added willpopscope

lib/pages/create_recipe_page.dart

@@ -16,47 +16,56 @@ class CreateRecipe extends StatefulWidget {
 class _CreateRecipeState extends State<CreateRecipe> {
   late RecipeProvider recipe;
 
+  @override
+  void dispose() {
+    super.dispose();
+    recipe.clearRecipe(silent: true);
+  }
+
   @override
   Widget build(BuildContext context) {
     recipe = Provider.of<RecipeProvider>(context);
-    return Scaffold(
-      appBar: AppBar(
-        title: const Text('Create Recipe'),
-      ),
-      body: Form(
-        child: Padding(
-          padding: const EdgeInsets.symmetric(horizontal: 20),
-          child: Column(
-            children: [
-              TextFormField(
-                onChanged: (value) => recipe.title = value,
-                decoration: const InputDecoration(
-                  label: Text('Title'),
+    return WillPopScope(
+      onWillPop: _onWillPop,
+      child: Scaffold(
+        appBar: AppBar(
+          title: const Text('Create Recipe'),
+        ),
+        body: Form(
+          child: Padding(
+            padding: const EdgeInsets.symmetric(horizontal: 20),
+            child: Column(
+              children: [
+                TextFormField(
+                  onChanged: (value) => recipe.title = value,
+                  decoration: const InputDecoration(
+                    label: Text('Title'),
+                  ),
                 ),
-              ),
-              TextFormField(
-                onChanged: (value) => recipe.description = value,
-                decoration: const InputDecoration(
-                  label: Text('Description'),
+                TextFormField(
+                  onChanged: (value) => recipe.description = value,
+                  decoration: const InputDecoration(
+                    label: Text('Description'),
+                  ),
                 ),
-              ),
-              DropdownMenu<Difficulty?>(
-                dropdownMenuEntries: DifficultyUtil.getDropdownList(),
-                onSelected: (value) => recipe.difficulty = value,
-                label: const Text('Difficulty'),
-              ),
-              ElevatedButton(
-                onPressed: _openIngredientBottomSheet,
-                child: const Text('Add Ingredient'),
-              ),
-              Expanded(
-                child: ListView.separated(
-                  itemCount: recipe.ingredients.length,
-                  itemBuilder: _ingredientListBuilder,
-                  separatorBuilder: (context, index) => const Divider(),
+                DropdownMenu<Difficulty?>(
+                  dropdownMenuEntries: DifficultyUtil.getDropdownList(),
+                  onSelected: (value) => recipe.difficulty = value,
+                  label: const Text('Difficulty'),
                 ),
-              )
-            ],
+                ElevatedButton(
+                  onPressed: _openIngredientBottomSheet,
+                  child: const Text('Add Ingredient'),
+                ),
+                Expanded(
+                  child: ListView.separated(
+                    itemCount: recipe.ingredients.length,
+                    itemBuilder: _ingredientListBuilder,
+                    separatorBuilder: (context, index) => const Divider(),
+                  ),
+                )
+              ],
+            ),
           ),
         ),
       ),
@@ -102,4 +111,29 @@ class _CreateRecipeState extends State<CreateRecipe> {
       ),
     );
   }
+
+  Future<bool> _onWillPop() {
+    if (recipe.isEmpty) {
+      return Future<bool>(
+        () {
+          return true;
+        },
+      );
+    }
+    return showDialog<bool>(
+      context: context,
+      builder: (context) => AlertDialog(
+        title: const Text('Leave the page?'),
+        content: const Text('Progress will be lost.'),
+        actions: [
+          TextButton(
+              onPressed: () => Navigator.of(context).pop(false),
+              child: const Text('cancel')),
+          TextButton(
+              onPressed: () => Navigator.of(context).pop(true),
+              child: const Text('leave')),
+        ],
+      ),
+    ).then((value) => value ?? false);
+  }
 }

lib/services/providers/recipe_provider.dart

@@ -12,13 +12,27 @@ class RecipeProvider extends ChangeNotifier implements Recipe {
   final List<IngredientListEntry> _ingredients = [];
   final List<CookingStep> _steps = [];
 
-  void clearRecipe() {
+  void clearRecipe({silent = false}) {
     _title = '';
     _description = '';
     _difficulty = null;
     _ingredients.clear();
     _steps.clear();
-    notifyListeners();
+    if (!silent) {
+      notifyListeners();
+    }
+  }
+
+  bool get isEmpty {
+    return _title.isEmpty &&
+        _description.isEmpty &&
+        _difficulty == null &&
+        _ingredients.isEmpty &&
+        steps.isEmpty;
+  }
+
+  bool get isNotEmpty {
+    return !isEmpty;
   }
 
   @override