通过处理按键模拟加速度，刹车等功能

import java.lang.*;
import java.io.*;
import java.util.*;
import javax.microedition.lcdui.*;

public class gKey {
public int key_UP;
public int key_DOWN;
public int key_LEFT;
public int key_RIGHT;
public int key_A;
public int key_B;
public int key_C;
public int key_D;
public int key_STAR;
public int key_POUND;
public int key_TIMER;
public int movespeed ;
public int leftvalue ;
public int upvalue ;
public int rightvalue ;
public int downvalue ;

public gKey ( int keytime , int mspeed )
{
key_TIMER = keytime ;
refreshKey() ;
movespeed = mspeed ;
}

public void refreshKey ()
{
key_UP = 0 ;
key_DOWN = 0 ;
key_LEFT = 0 ;
key_RIGHT = 0 ;
key_A = 0 ;
key_B = 0 ;
key_C = 0 ;
key_D = 0 ;
key_STAR = 0 ;
key_POUND = 0 ;
}

public void flushKey ()
{
if ( key_UP > 0 )
if ( key_UP < key_TIMER ) key_UP += upvalue ;
if ( key_DOWN > 0 )
if ( key_DOWN < key_TIMER ) key_DOWN += downvalue ;
if ( key_LEFT > 0 )
if ( key_LEFT < key_TIMER ) key_LEFT += leftvalue;
if ( key_RIGHT > 0 )
if ( key_RIGHT < key_TIMER ) key_RIGHT += rightvalue ;
}

public void keyPressed(int keyCode,Canvas canvas)
{
switch (canvas.getGameAction(keyCode)) {
case Canvas.UP:
key_UP = (key_UP < key_TIMER)?key_UP+movespeed:key_TIMER ;
upvalue = movespeed ;
break;
case Canvas.DOWN:
key_DOWN = (key_DOWN < key_TIMER )?key_DOWN+movespeed:key_TIMER ;
upvalue = movespeed ;
break;
case Canvas.LEFT:
key_LEFT = (key_LEFT < key_TIMER )?key_LEFT+movespeed:key_TIMER ;
leftvalue = movespeed ;
break;
case Canvas.RIGHT:
key_RIGHT = (key_RIGHT < key_TIMER )?key_RIGHT+movespeed:key_TIMER ;
rightvalue = movespeed ;
break;
case Canvas.GAME_A:
key_A = (key_A < key_TIMER )?key_A+1:key_TIMER ;
break;
case Canvas.GAME_B:
key_B = (key_B < key_TIMER )?key_B+1:key_TIMER ;
break;
case Canvas.GAME_C:
key_C = (key_C < key_TIMER )?key_C+1:key_TIMER ;
break;
case Canvas.GAME_D:
key_D = (key_D < key_TIMER )?key_D+1:key_TIMER ;
break;
case 0:
switch (keyCode) {
case Canvas.KEY_NUM2:
key_UP = (key_UP < key_TIMER )?key_UP+movespeed:key_TIMER ;
upvalue = movespeed ;
break;
case Canvas.KEY_NUM8:
key_DOWN = (key_DOWN < key_TIMER )?key_DOWN+movespeed:key_TIMER ;
upvalue = movespeed ;
break;
case Canvas.KEY_NUM4:
key_LEFT = (key_LEFT < key_TIMER )?key_LEFT+movespeed:key_TIMER ;
leftvalue = movespeed ;
break;
case Canvas.KEY_NUM6:
key_RIGHT = (key_RIGHT < key_TIMER )?key_RIGHT+movespeed:key_TIMER ;
rightvalue = movespeed ;
break;
case Canvas.KEY_POUND:
key_POUND = (key_POUND < key_TIMER )?key_POUND+1:key_TIMER ;
break;
case Canvas.KEY_STAR:
key_STAR = (key_STAR < key_TIMER )?key_STAR+1:key_TIMER ;
break;
}
break;
}
}

public void keyReleased(int keyCode,Canvas canvas) {
switch (canvas.getGameAction(keyCode)) {
case Canvas.UP:
upvalue = - (key_UP / 4) ;
break;
case Canvas.DOWN:
downvalue = - (key_DOWN / 4) ;
break;
case Canvas.LEFT:
leftvalue = - (key_LEFT / 4) ;
break;
case Canvas.RIGHT:
rightvalue = -(key_RIGHT / 4) ;
break;
case Canvas.GAME_A:
key_A = 0 ;
break;
case Canvas.GAME_B:
key_B = 0 ;
break;
case Canvas.GAME_C:
key_C = 0 ;
break;
case Canvas.GAME_D:
key_D = 0 ;
break;
case 0:
switch (keyCode) {
case Canvas.KEY_NUM2:
upvalue = -(key_UP / 4) ;
break;
case Canvas.KEY_NUM8:
downvalue = -(key_DOWN / 4) ;
break;
case Canvas.KEY_NUM4:
leftvalue = -(key_LEFT / 4) ;
break;
case Canvas.KEY_NUM6:
rightvalue = -(key_RIGHT / 4) ;
break;
case Canvas.KEY_POUND:
key_POUND = 0 ;
break;
case Canvas.KEY_STAR:
key_STAR = 0 ;
break;
}
break;
}
}

}

import java.lang.*;
import java.io.*;
import java.util.*;
import javax.microedition.lcdui.*;

public class gCanvas extends Canvas implements Runnable {

private Graphics bgGraphics;
private Image bgBuf;
private int width ;
private int height ;
private int dfwidth ;
private int dfheight ;
private int snoffx ;
private int snoffy ;
private boolean isOver;
private boolean isFirstRun ;
public gKey keyParam ;
public int thDelay ;
private Thread mThread ;


// test
private int x,y ;

public gCanvas (int w,int h,int keytimer,int thdelay)
{
try{
width = getWidth() ;
height = getHeight() ;
dfwidth = w ;
dfheight = h ;
isFirstRun = true ;
snoffx = ( width - dfwidth ) / 2 ;
snoffy = ( height - dfheight ) / 2 ;
isOver = false ;
bgBuf = Image.createImage ( dfwidth, dfheight ) ;
bgGraphics = bgBuf.getGraphics() ;
mThread = new Thread(this) ;
x = 0 ;
y = 0 ;
keyParam = new gKey ( keytimer) ;
thDelay = thdelay ;
// test
}
catch(Exception ex){
isOver = true ;
}

}


public void OverProcess ()
{
isOver = true ;
// add destroy code
}

public void run ()
{
try{
while ( !isOver )
{
// add execute code
if ( keyParam.key_A > 0 ){
keyParam.refreshKey() ;// 键按下后只响应一次要调用这个函数
OverProcess() ;
}

if ( y > 0 ) y -= keyParam.key_UP ;
if ( y < width - 32 ) y += keyParam.key_DOWN ;//这里读出来的值不是顾定的，你按的越长值越大，上限是keytime，表示加速度，当你松开键时这里的值不会马上为0，但是会很快变成0，表示惯性
if ( x > 0 ) x -= keyParam.key_LEFT ;
if ( x < height - 32 ) x += keyParam.key_RIGHT ;
keyParam.flushKey() ;


repaint() ;
mThread.sleep(thDelay);
}
}
catch(Exception ex)
{}
}

public void paint (Graphics g)
{
// clear screen
if ( isFirstRun == true ){
g.setColor(0) ;
g.fillRect ( 0 , 0 , width , height ) ;
}


// add draw function

g.drawImage (bgBuf,snoffx,snoffy,g.LEFT|g.TOP) ;
}


public void keyPressed(int keyCode) {
keyParam.keyPressed(keyCode,this) ;
}

public void keyReleased(int keyCode) {
keyParam.keyReleased(keyCode,this) ;
}

}