Java 手機遊戲開發：MIDP 圖形編程實戰——九宮格遊戲（中）

九宮格遊戲：高低級 UI 混合開發完整案例

本案例實現人機對戰「九宮格」（井字棋），展示 MIDP 核心技術：多屏幕流程控制、高級列表選擇、Canvas 遊戲繪圖、鍵盤事件映射、動態屏幕適配。

遊戲流程與屏幕結構

1. SplashScreen (Alert)：啟動畫面，顯示 4 秒 Logo
2. ChoosePieceScreen (List)：高級 API，讓玩家選擇棋子（○/×）
3. GameScreen (Canvas)：低級 API，遊戲主場景，處理繪圖、輸入、AI 對戰

屏幕切換由 TicTacToeMIDlet 統一管理，各屏通過回調方法通知 MIDlet 切換。

ChoosePieceScreen：高級 List 實現

public class ChoosePieceScreen extends List implements CommandListener {
    private TicTacToeMIDlet midlet;
    public ChoosePieceScreen(TicTacToeMIDlet midlet) {
        super("Choose your piece", List.IMPLICIT);
        this.midlet = midlet;
        append("Circle (O)", null);
        append("Cross (X)", null);
        addCommand(new Command("OK", Command.OK, 1));
        setCommandListener(this);
    }
    public void commandAction(Command c, Displayable d) {
        if (c.getCommandType() == Command.OK) {
            boolean isCircle = (getSelectedIndex() == 0);
            midlet.choosePieceScreenDone(isCircle); // 回調 MIDlet
        }
    }
}

使用 IMPLICIT 模式，選中項自動高亮，按「OK」觸發回調傳遞玩家選擇。

GameScreen：Canvas 遊戲核心

棋盤自適應佈局

private void initializeBoard() {
    screenWidth = getWidth();
    screenHeight = getHeight();
    if (screenWidth > screenHeight) { // 橫屏
        boardCellSize = (screenHeight - 2) / 3;
        boardLeft = (screenWidth - boardCellSize * 3) / 2;
        boardTop = 1;
    } else { // 豎屏
        boardCellSize = (screenWidth - 2) / 3;
        boardLeft = 1;
        boardTop = (screenHeight - boardCellSize * 3) / 2;
    }
}

根據畫布實際尺寸動態計算格子大小、棋盤左上角偏移，確保棋盤居中、最大化、不變形。

鍵盤映射與光標控制

protected void keyPressed(int keyCode) {
    if (game.isGameOver()) return;
    int action = getGameAction(keyCode); // 映射為標準遊戲動作
    switch (action) {
        case FIRE: doPlayerMove(); break;
        case RIGHT: moveCursor(1, 0); break;
        case LEFT: moveCursor(-1, 0); break;
        case DOWN: moveCursor(0, 1); break;
        case UP: moveCursor(0, -1); break;
    }
}
private void moveCursor(int dx, int dy) {
    int newPos = cursorPosition + dx + 3 * dy;
    if (newPos >= 0 && newPos < 9) {
        preCursorPosition = cursorPosition;
        cursorPosition = newPos;
        repaint();
    }
}

getGameAction() 關鍵作用：屏蔽設備鍵盤差異，將數字鍵、方向鍵、軟鍵統一映射為 UP/DOWN/LEFT/RIGHT/FIRE。

public void paint(Graphics g) {
    if (game.isGameOver()) paintGameOver(g);
    else paintGame(g);
}
private void paintGame(Graphics g) {
    if (isRestart) { // 首幀或重新開始
        g.setColor(WHITE); g.fillRect(0, 0, screenWidth, screenHeight);
        drawBoard(g); isRestart = false;
    }
    drawCursor(g); // 畫光標（黑框/白框切換實現閃爍效果）
    if (playerMove != NO_MOVE) drawPiece(g, playerIsCircle, playerMove);
    if (computerMove != NO_MOVE) drawPiece(g, computerIsCircle, computerMove);
}

private void drawCircle(Graphics g, int x, int y) {
    g.setColor(BLUE);
    g.fillArc(x + boardLeft, y + boardTop, cellSize-4, cellSize-4, 0, 360);
    g.setColor(WHITE);
    g.fillArc(x+4+boardLeft, y+4+boardTop, cellSize-12, cellSize-12, 0, 360); // 內圓挖空
}
private void drawCross(Graphics g, int x, int y) {
    g.setColor(RED);
    for (int i=0; i<4; i++) { // 畫粗線模擬寬度
        g.drawLine(x+1+i+boardLeft, y+boardTop, x+cellSize-8+i+boardLeft, y+cellSize-5+boardTop);
        g.drawLine(x+1+i+boardLeft, y+cellSize-5+boardTop, x+cellSize-8+i+boardLeft, y+boardTop);
    }
}

exitCommand = new Command("Exit", Command.EXIT, 1);
newGameCommand = new Command("New", Command.SCREEN, 2);
addCommand(exitCommand); addCommand(newGameCommand);
setCommandListener(this);
public void commandAction(Command c, Displayable d) {
    if (c == exitCommand) midlet.quit();
    else if (c == newGameCommand) initialize();
}