car.java

Programming java 2 microedition symbian os一书中作者编写的一个赛车游戏的半成品

/*
 * Copyright 2003, 2004 Symbian Ltd.
 * For License terms see http://www.symbian.com/developer/techlib/codelicense.html
 */

package demoracer;

/**
 * <p>Title: DemoRacer</p>
 * <p>Description: Game API Demo for Symbian MIDP 2.0 Book.</p>
 * @author Alan Newman - [e-mail]
 * @version 1.0
 */


/*
 * This class extends Sprite and provides the car animation for the app.
 * It is made up from 4 frames which are supplied by the image car.png
 * LayerManager instatiates the class and also makes calls to its tick method
 * to set the next frame to be shown on the display.
 * tick() also checks for collisions with other sprites on the display
 * such as 'StartFinish' and 'Puddle'
 */
import javax.microedition.lcdui.Image;
import javax.microedition.lcdui.game.Sprite;

public class Car extends Sprite {
    static final int RAW_FRAMES = 4;
    static final int DRIVE_NORMAL = 0;
    static final int DRIVE_WET = 1;
    private int frameOrder[][] = {{0, 1}, {2, 3}};
    private StartFinish startFinish;
    private Puddle puddle;
    private RacerLayerManager layerManager;
    private int puddleCount;
    private boolean wet = false;
    
    public Car(Image image, int width, int height, int x, int y, RacerLayerManager layerManager) {
        super(image, width, height);
        //Set the frame sequence according to frameOrder this is a 2x2 array, row 0 is used
        //for normal animation whereas row 1 is used when the car hits a puddle
        setFrameSequence(frameOrder[DRIVE_NORMAL]);
        setPosition(x, y);
        // define the part of the car that needs to detect whether it has "hit" anything
        // this saves it checking the whole sprite
        defineCollisionRectangle(getWidth()-1,0,1,getHeight());
        layerManager=layerManager;
        puddle=layerManager.getPuddle();
        startFinish=layerManager.getStartFinish();
    }
    
    public void tick() {
        checkCollisions();
        nextFrame();
    }
    
    public void checkCollisions() {
        //if the start finish line is visible then check for a collision
        //if collision is true then set "Lap Complete" toggle to true, elses false
        //LayerManager will draw the message as required
        if(startFinish.isVisible()) {
            if (this.collidesWith(startFinish, true)) {
                startFinish.setLapComplete(true);
            } else {
                startFinish.setLapComplete(false);
            }
        }
        
        //if the puddle is visible on the display then check for a collision with the car
        //if true then change the row of the array that is the frame to be displayed.
        //row 0 for normal and row 1 for puddle collision true.
        if(puddle.isVisible()) {
            if (!wet && this.collidesWith(puddle, true)) {
                setFrameSequence(frameOrder[DRIVE_WET]);
                puddleCount = puddle.getWidth()/2;
                wet = true;
            } else if (--puddleCount == 0) {
                setFrameSequence(frameOrder[DRIVE_NORMAL]);
                wet = false;
            }
        }
    }
}