MIDP图形设计5

　　5、GameScreen.java

　　GameScreen使用了一个低级应用编程接口Canvas屏幕，和Image、Graphics类来绘制游戏面板、棋子，以及游戏的最终结果状态。要获取更详细的信息，请参阅各种绘画方法和drawCircle、drawCross、drawPiece、drawPlayerCursor、drawBoard等方法。这个屏幕使用MIDlet的quit回调方法来指示游戏结束。
此屏幕可适应各种可用显示性能(高、宽、色彩等)。此外还要注意到可以使用四向导航键，也可以使用双向导航键来移动光标。

　　它使用了封装了主游戏程序逻辑的Game类。

package example.tictactoe; import java.util.Random; import javax.microedition.midlet.*; import javax.microedition.lcdui.*; class GameScreen extends Canvas implements CommandListener { private static final int BLACK = 0x00000000; private static final int WHITE = 0x00FFFFFF; private static final int RED = 0x00FF0000; private static final int BLUE = 0x000000FF; private static final int NO_MOVE = -1; private final TicTacToeMIDlet midlet; private final Game game; private final Command exitCommand; private final Command newGameCommand; private final Random random = new Random(); private int screenWidth, screenHeight; private int boardCellSize, boardSize, boardTop, boardLeft; private boolean playerIsCircle; private boolean computerIsCircle; private int preCursorPosition, cursorPosition; private int computerMove = NO_MOVE; private int playerMove = NO_MOVE; private int computerGamesWonTally = 0; private int playerGamesWonTally = 0; private boolean isRestart; public GameScreen(TicTacToeMIDlet midlet, boolean playerIsCircle) { this.midlet = midlet; this.playerIsCircle = playerIsCircle; computerIsCircle = !playerIsCircle; game = new Game(random); initializeBoard(); // configure Screen commands exitCommand = new Command("Exit", Command.EXIT, 1); newGameCommand = new Command("New", Command.SCREEN, 2); addCommand(exitCommand); addCommand(newGameCommand); setCommandListener(this); // begin the game play initialize(); } // Initialize the Game and Game screen. Also used for game restarts. private void initialize() { game.initialize(); preCursorPosition = cursorPosition = 0; playerMove = NO_MOVE; boolean computerFirst = ((random.nextInt() & 1) == 0); if (computerFirst) { computerMove = game.makeComputerMove(); } else { computerMove = NO_MOVE; } isRestart = true; repaint(); } public void paint(Graphics g) { if (game.isGameOver()) { paintGameOver(g); } else { paintGame(g); } } private void paintGame(Graphics g) { if (isRestart) { // clean the canvas g.setColor(WHITE); g.fillRect(0, 0, screenWidth, screenHeight); drawBoard(g); isRestart = false; } drawCursor(g); if (playerMove != NO_MOVE) { drawPiece(g, playerIsCircle, playerMove); } if (computerMove != NO_MOVE) { drawPiece(g, computerIsCircle, computerMove); } } private void paintGameOver(Graphics g) { String statusMsg = null; if(game.isComputerWinner()) { statusMsg = "I win !"; computerGamesWonTally++; } else if (game.isPlayerWinner()) { statusMsg = "You win"; playerGamesWonTally++; } else { statusMsg = "Stalemate"; } String tallyMsg = "You:" + playerGamesWonTally + " Me:" + computerGamesWonTally; Font font = Font.getFont(Font.FACE_SYSTEM, Font.STYLE_PLAIN, Font.SIZE_MEDIUM); int strHeight = font.getHeight(); int statusMsgWidth = font.stringWidth(statusMsg); int tallyMsgWidth = font.stringWidth(tallyMsg); int strWidth = tallyMsgWidth; if (statusMsgWidth > tallyMsgWidth) { strWidth = statusMsgWidth; } // Get the { x, y } position for painting the strings. int x = (screenWidth - strWidth) / 2; x = x < 0 ? 0 : x; int y = (screenHeight - 2 * strHeight) / 2; y = y < 0 ? 0 : y; // clean the canvas g.setColor(WHITE); g.fillRect(0, 0, screenWidth, screenHeight); // paint the strings' text g.setColor(BLACK); g.drawString(statusMsg, x, y, (Graphics.TOP | Graphics.LEFT)); g.drawString(tallyMsg, x, (y + 1 + strHeight), (Graphics.TOP | Graphics.LEFT)); } public void commandAction(Command c, Displayable d) { if (c == exitCommand) { midlet.quit(); } else if (c == newGameCommand) { initialize(); } } private void initializeBoard() { screenWidth = getWidth(); screenHeight = getHeight(); if (screenWidth > screenHeight) { boardCellSize = (screenHeight - 2) / 3; boardLeft = (screenWidth - (boardCellSize * 3)) / 2; boardTop = 1; } else { boardCellSize = (screenWidth - 2) / 3; boardLeft = 1; boardTop = (screenHeight - boardCellSize * 3) / 2; } } protected void keyPressed(int keyCode) { // can't continue playing until the player restarts if (game.isGameOver()) { return; } int gameAction = getGameAction(keyCode); switch (gameAction) { case FIRE: doPlayerMove(); break; case RIGHT: doMoveCursor(1, 0); break; case DOWN: doMoveCursor(0, 1); break; case LEFT: doMoveCursor(-1, 0); break; case UP: doMoveCursor(0, -1); break; default: break; } } private void doPlayerMove() { if (game.isFree(cursorPosition)) { // player move game. makePlayerMove(cursorPosition); playerMove = cursorPosition; // computer move if (!game.isGameOver()) { computerMove = game.makeComputerMove(); } repaint(); } } private void doMoveCursor(int dx, int dy) { int newCursorPosition = cursorPosition + dx + 3 * dy; if ((newCursorPosition >= 0) && (newCursorPosition < 9)) { preCursorPosition = cursorPosition; cursorPosition = newCursorPosition; repaint(); } } // Draw a CIRCLE or CROSS piece on the board private void drawPiece(Graphics g, boolean isCircle, int pos) { int x = ((pos % 3) * boardCellSize) + 3; int y = ((pos / 3) * boardCellSize) + 3; if (isCircle) { drawCircle(g, x, y); } else { drawCross(g, x, y); } } // Draw blue CIRCLE onto the board image private void drawCircle(Graphics g, int x, int y) { g.setColor(BLUE); g.fillArc(x + boardLeft, y + boardTop, boardCellSize - 4, boardCellSize - 4, 0, 360); g.setColor(WHITE); g.fillArc(x + 4 + boardLeft, y + 4 + boardTop, boardCellSize - 4 - 8, boardCellSize - 4 - 8, 0, 360); } // Draw red CROSS onto the board image private void drawCross(Graphics g, int x, int y) { g.setColor(RED); for (int i = 0; i < 4; i++) { g.drawLine(x + 1 + i + boardLeft, y + boardTop, x + boardCellSize - 4 - 4 + i + boardLeft, y + boardCellSize - 5 + boardTop); g.drawLine(x + 1 + i + boardLeft, y + boardCellSize - 5 + boardTop, x + boardCellSize - 4 - 4 + i + boardLeft, y + boardTop); } } // Visually indicates a Player selected square on the board image private void drawCursor(Graphics g) { // draw cursor at selected Player square. g.setColor(WHITE); g.drawRect(((preCursorPosition % 3) * boardCellSize) + 2 + boardLeft, ((preCursorPosition/3) * boardCellSize) + 2 + boardTop, boardCellSize - 3, boardCellSize - 3); // draw cursor at selected Player square. g.setColor(BLACK); g.drawRect(((cursorPosition % 3) * boardCellSize) + 2 + boardLeft, ((cursorPosition/3) * boardCellSize) + 2 + boardTop, boardCellSize - 3, boardCellSize - 3); } private void drawBoard(Graphics g) { // clean the board g.setColor(WHITE); g.fillRect(0, 0, screenWidth, screenHeight); // draw the board g.setColor(BLACK); for (int i = 0; i < 4; i++) { g.fillRect(boardLeft, boardCellSize * i + boardTop, (boardCellSize * 3) + 2, 2); g.fillRect(boardCellSize * i + boardLeft, boardTop, 2, boardCellSize * 3); } } }

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