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Lab 10 Requirements
Create a new Eclipse workspace named "Lab10_1234567890" on the desktop of your computer (replace
1234567890 with your student ID number). For each question below, create a new project in that workspace. Call
each project by its question number: "Question1", "Question2", etc. If you do not remember how to create a
workspace or projects, read the "Introduction to Eclipse" document which is on iSpace. Answer all the questions below.
At the end of the lab, create a ZIP archive of the whole workspace folder. The resulting ZIP file must be called
"Lab10_1234567890.zip" (replace 1234567890 with your student ID number). Upload the ZIP file on iSpace.
Question 1
Create a MyFrame class that extends JFrame. In the constructor of MyFrame, add all the necessary code to create a
window of size 400 x 300 (check your lecture notes if you forgot how to do this). Then in the main method of the
Start class, create an anonymous class that implements the Runnable interface with a run method that creates a
MyFrame object, and use the javax.swing.SwingUtilities.invokeLater method to run that code on the
event dispatch thread.
Check that your program works correctly.
In the constructor of the MyFrame class, comment out the call to the setTitle method. Run the program. What
happens? Then undo the commenting out.
Comment out the call to the setSize method. Run the program. What happens? Then undo the commenting out.
Comment out the call to the setDefaultCloseOperation method. Run the program and close the window. Is the
program still running or not? (Use Eclipe’s Window → Show View → Console menu to check whether the program is
running or not: the program is running if the red square button is visible in the console.) Then undo the commenting out.
Comment out the call to the setVisible method. Run the program. What happens? Then undo the commenting out.
In a line before the call to the setVisible method, add a call to the setLocationRelativeTo method of the
frame and give it an argument of null. Run the program. What happens?
In the run method of the anonymous class inside the Start class, add a second MyFrame object. Run the program.
What happens? (Use the mouse to move the frame to check what happens!) What happens when you close one of the
two frames? Then undo the change in the run method.
Question 2
In the constructor of the MyFrame class, add two buttons, each with different text. Run the program. What happens?
Note: make sure you add the buttons before calling setVisible, otherwise the buttons might not be visible in the
frame!
Note: be careful to use the JButton class from the Swing GUI library, not the Button class from the old AWT GUI
library!
Note: clicking on the buttons does nothing. This is because no action is currently associated with the buttons. You will
learn later how to do that, for now we are only concerned with the placement of components in a frame.
In a line before the call to the setVisible method, add a flow layout manager to the frame. The flow layout manager
should left-justify rows of components, use a horizontal gap of 20 pixels between components, and a vertical gap of 40
pixels between rows of components. What happens now when you run the program?
Instead of adding to the frame two different buttons, add twice the same button object. Run the program. What
happens? Then undo the change.
Question 3
Create the following components in the constructor of MyFrame and then add all these new components to the frame
in a line before the call to the setVisible method:
JLabel l = new JLabel("Enter your name: ");
JTextField tx = new JTextField("Type Text Here");
JCheckBox cb = new JCheckBox("I agree");
JRadioButton rb = new JRadioButton("Yes");
JComboBox cb1 = new JComboBox(new String[]{"Red", "Green", "Blue"});
JComboBox cb2 = new JComboBox(new Integer[]{2, 7, -3, 24});
Add imports to your program as necessary. Then run the program to see what the different components do (click
everywhere to test things!) Also use the mouse to resize the frame and check what happens with the components.
Question 4
Change your code to use a grid layout manager instead of using a flow layout manager. Set the number of rows to 5 and
the number of columns to 5. What happens when you run the program? Does the program use the number of rows that
you specified? Does the program use the number of columns that you specified?
Use the mouse to resize the frame. Does the layout change?
Set the number of rows to zero in the grid layout manager and try again. What happens?
Change your code to use a border layout manager instead of using a grid layout manager. A border layout manager
defines 5 areas in the frame: BorderLayout.PAGE_START (top), BorderLayout.PAGE_END (bottom),
BorderLayout.LINE_START (left), BorderLayout.LINE_END (right), and BorderLayout.CENTER. Therefore, after
changing your code to use the border layout manager, you also need to modify all the method calls to the add method
of the frame to specify as second argument of the method in which of the five areas each component should be added.
If you do not specify a specific area in which to add a component then Java will add the component in the
BorderLayout.CENTER area by default.
What happens when you add more than one component to one of the five areas of the frame? What happens when one
of the five areas does not contain any component?
Question 5
So far all the different components have been simply placed in the frame without regard for aesthetics or for the logical
connection between some of the components. To fix this problem, use three JPanel to organize all the different
components into three separate groups inside the frame:
 The first panel must use a border layout manager and must contain the two buttons, with one button in each of
the two BorderLayout.LINE_START (left) and BorderLayout.LINE_END (right) zones of the panel.
 The second panel must use a flow layout manager with centered justification and must contain the JLabel and
the JTextField components.
 The third panel must use a 2 x 2 grid layout manager for the JCheckBox, JRadioButton, and the two
JComboBox components.
The frame itself must use a border layout manager and the three panels must appear in the
BorderLayout.PAGE_START (top), BorderLayout.CENTER, and BorderLayout.PAGE_END (bottom) zones of the
frame.
Use the setBackground method of each JPanel to give a different color to each panel. This will help you see where
the panels are inside the frame.
Run the program and see what happens when you resize the window to make it very small or very big.
Question 6
Create a MyPanel class that extends JPanel. Override the protected void paintComponent(Graphics g)
method inherited from JPanel, and, inside your new paintComponent method, use the drawString method of
the Graphics object g to draw the string "hello" at coordinates (20, 80). Do not forget to call the
paintComponent method of the superclass JPanel to clean the panel before drawing anything on it.
In the constructor of MyFrame, remove all the components (including all the panels) and all the layout managers
(including the layout manager of the frame itself), then add a MyPanel object to the frame in a line before the call to
the setVisible method.
Run the program and check that you correctly see the string "hello".
Note: if you do not remove the layout manager for the frame itself then the layout manager might shrink the size of the
MyPanel until it is invisible inside the frame! If you remove the layout manager for the frame itself then the frame
automatically uses its default layout manager which then expends the size of the MyPanel to be the full size of the
frame.
Note: drawing a string inside the MyPanel using the drawString method of the Graphics object g is different
from adding a JLabel component to the MyPanel. A JLabel object is a Swing component that can be added (and
later removed) to the panel (or to the frame) to display a string, while drawing a string does not involve adding any
component: when drawing a string, it is the pixels of the MyPanel itself which are directly modified.
To illustrate the fact that the paintComponent method of MyPanel is automatically called by the Java system every
time the frame content needs to be redrawn, replace the call to the drawString method in the paintComponent
method with the following method call, which draws the string "hello" at a random position inside the panel:
g.drawString("hello",
(int)Math.round(Math.random() * this.getWidth()),
(int)Math.round(Math.random() * this.getHeight()));
Run the program and slightly resize the window several times to see what happens. Also use the leftmost button in the
top right corner of the window to minimize the window, then unminimize it. Also hide the window under another
window (using for example the window of a web browser), then unhide it.
Note: how many times the paintComponent method is called and when it is called depends partly on which
operating system you are using. You might get slightly different results on different operating systems.
Question 7
Remove the drawString method call from the paintComponent method of MyPanel, then use the setColor,
drawRect, drawOval, and drawLine methods of the Graphics object g to draw a red 3D cube and a blue 3D
cylinder, like this:
Hint: remember that the point with coordinates (0, 0) is in the top left corner of the panel, and that the horizontal x
coordinate increases from left to right but that the vertical y coordinate increases from top to bottom!

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