Java Tutorial/J2ME/Key Event

Canvas key events

import javax.microedition.lcdui.Canvas;
import javax.microedition.lcdui.rumand;
import javax.microedition.lcdui.rumandListener;
import javax.microedition.lcdui.Display;
import javax.microedition.lcdui.Displayable;
import javax.microedition.lcdui.Graphics;
import javax.microedition.midlet.MIDlet;
public class EventsMIDlet extends MIDlet 
                        implements CommandListener {
    private Display display;
    protected boolean started;
    private Command exitCommand = new Command("Exit", Command.EXIT, 0);
    
    protected void startApp() {
        if (!started) {
            display = Display.getDisplay(this);
            Canvas canvas = new EventsCanvas();            
            canvas.addCommand(exitCommand);
            canvas.setCommandListener(this);
            display.setCurrent(canvas);
            started = true;
        }
    }
    protected void pauseApp() {
    }
    protected void destroyApp(boolean unconditional) {
    }
    public void commandAction(Command c, Displayable d) {
        if (c == exitCommand) {
            notifyDestroyed();
        }
    }     
}
class EventsCanvas extends Canvas {
    
    static int[] keyCodes = {KEY_NUM0, KEY_NUM1, KEY_NUM2, KEY_NUM3, KEY_NUM4,
                             KEY_NUM5, KEY_NUM6, KEY_NUM7, KEY_NUM8, KEY_NUM9,
                             KEY_POUND, KEY_STAR};
    static String[] keyNames = {"KEY_NUM0", "KEY_NUM1", "KEY_NUM2", "KEY_NUM3", "KEY_NUM4",
                             "KEY_NUM5", "KEY_NUM6", "KEY_NUM7", "KEY_NUM8", "KEY_NUM9",
                             "KEY_POUND", "KEY_STAR"};
                             
    static int[] gameActions = {
                            UP, DOWN, LEFT, RIGHT, FIRE,
                            GAME_A, GAME_B, GAME_C, GAME_D};
    static String[] gameNames = {
                            "UP", "DOWN", "LEFT", "RIGHT", "FIRE",
                            "GAME_A", "GAME_B", "GAME_C", "GAME_D" };
    
    int lastKeyCode = 0;
    
    int lastX;
    
    int lastY;
    
    boolean pointer;
    protected void keyPressed(int keyCode) {
        lastKeyCode = keyCode;
        repaint();
    }
        
    protected void keyRepeated(int keyCode) {
        lastKeyCode = keyCode;
        repaint();
    }
        
    protected void keyReleased(int keyCode) {
        lastKeyCode = 0;
        repaint();
    }    
    protected void pointerPressed(int x, int y) {
        lastX = x;
        lastY = y;
        pointer = true;
        repaint();
    }
        
    protected void pointerDragged(int x, int y) {
        lastX = x;
        lastY = y;
        pointer = true;
        repaint();
    }
    
    protected void pointerReleased(int x, int y) {
        pointer = false;
        repaint();
    }
    
    protected void paint(Graphics g) {
        g.setColor(0xffffff);
        g.fillRect(0, 0, getWidth(), getHeight());
        
        g.setColor(0);
        if (lastKeyCode != 0) {
            String keyText = "keyCode " + lastKeyCode;
            String keyName = null;
            for (int i = 0; i < keyCodes.length; i++) {
                if (lastKeyCode == keyCodes[i]) {
                    keyName = keyNames[i];
                    break;
                }
            }   
            if (keyName == null) {
                for (int i = 0; i < gameActions.length; i++) {
                    if (lastKeyCode == getKeyCode(gameActions[i])) {
                        keyName = gameNames[i];
                        break;
                    }
                }
            }
            g.drawString(keyText, getWidth()/2, getHeight()/2, 
                            Graphics.BASELINE|Graphics.HCENTER);
                    
            if (keyName != null) {
                g.drawString(keyName, getWidth()/2, getHeight()/2 + g.getFont().getHeight(), 
                            Graphics.BASELINE|Graphics.HCENTER);    
            }
        } else if (pointer) {
            g.drawString("(" + lastX + ", " + lastY + ")", getWidth()/2, getHeight()/2, 
                            Graphics.BASELINE|Graphics.HCENTER);
        }
    }
}

Check the key event

import javax.microedition.lcdui.Canvas;
import javax.microedition.lcdui.rumand;
import javax.microedition.lcdui.rumandListener;
import javax.microedition.lcdui.Display;
import javax.microedition.lcdui.Displayable;
import javax.microedition.lcdui.Font;
import javax.microedition.lcdui.Graphics;
import javax.microedition.midlet.MIDlet;
public class KeyMIDlet extends MIDlet {
  public void startApp() {
    Displayable d = new KeyCanvas();
    d.addCommand(new Command("Exit", Command.EXIT, 0));
    d.setCommandListener(new CommandListener() {
      public void commandAction(Command c, Displayable s) {
        notifyDestroyed();
      }
    });
    Display.getDisplay(this).setCurrent(d);
  }
  public void pauseApp() {
  }
  public void destroyApp(boolean unconditional) {
  }
}
class KeyCanvas extends Canvas {
  private Font mFont= Font.getFont(Font.FACE_PROPORTIONAL, Font.STYLE_PLAIN, Font.SIZE_MEDIUM);
  private String mMessage = "[Press keys]";
  public void paint(Graphics g) {
    int w = getWidth();
    int h = getHeight();
    int x = w / 2;
    int y = h / 2;
    g.drawString(mMessage, x, y, Graphics.BASELINE | Graphics.HCENTER);
  }
  protected void keyPressed(int keyCode) {
    int gameAction = getGameAction(keyCode);
    switch (gameAction) {
    case UP:
      mMessage = "UP";
      break;
    case DOWN:
      mMessage = "DOWN";
      break;
    case LEFT:
      mMessage = "LEFT";
      break;
    case RIGHT:
      mMessage = "RIGHT";
      break;
    case FIRE:
      mMessage = "FIRE";
      break;
    case GAME_A:
      mMessage = "GAME_A";
      break;
    case GAME_B:
      mMessage = "GAME_B";
      break;
    case GAME_C:
      mMessage = "GAME_C";
      break;
    case GAME_D:
      mMessage = "GAME_D";
      break;
    default:
      mMessage = "";
      break;
    }
    repaint();
  }
}

Game action

import javax.microedition.lcdui.Canvas;
import javax.microedition.lcdui.rumand;
import javax.microedition.lcdui.rumandListener;
import javax.microedition.lcdui.Display;
import javax.microedition.lcdui.Displayable;
import javax.microedition.lcdui.Graphics;
import javax.microedition.midlet.MIDlet;
public class GameActionMIDlet extends MIDlet implements CommandListener {
  private Command exitCommand;
  Display display;
  Displayable d;
  public void startApp() {
    Display display = Display.getDisplay(this);
    d = new GameActionCanvas();
    exitCommand = new Command("Exit", Command.EXIT, 1);
    d.addCommand(exitCommand);
    d.setCommandListener(this);
    display.setCurrent(d);
  }
  public void pauseApp() {
  }
  public void destroyApp(boolean unconditional) {
  }
  public void commandAction(Command c, Displayable s) {
    notifyDestroyed();
  }
}
class GameActionCanvas extends Canvas {
  int width = 0;
  int height = 0;
  String aMessage = "message";
  public void paint(Graphics g) {
    width = getWidth();
    height = getHeight();
    g.setGrayScale(255);
    g.fillRect(0, 0, width - 1, height - 1);
    g.setGrayScale(0);
    g.drawRect(0, 0, width - 1, height - 1);
    g.drawString(aMessage, 10, 10, Graphics.TOP | Graphics.LEFT);
  }
  protected void keyPressed(int keyCode) {
    int gameAction = getGameAction(keyCode);
    switch (gameAction) {
    case UP:
      aMessage = "Up";
      break;
    case DOWN:
      aMessage = "Down";
      break;
    case LEFT:
      aMessage = "Left";
      break;
    case RIGHT:
      aMessage = "Right";
      break;
    case FIRE:
      aMessage = "Send";
      break;
    case GAME_A:
      aMessage = "GAME_A";
      break;
    case GAME_B:
      aMessage = "GAME_B";
      break;
    case GAME_C:
      aMessage = "GAME_C";
      break;
    case GAME_D:
      aMessage = "GAME_D";
      break;
    default:
      aMessage = "";
      break;
    }
    repaint();
  }
}

Get key code

import javax.microedition.lcdui.Canvas;
import javax.microedition.lcdui.rumand;
import javax.microedition.lcdui.rumandListener;
import javax.microedition.lcdui.Display;
import javax.microedition.lcdui.Displayable;
import javax.microedition.lcdui.Graphics;
import javax.microedition.midlet.MIDlet;
public class KeyEventsMIDlet extends MIDlet implements CommandListener {
  private Command exitCommand;
  Display display;
  Displayable d;
  public void startApp() {
    Display display = Display.getDisplay(this);
    d = new KeyEventsCanvas();
    exitCommand = new Command("Exit", Command.EXIT, 1);
    d.addCommand(exitCommand);
    d.setCommandListener(this);
    display.setCurrent(d);
  }
  public void pauseApp() {
  }
  public void destroyApp(boolean unconditional) {
  }
  public void commandAction(Command c, Displayable s) {
    notifyDestroyed();
  }
}
class KeyEventsCanvas extends Canvas {
  int width = 0;
  int height = 0;
  String aMessage = "message";
  public void paint(Graphics g) {
    width = getWidth();
    height = getHeight();
    g.setGrayScale(255);
    g.fillRect(0, 0, width - 1, height - 1);
    g.setGrayScale(0);
    g.drawRect(0, 0, width - 1, height - 1);
    g.drawString(aMessage, 10, 10, Graphics.TOP | Graphics.LEFT);
  }
  protected void keyPressed(int keyCode) {
    aMessage = getKeyName(keyCode);
    if (aMessage.equals("2"))
      aMessage = "2";
    repaint();
  }
}