AndEngine学习 ： BasePhysicsJoint（简单地和物理模型的联系）

　　和以前一样，代码一目了然，我把该写的东西都写到注释里边了，和大家分享！

　　所需图片：

face_box_tiled.png

face_circle_tiled.png

public class BasePhysicsJoint extends BaseGameActivity implements
        IAccelerometerListener, IOnSceneTouchListener 
{
    // ===========================================================
    // Constants
    // ===========================================================

    protected static final int CAMERA_WIDTH = 720;
    protected static final int CAMERA_HEIGHT = 480;

    // ===========================================================
    // Fields
    // ===========================================================

    private BitmapTextureAtlas mBitmapTextureAtlas;

    private Scene mScene;

    protected TiledTextureRegion mBoxFaceTextureRegion;
    protected TiledTextureRegion mCircleFaceTextureRegion;
    
    // mPhysicsWorld: 我们所有的有关Sprite的物理操作都需要通过该对象
    protected PhysicsWorld mPhysicsWorld;
    
    private int mFaceCount = 0;

    public Engine onLoadEngine() 
    {
        Toast.makeText(this, "Touch the screen to add objects", Toast.LENGTH_SHORT).show();
        
        final Camera camera = new Camera(0, 0, CAMERA_WIDTH, CAMERA_HEIGHT);
        final EngineOptions engineOptions = new EngineOptions(true, ScreenOrientation.LANDSCAPE, new RatioResolutionPolicy(CAMERA_WIDTH, CAMERA_HEIGHT), camera);
        engineOptions.getTouchOptions().setRunOnUpdateThread(true);
        return new Engine(engineOptions);
    }

    public void onLoadResources() 
    {
        this.mBitmapTextureAtlas = new BitmapTextureAtlas(64, 64, TextureOptions.BILINEAR_PREMULTIPLYALPHA);
        BitmapTextureAtlasTextureRegionFactory.setAssetBasePath("gfx/");
        this.mBoxFaceTextureRegion = BitmapTextureAtlasTextureRegionFactory.createTiledFromAsset(this.mBitmapTextureAtlas, this, "face_box_tiled.png", 0, 0, 2, 1); // 64x32
        this.mCircleFaceTextureRegion = BitmapTextureAtlasTextureRegionFactory.createTiledFromAsset(this.mBitmapTextureAtlas, this, "face_circle_tiled.png", 0, 32, 2, 1); // 64x32
        this.mEngine.getTextureManager().loadTexture(this.mBitmapTextureAtlas);
    }

    public Scene onLoadScene() 
    {
        this.mScene = new Scene();
        this.mScene.setBackground(new ColorBackground(0, 0, 0));
        this.mScene.setOnSceneTouchListener(this);
        
        // 创建物理世界
        this.mPhysicsWorld = new PhysicsWorld(new Vector2(0, 0), false);
        
        final Shape ground = new Rectangle(0, CAMERA_HEIGHT - 2, CAMERA_WIDTH, 2);
        final Shape roof = new Rectangle(0, 0, CAMERA_WIDTH, 2);
        final Shape left = new Rectangle(0, 0, 2, CAMERA_HEIGHT);
        final Shape right = new Rectangle(CAMERA_WIDTH - 2, 0, 2, CAMERA_HEIGHT);
        
        final FixtureDef wallFixtureDef = PhysicsFactory.createFixtureDef(0, 1f, 1f);
        
        // 创建刚体矩形，用来定义物理世界的边界
        PhysicsFactory.createBoxBody(this.mPhysicsWorld, ground, BodyType.StaticBody, wallFixtureDef);
        PhysicsFactory.createBoxBody(this.mPhysicsWorld, roof, BodyType.StaticBody, wallFixtureDef);
        PhysicsFactory.createBoxBody(this.mPhysicsWorld, left, BodyType.StaticBody, wallFixtureDef);
        PhysicsFactory.createBoxBody(this.mPhysicsWorld, right, BodyType.StaticBody, wallFixtureDef);

        this.mScene.attachChild(ground);
        this.mScene.attachChild(roof);
        this.mScene.attachChild(left);
        this.mScene.attachChild(right);
        
        this.mScene.registerUpdateHandler(this.mPhysicsWorld);
        
        return mScene;
    }

    public void onLoadComplete() 
    {

    }

    public boolean onSceneTouchEvent(Scene pScene, TouchEvent pSceneTouchEvent) 
    {
        if(mPhysicsWorld != null)
        {
            if(pSceneTouchEvent.isActionDown())
            {
                this.addFace(pSceneTouchEvent.getX(), pSceneTouchEvent.getY());
                return true;
            }
        }
        return false;
    }

    public void onAccelerometerChanged(AccelerometerData pAccelerometerData) 
    {
        // 根据重力感应计算重力加速度
        final Vector2 gravity = Vector2Pool.obtain(pAccelerometerData.getX(), pAccelerometerData.getY());
        this.mPhysicsWorld.setGravity(gravity);
        Vector2Pool.recycle(gravity);
    }
    
    @Override
    public void onResumeGame() 
    {
        super.onResumeGame();
        this.enableAccelerometerSensor(this);
    }
    
    // ===========================================================
    // Methods
    // ===========================================================

    private void addFace(final float pX, final float pY)
    {
        this.mFaceCount++;

        final AnimatedSprite face;
        final Body body;

        final FixtureDef objectFixtureDef = PhysicsFactory.createFixtureDef(1,
                0.5f, 0.5f);

        if (this.mFaceCount % 2 == 0) {
            face = new AnimatedSprite(pX, pY, this.mCircleFaceTextureRegion);
            face.setScale(MathUtils.random(0.5f, 1.25f));
            body = PhysicsFactory.createCircleBody(this.mPhysicsWorld, face,
                    BodyType.DynamicBody, objectFixtureDef);
        } else {
            face = new AnimatedSprite(pX, pY, this.mBoxFaceTextureRegion);
            face.setScale(MathUtils.random(0.5f, 1.25f));
            body = PhysicsFactory.createBoxBody(this.mPhysicsWorld, face,
                    BodyType.DynamicBody, objectFixtureDef);
        }

        face.animate(200);

        this.mScene.attachChild(face);
        this.mPhysicsWorld.registerPhysicsConnector(new PhysicsConnector(face,
                body, true, true));
    }
}