j2me竖向滚动菜单的基本做法

public class AppCanvas extends Canvas { int screen_width; int screen_height; String[] select; public final static int KEY_UP = -1; public final static int KEY_DOWN = -2; public AppCanvas() { this.setFullScreenMode(true); screen_width = this.getWidth(); screen_height = this.getHeight(); select = new String[] { "登 录", "注 册", "账户充值", "用户提款", "进出明细", "投注查询", "中奖查询", "个人资料", "密码修改" }; } private int itemsOnSceen = 5;//最多显示几条，需要根据屏幕大小判断 private int index = 0;//select的索引 private int delta = 0;//index超过itemsOnSceen后的偏移量 protected void paint(Graphics g) { // TODO Auto-generated method stub g.setColor(0xffffff); g.fillRect(0, 0, screen_width, screen_height); for (int i = 0; i < ((itemsOnSceen>select.length)?select.length:itemsOnSceen); i++) { if (i == index - delta) { g.setColor(0xff0000); } else { g.setColor(0); } g.drawString(select[i + delta], screen_width >> 1, 40 + 20 * i, Graphics.BASELINE | Graphics.HCENTER); } } protected void keyPressed(int keyCode) { // TODO Auto-generated method stub switch (keyCode) { case KEY_UP: if (index > 0) { index--; } if (index - delta < 0) { //小屏 delta--; } break; case KEY_DOWN: if (index < select.length - 1) { index++; } if (index - delta > itemsOnSceen - 1) { //小屏 delta++; } break; } repaint(); } }