let refreshControl = UIRefreshControl()
refreshControl.addTarget(self, action: #selector(refreshData), for: .valueChanged)
tableView.refreshControl = refreshControl

@objc func refreshData() {
    // 立即显示刷新指示器
    DispatchQueue.main.async {
        self.tableView.setContentOffset(CGPoint(x: 0, y: -self.refreshControl.frame.size.height), animated: true)
    }
    
    // 执行数据加载
    loadData { [weak self] in
        // 数据加载完成后结束刷新
        DispatchQueue.main.async {
            self?.refreshControl.endRefreshing()
        }
    }
}

override func viewDidLayoutSubviews() {
    super.viewDidLayoutSubviews()
    if let refreshControl = tableView.refreshControl {
        tableView.contentInset = UIEdgeInsets(top: refreshControl.frame.height, left: 0, bottom: 0, right: 0)
    }
}

func loadData(completion: @escaping () -> Void) {
    DispatchQueue.global(qos: .userInitiated).async {
        // 模拟网络请求
        Thread.sleep(forTimeInterval: 2)
        
        // 数据处理...
        
        DispatchQueue.main.async {
            self.tableView.reloadData()
            completion()
        }
    }
}