gamecanvas.java

来自「This is a resource based on j2me embedde」· Java 代码 · 共 373 行 · 第 1/2 页

/*
 *   
 *
 * Copyright  1990-2007 Sun Microsystems, Inc. All Rights Reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER
 * 
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License version
 * 2 only, as published by the Free Software Foundation.
 * 
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * General Public License version 2 for more details (a copy is
 * included at /legal/license.txt).
 * 
 * You should have received a copy of the GNU General Public License
 * version 2 along with this work; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 * 02110-1301 USA
 * 
 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa
 * Clara, CA 95054 or visit www.sun.com if you need additional
 * information or have any questions.
 */

package javax.microedition.lcdui.game;

import javax.microedition.lcdui.Graphics;
import javax.microedition.lcdui.Canvas;
import com.sun.midp.lcdui.GameMap;
import com.sun.midp.lcdui.GameCanvasLFImpl;
import com.sun.midp.lcdui.GameAccess;


/**
 * The GameCanvas class provides the basis for a game user interface.  In
 * addition to the features inherited from Canvas (commands, input events,
 * etc.) it also provides game-specific capabilities such as an
 * off-screen graphics buffer and the ability to query key status.
 * <p>
 * A dedicated buffer is created for each GameCanvas instance.  Since a
 * unique buffer is provided for each GameCanvas instance, it is preferable
 * to re-use a single GameCanvas instance in the interests of minimizing
 * heap usage.  The developer can assume that the contents of this buffer
 * are modified only by calls to the Graphics object(s) obtained from the
 * GameCanvas instance; the contents are not modified by external sources
 * such as other MIDlets or system-level notifications.  The buffer is
 * initially filled with white pixels.
 * <p>
 * The buffer's size is set to the maximum dimensions of the GameCanvas.
 * However, the area that may be flushed is limited by the current
 * dimensions of the GameCanvas (as influenced by the presence of a Ticker,
 * Commands, etc.) when the flush is requested.  The current dimensions of
 * the GameCanvas may be obtained by calling
 * {@link javax.microedition.lcdui.Canvas#getWidth getWidth} and
 * {@link javax.microedition.lcdui.Canvas#getHeight getHeight}.
 * <p>
 * A game may provide its own thread to run the game loop.  A typical loop
 * will check for input, implement the game logic, and then render the updated
 * user interface. The following code illustrates the structure of a typical
 * game loop: <code>
 * <pre>
 * // Get the Graphics object for the off-screen buffer
 * Graphics g = getGraphics();
 *
 * while (true) {
 *      // Check user input and update positions if necessary
 *      int keyState = getKeyStates();
 *      if ((keyState & LEFT_PRESSED) != 0) {
 *          sprite.move(-1, 0);
 *      }
 *      else if ((keyState & RIGHT_PRESSED) != 0) {
 *          sprite.move(1, 0);
 *      }
 *
 *	// Clear the background to white
 *	g.setColor(0xFFFFFF);
 *	g.fillRect(0,0,getWidth(), getHeight());
 *
 *      // Draw the Sprite
 *      sprite.paint(g);
 *
 *      // Flush the off-screen buffer
 *      flushGraphics();
 * }
 * </pre>
 * </code>
 * <P>
 **/

public abstract class GameCanvas extends Canvas
{
    /** The look&feel implementation associated with this GameCanvas */
    private GameCanvasLFImpl gameCanvasLF;

    /** Implementor of GameAccess interface handed out to external packages */ 
    private static GameAccess gameAccess;

    /**
     * The bit representing the UP key.  This constant has a value of 
     * <code>0x0002</code> (1 << Canvas.UP).
     */
    public static final int UP_PRESSED = 1 << Canvas.UP;

    /**
     * The bit representing the DOWN key.  This constant has a value of 
     * <code>0x0040</code> (1 << Canvas.DOWN).
     */
    public static final int DOWN_PRESSED = 1 << Canvas.DOWN;

    /**
     * The bit representing the LEFT key.  This constant has a value of 
     * <code>0x0004</code> (1 << Canvas.LEFT).
     */
    public static final int LEFT_PRESSED = 1 << Canvas.LEFT;

    /**
     * The bit representing the RIGHT key.  This constant has a value of 
     * <code>0x0020</code> (1 << Canvas.RIGHT).
     */
    public static final int RIGHT_PRESSED = 1 << Canvas.RIGHT;

    /**
     * The bit representing the FIRE key.  This constant has a value of 
     * <code>0x0100</code> (1 << Canvas.FIRE).
     */
    public static final int FIRE_PRESSED = 1 << Canvas.FIRE;

    /**
     * The bit representing the GAME_A key (may not be supported on all 
     * devices).  This constant has a value of 
     * <code>0x0200</code> (1 << Canvas.GAME_A).
     */
    public static final int GAME_A_PRESSED = 1 << Canvas.GAME_A;

    /**
     * The bit representing the GAME_B key (may not be supported on all 
     * devices).  This constant has a value of 
     * <code>0x0400</code> (1 << Canvas.GAME_B).
     */
    public static final int GAME_B_PRESSED = 1 << Canvas.GAME_B;

    /**
     * The bit representing the GAME_C key (may not be supported on all 
     * devices).  This constant has a value of 
     * <code>0x0800</code> (1 << Canvas.GAME_C).
     */
    public static final int GAME_C_PRESSED = 1 << Canvas.GAME_C;

    /**
     * The bit representing the GAME_D key (may not be supported on all 
     * devices).  This constant has a value of 
     * <code>0x1000</code> (1 << Canvas.GAME_D).
     */
    public static final int GAME_D_PRESSED = 1 << Canvas.GAME_D;


    /**
     * Creates a new instance of a GameCanvas.  A new buffer is also created
     * for the GameCanvas and is initially filled with white pixels.
     * <p>
     * If the developer only needs to query key status using the getKeyStates
     * method, the regular key event mechanism can be suppressed for game keys
     * while this GameCanvas is shown.  If not needed by the application, the 
     * suppression of key events may improve performance by eliminating 
     * unnecessary system calls to keyPressed, keyRepeated and keyReleased 
     * methods. 
     * <p>
     * If requested, key event suppression for a given GameCanvas is started 
     * when it is shown (i.e. when showNotify is called) and stopped when it
     * is hidden (i.e. when hideNotify is called).  Since the showing and 
     * hiding of screens is serialized with the event queue, this arrangement
     * ensures that the suppression effects only those key events intended for
     * the corresponding GameCanvas.  Thus, if key events are being generated
     * while another screen is still shown, those key events will continue to
     * be queued and dispatched until that screen is hidden and the GameCanvas
     * has replaced it.
     * <p>
     * Note that key events can be suppressed only for the defined game keys 
     * (UP, DOWN, FIRE, etc.); key events are always generated for all other 
     * keys.  
     * <p>
     * @param suppressKeyEvents <code>true</code> to suppress the regular
     * key event mechanism for game keys, otherwise <code>false</code>.
     */
    protected GameCanvas(boolean suppressKeyEvents) {