CS351 Spring 2004 Lab 10

Swing: Making Stuff Do Stuff


JComponent Manipulation

JTextField:
From a data point of view, a JTextField is basically a String. It has methods .getText() and .setText(String) which let you pull the String out and modify its contents.
JTextArea:
In addition to the basic text methods of JTextField, JTextArea provides the method .append(String) which is hand to add more data to the JTextArea
JLabel:
The text half of JLabel can be access the same way as a JTextField. For the icon has, there are, of course, methods .getIcon and .setIcon.
JRadioButton:
The JRadioButton itself doesn't have any state, it's contained in the ButtonGroup which you put the buttons into. This class provides methods .setSelected and .getSelection which let you set/get which button in the group is selected. Note these methods use the class ButtonModel, which represents the actual state of a button. So get check if the JRadioButton q is currently selected in the ButtonGroup bg: 
	ButtonModel selected = bg.getSelection();
	if(selected.equals(q.getModel())
	{
		//q is the selected button
	}

ActionListeners

The basic event model of Swing is that when an event happens (such as a user clicking on a button) an ActionEvent is sent to the button in question. In order to be aware of this event (sometimes termed catching the event), we have to an ActionListener class attached to the button.

ActionListener is a simple Interface: 
	public interface ActionListener extends EventListener
	{
		void actionPerformed(ActionEvent e);
	}
So basic ActionListener would be: 
	public class DebugActionListener implements ActionListener
	{
		void actionPerformed(ActionEvent e)
		{
			System.out.println("Event Performed:\n" + e.toString());
		}

	}
DebugActionListener.java

Once we have an ActionListener, we then just just attached it to one or more JComponents: 

	JButton button = new JButton("Click Me1");
	button.addActionListener(new DebugActionListener());
Source code

Notice there is a lot of information in an ActionEvent, a handy method is .getSource() which gives the Object which was the source of the Event.

The Observer Pattern

Java provides an implementation of this pattern with Observer and Observable

Example:

Jarfile of Example
ObservableInteger.java
JIntegerLabel.java
OTestGUI.java

Notice how this model not only allows the GUI to update itself whenever the data changes, but it doesn't require an ActionListeners

Quick and Dirty Dialog Boxes

To pop up a dialog box with an acknowledge button: 
JOptionPane.showMessageDialog(parent, String);

Where parent is the JFrame that is popping up the dialog and String is the message you want to display.

Exercise

Add an ActionListener to the GUI you wrote last week so that when a user clicks on the Compute button, it performs the calculation and displays the result. Emulate the behavior in SimpleApplication5.class basically.

Feel free to SimpleApplication3.java if you had difficult getting a reasonable window layout.

In addition, modify the code provided for the Observer Pattern so that in addition to displaying the current matrix values, it displays the sum of the matrix.

For Monday, Due Wednesday 5PM
For Wednesday, Due Friday 5PM