Mostly) excellent documentation Using the API is a critical skill Creating an API is even more critical Model for student-created

documentation

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OOP and GUI Programming Inclusion of design patterns

Observers = MVC architecture & listeners

Strategies = layout managers Composites = UI components &

containers Decorators = scroll panes and

borders Singletons = calendars Factories = borders Commands = menus

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Lecture: Building Bridges Problem: Set the text of the root

node of an existing JTree control Subproblem: There is no method of

the JTree object to set a node’s text Solution: Build

a bridge from the control’s model This requires

understanding relationshipsbetween objects

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Lecture: Building Bridges Step 1: Create a new root node

DefaultMutableTreeNode root = new DefaultMutableTreeNode ( "New Text" );

Step 2: Get reference to the tree model

TreeModel myTM = myJTree.getModel();

Step 3: Cast the tree model referenceDefaultTreeModel myDTM =

(DefaultTreeModel) myTM; Step 4: Set the tree root

myDTM.setRoot( root );

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Lecture: Building Bridges Note that this is a very practical

problem with code generators For example, NetBeans always calls

the default JTree constructor

myJTree = new JTree(); One could write “post-creation” code

to set the root node text, but this is a static change, not a dynamic one

Thus, this problem forces students to use the API and think about the objects involved and their relationships

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Assignment: Object Comm. Problem: Pass data from a custom

dialog box (JFrame) to its parent class Subproblem: Default

member variable access method is private

Solutions: Change access method Use Component.getParent()method

Pass reference to parent in overloaded constructor

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Exam: FocusTraversalPolicy Center questions around a concept

that students are familiar with (focus traversal), but a class that students have not worked with

Actual questions are in Figure 5 in paper

7 questions address 5 OOP areas Human Factors Issues Use of the API Deprecated Code Class Relationships Application of the concept

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Additional Information Course websites

Lecture notes, assignments, and examples

teaching.cs.uml.edu/~heines See courses 91.461 and 91.462 on the

Teaching page Contact us

heines@cs.uml.edu mschedlb@cs.uml.edu

Our websites http://www.cs.uml.edu/~heines http://www.cs.uml.edu/~mschedlb

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Jesse M. Heines, Ed.D.Martin J. Schedlbauer,

Sc.D.Dept. of Computer Science

Univ. of Massachusetts Lowell

Thank You