Imshow in main thread not responding


I’ve a problem with imshow. The situation is as following.

I have a camera and write a class for grabbing images and saving them to a video. The Class also has a ring-buffer, so that the newest image can be gotten. I started a thread to update this class by calling procced method and get the latest image to main thread by calling get_latest method. But why doesn’t the window update automatically. So the codes worked well if I dont use multi-threading. Here are the codes.

class ResourceTest:
    def __init__(self) -> None: = Camera(1)
        self.gen =
        self.gas = GrabberAndSaver(self.gen,10,1,(1080,1440,3),cv2.VideoWriter('test.mp4',cv2.VideoWriter_fourcc(*'mp4v'),18,(1440,1080)))
        cv2.namedWindow('resource test') = Thread(target=self.gas.proceed)
        while True:
            im = self.gas.get_latest()[0,...,::-1]
            #im = next(self.gen)[0,...,::-1]
            cv2.imshow('resource test',im)
            if cv2.waitKey(1) & 0xFF == ord('q'):
class GrabberAndSaver:
    cache = None
    ptr_latest = 0
    ptr_earliest = 0
    def __init__(self,gen: Generator,cache_len:int,cam_num:int,im_shape:Union[list,tuple,np.ndarray],video_writer:Union[list,tuple]) -> None:
        self.gen = gen
        self.cache = np.zeros((cache_len,cam_num,*im_shape),dtype = np.uint8)
        self.saver = Saver(video_writer)
    def proceed(self):
        c = 0
        while True:
            im = next(self.gen)
            c += 1
            if c == 150:
    def _push(self,value:Any):
        for i in range(len(value)):
            self.cache[self.ptr_latest,i] = value[i]
        if self.ptr_latest == len(self.cache) - 1:
            self.ptr_latest = 0
            self.ptr_latest += 1
    def get_latest(self):
        return self.cache[self.ptr_latest-1]

Thanks for helping

Best wishes