AndEngine学习：CollisionDetectionExample（碰撞检测）

首先让我们看一下测试代码：

public class CollisionDetectionTestActivity extends BaseGameActivity 
{
    private static final int CAMERA_WIDTH = 480;
    private static final int CAMERA_HEIGHT = 320;
    
    private Camera mCamera;
    
    @Override
    public Engine onLoadEngine() 
    {
        this.mCamera = new Camera(0, 0, CAMERA_WIDTH, CAMERA_HEIGHT);
        final Engine engine = new Engine(new EngineOptions(true, ScreenOrientation.LANDSCAPE, new RatioResolutionPolicy(CAMERA_WIDTH, CAMERA_HEIGHT), this.mCamera));
        
        return engine;
    }

    @Override
    public void onLoadResources() 
    {
        
    }

    @Override
    public Scene onLoadScene() 
    {
        this.mEngine.registerUpdateHandler(new FPSLogger());
        
        final Scene scene = new Scene();
        scene.setBackground(new ColorBackground(0.09804f, 0.6274f, 0.8784f));
        
        int centerX = CAMERA_WIDTH / 2;
        int centerY = CAMERA_HEIGHT / 2;
        
        final LoopEntityModifier entityModifier = 
                new LoopEntityModifier(
                        new ParallelEntityModifier(
                                new RotationModifier(12, 0, 360)
                                ));
        
        final Rectangle rectangle = new Rectangle(centerX - 50, centerY - 16, 64, 64);
        rectangle.registerEntityModifier(entityModifier);
        
        final Line line = new Line(centerX, centerY, 32, 32);
        line.registerEntityModifier(entityModifier);
        
        scene.attachChild(rectangle);
        scene.attachChild(line);
        
        scene.registerUpdateHandler(new IUpdateHandler(){

            @Override
            public void onUpdate(float pSecondsElapsed) 
            {
                if(rectangle.collidesWith(line))
                {
                    rectangle.setColor(1, 0, 0);
                }
                else
                {
                    rectangle.setColor(0, 1, 0);
                }
                
                if(line.collidesWith(rectangle))
                {
                    line.setColor(1, 0, 0);
                }
                else
                {
                    line.setColor(0, 1, 0);
                }
            }

            @Override
            public void reset() 
            {
                
            }});
        
        return scene;
    }

    @Override
    public void onLoadComplete() 
    {
        
    }
    
}

　　OK，让我们逐一解释。

　　

private static final int CAMERA_WIDTH = 480;
    private static final int CAMERA_HEIGHT = 320;
    
    private Camera mCamera;
    
    @Override
    public Engine onLoadEngine() 
    {
        this.mCamera = new Camera(0, 0, CAMERA_WIDTH, CAMERA_HEIGHT);
        final Engine engine = new Engine(new EngineOptions(true, ScreenOrientation.LANDSCAPE, new RatioResolutionPolicy(CAMERA_WIDTH, CAMERA_HEIGHT), this.mCamera));
        
        return engine;
    }

    @Override
    public void onLoadResources() 
    {
        
    }
    
    @Override
    public void onLoadComplete() 
    {
        
    }

　　这些应该没什么问题。

　　我们主要看

public Scene onLoadScene();

　　这个函数。

　　在这个函数里边我们定义了一个矩形和一条直线，并且让他们两个旋转

final LoopEntityModifier entityModifier = 
                new LoopEntityModifier(
                        new ParallelEntityModifier(
                                new RotationModifier(12, 0, 360)
                                ));
        
        final Rectangle rectangle = new Rectangle(centerX - 50, centerY - 16, 64, 64);
        rectangle.registerEntityModifier(entityModifier);
        
        final Line line = new Line(centerX, centerY, 32, 32);
        line.registerEntityModifier(entityModifier);
        
        scene.attachChild(rectangle);
        scene.attachChild(line);

　　然后就是碰撞检测的部分了，当碰撞的时候，让矩形和直线都改变颜色。

        scene.registerUpdateHandler(new IUpdateHandler(){

            @Override
            public void onUpdate(float pSecondsElapsed) 
            {
                if(rectangle.collidesWith(line))
                {
                    rectangle.setColor(1, 0, 0);
                }
                else
                {
                    rectangle.setColor(0, 1, 0);
                }
                
                if(line.collidesWith(rectangle))
                {
                    line.setColor(1, 0, 0);
                }
                else
                {
                    line.setColor(0, 1, 0);
                }
            }

　　OK，由于代码非常简单，也就不多废话了。