import javax.swing.*;
import java.awt.*;  //this does NOT include java.awt.event classes
import java.awt.event.*;

public class SimpleGui
{
	//these objects are declared at the class level
	//if we declared them inside any one of the methods, the various OTHER methods
	//would not be able to see them (an issue of SCOPE)
	JFrame frame;
	JButton simpleB, exitB;

/*
- The bulk of this program's code is NOT inside main, instead, we use
main() only to instantiate the current class, and then use that instantiation
to invoke a method that DOES contain the bulk of the code
- This has to do with static/non-static issues.
*/
public static void main(String[] args)
{
  SimpleGui g = new SimpleGui();
  g.go();

} //end method main()


/*
This method contains the bulk of our program's code. See the comment preceding 'main()'
*/
public void go()
{
  frame = new JFrame("Practice GUI");
  frame.setSize(300, 300);
  frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

  simpleB = new JButton("Click Me");
  exitB = new JButton("Exit");

  //The first argument to the add() method will make more sense when we discuss layouts
  frame.add(BorderLayout.CENTER, simpleB);
  frame.add(BorderLayout.SOUTH, exitB);

  //Tell the button that this class is a 'listener'
  //This is known as "registering" as a listener
  //ANY class can be registered as a listener
  simpleB.addActionListener( new SimpleButtonHandler() );
  exitB.addActionListener( new ExitButtonHandler() );

  frame.setVisible(true);
} //end method go()

/*////////////////////////////////////////////
private class...  	-->  this class within a class is allowed in Java. It is known as an 'inner' or 'nested' class
					--> note the private visiblity; there is no need for it to be public

"...implements ActionListener":
- Implementing ActionListener interface
- Allows us to include the actionPerformed method below
*** When this class is registered with an event-generator such as a button with the command:
	button.addActionListener( new ButtonHandler() );
  the actionPerformed method will be called whenever the button is clicked

- Some of this will be explained in more detail when we cover interfaces.
*/
private class SimpleButtonHandler implements ActionListener
{
	//In order to implement the ActionListener interface, the body for the actionPerformed
	//method must be provided.
	public void actionPerformed(ActionEvent ae) {
	 	System.out.println("The Try Me! button was clicked!");
	} //end method actionPerformed()
} //end SimpleButtonHandler

private class ExitButtonHandler implements ActionListener
{
	public void actionPerformed(ActionEvent ae) {
	 System.exit(0);
	} //end method actionPerformed()
} //end ExitButtonHandler

} //end class SimpleGui