Android碰撞检测——矩形检查

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碰撞检测常用的分三类：圆形检测、矩形检测、像素检测。像素检测是最为精确的一种，但是它对性能消耗也是最大的一种，因为一般游戏中很少用到。

矩形检查

思路：可以检查两个矩形的相对位置，如果RectA在RectB的上下左右，且两个矩形没有挨着，则可以判定他们没有碰撞，反之就发生碰撞了。

    /**     *      * @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;    }

实现一个完整的例子

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;    }