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在java.util包中有一個(gè)TimerTask類，你可以擴(kuò)展這個(gè)類并且實(shí)現(xiàn)他的run()方法，在run()方法中編寫我們的邏輯代碼。如果我們想制作一個(gè)游戲時(shí)鐘，那么非常簡(jiǎn)單我們編寫一個(gè)GameClock類擴(kuò)展TimerTask，GameClock需要維持一個(gè)實(shí)例變量timeLeft，這樣我們就可以記錄游戲剩余的時(shí)間了，在每次run()運(yùn)行的時(shí)候把timeLeft減1就可以了。有時(shí)候我們需要始終暫停以及重新啟動(dòng)，這并不復(fù)雜，在GameClock中添加一個(gè)boolean類型的標(biāo)記就可以了。下面給出GameClock的代碼：
/*
* GameClock.java
*
* Created on 2005年7月18日, 上午11:00
*
* To change this template, choose Tools | Options and locate the template under
* the Source Creation and Management node. Right-click the template and choose
* Open. You can then make changes to the template in the Source Editor.
*/ package com.j2medev.gameclock;
import java.util.TimerTask;
/**
*
* @author Administrator
*/
public class GameClock extends TimerTask{
private int timeLeft = 60;//時(shí)鐘的默認(rèn)時(shí)間
private boolean pause = false;
/** Creates a new instance of GameClock */
public GameClock() {
}
public GameClock(int value){
timeLeft = value;
}
public void run(){
if(!pause){
timeLeft--;
}
}
public void pause(){
pause = true;
}
public void resume(){
pause = false;
}
public int getTimeLeft(){
return timeLeft;
}
public void setTimeLeft(int _value){
this.timeLeft = _value;
}
} 當(dāng)我們使用這個(gè)時(shí)鐘的時(shí)候，只需要把它的一個(gè)實(shí)例作為參數(shù)傳給Timer的schedule()方法即可。例如
clock = new GameClock(30);
timer.schedule(clock,0,1000); 接下來我們編寫一個(gè)簡(jiǎn)單的游戲界面測(cè)試一下時(shí)鐘。我們?cè)诔绦騿?dòng)的時(shí)候開始計(jì)時(shí)，每隔一秒鐘timeLeft會(huì)減少1，并且在手機(jī)屏幕上顯示當(dāng)前剩余的時(shí)間。如果timeLeft為0的時(shí)候代表游戲已經(jīng)結(jié)束了。因此我們需要這樣判斷游戲的狀態(tài)。
public void verifyGameState(){
timeLeft = clock.getTimeLeft();
if(timeLeft == 0){
going = false;
}
}
為了測(cè)試時(shí)鐘的暫停功能，我們接收用戶的按鍵行為，如果左鍵被按下，那么調(diào)用clock的pause()方法，如果右鍵被按下則調(diào)用clock的resume()方法。
public void userInput(){
int keyStates = this.getKeyStates();
if((keyStates & GameCanvas.LEFT_PRESSED) != 0){
clock.pause();
}else if((keyStates & GameCanvas.RIGHT_PRESSED) != 0){
clock.resume();
}
} 下面給出MIDlet和Canvas的代碼：
/*
* ClockCanvas.java
*
* Created on 2005年7月18日, 上午11:04
*
* To change this template, choose Tools | Options and locate the template under
* the Source Creation and Management node. Right-click the template and choose
* Open. You can then make changes to the template in the Source Editor.
*/ package com.j2medev.gameclock;
import java.util.Timer;
import javax.microedition.lcdui.Command;
import javax.microedition.lcdui.Graphics;
import javax.microedition.lcdui.game.*; /**
*
* @author Administrator
*/
public class ClockCanvas extends GameCanvas implements Runnable {
private Timer timer = new Timer();
private GameClock clock = null;
private boolean going = true;
int timeLeft = 0;
/** Creates a new instance of ClockCanvas */
public ClockCanvas() {
super(false);
}
public void run(){
clock = new GameClock(30);
timer.schedule(clock,0,1000);
while(going){
verifyGameState();
userInput();
repaint();
try{
Thread.sleep(100);
}catch(Exception e){
e.printStackTrace();
}
}
}
public void userInput(){
int keyStates = this.getKeyStates();
if((keyStates & GameCanvas.LEFT_PRESSED) != 0){
clock.pause();
}else if((keyStates & GameCanvas.RIGHT_PRESSED) != 0){
clock.resume();
}
}
public void paint(Graphics g){
int color = g.getColor();
g.setColor(0xffffff);
g.fillRect(0,0, this.getWidth(), this.getHeight());
g.setColor(color);
if(timeLeft == 0){
g.drawString("游戲結(jié)束", this.getWidth()/2, this.getHeight()/4, Graphics.HCENTER|Graphics.BOTTOM);
}else{
g.drawString("游戲剩余時(shí)間："+timeLeft, this.getWidth()/2, this.getHeight()/4, Graphics.HCENTER|Graphics.BOTTOM);
}
}
public void verifyGameState(){
timeLeft = clock.getTimeLeft();
if(timeLeft == 0){
going = false;
}
}
public void start(){
Thread t = new Thread(this);
t.start();
}
public void stop(){
going = false;
}
}
/*
* TestMidlet.java
*
* Created on 2005年7月18日, 上午11:00
*/ package com.j2medev.gameclock; import javax.microedition.midlet.*;
import javax.microedition.lcdui.*; /**
*
* @author Administrator
* @version
*/
public class TestMidlet extends MIDlet {
private Display display = null;
public void startApp() {
display = Display.getDisplay(this);
ClockCanvas canvas = new ClockCanvas();
canvas.start();
display.setCurrent(canvas);
}
public void pauseApp() {
}
public void destroyApp(boolean unconditional) {
}
}
程序運(yùn)行的截圖如下：
 總結(jié)：本文實(shí)現(xiàn)了一個(gè)游戲開發(fā)中可能用到的時(shí)鐘程序，代碼并不復(fù)雜。希望能對(duì)大家有所幫助。
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