improved ux

lib/pages/task_edit_page.dart

@@ -17,17 +17,20 @@ class TaskEditPage extends StatefulWidget {
 
 class _TaskEditPageState extends State<TaskEditPage> {
   Task? task;
-  bool isInitialized = true;
+  bool isInitialized = false;
   final titleController = TextEditingController();
   final descriptionController = TextEditingController();
   final categoryController = TextEditingController();
   final urlController = TextEditingController();
   final dueDateController = TextEditingController();
   final dueTimeController = TextEditingController();
-  late String pageTitle;
+  String pageTitle = 'Create Task';
   final dueDateFocusNode = FocusNode();
   final dueTimeFocusNode = FocusNode();
   final categoryFocusNode = FocusNode();
+  final formKey = GlobalKey<FormState>(debugLabel: 'taskEditFormKey');
+  bool didFormChange = false;
+  bool isDueTimeEnabled = false;
 
   @override
   void didChangeDependencies() {
@@ -38,15 +41,16 @@ class _TaskEditPageState extends State<TaskEditPage> {
       descriptionController.text = task!.description;
       categoryController.text = task!.category;
       urlController.text = task!.url;
-      dueDateController.text = task!.due != null
-          ? getIsoDateString(task!.due!)
-          : '';
-      dueTimeController.text = task!.due != null
-          ? TimeOfDay.fromDateTime(task!.due!).format(context)
-          : '';
-      isInitialized = true;
+      if (task!.due != null) {
+        dueDateController.text = getIsoDateString(task!.due!);
+        dueTimeController.text = TimeOfDay.fromDateTime(
+          task!.due!,
+        ).format(context);
+        isDueTimeEnabled = true;
+      }
+      isInitialized = true;
+      pageTitle = task!.title;
     }
-    pageTitle = task?.title ?? 'CreateTask';
   }
 
   @override
@@ -66,7 +70,11 @@ class _TaskEditPageState extends State<TaskEditPage> {
         ],
       ),
       body: Form(
+        canPop: !didFormChange,
+        onChanged: () => didFormChange = true,
+        onPopInvokedWithResult: onPopInvoked,
         autovalidateMode: AutovalidateMode.onUnfocus,
+        key: formKey,
         child: Padding(
           padding: EdgeInsets.symmetric(
             horizontal: MediaQuery.of(context).size.width * 0.05,
@@ -91,14 +99,22 @@ class _TaskEditPageState extends State<TaskEditPage> {
               TextFormField(
                 focusNode: dueDateFocusNode,
                 controller: dueDateController,
-                onFieldSubmitted: (_) => dueDateFocusNode.nextFocus(),
+                onChanged: maybeEnableDueTime,
+                onFieldSubmitted: (_) {
+                  isDueTimeEnabled
+                      ? dueDateFocusNode.nextFocus()
+                      : categoryFocusNode.requestFocus();
+                },
                 decoration: InputDecoration(
                   label: Text('Due Date'),
                   suffix: IconButton(
                     onPressed: () async {
                       final result = await onOpenCalendarPickerPressed();
                       if (result != null) {
-                        dueDateController.text = getIsoDateString(result);
+                        final dateString = getIsoDateString(result);
+                        dueDateController.text = dateString;
+                        maybeEnableDueTime(dateString);
+                        formKey.currentState?.validate();
                         dueTimeFocusNode.requestFocus();
                       }
                     },
@@ -113,9 +129,7 @@ class _TaskEditPageState extends State<TaskEditPage> {
                 focusNode: dueTimeFocusNode,
                 onFieldSubmitted: (_) => dueTimeFocusNode.nextFocus(),
                 controller: dueTimeController,
-                enabled: DateTime.tryParse(dueDateController.text) != null
-                    ? true
-                    : false,
+                enabled: isDueTimeEnabled,
                 decoration: InputDecoration(
                   label: Text('Due Time'),
                   suffix: IconButton(
@@ -172,8 +186,9 @@ class _TaskEditPageState extends State<TaskEditPage> {
   Future<TimeOfDay?> onOpenTimePickerPressed() {
     return showDialog<TimeOfDay?>(
       context: context,
-      builder: (context) =>
-          TimePickerDialog(initialTime: TimeOfDay(hour: 0, minute: 0)),
+      builder: (context) => TimePickerDialog(
+        initialTime: TimeOfDay.fromDateTime(task?.due ?? DateTime.now()),
+      ),
     );
   }
 
@@ -183,7 +198,7 @@ class _TaskEditPageState extends State<TaskEditPage> {
         title: titleController.text,
         description: descriptionController.text,
         start: null,
-        due: DateTime.tryParse(dueDateController.text),
+        due: null,
         isCompleted: false,
         category: categoryController.text,
         subtasks: [],
@@ -193,4 +208,46 @@ class _TaskEditPageState extends State<TaskEditPage> {
       ),
     );
   }
+
+  void onPopInvoked(bool didPop, Object? result) {
+    if (!didPop) {
+      showDialog<bool>(
+        context: context,
+        builder: (context) => AlertDialog(
+          title: Text('Unsaved Changes'),
+          content: Text(
+            'Are you sure you want to cancel editing? Unsaved changes will be lost.',
+          ),
+          actions: [
+            TextButton(
+              onPressed: () => Navigator.of(context).pop(false),
+              child: Text('No'),
+            ),
+            TextButton(
+              onPressed: () => Navigator.of(context).pop(true),
+              child: Text('Yes'),
+            ),
+          ],
+        ),
+      ).then((result) {
+        if (result != null && result && context.mounted) {
+          Navigator.of(context).pop();
+        }
+      });
+    }
+  }
+
+  void maybeEnableDueTime(String value) {
+    if (value.isNotEmpty &&
+        dateTimeValidator(value) == null &&
+        !isDueTimeEnabled) {
+      setState(() {
+        isDueTimeEnabled = true;
+      });
+    } else if (isDueTimeEnabled) {
+      setState(() {
+        isDueTimeEnabled = false;
+      });
+    }
+  }
 }