在游戏开发中为了记录的用户积分，就需要用户输入自己的名字，这时就需要我们自己实现字母的输入。下面的代码演示了实现这个要求的方法。

/*
 * MainCanvas.java
 *
 * Created on 2006年8月7日, 下午1:45
 *
 */

import javax.microedition.lcdui.Canvas;
import javax.microedition.lcdui.Graphics;

/**
 *
 * @author mydeman
 */
public class MainCanvas extends Canvas{
 
  //记录当前按了几次Fire键
  private static int keyPressedCount = 0;
  //当前显示的屏幕
  private static int screenIndex = -1;
  //定义字母表
  private static final String[] ALPHABET = {
    "A","B","C","D","E","F","G","H","I","J","K",
    "L","M","N","O","P","Q","R","S","T","U","V",
    "W","X","Y","Z"
  };
 
  /** Creates a new instance of MainCanvas */
  public MainCanvas() {
    setFullScreenMode(true);
  }
 
  //显示的字母的个数
  private static int alphaNum = 0;
 
  /**
   * 根据屏幕索引，绘制屏幕
   */
  protected void paint(Graphics g) {
    switch(screenIndex) {
      //绘制黑色背景
      case -1 :
        g.setColor(0, 0, 0);
        g.fillRect(0, 0, getWidth(), getHeight());
        break;
      //绘制字母
      case 1 :
        //设置重绘的区域
        g.setClip(30 + 15 * alphaNum, 100, 30 + 15 * (alphaNum + 1), 100);
        g.setColor(0, 0, 0);
        g.fillRect(30 + 15 * alphaNum, 100, 30 + 15 * (alphaNum + 1), 100);
        //绘制字母
        g.setColor(0, 255, 0);
        g.drawString(ALPHABET[keyPressedCount], 30 + 15 * alphaNum, 100,
          Graphics.TOP | Graphics.LEFT);
        break;
    }
  }
 
  /**
   * 刷新屏幕
   */
  private void refresh() {
    repaint();
    serviceRepaints();
  }
 
  private long old_time = 0;
  /**
   * 按键事件处理
   */
  public void keyPressed(int keyCode) {
    switch(getGameAction(keyCode)) {
      case Canvas.FIRE :
        //绘制的最大字母数为5个
        if(alphaNum <= 5) {
          //设置屏幕索引为1
          screenIndex = 1;
          //获得当前时间
          long current = System.currentTimeMillis();
          //如果当前时间和上次按键时间相差大于800ms，并且字母个数小于5个，
          //则绘制下一个字母，同时将按键的次数设为0
          if(current - old_time > 800 && alphaNum < 5) {
            alphaNum ++;
            keyPressedCount = 0;
          } else {
            //如果按键到了25次，也就是最后一个字母，则按键次数从0开始计数
            keyPressedCount = (keyPressedCount == 25) ? 0 : (keyPressedCount + 1);
          }
          //保存当前按键时间
          old_time = current;
          //刷新屏幕
          refresh();
        }
        break;
    }
  }
}