问题描述
我正在遵循此tutorial来练习sqflite，但是当我添加新变量时，它不再起作用。我正在添加String _image，并且为使用变量的位置添加了代码，但是当我运行代码时，它可以运行，但是add函数不起作用（即，当我单击浮动按钮时，它会显示添加页，但是当我单击save时，它不会显示更新后的列表。
任何帮助将不胜感激！
这是note.dart：
class Note {
int _id;
String _title;
String _description;
String _date;
int _priority;
String _image;
Note(this._title,this._date,this._image,this._priority,[this._description]);
Note.withId(this._id,this._title,[this._description]);
int get id => _id;
String get title => _title;
String get description => _description;
int get priority => _priority;
String get date => _date;
String get image => _image;
set title(String newTitle) {
if (newTitle.length <= 255) {
this._title = newTitle;
}
}
set description(String newDescription) {
if (newDescription.length <= 255) {
this._description = newDescription;
}
}
set priority(int newPriority) {
if (newPriority >= 1 && newPriority <= 2) {
this._priority = newPriority;
}
}
set date(String newDate) {
this._date = newDate;
}
set image(String newImage) {
this._image = newImage;
}
// 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['date'] = _date;
map['image'] = _image;
return map;
}
// Extract a Note object from a Map object
Note.fromMapObject(Map<String,dynamic> map) {
this._id = map['id'];
this._title = map['title'];
this._description = map['description'];
this._priority = map['priority'];
this._date = map['date'];
this._image = map['image'];
}
}
这里是note_detail.dart：
import 'dart:async';
import 'package:Flutter/material.dart';
import 'package:Flutter_app/models/note.dart';
import 'package:Flutter_app/utils/database_helper.dart';
import 'package:intl/intl.dart';
class NoteDetail extends StatefulWidget {
final String appBarTitle;
final Note note;
NoteDetail(this. note,this.appBarTitle);
@override
State<StatefulWidget> createState() {
return NoteDetailState(this.note,this.appBarTitle);
}
}
class NoteDetailState extends State<NoteDetail> {
static var _priorities = ['High','Low'];
DatabaseHelper helper = DatabaseHelper();
String appBarTitle;
Note note;
TextEditingController titleController = TextEditingController();
TextEditingController descriptionController = TextEditingController();
NoteDetailState(this.note,this.appBarTitle);
@override
Widget build(BuildContext context) {
TextStyle textStyle = Theme.of(context).textTheme.title;
titleController.text = note.title;
descriptionController.text = note.description;
return WillPopScope(
onWillPop: () {
// Write some code to control things,when user press Back navigation button in device navigationBar
movetoLastScreen();
},child: Scaffold(
appBar: AppBar(
title: Text(appBarTitle),leading: IconButton(icon: Icon(
Icons.arrow_back),onpressed: () {
// Write some code to control things,when user press back button in AppBar
movetoLastScreen();
}
),),body: Padding(
padding: EdgeInsets.only(top: 15.0,left: 10.0,right: 10.0),child: ListView(
children: <Widget>[
// First element
ListTile(
title: DropdownButton(
items: _priorities.map((String dropDownStringItem) {
return DropdownMenuItem<String> (
value: dropDownStringItem,child: Text(dropDownStringItem),);
}).toList(),style: textStyle,value: getPriorityAsstring(note.priority),onChanged: (valueSelectedByUser) {
setState(() {
debugPrint('User selected $valueSelectedByUser');
updatePriorityAsInt(valueSelectedByUser);
});
}
),// Second Element
Padding(
padding: EdgeInsets.only(top: 15.0,bottom: 15.0),child: TextField(
controller: titleController,onChanged: (value) {
debugPrint('Something changed in Title Text Field');
updateTitle();
},decoration: Inputdecoration(
labelText: 'Title',labelStyle: textStyle,border: OutlineInputBorder(
borderRadius: BorderRadius.circular(5.0)
)
),// Third Element
Padding(
padding: EdgeInsets.only(top: 15.0,child: TextField(
controller: descriptionController,onChanged: (value) {
debugPrint('Something changed in Description Text Field');
updateDescription();
},decoration: Inputdecoration(
labelText: 'Description',border: OutlineInputBorder(
borderRadius: BorderRadius.circular(5.0)
)
),// Fourth Element
Padding(
padding: EdgeInsets.only(top: 15.0,child: Row(
children: <Widget>[
Expanded(
child: RaisedButton(
color: Theme.of(context).primaryColorDark,textColor: Theme.of(context).primaryColorLight,child: Text(
'Save',textScaleFactor: 1.5,onpressed: () {
setState(() {
debugPrint("Save button clicked");
_save();
});
},Container(width: 5.0,Expanded(
child: RaisedButton(
color: Theme.of(context).primaryColorDark,child: Text(
'Delete',onpressed: () {
setState(() {
debugPrint("Delete button clicked");
_delete();
});
},],));
}
void movetoLastScreen() {
Navigator.pop(context,true);
}
// Convert the String priority in the form of integer before saving it to Database
void updatePriorityAsInt(String value) {
switch (value) {
case 'High':
note.priority = 1;
break;
case 'Low':
note.priority = 2;
break;
}
}
// Convert int priority to String priority and display it to user in DropDown
String getPriorityAsstring(int value) {
String priority;
switch (value) {
case 1:
priority = _priorities[0]; // 'High'
break;
case 2:
priority = _priorities[1]; // 'Low'
break;
}
return priority;
}
// Update the title of Note object
void updateTitle(){
note.title = titleController.text;
}
// Update the description of Note object
void updateDescription() {
note.description = descriptionController.text;
}
// Save data to database
void _save() async {
movetoLastScreen();
note.image = "123"; //FIXME: Replace with the right image
note.date = DateFormat.yMMMd().format(DateTime.Now());
int result;
if (note.id != null) { // Case 1: Update operation
result = await helper.updateNote(note);
} else { // Case 2: Insert Operation
result = await helper.insertNote(note);
}
if (result != 0) { // Success
_showAlertDialog('Status','Note Saved Successfully');
} else { // Failure
_showAlertDialog('Status','Problem Saving Note');
}
}
void _delete() async {
movetoLastScreen();
// Case 1: If user is trying to delete the NEW NOTE i.e. he has come to
// the detail page by pressing the FAB of NoteList page.
if (note.id == null) {
_showAlertDialog('Status','No Note was deleted');
return;
}
// Case 2: User is trying to delete the old note that already has a valid ID.
int result = await helper.deleteNote(note.id);
if (result != 0) {
_showAlertDialog('Status','Note Deleted Successfully');
} else {
_showAlertDialog('Status','Error Occured while Deleting Note');
}
}
void _showAlertDialog(String title,String message) {
AlertDialog alertDialog = AlertDialog(
title: Text(title),content: Text(message),);
showDialog(
context: context,builder: (_) => alertDialog
);
}
}
这是note_list.dart：
import 'dart:async';
import 'package:Flutter/material.dart';
import 'package:Flutter_app/models/note.dart';
import 'package:Flutter_app/utils/database_helper.dart';
import 'package:Flutter_app/screens/note_detail.dart';
import 'package:sqflite/sqflite.dart';
class NoteList extends StatefulWidget {
@override
State<StatefulWidget> createState() {
return NoteListState();
}
}
class NoteListState extends State<NoteList> {
DatabaseHelper databaseHelper = DatabaseHelper();
List<Note> noteList;
int count = 0;
@override
Widget build(BuildContext context) {
if (noteList == null) {
noteList = List<Note>();
updateListView();
}
return Scaffold(
appBar: AppBar(
title: Text('Notes'),body: getNoteListView(),floatingActionButton: FloatingActionButton(
onpressed: () {
debugPrint('FAB clicked');
navigatetoDetail(Note('','',2,'Add Note');
},tooltip: 'Add Note',child: Icon(Icons.add),);
}
ListView getNoteListView() {
TextStyle titleStyle = Theme.of(context).textTheme.subhead;
return ListView.builder(
itemCount: count,itemBuilder: (BuildContext context,int position) {
return Card(
color: Colors.white,elevation: 2.0,child: ListTile(
leading: CircleAvatar(
backgroundColor: getPriorityColor(this.noteList[position].priority),child: getPriorityIcon(this.noteList[position].priority),title: Text(this.noteList[position].title,style: titleStyle,subtitle: Text(this.noteList[position].date),trailing: GestureDetector(
child: Icon(Icons.delete,color: Colors.grey,onTap: () {
_delete(context,noteList[position]);
},onTap: () {
debugPrint("ListTile Tapped");
navigatetoDetail(this.noteList[position],'Edit Note');
},);
},);
}
// Returns the priority color
Color getPriorityColor(int priority) {
switch (priority) {
case 1:
return Colors.red;
break;
case 2:
return Colors.yellow;
break;
default:
return Colors.yellow;
}
}
// Returns the priority icon
Icon getPriorityIcon(int priority) {
switch (priority) {
case 1:
return Icon(Icons.play_arrow);
break;
case 2:
return Icon(Icons.keyboard_arrow_right);
break;
default:
return Icon(Icons.keyboard_arrow_right);
}
}
void _delete(BuildContext context,Note note) async {
int result = await databaseHelper.deleteNote(note.id);
if (result != 0) {
_showSnackBar(context,'Note Deleted Successfully');
updateListView();
}
}
void _showSnackBar(BuildContext context,String message) {
final snackBar = SnackBar(content: Text(message));
Scaffold.of(context).showSnackBar(snackBar);
}
void navigatetoDetail(Note note,String title) async {
bool result = await Navigator.push(context,MaterialPageRoute(builder: (context) {
return 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;
this.count = noteList.length;
});
});
});
}
}
这是database_helper.dart：
import 'package:sqflite/sqflite.dart';
import 'dart:async';
import 'dart:io';
import 'package:path_provider/path_provider.dart';
import 'package:Flutter_app/models/note.dart';
class DatabaseHelper {
static DatabaseHelper _databaseHelper; // Singleton DatabaseHelper
static Database _database; // Singleton Database
String noteTable = 'note_table';
String colId = 'id';
String colTitle = 'title';
String colDescription = 'description';
String colPriority = 'priority';
String colDate = 'date';
String colImage = 'image';
DatabaseHelper._createInstance(); // Named constructor to create instance of DatabaseHelper
factory DatabaseHelper() {
if (_databaseHelper == null) {
_databaseHelper = DatabaseHelper._createInstance(); // This is executed only once,singleton object
}
return _databaseHelper;
}
Future<Database> get database async {
if (_database == null) {
_database = await initializeDatabase();
}
return _database;
}
Future<Database> initializeDatabase() async {
// Get the directory path for both Android and iOS to store database.
Directory directory = await getApplicationDocumentsDirectory();
String path = directory.path + 'notes.db';
// Open/create the database at a given path
var notesDatabase = await openDatabase(path,version: 1,onCreate: _createDb);
return notesDatabase;
}
void _createDb(Database db,int newVersion) async {
await db.execute('CREATE TABLE $noteTable($colId INTEGER PRIMARY KEY AUTOINCREMENT,$colTitle TEXT,'
'$colDescription TEXT,$colPriority INTEGER,$colDate TEXT,$colImage TEXT)');
}
// Fetch Operation: Get all note objects from database
Future<List<Map<String,dynamic>>> getNoteMapList() async {
Database db = await this.database;
// var result = await db.rawQuery('SELECT * FROM $noteTable order by $colPriority ASC');
var result = await db.query(noteTable,orderBy: '$colPriority ASC');
return result;
}
// Insert Operation: Insert a Note object to database
Future<int> insertNote(Note note) async {
Database db = await this.database;
var result = await db.insert(noteTable,note.toMap());
return result;
}
// Update Operation: Update a Note object and save it to database
Future<int> updateNote(Note note) async {
var db = await this.database;
var result = await db.update(noteTable,note.toMap(),where: '$colId = ?',whereArgs: [note.id]);
return result;
}
// Delete Operation: Delete a Note object from database
Future<int> deleteNote(int id) async {
var db = await this.database;
int result = await db.rawDelete('DELETE FROM $noteTable WHERE $colId = $id');
return result;
}
// Get number of Note objects in database
Future<int> getCount() async {
Database db = await this.database;
List<Map<String,dynamic>> x = await db.rawQuery('SELECT COUNT (*) from $noteTable');
int result = Sqflite.firstIntValue(x);
return result;
}
// Get the 'Map List' [ List<Map> ] and convert it to 'Note List' [ List<Note> ]
Future<List<Note>> getNoteList() async {
var noteMapList = await getNoteMapList(); // Get 'Map List' from database
int count = noteMapList.length; // Count the number of map entries in db table
List<Note> noteList = List<Note>();
// For loop to create a 'Note List' from a 'Map List'
for (int i = 0; i < count; i++) {
noteList.add(Note.fromMapObject(noteMapList[i]));
}
return noteList;
}
}
解决方法
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