Java Reference
In-Depth Information
Alternatively, you could use new GridLayout(1, 0) . It is also possible to do
something similar with a BorderLayout manager or a FlowLayout manager, but
a GridLayout manager will work nicer here.
18. The argument should be new GridLayout(0,1) . So, the entire method invocation is
setLayout( new GridLayout(0, 1));
Alternatively, you could use new GridLayout(3, 1) , if you know there will be at
most three components added, but if more than three components are added, then
a second column will be added. It is also possible to do something similar with a
BorderLayout manager, but a GridLayout manager will work nicer here.
19. java.awt
20. An object of the class JPanel is both a container class and a component class.
21. To make it look as though you have an empty grid element, add an empty panel
to the grid element.
22. import javax.swing.JPanel;
import java.awt.Color;
public class PinkJPanel extends JPanel
{
public PinkJPanel()
{
setBackground(Color.PINK);
}
}
extra code
on website
The class PinkJPanel is on the website that accompanies this text.
23. It will not compile, but will give a compiler error message saying that
actionPerformed is not defined (because it claims to implement the
ActionListener interface).
24. It will not compile, but will give compiler error messages saying that, in effect, the
invocations of addActionListener such as
redButton.addActionListener( this );
have arguments of an incorrect type.
25. Clicking a JMenuItem fires an action event (that is, an object of the class
ActionEvent ). This is the same as with a JButton .
26. JButton b = new JButton("Hello");
b.setActionCommand("Bye");
27. JMenuItem m = new JMenuItem("Hello");
m.setActionCommand("Bye");
28. To change the action command for a JMenuItem , use the method setAction
Command , just as you would for a JButton .
29. Yes, it is legal.
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