how to convert a string to double in flutter?

Question

I've been trying for three days to convert the String named description to double but always find some error like invalid double where should i do some changement? can some one help me !

This code defines a Dart class named "Note".

class Note {
 int _id;
 String _title;
 String _description;
 String _date;
 int _priority, _color;

 Note(this._title, this._date, this._priority, this._color,
     this._description);

 Note.withId(this._id, this._title, this._date, this._priority, this._color,
     this._description);

 int get id => _id;

 String get title => _title;

 String get description => _description;

 int get priority => _priority;
 int get color => _color;
 String get date => _date;

 set title(String newTitle) {
   if (newTitle.length <= 255) {
     _title = newTitle;
   }
 }

 set description(String newDescription) {
   if (newDescription.length <= 255) {
     _description = newDescription;
   }
 }

 set priority(int newPriority) {
   if (newPriority >= 1 && newPriority <= 3) {
     _priority = newPriority;
   }
 }

 set color(int newColor) {
   if (newColor >= 0 && newColor <= 9) {
     _color = newColor;
   }
 }

 set date(String newDate) {
   _date = newDate;
 }

 // Convert a Note object into a Map object
 Map<String, dynamic> toMap() {
   var map = Map<String, dynamic>();
   if (id != null) {
     map['id'] = _id;
   }
   map['title'] = _title;
   map['description'] = _description;
   map['priority'] = _priority;
   map['color'] = _color;
   map['date'] = _date;

   return map;
 }

 Note.fromMapObject(Map<String, dynamic> map) {
   _id = map['id'];
   _title = map['title'];
   _description = map['description'];
   _priority = map['priority'];
   _color = map['color'];
   _date = map['date'];
 }
}

The NoteDetail class is passed an instance of the Note class and the title of the appbar when it is created

note_detail.dart

class NoteDetail extends StatefulWidget {
 final String appBarTitle;
 final Note note;

 const NoteDetail(this.note, this.appBarTitle, {Key key}) : super(key: key);

 @override
 State<StatefulWidget> createState() {
   return NoteDetailState(this.note, this.appBarTitle);
 }
}

class NoteDetailState extends State<NoteDetail> {
 DatabaseHelper helper = DatabaseHelper();

 String appBarTitle;
 Note note;
 TextEditingController titleController = TextEditingController();
 TextEditingController descriptionController = TextEditingController();
 int color;
 bool isEdited = false;

 NoteDetailState(this.note, this.appBarTitle);

 @override
 Widget build(BuildContext context) {
   titleController.text = note.title;
   descriptionController.text = note.description;
   color = note.color;
   return WillPopScope(
       onWillPop: () async {
         isEdited ? showDiscardDialog(context) : moveToLastScreen();
         return false;
       },
       child: Scaffold(
         appBar: AppBar(
           elevation: 0,
           title: Text(
             appBarTitle,
             style: Theme.of(context).textTheme.headline5,
           ),
           backgroundColor: colors[color],
           leading: IconButton(
               splashRadius: 22,
               icon: const Icon(Icons.arrow_back_ios, color: Colors.black),
               onPressed: () {
                 isEdited ? showDiscardDialog(context) : moveToLastScreen();
               }),
           actions: <Widget>[
             IconButton(
               splashRadius: 22,
               icon: const Icon(
                 Icons.save,
                 color: Colors.black,
               ),
               onPressed: () {
                 titleController.text.isEmpty
                     ? showEmptyTitleDialog(context)
                     : _save();
               },
             ),
             IconButton(
               splashRadius: 22,
               icon: const Icon(Icons.delete, color: Colors.black),
               onPressed: () {
                 showDeleteDialog(context);
               },
             )
           ],
         ),
         body: Container(
           color: colors[color],
           child: Column(
             children: <Widget>[
               PriorityPicker(
                 selectedIndex: 3 - note.priority,
                 onTap: (index) {
                   isEdited = true;
                   note.priority = 3 - index;
                 },
               ),
               ColorPicker(
                 selectedIndex: note.color,
                 onTap: (index) {
                   setState(() {
                     color = index;
                   });
                   isEdited = true;
                   note.color = index;
                 },
               ),
               Padding(
                 padding: const EdgeInsets.all(16.0),
                 child: TextField(
                   controller: titleController,
                   maxLength: 255,
                   style: Theme.of(context).textTheme.bodyText2,
                   onChanged: (value) {
                     updateTitle();
                   },
                   decoration: const InputDecoration.collapsed(
                     hintText: 'Title',
                   ),
                 ),
               ),
               Expanded(
                 child: Padding(
                   padding: const EdgeInsets.all(16.0),
                   child: TextField(
                     keyboardType: TextInputType.multiline,
                     maxLines: 10,
                     maxLength: 255,
                     controller: descriptionController,
                     style: Theme.of(context).textTheme.bodyText1,
                     onChanged: (value) {
                       updateDescription();
                     },
                     decoration: const InputDecoration.collapsed(
                       hintText: 'Description',
                     ),
                   ),
                 ),
               ),
             ],
           ),
         ),
       ));
 }





 void moveToLastScreen() {
   Navigator.pop(context, true);
 }

 void updateTitle() {
   isEdited = true;
   note.title = titleController.text;
 }

 void updateDescription() {
   isEdited = true;
   note.description = descriptionController.text;
 }

 // Save data to database
 void _save() async {
   moveToLastScreen();

   note.date = DateFormat.yMMMd().format(DateTime.now());

   if (note.id != null) {
     await helper.updateNote(note);
   } else {
     await helper.insertNote(note);
   }
 }

 void _delete() async {
   await helper.deleteNote(note.id);
   moveToLastScreen();
 }
}

note_list.dart

class NoteList extends StatefulWidget {
 const NoteList({Key key}) : super(key: key);

 @override
 State<StatefulWidget> createState() {
   return NoteListState();
 }
}

class NoteListState extends State<NoteList> {
 DatabaseHelper databaseHelper = DatabaseHelper();
 List<Note> noteList;
 int count = 0;
 int axisCount = 2;

 @override
 Widget build(BuildContext context) {
   if (noteList == null) {
     noteList = [];
     updateListView();
   }

   Widget myAppBar() {
     return AppBar(
       title: Text('Notes', style: Theme.of(context).textTheme.headline5),
       centerTitle: true,
       elevation: 0,
       backgroundColor: Colors.white,
       leading: noteList.isEmpty
           ? Container()
           : IconButton(
               splashRadius: 22,
               icon: const Icon(
                 Icons.search,
                 color: Colors.black,
               ),
               onPressed: () async {
                 final Note result = await showSearch(
                     context: context, delegate: NotesSearch(notes: noteList));
                 if (result != null) {
                   navigateToDetail(result, 'Edit Note');
                 }
               },
             ),
       actions: <Widget>[
         noteList.isEmpty
             ? Container()
             : IconButton(
                 splashRadius: 22,
                 icon: Icon(
                   axisCount == 2 ? Icons.list : Icons.grid_on,
                   color: Colors.black,
                 ),
                 onPressed: () {
                   setState(() {
                     axisCount = axisCount == 2 ? 4 : 2;
                   });
                 },
               )
       ],
     );
   }

   return Scaffold(
     appBar: myAppBar(),
     body: noteList.isEmpty
         ? Container(
             color: Colors.white,
             child: Center(
               child: Padding(
                 padding: const EdgeInsets.all(16.0),
                 child: Text('Click on the add button to add a new note!',
                     style: Theme.of(context).textTheme.bodyText2),
               ),
             ),
           )
         : Container(
             color: Colors.white,
             child: getNotesList(),
           ),
     floatingActionButton: FloatingActionButton(
       onPressed: () {
         navigateToDetail(Note('', '', 3, 0,''), 'Add Note');
       },
       tooltip: 'Add Note',
       shape: const CircleBorder(
           side: BorderSide(color: Colors.black, width: 2.0)),
       child: const Icon(Icons.add, color: Colors.black),
       backgroundColor: Colors.white,
     ),
   );
 }

 Widget getNotesList() {
   return StaggeredGridView.countBuilder(
     physics: const BouncingScrollPhysics(),
     crossAxisCount: 4,
     itemCount: count,
     itemBuilder: (BuildContext context, int index) => GestureDetector(
       onTap: () {
         navigateToDetail(noteList[index], 'Edit Note');
       },
       child: Padding(
         padding: const EdgeInsets.all(8.0),
         child: Container(
           padding: const EdgeInsets.all(8.0),
           decoration: BoxDecoration(
               color: colors[noteList[index].color],
               border: Border.all(width: 2, color: Colors.black),
               borderRadius: BorderRadius.circular(8.0)),
           child: Column(
             children: <Widget>[
               Row(
                 mainAxisAlignment: MainAxisAlignment.spaceBetween,
                 children: <Widget>[
                   Expanded(
                     child: Padding(
                       padding: const EdgeInsets.all(8.0),
                       child: Text(
                         noteList[index].title,
                         style: Theme.of(context).textTheme.bodyText2,
                       ),
                     ),
                   ),
                   Text(
                     getPriorityText(noteList[index].priority),
                     style: TextStyle(
                         color: getPriorityColor(noteList[index].priority)),
                   ),
                 ],
               ),
               Padding(
                 padding: const EdgeInsets.all(8.0),
                 child: Row(
                   mainAxisAlignment: MainAxisAlignment.start,
                   children: <Widget>[
                     Expanded(
                       child: Text(
                           noteList[index].description ?? '',
                           style: Theme.of(context).textTheme.bodyText1),
                     )
                   ],
                 ),
               ),
               Row(
                   mainAxisAlignment: MainAxisAlignment.end,
                   children: <Widget>[
                     Text(noteList[index].date,
                         style: Theme.of(context).textTheme.subtitle2),
                   ])
             ],
           ),
         ),
       ),
     ),
     staggeredTileBuilder: (int index) => StaggeredTile.fit(axisCount),
     mainAxisSpacing: 4.0,
     crossAxisSpacing: 4.0,
   );
 }

 // Returns the priority color
 Color getPriorityColor(int priority) {
   switch (priority) {
     case 1:
       return Colors.red;
       break;
     case 2:
       return Colors.yellow;
       break;
     case 3:
       return Colors.green;
       break;

     default:
       return Colors.yellow;
   }
 }

 // Returns the priority icon
 String getPriorityText(int priority) {
   switch (priority) {
     case 1:
       return '!!!';
       break;
     case 2:
       return '!!';
       break;
     case 3:
       return '!';
       break;

     default:
       return '!';
   }
 }


 void navigateToDetail(Note note, String title) async {
   bool result = await Navigator.push(context,
       MaterialPageRoute(builder: (context) => NoteDetail(note, title)));

   if (result == true) {
     updateListView();
   }
 }

 void updateListView() {
   final Future<Database> dbFuture = databaseHelper.initializeDatabase();
   dbFuture.then((database) {
     Future<List<Note>> noteListFuture = databaseHelper.getNoteList();
     noteListFuture.then((noteList) {
       setState(() {
         this.noteList = noteList;
         count = noteList.length;
       });
     });
   });
 }
}

Answer 1

i solve it by change this instruction

descriptionController.text = note.description;

to

note.description = double.tryParse(descriptionController.text)?? 00.00;