code 105.txt

/*
	Having a form with controls is one thing 
	- Now we need to consider how to react to a user actually interacting 
	- with the form - respond to EVENTS ...
	- We will use something called a listener ... Java uses this term and other languages have other words 
	- for the same thing ... 

	- another phrase that also is important is event-driven programming - because our program 
	- must react to the events that are coded for using the listeners 

	- Also many 'things' happen when you as a user are intereacting with a form 
	- Only if you the developer have "registered" listeners to listen for an event and you have code 
	- associated to that event - then will only something happen ... 

	- Saying many 'things' is referencing the many listeners we have available to the controls 
	
*/

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;

public class JHelloFrame extends JFrame implements ActionListener {

	JLabel lblQuestion = new JLabel("What is your name?");
	Font bigFont = new Font("Arial", Font.BOLD, 16);

	JTextField txtAnswer = new JTextField(10);
	
	JButton btnSubmit = new JButton("Press me");
	
	JLabel lblGreeting = new JLabel("");
	

	public JHelloFrame() {
		super("Greeting Frame");
		setSize(250, 250);
		
		setLayout(new FlowLayout());

		lblQuestion.setFont(bigFont);
		lblGreeting.setFont(bigFont);
		
		add(lbllblQuestion);
		add(txtAnswer);
		add(btnSubmit);
		add(lblGreeting);

		setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

		// TheSourceOfTheEvent.addListenerMethod(TheClassThatShouldRespond); //format of the line below

		btnSubmit.addActionListener(this);
		// txtAnswer.addActionListener(this);
	}

	@Override
	public void actionPerformed(ActionEvent e) {
		String strName = txtAnswer.getText();
		String strGreet = "Hello, " + strName;
		lblGreeting.setText(strGreet);
	}

	// Page 760 speaks of the idea that is 2 controls are attached to the same listener and in-turn
	// is going to access the same code - how would you diffrentiate between the 2 
	// the following code would help 
	
	/*
	@Override
	void actionPerformed(ActionEvent e) {
		Object source = e.getSource(); // get the control that activated this code

		if(source instanceof JTextField) {
			// execute these statements when any JTextField
			// generates the event
			// but not when a JButton or other Component does
		}
	}
	*/

	// See the table on Page 765 for some of the other common listeners we might make use of 
	// See the table on Page 766 for the listeners associated to their controls 
}

//**************************************************************************************************************

public class GreetingProgram {

	public static void main(String[] args) {
		JHelloFrame frmHello = new JHelloFrame();	
		frmHello.setVisible(true);
	}
}