fix & opt appsign (#1761)

Signed-off-by: bggRGjQaUbCoE <githubaccount56556@proton.me>

lib/utils/app_sign.dart

@@ -10,15 +10,41 @@ abstract class AppSign {
     String appsec = Constants.appSec,
   }) {
     params['appkey'] = appkey;
-    var searchParams = Uri(
-      queryParameters: params.map(
-        (key, value) => MapEntry(key, value.toString()),
-      ),
-    ).query;
-    var sortedQueryString = (searchParams.split('&')..sort()).join('&');
-
+    final sorted = Map.fromEntries(
+      params.entries.toList()..sort((a, b) => a.key.compareTo(b.key)),
+    );
     params['sign'] = md5
-        .convert(utf8.encode(sortedQueryString + appsec))
+        .convert(utf8.encode(_makeQueryFromParametersDefault(sorted) + appsec))
         .toString(); // 获取MD5哈希值
   }
+
+  /// from [Uri]
+  static String _makeQueryFromParametersDefault(
+    Map<String, dynamic /*String?|Iterable<String>*/> queryParameters,
+  ) {
+    var result = StringBuffer();
+    var separator = '';
+
+    void writeParameter(String key, String? value) {
+      result.write(separator);
+      separator = '&';
+      result.write(Uri.encodeQueryComponent(key));
+      if (value != null && value.isNotEmpty) {
+        result
+          ..write('=')
+          ..write(Uri.encodeQueryComponent(value));
+      }
+    }
+
+    queryParameters.forEach((key, value) {
+      if (value case Iterable<String> values) {
+        for (final String value in values) {
+          writeParameter(key, value);
+        }
+      } else {
+        writeParameter(key, value?.toString());
+      }
+    });
+    return result.toString();
+  }
 }