j2me学习笔记【12】——游戏操作Canvas类的up、down、left、right、fire属性使用实例

一个游戏操作会根据游戏者按下的按键调用keyPresed()、keyReleased()、keyRepeated()方法。可以调用getGameAction()方法探测发生了哪些游戏操作。getGameAction()方法需要一个参数，即游戏者选择的按键的按键编码，这个编码会作为参数传给keyPressed()、keyReleased()和keyRepeated()方法。

    使用两种方法可以探测游戏者所选择的游戏操作按键。

    第一种：调用getKeyCode()方法比较按键编码值。

if(getKeyCode(FIRE)==keycode){ //fire}    

    第二种：调用getKeyName()方法，获得和输入的按键编码相关联的按键的名称。if(getKeyName(getKeyCode(FIRE).equeals(getKeyName(keycode)))){ //fire}

 

package mtk;import javax.microedition.lcdui.Canvas;import javax.microedition.lcdui.Command;import javax.microedition.lcdui.CommandListener;import javax.microedition.lcdui.Display;import javax.microedition.lcdui.Displayable;import javax.microedition.lcdui.Graphics;import javax.microedition.midlet.MIDlet;import javax.microedition.midlet.MIDletStateChangeException;public class GameActionExample extends MIDlet {private Display display;private MyCan canvas;public GameActionExample() {display=Display.getDisplay(this);canvas=new MyCan(this);}protected void destroyApp(boolean arg0){}protected void pauseApp() {}public void exitMidlet(){destroyApp(true);notifyDestroyed();}protected void startApp() throws MIDletStateChangeException {display.setCurrent(canvas);}}class MyCan extends Canvas implements CommandListener{private Command CMD_EXIT=new Command("退出",Command.EXIT,1);private String message;private GameActionExample gameActionExample;private int x,y;public MyCan(GameActionExample gameActionExample){x=5;y=5;message="使用游戏键";this.gameActionExample=gameActionExample;addCommand(CMD_EXIT);setCommandListener(this);}protected void paint(Graphics graphics) {graphics.setColor(255,255,255);graphics.fillRect(0, 0, getWidth(), getHeight());graphics.setColor(255,0,0);graphics.drawString(message, x, y, Graphics.TOP|Graphics.LEFT);}public void commandAction(Command c, Displayable d) {if(c==CMD_EXIT){gameActionExample.exitMidlet();}}protected void keyPressed(int key){switch(getGameAction(key)){case Canvas.UP:message="up";y--;break;case Canvas.DOWN:message="down";y++;break;case Canvas.LEFT:message="left";x--;break;case Canvas.RIGHT:message="right";x++;break;case Canvas.FIRE:message="fire";break;}repaint();} }