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Lab Handout A Widget System

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SWEN221: Software Development
Lab Handout
The purpose of this Lab is to give you hands on practice using Java reflection. Before the end of
the lab, you should submit your solutions via the online submission system which will automatically
mark it.
1 A Widget System
The program provided with this lab implements a very primitive widget system which is inspired by
modern windowing systems. In this system widgets occupy areas on the screen and can respond to
mouse clicks. Widgets have internal state which they can use to control how they look. The following
illustrates a simple widget system:

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SWEN221: Software Development
Lab Handout
The purpose of this Lab is to give you hands on practice using Java reflection. Before the end of
the lab, you should submit your solutions via the online submission system which will automatically
mark it.
1 A Widget System
The program provided with this lab implements a very primitive widget system which is inspired by
modern windowing systems. In this system widgets occupy areas on the screen and can respond to
mouse clicks. Widgets have internal state which they can use to control how they look. The following
illustrates a simple widget system:
Here we see a very simple widget systems constructed from five widgets. The four visible squares each
constitute one widget, whilst the background itself constitutes another widget. The two widgets on
the top row are toggles — when clicked on, they will change to either the on or o↵ state. The two
widgets on the bottom row are counters — when clicked on, they will increment an internal counter
and set their counter according to this.
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2 What to do
The key challenge in this lab lies in interacting with widgets through reflection. In particular, you
will be unable to see the source code for one of the widgets. This means that reflection provides the
only way in which you can interact with this widget. The Inspector provides the skeleton for a suite
of methods for creating widgets and reading/writing their attributes. Some notes:
• Inspector.newWidget(String name, Rectangle dimensions). This instantiates a new instance of the class given by name. To do this, you will need to first find the appropriate constructor in the widget’s class, and then instantiate a new object using Constructor.newInstance().
• Inspector.getAttribute(Widget widget, String name). This reads the value of field name
in the given widget. To do this, it must call the corresponding “getter” method. For example,
for a field called color the corresponding getter would be getColor().
• Inspector.setAttribute(Widget widget, String name, Object value). This writes a given
value into field name in the given widget. To do this, it must call the corresponding “setter”
method. For example, for a field named color of type Color the corresponding setter would be
setColor(Color).
Your goal in this lab is to complete the above methods in the Inspector class.
Submission
Your lab solution should be submitted electronically via the online submission system, linked from
the course homepage. The required files are:
swen221/core/Canvas.java
swen221/core/Inspector.java
swen221/core/Widget.java
swen221/Main.java
swen221/tests/WidgetTests.java
swen221/util/AbstractWidget.java
swen221/util/Point.java
swen221/util/Rectangle.java
swen221/views/WidgetViewer.java
swen221/widgets/Background.java
swen221/widgets/Counter.java
swen221/widgets/Toggle.java
You must ensure your submission meets the following requirements (which are needed for the
automatic marking script):
1. Your submission is packaged into a jar file, including the source code. Note, the jar
file does not need to be executable. See the following Eclipse tutorials for more on this:
http://ecs.victoria.ac.nz/Support/TechNoteEclipseTutorials
2. The names of all classes, methods and packages remain unchanged. That is, you
may add new classes and/or new methods and you may modify the body of existing methods.
However, you may not change the name of any existing class, method or package. This is to
ensure the automatic marking script can test your code.
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3. All JUnit test files supplied for the assignment remain unchanged. Specifically, you
cannot alter the way in which your code is tested as the marking script relies on this. This does
not prohibit you from adding new tests, as you can still create additional JUnit test files. This
is to ensure the automatic marking script can test your code.
4. You have removed any debugging code that produces output, or otherwise a↵ects
the computation. This ensures the output seen by the automatic marking script does not
include spurious information.
Note: Failure to meet these requirements could result in your submission being reject by the submission system and/or zero marks being awarded.
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