Chapter 11 Java AWT Part I: Mouse Events (Optional)

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Chapter 11Java AWT Part I Mouse
Events(Optional)

• Lecture Slides to Accompany
• An Introduction to Computer Science Using Java
  (2nd Edition)
• by
• S.N. Kamin, D. Mickunas, E. Reingold

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Chapter Preview

• In this chapter we will
• introduce event driven programming
• show how a program can respond to mouse events
  (e.g. clicks and mouse movements)
• demonstrate how to implement a listener interface
• show how mouse events can be used to build highly
  interactive programs

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Abstract Windowing Toolkit (AWT)

• Part of the Java distribution, but not part of
  the Java language itself
• AWT is library of classes and methods used by
  Java programmers that supported are by the basic
  Java runtime libraries
• Even though this chapter is labeled optional, it
  is not possible to be a complete Java programmer
  without understanding the AWT

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Java Events

• Events are occurrences outside of the program to
  which the program must respond (e.g. user key
  press)
• Event managers are methods that first catch the
  event
• Listener classes send messages to an event
  manager requesting to be notified when a
  particular message occurs
• Event managers send messages to listeners
  notifying them when a particular event occurs

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Creating Mouse Click Listeners

1. Import the java.awt.event package
2. In the class header, add the words implements
   MouseListener
3. Send the addMouseListerner(this) message to the
   mouse event manager (should be done in the
   constructor method)
4. Define methods mouseClicked, mousePressed,
   mouseReleased, mouseEntered, mouseExited

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Mouse Click Listener Template

• import java.awt.event.
• public class classname implements MouseListener
• // include manager.addMouseListener(this)
• // in some initialization method
• public void mouseClicked (MouseEvent e)
• public void mousePressed (MouseEvent e)
• public void mouseReleased (MouseEvent e)
• public void mouseEntereded (MouseEvent e)
  
• public void mouseExited (MouseEvent e)

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Finding Mouse Location

• Inside mouseClicked the argument e of type
  MouseEvent can be used to find the location of
  the mouse cursor
• The call e.getX( ) returns the value of the
  horizontal coordinate of the mouse cursor
  position
• The call e.getY( ) returns the value of the
  vertical coordinate of the mouse cursor position

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Creating Mouse Motion Listeners

1. Import the java.awt.event package
2. In the class header, add the words implements
   MouseMotionListener
3. Send the message addMouseMotionListerner(this)
   to the mouse event manager (should be done in
   the constructor method)
4. Define methods mouseMoved and mouseDragged

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Mouse Motion Listener Template

• import java.awt.event.
• public class classname implements
  MouseMotionListener
• // include manager.addMouseListener(this)
• // in some initialization method
• public void mouseMoved (MouseEvent e)
• public void mouseDragged (MouseEvent e)

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Mouse Motion

• mouseMoved will be called each time the mouse
  makes a significantly large movement
• mouseDragged will be called instead if thre mouse
  button is pressed and the mouse makes a
  significantly large movement

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Listening to All Mouse Events

• Two catch all seven mouse events use the
  following class header
• public class classname implements MouseListener,
  MouseMotionListener
• You then need to define all seven mouse methods
  mouseMoved, mouseDragged, mouseClicked,
  mousePressed, mouseReleased, mouseEntered,
  mouseExited