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

• Import the java.awt.event package
• In the class header, add the words implements
  MouseListener
• Send the addMouseListerner(this) message to the
  mouse event manager (should be done in the
  constructor method)
• 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

• Import the java.awt.event package
• In the class header, add the words implements
  MouseMotionListener
• Send the message addMouseMotionListerner(this)
  to the mouse event manager (should be done in
  the constructor method)
• 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