Programming Tutorials

import java.lang.*;
import java.io.*;
import java.util.*;
import javax.microedition.lcdui.*;
import javax.microedition.midlet.*;
public class TimerMIDlet extends MIDlet implements CommandListener {
 // number of elements in gauge
 final private static int GAUGE_MAX = 10;
 private boolean timersRunning; // tracks state of timers
 private Display myDisplay; // handle to the display
 private Gauge gaugeOne; // "going up" gauge
 private Gauge gaugeTwo; // "going down" gauge
 private Form myScreen; // form on which to 
 // place gauges
 private Command cmdOK; // OK command
 private Command cmdExit; // EXIT command
 private Timer timer;
 private MyTimerTask timerTaskOne;
 private MyTimerTask timerTaskTwo;
 /**
 * Internal class that provides a TimerTask.
 */
 private class MyTimerTask extends TimerTask {
 private Gauge myGauge; // reference to gauge
 private boolean goUp; // if true, go up
 private int num; // number of times called
 /**
 * Public constructor: stores "direction" and a reference to
 * a gauge.
 */
 public MyTimerTask(Gauge g, boolean up) {
 myGauge = g;
 goUp = up;
 }
 /**
 * As the timer fires, this method is invoked. Set gauge
 * based on goUp
 */
 public void run() {
 num++;
 myGauge.setValue(goUp ?
 GAUGE_MAX -(num % GAUGE_MAX) :
 num % GAUGE_MAX);
 }
 }
 /**
 * Public constructor: gets handle to display,
 * creates form, gauges, and commands.
 */
 public TimerMIDlet() {
 myDisplay = Display.getDisplay(this);
 myScreen = new Form("TimerMIDlet");
 gaugeOne = new Gauge("Up Gauge",
 false,
 GAUGE_MAX,
 0);
 myScreen.append(gaugeOne);
 gaugeTwo = new Gauge("Down Gauge",
 false,
 GAUGE_MAX,
 GAUGE_MAX);
 myScreen.append(gaugeTwo);
 cmdOK = new Command("OK", Command.OK, 1);
 cmdExit = new Command("Exit", Command.EXIT, 1);
 myScreen.addCommand(cmdOK);
 myScreen.addCommand(cmdExit);
 myScreen.setCommandListener(this);
 }
 /**
 * Changes the state of timers to/from active to/from
 * not-active.
 */
 private void flipFlop() {
 if (timersRunning) {
 timerTaskOne.cancel();
 timerTaskTwo.cancel();
 timer.cancel();
 timersRunning = false;
 } else {
 timer = new Timer();
 timerTaskOne = new MyTimerTask(gaugeOne, false);
 timerTaskTwo = new MyTimerTask(gaugeTwo, true);
 timer.schedule(timerTaskOne, 0, 1000);
 timer.schedule(timerTaskTwo, 0, 1500);
 timersRunning = true;
 }
 }
 /**
 * Called by the system to start our MIDlet.
 * @exception MIDletStateChangeException
 */
 protected void startApp() throws MIDletStateChangeException {
 myDisplay.setCurrent(myScreen);
 flipFlop();
 }
 /**
 * Called by the system to pause our MIDlet.
 * No actions required by our MIDLet.
 */
 protected void pauseApp() {}
 /**
 * Called by the system to end our MIDlet.
 * No actions required by our MIDLet.
 */
 protected void destroyApp(boolean unconditional) {}
 /***
 * Respond to command selections. Process two commands:
 * 
 * OK: flip flop the timers to/from active
 * EXIT: exit this MIDlet
 * 
 */
 public void commandAction(Command c, Displayable d) {
 if (c == cmdOK) {
 flipFlop();
 } else if (c == cmdExit) {
 destroyApp(false);
 notifyDestroyed();
 }
 }
}