feat: extension support (#78)

ui/flutter/lib/app/views/text_button_loading.dart

@@ -0,0 +1,53 @@
+import 'package:flutter/material.dart';
+
+class TextButtonLoading extends StatefulWidget {
+  final Widget child;
+  final VoidCallback? onPressed;
+  final TextButtonLoadingController controller;
+
+  const TextButtonLoading(
+      {Key? key,
+      required this.child,
+      required this.onPressed,
+      required this.controller})
+      : super(key: key);
+
+  @override
+  State<TextButtonLoading> createState() => _TextButtonLoadingState();
+}
+
+class _TextButtonLoadingState extends State<TextButtonLoading> {
+  @override
+  Widget build(BuildContext context) {
+    return ValueListenableBuilder<bool>(
+      valueListenable: widget.controller,
+      builder: (context, value, child) {
+        return TextButton(
+          key: widget.key,
+          onPressed: value ? null : widget.onPressed,
+          child: value
+              ? const SizedBox(
+                  height: 20,
+                  width: 20,
+                  child: CircularProgressIndicator(
+                    strokeWidth: 2,
+                  ),
+                )
+              : widget.child,
+        );
+      },
+    );
+  }
+}
+
+class TextButtonLoadingController extends ValueNotifier<bool> {
+  TextButtonLoadingController() : super(false);
+
+  void start() {
+    value = true;
+  }
+
+  void stop() {
+    value = false;
+  }
+}