Computer Science 120
Introduction to Programming

Spring 2012, Siena College

Home     Syllabus     Teresco Schedule     Small Schedule     Examples

HandlingArrowKeys Demo

A working demo of HandlingArrowKeys will appear below. Click inside the applet to interact with it.

HandlingArrowKeys BlueJ Project

Click here to download a BlueJ project for HandlingArrowKeys.

HandlingArrowKeys Source Code

The Java source code for HandlingArrowKeys is below. Click on a file name to download it.

HandlingArrowKeys.java

import objectdraw.*;
import java.awt.event.*;

/*
 * Example HandlingArrowKeys.  Example to show how to set up to handle
 * arrow key press/release events.  Note that similar techniques can be
 * used to check other keys.
 *
 * Jim Teresco, Siena College, CSIS 120, Spring 2012
 *
 * $Id: HandlingArrowKeys.java 1853 2012-04-21 00:02:47Z terescoj $
 */

public class HandlingArrowKeys extends WindowController implements KeyListener {

    // text objects to help demonstrate which arrow key
    // is currently and was most recently pressed
    private Text currentPress;
    private Text mostRecentPress;
    
    // is a key currently down?
    private boolean keyDown;
    
    public void begin() {
    
        currentPress = new Text("No arrow keys pressed yet", 10, 100, canvas);
        mostRecentPress = new Text("No arrow keys pressed yet", 10, 200, canvas);
        keyDown = false;

        // Get ready to handle the arrow keys
        requestFocus();
        addKeyListener(this);
        canvas.addKeyListener(this);
    }
    
    // Required by KeyListener interface, but not used here.
    public void keyTyped(KeyEvent e) { }
    
    // Remember that the key is no longer down.
    public void keyReleased(KeyEvent e) {
        
        keyDown = false;
        currentPress.setText("No arrow keys currently pressed.");
    }
    
    /**
     * Handle the arrow key press.
     *
     * @param e the KeyEvent to determine direction
     */
    public void keyPressed(KeyEvent e) {
        if (!keyDown) {
            if (e.getKeyCode() == KeyEvent.VK_UP) {
                currentPress.setText("Up arrow key currently pressed.");
                mostRecentPress.setText("Up arrow key most recently pressed.");
            } else if (e.getKeyCode() == KeyEvent.VK_DOWN) {
                currentPress.setText("Down arrow key currently pressed.");
                mostRecentPress.setText("Down arrow key most recently pressed.");
            } else if (e.getKeyCode() == KeyEvent.VK_LEFT ) {
                currentPress.setText("Left arrow key currently pressed.");
                mostRecentPress.setText("Left arrow key most recently pressed.");
            } else if (e.getKeyCode() == KeyEvent.VK_RIGHT ) {
                currentPress.setText("Right arrow key currently pressed.");
                mostRecentPress.setText("Right arrow key most recently pressed.");
            }
        }
      
        keyDown = true;  
    }

}