Lecture 17

• JFrame is the class that handles windows in Java
• import 'javax.Swing.JFrame;
• creating a window is equivalent to creating an object of type JFrame
• JFrame has an extensive public interface

public void setSize(int width, int height)
public void setTitle(String title)
public JFrame(String title)
public void setVisible(boolean v)
public void add(Component x)

• notice that the program didn't end when the window closes by default
• default window close behaviour is to hide the window (but not exit the program)
• we have to handle the event where the user clicks close

public void setDefaultCloseOperation(int x)

• we can use
  

JFrame.EXIT_ON_CLOSE
JFrame.HIDE_ON_CLOSE
JFrame.DO_NOTHING_ON_CLOSE

• These are given integer values (in order) 3,0,1
• do not use these values as Java might change those numbers in an update

Action Listeners and Action Events

• each component must register the listener that handles its events
• Java interface ActionListener
• event type is a class called ActionEvent
• a listener you define must implement the interface ActionListener

public void actionPerform(ActionEvent e)
{

}

1. Create the component
1. JButton myButton = new JButton(" ");
2. Write a listener class
1. public void myListener implements ActionListener
   {
   public void actionPerformed(ActionEvent c)
   {
   }
   }
3. Create an instance of the listener
1. MyListener m = new myListener();
4. register the listener with the component
1. myButton.addActionListener(m)
5. add the component to the JFrame
1. myWindow.add(MyButton);