Input.GetMouseButtonDown(0)の操作が何回も検知されてしまう

    Vector3 startTouchPos;
    Vector3 endTouchPos;
    float flickVlaue_x;
    float flickVlaue_y;

    float dirX = 0;
    float dirY = 0;
    float time = 0;
    float speedX = 0;
    float speedY = 0;

if (Input.GetMouseButtonDown(0))
        {
            startTouchPos = new Vector3(Input.mousePosition.x, Input.mousePosition.y, Input.mousePosition.z);
            this.time = 0;
        }

        if (Input.GetMouseButton(0))
        {
            this.time += Time.deltaTime;
        }

        if (Input.GetMouseButtonUp(0))
        {
            endTouchPos = new Vector3(Input.mousePosition.x, Input.mousePosition.y, Input.mousePosition.z);
        }
        FlickDirection();
        GetDirection();
    }

void FlickDirection()
    {
        flickVlaue_x = endTouchPos.x - startTouchPos.x;
        flickVlaue_y = endTouchPos.y - startTouchPos.y;
      if (flickVlaue_x > 50)
        {
          Debug.Log("x is" + flickVlaue_x);
        }
      if (flickVlaue_y > 50)
        {
          Debug.Log("y is" + flickVlaue_y);
        }
    }

    void GetDirection()
    {
      if (flickVlaue_x > flickVlaue_y && flickVlaue_x > 50)
      {
        this.dirX = Mathf.Abs(flickVlaue_x);
        this.speedX = this.dirX / this.time / 27;
        Debug.Log("Xspeed is" + this.speedX);
      }

      if (flickVlaue_y > flickVlaue_x && flickVlaue_y > 50)
      {
        this.dirY = Mathf.Abs(flickVlaue_y);
        this.speedY = this.dirX / this.time / 27;
        Debug.Log("Yspeed is" + this.speedY);
      }
    }