第 12 章 实用插件速查与入门

以下均为 pub.dev 官方或社区验证的高口碑包（版本号以 pub.dev 最新稳定版为准）。每个给出最小可运行示例。

12.1 dio：拦截器与统一错误处理

dependencies:
  dio: ^5.7.0

final dio = Dio(BaseOptions(
  baseUrl: 'https://api.example.com',
  connectTimeout: const Duration(seconds: 10),
  receiveTimeout: const Duration(seconds: 15),
));

// 拦截器：统一加 token、打日志
dio.interceptors.add(InterceptorsWrapper(
  onRequest: (options, handler) {
    options.headers['Authorization'] = 'Bearer <token>';
    handler.next(options);
  },
  onError: (e, handler) {
    if (e.response?.statusCode == 401) {/* 跳转登录页 */}
    handler.next(e);
  },
));

// 用法与 http 类似但返回已解析的对象
final resp = await dio.get('/user/1');
final user = resp.data; // Map

12.2 cached_network_image：带缓存的图片

CachedNetworkImage(
  imageUrl: 'https://picsum.photos/300/200',
  placeholder: (_, __) => const Center(child: CircularProgressIndicator()),
  errorWidget: (_, __, ___) => const Icon(Icons.broken_image),
  fit: BoxFit.cover,
)

12.3 image_picker + permission_handler：拍照上传

final picker = ImagePicker();
final XFile? photo = await picker.pickImage(source: ImageSource.camera, imageQuality: 80);
if (photo != null) {
  final file = File(photo.path); // 之后可 multipart 上传
}

// 动态权限（相机等敏感权限要先申请）
final status = await Permission.camera.request();
if (status.isGranted) {/* 已授权 */}