Android碰撞检测——圆形检查

圆形检查的思路：两个圆的圆心距小于两个圆的半径之和则相碰撞了，反之，没有发生碰撞

    /**
     * 两个圆的碰撞检测
     * @param x1
     * @param y1
     * @param r1
     * @param x2
     * @param y2
     * @param r2
     * @return
     */
    public static boolean CheckCollideCircle(int x1, int y1, int r1, int x2,
            int y2, int r2) {
        boolean iscollide=false;
        //两点之间的距离 小于两半径之和就发生了碰撞
        if(Math.sqrt(Math.pow(x1-x2,2)+Math.pow(y1-y2, 2))<=r1+r2){
            iscollide=true;
        }
        return iscollide;
    }

下面用一个完整列子说明

public class CircleSurfaceView extends SurfaceView implements Callback,Runnable {
    int x1=70,y1=110,r1=40;
    int x2=220,y2=110,r2=40;
    boolean isCollide=false;//是否发生碰撞
    SurfaceHolder surfaceHolder;
    Paint paint;
    boolean flag=false;
    int sleeptime=100;
    Thread thread;
    public CircleSurfaceView(Context context) {
        super(context);
        surfaceHolder=getHolder();
        surfaceHolder.addCallback(this);
        paint=new Paint();
        paint.setTextSize(12);
        thread=new Thread(this);
        flag=true;
    }
    
    public void draw(Canvas canvas) {
        canvas.drawColor(Color.BLACK);
        if(isCollide){
            paint.setColor(Color.RED);
            canvas.drawText("Collide", 0, 30, paint);
        }
        else {
            paint.setColor(Color.WHITE);
            canvas.drawText("Not Collide", 0, 30, paint);
        }
        canvas.drawCircle(x1, y1, r1, paint);
        canvas.drawCircle(x2, y2, r2,paint);
    }
    /**
     * 触屏点击事件
     */
    @Override
    public boolean onTouchEvent(MotionEvent event){
        x1=(int)event.getX()-r1/2; //圆心坐标
        if(CheckCollide.CheckCollideCircle(x1, y1, r1, x2, y2, r2)){//检查碰撞的方法
            isCollide=true;
        }
        else {
            isCollide=false;
        }
        return true;
    }

    
    @Override
    public void surfaceCreated(SurfaceHolder holder) {
        // TODO Auto-generated method stub
        if(!thread.isAlive()){
            thread.start();
        }
    }

    @Override
    public void surfaceDestroyed(SurfaceHolder holder) {
        // TODO Auto-generated method stub
        flag=false;
        thread=null;
    }
    @SuppressLint("WrongCall")
    @Override
    public void run() {
        // TODO Auto-generated method stub
        Canvas canvas=null;
        while (flag) {
            try {
                canvas=surfaceHolder.lockCanvas();
                synchronized (canvas) {
                    draw(canvas);    
                }
            } catch (Exception e) {
                Log.e("Collide", e.getMessage());
            }finally{
                if(canvas!=null){
                    surfaceHolder.unlockCanvasAndPost(canvas);
                }
            }
            try {
                Thread.sleep(sleeptime);
            } catch (Exception e) {
                Log.e("Collide", e.getMessage());
            }
        }
    }

    @Override
    public void surfaceChanged(SurfaceHolder holder, int format, int width,
            int height) {
        // TODO Auto-generated method stub
        
    }

}