CST8221 – JAP Lab 3 – Event Handling – Mouse Events and Cursors


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The purpose of the lab is to give you a hand-on experience of how to track the mouse actions
and how to change the mouse cursor.
The Nature of Things
Event handling is one of the fundamental tasks in programming with GUI. To implement useful
user interfaces, you must master the way in which Java handles events generated by different
input devices such as mouse and keyboard.
Any operating environment that supports GUIs monitors events such as mouse movements
and clicks or keystrokes. The operating environment reports these events to the running
applications. Each application then decides what, if anything, to do in response to these events.
In Java GUI API (both Swing and JavaFX), you completely control how events are transmitted
from even sources (such as buttons) to event listeners. You can designate any object to be an
event listener. A listener object is an instance of a class that implements a special interface called
a listener interface. The information about the event is encapsulated in an event object (such as
MouseEvent) which is sent to an appropriate listener method. Which listener method is called on
the listener object depends on the nature of the event generated by the event source. For
example, whenever a user clicks on a button, the JButton (or Button) object creates an
ActionEvent and a MouseEvent objects (both in Swing and JavaFX) and calls the appropriate
listener method (actionPerformed() (or handle(ActionEvent)- see Eample 4 in Lab 1) in the case
of ActionEvent, or one of the mouse listener methods). In order to transmit the event form the
event source to the event listener object, the event listener object must be registered with the
event source. Event sources have specialized registering methods with convenient names. For
example, JButton has a method called addActionListener() which is used to register action
listeners. It has similar methods for registering different mouse listeners (addMouseListener() and
so on).
When a mouse cursor hovers over a GUI it is customary to change the cursor shape to
indicate to the user what action they can perform. Usually the operating environment provides a
set of standard shapes, but the user can create shapes of their own.
Useful links: http://download.oracle.com/javase/tutorial/uiswing/events/intro.html
Download the CST8221_Lab3_code.zip file from Blackboard. Extract the contents. Two sets
of code files are provided for you – one for Swing GUI and one for JavaFX GUI. Swing GUI:
MouseTest.jar, MouseTest.java, CursorTest.jar, CursorTest.java, and happy.gif. JavaFX
GUI: CursorDemoFX.java , MouseDemoFX.java and happy.gif. The Swing classes
MouseTest.java and CursorTest.java are incomplete. You are to complete them during this lab
Exercise 1 – Handling the Mouse Events
You have to modify MouseTest.java so it handles all possible mouse events defined by the three
mouse listeners the class implements. To do so, follow the steps:
0. Run the Mouse Test reference implementation. To do so, open a command window and
type at the command prompt java -jar MouseTest.jar and press Enter. Play with
the application to see what you are expected to do. Your application should mimic the
reference implementation.
CST8221 – JAP, Lab 3, MMXVII Page 2 of 3
1. Implement all listener methods with NOP operation (empty braces { }). You will find the
names of the methods in the documentation of the corresponding interfaces which are
part of java.awt.event package.
2. Register the three listeners with the button object.
3. Compile and run the application. When you click on the button the following message must
be displayed in the Console window: Method actionPerformed called
4. Working method by method using System.out.println() print an appropriate message in
each of the methods. For example, Method mouseClicked called and so on. Every
time you implement a method, run the application and try to find what mouse action will
invoke the method.
5. Once you finish all the methods, modify the mouseClicked() so that it reports the number
of button clicks and the mouse button (left, middle, right) that has been clicked. Look at
the MouseEvent class to find an appropriate method. Next, add more code that will report
which mouse button is clicked. Use the getButton() method and compare the return value
with one of the three constants (BUTTON1, BUTTON2, BUTTON3) defined in the
MouseEvent class. Print the type of the button.
6. Modify the mouseMoved() so that it reports the coordinates of the mouse cursor when it
enters the button. You will find two suitable methods inside the MouseEvent class. Record
on paper the coordinates of the four corners of the button and the center of the image.
You have to show the numbers to me during the demonstration.
7. Finally, modify the mouseWheelMoved() so that it displays the notches and the direction
the wheel moved. Use the getWheelRotation() of the MouseWheelEvent class to get the
8. Demonstrate your work if you want to earn some marks.
Exercise 2 – Changing the Mouse Cursor Shape
You have to modify CursorTest.java so it handles displays all standard cursor shape provider
by the Cursor class in java.awt package. To do so, follow the steps:
0. Run the Cursor Test reference implementation. To do so, open a command window and
type at the command prompt java -jar CursorTest.jar and press Enter. Play with
the application to see what you are expected to do. Your application should mimic the
reference implementation.
1. Initialize the cursor array with the following Cursor class constants:
CST8221 – JAP, Lab 3, MMXVII Page 3 of 3
2. Add some code to the actionPerformed() so that it changes the cursor shape every the
time the button is clicked. The logic of the code is very similar to the implementation of the
same method in SimpleSwingGUIe3.java provided for you in Lab 1. Here you have to use
the cursors array instead of the “look and feel” array.
3. Demonstrate your work if you want to earn some marks
Compile and run the JavaFX examples. Examine the code. See the differences between Swing
and JavaFX in the implementation of the same tasks.
Before the lab
Enjoy Java.
During the lab
Ask questions and modify the programs.
Before leaving the lab
Demonstrate your work.
Sign the attendance sheet.
After the lab
Remember what you have learned. You will need it later.
No submission is required for this lab but you have to demonstrate your work
before the end of the lab period if you want to earn some marks.
Marks: 2% (1%+1%) of your course mark
The lab exercises will be marked according to the following marking method:
public int markLab3(boolean demonstration,
boolean workingProgram){
int mark = 0;
if(demonstration & workingProgram) ++mark;++mark;
return mark;
“The best laid schemes o’ mice an’ men / Gang aft agley(Often go wrong) ” Robert Burns