基于MIDP1.0实现组合按键

我们知道有些手机是不支持重复按键功能，为了模拟重复按键的功能，我们不得不使用一个线程来进行处理。对于重复按键网上已经有一些文章进行了探讨，其实利 用线程我们还可以实现组合按键的功能。当然，在手机这种设备上，利用组合按键进行游戏，有一定的限制，因为手机各个按键排列比较紧凑，同时按下两个甚至三 个按键在操作上会有局限性。但这也是仁者见仁、智者见智的问题，如果你想提高游戏的可玩性和娱乐性，组合按键仍是必不可少的条件。

我定义 了一个进行按键监听的类，这个类实现了Runnable接口。在这个类里关键的一个数据结构就是一个字节型的数组，它是用来存储当前所有被按下的键。我这 里把数组的长度设定为2，主要是从应用的角度来考虑的，因为毕竟在当前手机设备上同时按三个键进行游戏的不多。下面就是实现组合按键的核心代码。

按键事件类：

import javax.microedition.lcdui.*;



public class NewEvent implements Runnable{



        KeyEventCanvas c=null;



        /*

         * 用来判断是否有键被按下

         */

        protected boolean switchPoint;



        /*

         * 这个数组用来存储所有同时被按键的键码

         */

        protected byte[] keyCode;



        /*

         * 访问数组的索引

         */

        byte index;





        public NewEvent(KeyEventCanvas c){

                this.c=c;

                keyCode=new byte[2];

        }



        /*

         * 这个方法把被按键的键码存储到数组中

         */

        public synchronized void startAction(int keyCode){

                this.keyCode[index]=(byte)keyCode;

                index=(byte)((index+1)%this.keyCode.length);

        }



        /*

         * 当某个键被释放时，这个方法把该键存储在数组中的键码置为0

         */

        public synchronized void stopAction(int keyCode){

                for(int i=0;i<=this.keyCode.length-1;i++){

                        if(this.keyCode[i]==(byte)keyCode){

                                this.keyCode[i]=0;

                                break;

                        }

                }

        }

        

        /*

         * 这个方法用来判断是否有被按下的键，返回true表示有键按下，返回false表示没有键被按下

         */

        public synchronized boolean getSwitchPoint(){

                this.switchPoint=false;

                for(int i=0;i<=this.keyCode.length-1;i++){

                        if(this.keyCode[i]!=0){

                                this.switchPoint=true;

                                break;

                        }

                }

                return this.switchPoint;

        }



        /*

         * 返回字节数组

         */

        public synchronized byte[] getKeyCode(){

                return this.keyCode;

        }

        

        public void run(){

                byte[] tmp=this.getKeyCode();

                while(true){

                        while(this.getSwitchPoint()){

                                /*

                                 * 通过这个循环遍历数组，遇到被按下的键就进行处理

                                 */

                                for(int i=0;i<=tmp.length-1;i++){



                                        if(tmp[i]!=0){

                                                switch(c.getGameAction(tmp[i])){

                                                

                                                case Canvas.UP:

                                                        c.y--;//y是在Canvas中定义的一个属性，表示y轴坐标

                                                        break;

                                                case Canvas.DOWN:

                                                        c.y++;

                                                        break;

                                                case Canvas.LEFT:

                                                        c.x--;//x是在Canvas中定义的一个属性，表示x轴坐标

                                                        break;

                                                case Canvas.RIGHT:

                                                        c.x++;

                                                        break;

                                                }

                                        }

                                }

                                c.repaint();

                                try{

                                        Thread.sleep(10);

                                }catch(InterruptedException e){

                                        

                                }

                        }

                }

        }

}

Canvas类：

import javax.microedition.lcdui.*;



public class KeyEventCanvas extends Canvas{



        int x,y;

        NewEvent mke=null;

        

        public KeyEventCanvas(){

                mke=new NewEvent(this);

                new Thread(mke).start();

        }



        public void keyPressed(int keyCode){

                mke.startAction(keyCode);

        }

        

        public void keyReleased(int keyCode){

                mke.stopAction(keyCode);

        }



        public void paint(Graphics g){

                g.setColor(0xffffff);

                g.fillRect(0,0,this.getWidth(),this.getHeight());

                g.setColor(0xff0000);

                g.fillRect(x,y,8,8);

        }

}