Allow swiping back to revisit previous answered questions

Prerequisite for #64
ttencate · Jun 10, 2020 · 8fdba41 · 8fdba41
1 parent 4ac3714
commit 8fdba41
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Showing 3 changed files with 35 additions and 12 deletions.
diff --git a/app/lib/model/user_model.dart b/app/lib/model/user_model.dart
@@ -102,25 +102,39 @@ class Quiz {
   bool get isComplete => _currentQuestionIndex >= questionCount;
 
   int get currentQuestionIndex => _currentQuestionIndex;
+
+  set currentQuestionIndex(int index) {
+    if (index < 0) index = 0;
+    if (index > questionCount) index = questionCount;
+    _currentQuestionIndex = index;
+  }
+
+  int get firstUnansweredQuestionIndex {
+    final index = questions.indexWhere((question) => !question.isAnswered);
+    return index >= 0 ? index : questionCount;
+  }
+
   int get currentQuestionNumber => _currentQuestionIndex + 1;
 
   Question get currentQuestion => isComplete ? null : questions[_currentQuestionIndex];
 
   void proceedToNextQuestion() {
     assert(!isComplete);
-    _currentQuestionIndex++;
+    while (currentQuestion?.isAnswered ?? false) {
+      _currentQuestionIndex++;
+    }
   }
 
   int get correctAnswerCount => questions.where((question) => question.isCorrect == true).length;
 
   int get scorePercent => correctAnswerCount * 100 ~/ questionCount;
 
   Set<Species> get fullyCorrectSpecies =>
-      questions
-          .map((question) => question.correctAnswer)
-          .toSet()
-        ..removeAll(incorrectQuestions.map((question) => question.correctAnswer))
-        ..removeAll(incorrectQuestions.map((question) => question.givenAnswer));
+  questions
+      .map((question) => question.correctAnswer)
+      .toSet()
+    ..removeAll(incorrectQuestions.map((question) => question.correctAnswer))
+    ..removeAll(incorrectQuestions.map((question) => question.givenAnswer));
 
   List<Question> get correctQuestions => questions.where((question) => question.isCorrect == true).toList();
   List<Question> get incorrectQuestions => questions.where((question) => question.isCorrect == false).toList();

diff --git a/app/lib/screens/quiz_page.dart b/app/lib/screens/quiz_page.dart
@@ -69,7 +69,8 @@ class _QuizPageState extends State<QuizPage> {
           body: PageView.builder(
             controller: _pageController,
             scrollDirection: Axis.horizontal,
-            physics: NeverScrollableScrollPhysics(),
+            physics: PageScrollPhysics(),
+            onPageChanged: _showQuestion,
             // We don't pass `itemCount` because if we set it to `quiz.questionCount + 1`,
             // the `PageView` sometimes creates pages before they are visible, causing
             // https://github.com/ttencate/papageno/issues/58.
@@ -78,21 +79,22 @@ class _QuizPageState extends State<QuizPage> {
             // (shouldn't keys prevent this?).
             itemCount: null,
             itemBuilder: (BuildContext context, int index) {
+              if (index > quiz.firstUnansweredQuestionIndex) {
+                return null;
+              }
               if (index < quiz.questionCount) {
                 return QuestionScreen(
                   key: ObjectKey(quiz.questions[index]),
                   question: quiz.questions[index],
                   onAnswer: _storeAnswer,
                   onProceed: _showNextQuestion,
                 );
-              } else if (index == quiz.questionCount) {
+              } else {
                 return QuizResult(
                   quiz: quiz,
                   onRetry: _restart,
                   onBack: _back,
                 );
-              } else {
-                return null;
               }
             },
           ),
@@ -118,6 +120,10 @@ class _QuizPageState extends State<QuizPage> {
     }
   }
 
+  void _showQuestion(int index) {
+    setState(() { quiz.currentQuestionIndex = index; });
+  }
+
   void _restart() {
     Navigator.of(context).pop(QuizPageResult(restart: true));
   }
@@ -175,7 +181,7 @@ class _QuestionScreenState extends State<QuestionScreen> {
   @override
   void initState() {
     super.initState();
-    _playerController = PlayerController(playing: true, looping: true);
+    _playerController = PlayerController(playing: !_question.isAnswered, looping: !_question.isAnswered);
   }
 
   @override
@@ -217,7 +223,7 @@ class _QuestionScreenState extends State<QuestionScreen> {
                 fit: StackFit.expand,
                 alignment: Alignment.center,
                 children: <Widget>[
-                  if (_image == null) Placeholder(),
+                  if (_image == null) Container(),
                   if (_image != null) material.Image(
                     image: AssetImage(join('assets', 'images', _image.fileName)),
                     fit: BoxFit.cover,

diff --git a/app/lib/widgets/revealing_image.dart b/app/lib/widgets/revealing_image.dart
@@ -48,6 +48,9 @@ class _RevealingImageState extends State<RevealingImage> with SingleTickerProvid
     animation = Tween<double>(begin: 0.0, end: 1.0).animate(controller)
         // TODO figure out why we need this -- CustomClipper.reclip is tied to this animation so it should be updating outside the build cycle, right?
         ..addListener(() { setState(() {}); });
+    if (widget.revealed) {
+      controller.forward(from: 1.0); // Skip to end.
+    }
   }
 
   @override