Changed MorpheusTabView behavior.

CHANGELOG.md

@@ -1,5 +1,10 @@
 # Changelog
 
+## [1.2.1] - 2019-09-02
+
+### Changed
+- `MorpheusTabView` only transitions when a new child is provided.
+
 ## [1.2.0+6] - 2019-08-30
 
 ### Fixes

example/lib/main.dart

@@ -1,5 +1,4 @@
 import 'package:flutter/material.dart';
-
 import 'package:morpheus/morpheus.dart';
 
 void main() => runApp(MyApp());
@@ -55,42 +54,25 @@ class MyApp extends StatelessWidget {
   }
 }
 
-class HomeScreen extends StatelessWidget {
+class HomeScreen extends StatefulWidget {
+  @override
+  _HomeScreenState createState() => _HomeScreenState();
+}
+
+class _HomeScreenState extends State<HomeScreen> {
   final profileKey = GlobalKey();
   final settingsKey = GlobalKey();
   final createKey = GlobalKey();
+  int _currentIndex = 0;
 
   @override
   Widget build(BuildContext context) {
     return Scaffold(
-      appBar: AppBar(
-        title: Text('Home'),
-      ),
-      body: ListView(
-        children: <Widget>[
-          ListTile(
-            key: profileKey,
-            title: Text('Profile'),
-            onTap: () => Navigator.of(context).pushNamed(
-              '/profile',
-              arguments: MorpheusRouteArguments(
-                parentKey: profileKey,
-              ),
-            ),
-          ),
-          Divider(height: 1.0),
-          ListTile(
-            key: settingsKey,
-            title: Text('Settings'),
-            onTap: () => Navigator.of(context).pushNamed(
-              '/settings',
-              arguments: MorpheusRouteArguments(
-                parentKey: settingsKey,
-              ),
-            ),
-          ),
-          Divider(height: 1.0),
-        ],
+      body: MorpheusTabView(
+        child: <Widget>[
+          ProfileScreen(),
+          SettingsScreen(),
+        ][_currentIndex],
       ),
       floatingActionButtonLocation: FloatingActionButtonLocation.centerFloat,
       floatingActionButton: FloatingActionButton.extended(
@@ -106,6 +88,20 @@ class HomeScreen extends StatelessWidget {
           ),
         ),
       ),
+      bottomNavigationBar: BottomNavigationBar(
+        currentIndex: _currentIndex,
+        onTap: (index) => setState(() => _currentIndex = index),
+        items: [
+          BottomNavigationBarItem(
+            icon: Icon(Icons.account_circle),
+            title: Text('Profile'),
+          ),
+          BottomNavigationBarItem(
+            icon: Icon(Icons.settings),
+            title: Text('Settings'),
+          ),
+        ],
+      ),
     );
   }
 }

example/pubspec.lock

@@ -66,7 +66,7 @@ packages:
       path: ".."
       relative: true
     source: path
-    version: "1.0.2"
+    version: "1.2.0+6"
   path:
     dependency: transitive
     description:

lib/widgets/morpheus_tab_view.dart

@@ -27,15 +27,52 @@ class _MorpheusTabViewState extends AnimatedWidgetBaseState<MorpheusTabView> {
   _TopLevelScaleTween _scaleTween;
   _TopLevelChildTween _childTween;
 
+  /// Change the value of this property after the initial build to make sure
+  /// that the transition isn't built when the user hasn't changed screens.
+  bool _initialBuild = true;
+
+  /// Used to compare with the new [widget.child] to determine whether to
+  /// animate a change or not.
+  Widget _oldWidget;
+
+  /// Returns true if [widget.child] is different from [_oldWidget].
+  bool get _isNewWidget => !Widget.canUpdate(_oldWidget, widget.child);
+
+  @override
+  void initState() {
+    super.initState();
+
+    // Update [_oldWidget] when the animation ends.
+    controller.addStatusListener((status) {
+      if (status == AnimationStatus.completed) {
+        setState(() => _oldWidget = widget.child);
+
+        // Mark [_initialBuild] as false after the first screen has appeared.
+        if (_initialBuild) {
+          _initialBuild = false;
+        }
+      }
+    });
+  }
+
+  /// Builds the top-level transition.
+  ///
+  /// The transition is only built when [widget.child] changes as defined by
+  /// [_isNewWidget] and if [_initialBuild] is false.
   @override
   Widget build(BuildContext context) {
-    return Opacity(
-      opacity: _opacityTween.evaluate(animation),
-      child: Transform.scale(
-        scale: _scaleTween.evaluate(animation),
-        child: _childTween.evaluate(animation),
-      ),
-    );
+    // Build transition if a new widget has been supplied.
+    if (_isNewWidget && !_initialBuild) {
+      return Opacity(
+        opacity: _opacityTween.evaluate(animation),
+        child: Transform.scale(
+          scale: _scaleTween.evaluate(animation),
+          child: _childTween.evaluate(animation),
+        ),
+      );
+    } else {
+      return widget.child;
+    }
   }
 
   @override

pubspec.lock

@@ -1,13 +1,13 @@
 # Generated by pub
-# See https://www.dartlang.org/tools/pub/glossary#lockfile
+# See https://dart.dev/tools/pub/glossary#lockfile
 packages:
   async:
     dependency: transitive
     description:
       name: async
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.1.0"
+    version: "2.2.0"
   boolean_selector:
     dependency: transitive
     description:
@@ -73,14 +73,14 @@ packages:
       name: pedantic
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "1.5.0"
+    version: "1.7.0"
   quiver:
     dependency: transitive
     description:
       name: quiver
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "2.0.2"
+    version: "2.0.3"
   sky_engine:
     dependency: transitive
     description: flutter
@@ -127,7 +127,7 @@ packages:
       name: test_api
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "0.2.4"
+    version: "0.2.5"
   typed_data:
     dependency: transitive
     description:
@@ -143,4 +143,4 @@ packages:
     source: hosted
     version: "2.0.8"
 sdks:
-  dart: ">=2.2.0 <3.0.0"
+  dart: ">=2.2.2 <3.0.0"

pubspec.yaml

@@ -1,6 +1,6 @@
 name: morpheus
 description: A Flutter package for easily implementing Material Design navigation transitions.
-version: 1.2.0+6
+version: 1.2.1
 author: Sander Dalby Larsen <[email protected]>
 homepage: https://github.com/salby/morpheus