add structure

lib/widget/badge.dart

@@ -0,0 +1,43 @@
+import 'package:flutter/cupertino.dart';
+import 'package:flutter/material.dart';
+
+Widget badgeCounter(int counter, {VoidCallback onPressed}) {
+  return InkWell(
+    onTap: () => onPressed(),
+    child: new Stack(
+      children: <Widget>[
+        new IconButton(
+          padding: EdgeInsets.only(top: 10),
+            icon: Icon(Icons.notifications),
+            onPressed: () {
+              onPressed();
+            }),
+        counter != 0
+            ? new Positioned(
+                right: 11,
+                top: 11,
+                child: new Container(
+                  padding: EdgeInsets.all(2),
+                  decoration: new BoxDecoration(
+                    color: Colors.blue,
+                    borderRadius: BorderRadius.circular(6),
+                  ),
+                  constraints: BoxConstraints(
+                    minWidth: 14,
+                    minHeight: 14,
+                  ),
+                  child: Text(
+                    '+${counter > 99 ? 99 : counter}',
+                    style: TextStyle(
+                      color: Colors.white,
+                      fontSize: 10,
+                    ),
+                    textAlign: TextAlign.center,
+                  ),
+                ),
+              )
+            : new Container()
+      ],
+    ),
+  );
+}