大大帮我看看代码有啥问题，图像不能移动

import sys
import pygame

class rocaket:

def __init__(self):
        pygame.init()
        self.screen = pygame.display.set_mode((1200, 800))
        self.ship = pygame.image.load("image/ship.bmp")
        pygame.display.set_caption("小火箭")
        self.screen.fill((230, 230, 230))
        self.rect = self.ship.get_rect()
        self.screen_rect = self.screen.get_rect()
        self.rect.midbottom = self.screen_rect.center
        self.screen.blit(self.ship, self.rect)
        pygame.display.flip()

        self.x = self.rect.x
        self.y = self.rect.y

        self.moving_right = False
        self.moving_left = False
        self.moving_up = False
        self.moving_down = False

    def run_game(self):
        while True:
            self._check_events()
            self.update()

    def _check_events(self):
        for event in pygame.event.get():
            if event.type == pygame.KEYDOWN:
                self._check_keydown_events(event)
            elif event.type == pygame.KEYUP:
                self._check_keyup_events(event)
            elif event.type == pygame.QUIT:
                sys.exit()

    def _check_keydown_events(self, event):
        if event.key == pygame.K_UP:
            self.moving_up = True
        elif event.key == pygame.K_DOWN:
            self.moving_down = True
        elif event.key == pygame.K_LEFT:
            self.moving_left = True
        elif event.key == pygame.K_RIGHT:
            self.moving_right = True
        elif event.key == pygame.K_q:
            sys.exit()

    def _check_keyup_events(self, event):
        if event.key == pygame.K_UP:
            self.moving_up = False
        elif event.key == pygame.K_DOWN:
            self.moving_down = False
        elif event.key == pygame.K_LEFT:
            self.moving_left = False
        elif event.key == pygame.K_RIGHT:
            self.moving_right = False

    def update(self):
        """根据移动标志调整飞船的位置"""
        if self.moving_right and self.rect.right < self.screen_rect.right:
            self.x += 1
        if self.moving_left and self.rect.left > 0:
            self.x -= 1
        if self.moving_up and self.rect.y > 0:
            self.y -= 1
        if self.moving_down and self.rect.y < self.screen_rect.top:
            self.y += 1

        self.rect.x = self.x
        self.rect.y = self.y

if name == 'main':
# 创建游戏实例并运行游戏
ai = rocaket()
ai.run_game()

```

你代码里面只写了坐标移动的代码,但是没有刷新画面的代码