From e3d4f293bb771eafe389665b26dbb08b04e2c3d4 Mon Sep 17 00:00:00 2001
From: Lucas Aschenbach <Lucas.Aschenbach@gmail.com>
Date: Thu, 1 Apr 2021 12:02:18 +0200
Subject: [PATCH] Add NestedBackButtonDispatcher

---
 lib/src/advanced_navigator.dart     |  1 +
 lib/src/back_button_dispatcher.dart | 24 ++++++++++++++++++++++++
 2 files changed, 25 insertions(+)
 create mode 100644 lib/src/back_button_dispatcher.dart

diff --git a/lib/src/advanced_navigator.dart b/lib/src/advanced_navigator.dart
index 6cf20d8..9a4065e 100644
--- a/lib/src/advanced_navigator.dart
+++ b/lib/src/advanced_navigator.dart
@@ -2,6 +2,7 @@ import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
 
 part 'route_information_provider.dart';
+part 'back_button_dispatcher.dart';
 
 /// A function for building a page stack from route information
 typedef PathFactory = RouterConfiguration Function(RouteInformation);
diff --git a/lib/src/back_button_dispatcher.dart b/lib/src/back_button_dispatcher.dart
new file mode 100644
index 0000000..780ae9a
--- /dev/null
+++ b/lib/src/back_button_dispatcher.dart
@@ -0,0 +1,24 @@
+part of 'advanced_navigator.dart';
+
+class NestedBackButtonDispatcher extends ChildBackButtonDispatcher {
+  NestedBackButtonDispatcher(
+    BackButtonDispatcher parent, {
+    @required Route route,
+  }) : _route = route,
+       super(parent);
+
+  final Route _route;
+
+  @override
+  Future<bool> invokeCallback(Future<bool> defaultValue) {
+    // only pop if navigator is contained in top-most route
+    if (_route.isCurrent) {
+      return super.invokeCallback(defaultValue);
+    } else {
+      parent.forget(this);
+      var value = parent.invokeCallback(defaultValue);
+      parent.deferTo(this);
+      return value;
+    }
+  }
+}
\ No newline at end of file