getListAndParameters method
处理请求头和参数列表
Implementation
List<String> getListAndParameters(Map<String, String?> params) {
params = params.map((key, value) => MapEntry(
Uri.encodeComponent(key).toLowerCase(),
Uri.encodeComponent(value ?? "")));
var keys = params.keys.toList();
keys.sort();
String urlParamList = keys.join(";");
String httpParameters =
keys.map((e) => e + "=" + (params[e] ?? "")).join("&");
return [urlParamList, httpParameters];
}