Android collision detection - Rectangle check

 

collision detection commonly divided into three types : round testing, rectangle detection , pixel detection . Pixel detection is the most accurate one, but it is also the largest consumption of a performance , because the general game rarely used .

 

rectangular checks

 

ideas : You can check the relative position of the two rectangles , if RectA in RectB up and down about , and have not slept in two rectangles , you can determine that they do not collide , contrary to the collision .

 

  

    /** 
     *  
     * @param x1 矩形1的X坐标 
     * @param y1 矩形1的Y坐标 
     * @param w1 矩形1的宽 
     * @param h1 矩形1的高 
     * @param x2 矩形2的X坐标 
     * @param y2  矩形2的Y坐标 
     * @param w2 矩形2的宽 
     * @param h2 矩形的高 
     * @return 
     */ 
    public boolean CheckRectCollsion(int x1, int y1, int w1, int h1, int x2, int y2, int w2, int h2) { 
        if (x1 >= x2 && x1 >= x2 + w2) { 
            return false; 
        } else if (x1 <= x2 && x1 + w1 <= x2) { 
            return false; 
        } else if (y1 >= y2 && y1 >= y2 + h2) { 
            return false; 
        } else if (y1 <= y2 && y1 + h1 <= y2) { 
            return false; 
        } 
        return true; 
    }

 

 

achieve a complete example

 

  

public class MySurfaceView extends SurfaceView implements Callback,Runnable { 
    private SurfaceHolder surfaceHolder; 
    private Paint paint; 
    private Thread thread; 
    private boolean flag; 
    int sleeptime=100; 
    //定义两个矩形的宽高坐标 
    private int x1 = 10, y1 = 110, w1 = 40, h1 = 40; 
    private int x2 = 100, y2 = 110, w2 = 40, h2 = 40; 
    //便于观察是否发生了碰撞设置一个标识位 
    private boolean isCollsion; 
    public MySurfaceView(Context context) { 
        super(context); 
        surfaceHolder = this.getHolder(); 
        surfaceHolder.addCallback(this); 
        paint = new Paint(); 
        paint.setColor(Color.WHITE); 
        paint.setAntiAlias(true); 
        setFocusable(true); //设置焦点 
    } 
 
    @Override 
    public void run() { 
        Canvas canvas=null; 
        while (flag) { 
            try { 
                canvas=surfaceHolder.lockCanvas(); 
                synchronized (canvas) { 
                    myDraw(canvas); 
                } 
            } catch (Exception e) { 
                Log.e("collsion", e.getMessage()); 
            }finally{ 
                if(canvas!=null){ 
                    surfaceHolder.unlockCanvasAndPost(canvas); 
                } 
            } 
            try { 
                Thread.sleep(sleeptime); 
            } catch (Exception e) { 
                Log.e("collsion", e.getMessage()); 
            } 
        } 
    } 
     
    /** 
     * 触屏事件监听 
     */ 
    @Override 
    public boolean onTouchEvent(MotionEvent event) { 
        //让矩形1随着触屏位置移动 
        x1 = (int) event.getX() - w1 / 2; 
        y1 = (int) event.getY() - h1 / 2; 
        if (CheckRectCollsion(x1, y1, w1, h1, x2, y2, w2, h2)) { 
            isCollsion = true; 
        } else { 
            isCollsion = false; 
        } 
        return true; 
    } 
     
    public void myDraw(Canvas canvas) { 
            canvas.drawColor(Color.BLACK); 
            if (isCollsion) { 
                paint.setColor(Color.RED); 
                paint.setTextSize(20); 
                canvas.drawText("碰撞了！", 0, 30, paint); 
            } else { 
                paint.setColor(Color.WHITE); 
            } 
            //绘制两个矩形 
            canvas.drawRect(x1, y1, x1 + w1, y1 + h1, paint); 
            canvas.drawRect(x2, y2, x2 + w2, y2 + h2, paint); 
        } 
     
    @Override 
    public void surfaceChanged(SurfaceHolder arg0, int arg1, int arg2, int arg3) { 
        // TODO Auto-generated method stub 
         
    } 
 
    @Override 
    public void surfaceCreated(SurfaceHolder arg0) { 
        flag = true; 
        //实例线程 
        thread = new Thread(this); 
        if(!thread.isAlive()){ 
        //启动线程 
        thread.start(); 
        } 
    } 
 
    @Override 
    public void surfaceDestroyed(SurfaceHolder arg0) { 
        // TODO Auto-generated method stub 
         
    } 
    /** 
     *  
     * @param x1 矩形1的X坐标 
     * @param y1 矩形1的Y坐标 
     * @param w1 矩形1的宽 
     * @param h1 矩形1的高 
     * @param x2 矩形2的X坐标 
     * @param y2  矩形2的Y坐标 
     * @param w2 矩形2的宽 
     * @param h2 矩形的高 
     * @return 
     */ 
    public boolean CheckRectCollsion(int x1, int y1, int w1, int h1, int x2, int y2, int w2, int h2) { 
        if (x1 >= x2 && x1 >= x2 + w2) { 
            return false; 
        } else if (x1 <= x2 && x1 + w1 <= x2) { 
            return false; 
        } else if (y1 >= y2 && y1 >= y2 + h2) { 
            return false; 
        } else if (y1 <= y2 && y1 + h1 <= y2) { 
            return false; 
        } 
        return true; 
    }