一、Async Await概述

Async/Await是Dart处理异步操作的语法糖，使异步代码像同步代码一样易读。

|| 特性 | 说明 |
|------|------|
| 语法简洁 | 代码线性化 |
| 错误处理 | try-catch机制 |
| 链式调用 | 避免回调地狱 |
| 性能优化 | 非阻塞执行 |

二、示例代码

class _Page06AsyncDemo extends StatefulWidget {
  const _Page06AsyncDemo();

  @override
  State<_Page06AsyncDemo> createState() => _Page06AsyncDemoState();
}

class _Page06AsyncDemoState extends State<_Page06AsyncDemo> {
  bool _isLoading = false;
  String _result = '';

  Future<String> _fetchData() async {
    await Future.delayed(const Duration(seconds: 2));
    return '数据加载成功: ${DateTime.now().toLocal()}';
  }

  Future<void> _loadData() async {
    setState(() {
      _isLoading = true;
      _result = '';
    });

    try {
      final data = await _fetchData();
      if (mounted) {
        setState(() {
          _result = data;
          _isLoading = false;
        });
      }
    } catch (e) {
      if (mounted) {
        setState(() {
          _result = '错误: $e';
          _isLoading = false;
        });
      }
    }
  }

  @override
  Widget build(BuildContext context) {
    return Container(
      color: Colors.cyan.shade50,
      padding: const EdgeInsets.all(20),
      child: Column(
        children: [
          Container(
            padding: const EdgeInsets.all(20),
            decoration: BoxDecoration(
              color: Colors.cyan.shade600,
              borderRadius: BorderRadius.circular(20),
            ),
            child: const Column(
              children: [
                Icon(Icons.sync, size: 48, color: Colors.white),
                SizedBox(height: 16),
                Text(
                  'Async Await',
                  style: TextStyle(fontSize: 28, fontWeight: FontWeight.bold, color: Colors.white),
                ),
                SizedBox(height: 8),
                Text('异步编程 - 页面 6/10', style: TextStyle(color: Colors.white70)),
              ],
            ),
          ),
          const SizedBox(height: 24),
          Expanded(
            child: Container(
              padding: const EdgeInsets.all(20),
              decoration: BoxDecoration(color: Colors.white, borderRadius: BorderRadius.circular(20)),
              child: Column(
                children: [
                  if (_isLoading)
                    const Center(child: CircularProgressIndicator())
                  else if (_result.isNotEmpty)
                    Text(_result, style: const TextStyle(fontSize: 18))
                  else
                    const Text('点击按钮加载数据', style: TextStyle(fontSize: 16, color: Colors.grey)),
                  const Spacer(),
                  ElevatedButton(
                    onPressed: _isLoading ? null : _loadData,
                    style: ElevatedButton.styleFrom(backgroundColor: Colors.cyan.shade600),
                    child: const Text('加载数据', style: TextStyle(color: Colors.white)),
                  ),
                ],
              ),
            ),
          ),
        ],
      ),
    );
  }
}

三、异步流程

四、最佳实践

• ✅ 始终检查mounted
• ✅ 使用try-catch处理错误
• ✅ 提供加载状态反馈
• ❌ 避免阻塞主线程
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