Current User
13 min
Get current User on session
Introduction
It would not be enjoyable if the user had to log in every time they open your app. You can avoid this by using the cached current ParseUser object. Whenever you use any signup or login methods, the user is cached locally. You can manage this cache as a session, and automatically assume the user is logged in. In this guide, you will learn how to use the Flutter plugin for Parse Server to get current User on session using ParseUser class for your Flutter App.
Goal
Get current User on session using Parse for a Flutter App.
Prerequisites
To complete this tutorial, you will need:
- A Flutter app created and connected to Back4App.
- Note: Follow the Install Parse SDK on Flutter project to create an Flutter Project connected to Back4App.
- Complete the previous guide so ou can have a better understanding of the ParseUser class.
- A device (not Simulator) running Android or iOS.
Understanding the Get Current User App
To better understand the get current User on session process, we will create an app to signUp, login e logout a user. The application is similar to the previous guide, where we perform the signup, login, and logout. As we’re going to use the same project in the following guides, you can find some not yet available functions. We won’t explain the Flutter application code once this guide’s primary focus is using the Flutter with Parse. Following the next steps, you will build a Login e Logout App at Back4App Database.
Let’s get started!
In the following steps, you will be able to build app a get current user.
1 - Create the Login/Logout App Template
Open your Flutter project from the previous guide Flutter plugin for Parse Server. Go to the main.dart file, clean up all the code, and replace it with:
1 import 'package:flutter/material.dart';
2 import 'package:parse_server_sdk_flutter/parse_server_sdk.dart';
3
4 void main() async {
5 WidgetsFlutterBinding.ensureInitialized();
6
7 final keyApplicationId = 'YOUR_APP_ID_HERE';
8 final keyClientKey = 'YOUR_CLIENT_KEY_HERE';
9 final keyParseServerUrl = 'https://parseapi.back4app.com';
10
11 await Parse().initialize(keyApplicationId, keyParseServerUrl,
12 clientKey: keyClientKey,
13 debug: true);
14
15 runApp(MyApp());
16 }
17
18 class MyApp extends StatelessWidget {
19 Future<bool> hasUserLogged() async {
20 return Future.value(false);
21 }
22
23 @override
24 Widget build(BuildContext context) {
25 return MaterialApp(
26 title: 'Flutter - Parse Server',
27 theme: ThemeData(
28 primarySwatch: Colors.blue,
29 visualDensity: VisualDensity.adaptivePlatformDensity,
30 ),
31 home: FutureBuilder<bool>(
32 future: hasUserLogged(),
33 builder: (context, snapshot) {
34 switch (snapshot.connectionState) {
35 case ConnectionState.none:
36 case ConnectionState.waiting:
37 return Scaffold(
38 body: Center(
39 child: Container(
40 width: 100,
41 height: 100,
42 child: CircularProgressIndicator()),
43 ),
44 );
45 default:
46 if (snapshot.hasData && snapshot.data!) {
47 return UserPage();
48 } else {
49 return LoginPage();
50 }
51 }
52 }),
53 );
54 }
55 }
56
57 class LoginPage extends StatefulWidget {
58 @override
59 _LoginPageState createState() => _LoginPageState();
60 }
61
62 class _LoginPageState extends State<LoginPage> {
63 final controllerUsername = TextEditingController();
64 final controllerPassword = TextEditingController();
65 bool isLoggedIn = false;
66
67 @override
68 Widget build(BuildContext context) {
69 return Scaffold(
70 appBar: AppBar(
71 title: const Text('Flutter - Parse Server'),
72 ),
73 body: Center(
74 child: SingleChildScrollView(
75 padding: const EdgeInsets.all(8),
76 child: Column(
77 crossAxisAlignment: CrossAxisAlignment.stretch,
78 children: [
79 Container(
80 height: 200,
81 child: Image.network(
82 'https://blog.back4app.com/wp-content/uploads/2017/11/logo-b4a-1-768x175-1.png'),
83 ),
84 Center(
85 child: const Text('Flutter on Back4App',
86 style:
87 TextStyle(fontSize: 18, fontWeight: FontWeight.bold)),
88 ),
89 SizedBox(
90 height: 16,
91 ),
92 TextField(
93 controller: controllerUsername,
94 enabled: !isLoggedIn,
95 keyboardType: TextInputType.text,
96 textCapitalization: TextCapitalization.none,
97 autocorrect: false,
98 decoration: InputDecoration(
99 border: OutlineInputBorder(
100 borderSide: BorderSide(color: Colors.black)),
101 labelText: 'Username'),
102 ),
103 SizedBox(
104 height: 8,
105 ),
106 TextField(
107 controller: controllerPassword,
108 enabled: !isLoggedIn,
109 obscureText: true,
110 keyboardType: TextInputType.text,
111 textCapitalization: TextCapitalization.none,
112 autocorrect: false,
113 decoration: InputDecoration(
114 border: OutlineInputBorder(
115 borderSide: BorderSide(color: Colors.black)),
116 labelText: 'Password'),
117 ),
118 SizedBox(
119 height: 16,
120 ),
121 Container(
122 height: 50,
123 child: ElevatedButton(
124 child: const Text('Login'),
125 onPressed: isLoggedIn ? null : () => doUserLogin(),
126 ),
127 ),
128 SizedBox(
129 height: 16,
130 ),
131 Container(
132 height: 50,
133 child: ElevatedButton(
134 child: const Text('Sign Up'),
135 onPressed: () => navigateToSignUp(),
136 ),
137 ),
138 SizedBox(
139 height: 16,
140 ),
141 Container(
142 height: 50,
143 child: ElevatedButton(
144 child: const Text('Reset Password'),
145 onPressed: () => navigateToResetPassword(),
146 ),
147 )
148 ),
149 ),
150 ),
151 ));
152 }
153
154 void doUserLogin() async {
155 final username = controllerUsername.text.trim();
156 final password = controllerPassword.text.trim();
157
158 final user = ParseUser(username, password, null);
159
160 var response = await user.login();
161
162 if (response.success) {
163 navigateToUser();
164 } else {
165 Message.showError(context: context, message: response.error!.message);
166 }
167 }
168
169 void navigateToUser() {
170 Navigator.pushAndRemoveUntil(
171 context,
172 MaterialPageRoute(builder: (context) => UserPage()),
173 (Route<dynamic> route) => false,
174 );
175 }
176
177 void navigateToSignUp() {
178 Navigator.push(
179 context,
180 MaterialPageRoute(builder: (context) => SignUpPage()),
181 );
182 }
183
184 void navigateToResetPassword() {
185 Navigator.push(
186 context,
187 MaterialPageRoute(builder: (context) => ResetPasswordPage()),
188 );
189 }
190 }
191
192 class SignUpPage extends StatefulWidget {
193 @override
194 _SignUpPageState createState() => _SignUpPageState();
195 }
196
197 class _SignUpPageState extends State<SignUpPage> {
198 final controllerUsername = TextEditingController();
199 final controllerPassword = TextEditingController();
200 final controllerEmail = TextEditingController();
201
202 @override
203 Widget build(BuildContext context) {
204 return Scaffold(
205 appBar: AppBar(
206 title: const Text('Flutter Sign Up'),
207 ),
208 body: Center(
209 child: SingleChildScrollView(
210 padding: const EdgeInsets.all(8),
211 child: Column(
212 crossAxisAlignment: CrossAxisAlignment.stretch,
213 children: [
214 Container(
215 height: 200,
216 child: Image.network(
217 'https://blog.back4app.com/wp-content/uploads/2017/11/logo-b4a-1-768x175-1.png'),
218 ),
219 Center(
220 child: const Text('Flutter on Back4App',
221 style:
222 TextStyle(fontSize: 18, fontWeight: FontWeight.bold)),
223 ),
224 SizedBox(
225 height: 16,
226 ),
227 Center(
228 child: const Text('User registration',
229 style: TextStyle(fontSize: 16)),
230 ),
231 SizedBox(
232 height: 16,
233 ),
234 TextField(
235 controller: controllerUsername,
236 keyboardType: TextInputType.text,
237 textCapitalization: TextCapitalization.none,
238 autocorrect: false,
239 decoration: InputDecoration(
240 border: OutlineInputBorder(
241 borderSide: BorderSide(color: Colors.black)),
242 labelText: 'Username'),
243 ),
244 SizedBox(
245 height: 8,
246 ),
247 TextField(
248 controller: controllerEmail,
249 keyboardType: TextInputType.emailAddress,
250 textCapitalization: TextCapitalization.none,
251 autocorrect: false,
252 decoration: InputDecoration(
253 border: OutlineInputBorder(
254 borderSide: BorderSide(color: Colors.black)),
255 labelText: 'E-mail'),
256 ),
257 SizedBox(
258 height: 8,
259 ),
260 TextField(
261 controller: controllerPassword,
262 obscureText: true,
263 keyboardType: TextInputType.text,
264 textCapitalization: TextCapitalization.none,
265 autocorrect: false,
266 decoration: InputDecoration(
267 border: OutlineInputBorder(
268 borderSide: BorderSide(color: Colors.black)),
269 labelText: 'Password'),
270 ),
271 SizedBox(
272 height: 8,
273 ),
274 Container(
275 height: 50,
276 child: ElevatedButton(
277 child: const Text('Sign Up'),
278 onPressed: () => doUserRegistration(),
279 ),
280 )
281 ],
282 ),
283 ),
284 ));
285 }
286
287 void doUserRegistration() async {
288 final username = controllerUsername.text.trim();
289 final email = controllerEmail.text.trim();
290 final password = controllerPassword.text.trim();
291
292 final user = ParseUser.createUser(username, password, email);
293
294 var response = await user.signUp();
295
296 if (response.success) {
297 Message.showSuccess(
298 context: context,
299 message: 'User was successfully created!',
300 onPressed: () async {
301 Navigator.pushAndRemoveUntil(
302 context,
303 MaterialPageRoute(builder: (context) => UserPage()),
304 (Route<dynamic> route) => false,
305 );
306 });
307 } else {
308 Message.showError(context: context, message: response.error!.message);
309 }
310 }
311 }
312
313 class UserPage extends StatelessWidget {
314 ParseUser? currentUser;
315
316 Future<ParseUser?> getUser() async {
317 }
318
319 @override
320 Widget build(BuildContext context) {
321 void doUserLogout() async {
322 var response = await currentUser!.logout();
323 if (response.success) {
324 Message.showSuccess(
325 context: context,
326 message: 'User was successfully logout!',
327 onPressed: () {
328 Navigator.pushAndRemoveUntil(
329 context,
330 MaterialPageRoute(builder: (context) => LoginPage()),
331 (Route<dynamic> route) => false,
332 );
333 });
334 } else {
335 Message.showError(context: context, message: response.error!.message);
336 }
337 }
338
339 return Scaffold(
340 appBar: AppBar(
341 title: Text('User logged in - Current User'),
342 ),
343 body: FutureBuilder<ParseUser?>(
344 future: getUser(),
345 builder: (context, snapshot) {
346 switch (snapshot.connectionState) {
347 case ConnectionState.none:
348 case ConnectionState.waiting:
349 return Center(
350 child: Container(
351 width: 100,
352 height: 100,
353 child: CircularProgressIndicator()),
354 );
355 default:
356 return Padding(
357 padding: const EdgeInsets.all(8.0),
358 child: Column(
359 crossAxisAlignment: CrossAxisAlignment.stretch,
360 mainAxisAlignment: MainAxisAlignment.center,
361 children: [
362 Center(
363 child: Text('Hello, ${snapshot.data!.username}')),
364 SizedBox(
365 height: 16,
366 ),
367 Container(
368 height: 50,
369 child: ElevatedButton(
370 child: const Text('Logout'),
371 onPressed: () => doUserLogout(),
372 ),
373 ),
374 ],
375 ),
376 );
377 }
378 }));
379 }
380 }
381
382 class ResetPasswordPage extends StatefulWidget {
383 @override
384 _ResetPasswordPageState createState() => _ResetPasswordPageState();
385 }
386
387 class _ResetPasswordPageState extends State<ResetPasswordPage> {
388 final controllerEmail = TextEditingController();
389
390 @override
391 Widget build(BuildContext context) {
392 return Scaffold(
393 appBar: AppBar(
394 title: Text('Reset Password'),
395 ),
396 body: SingleChildScrollView(
397 padding: const EdgeInsets.all(8),
398 child: Column(
399 crossAxisAlignment: CrossAxisAlignment.stretch,
400 children: [
401 TextField(
402 controller: controllerEmail,
403 keyboardType: TextInputType.emailAddress,
404 textCapitalization: TextCapitalization.none,
405 autocorrect: false,
406 decoration: InputDecoration(
407 border: OutlineInputBorder(
408 borderSide: BorderSide(color: Colors.black)),
409 labelText: 'E-mail'),
410 ),
411 SizedBox(
412 height: 8,
413 ),
414 Container(
415 height: 50,
416 child: ElevatedButton(
417 child: const Text('Reset Password'),
418 onPressed: () => doUserResetPassword(),
419 ),
420 )
421 ],
422 ),
423 ));
424 }
425
426 void doUserResetPassword() async {}
427 }
428
429 class Message {
430 static void showSuccess(
431 {required BuildContext context,
432 required String message,
433 VoidCallback? onPressed}) {
434 showDialog(
435 context: context,
436 builder: (BuildContext context) {
437 return AlertDialog(
438 title: const Text("Success!"),
439 content: Text(message),
440 actions: <Widget>[
441 new ElevatedButton(
442 child: const Text("OK"),
443 onPressed: () {
444 Navigator.of(context).pop();
445 if (onPressed != null) {
446 onPressed();
447 }
448 },
449 ),
450 ],
451 );
452 },
453 );
454 }
455
456 static void showError(
457 {required BuildContext context,
458 required String message,
459 VoidCallback? onPressed}) {
460 showDialog(
461 context: context,
462 builder: (BuildContext context) {
463 return AlertDialog(
464 title: const Text("Error!"),
465 content: Text(message),
466 actions: <Widget>[
467 new ElevatedButton(
468 child: const Text("OK"),
469 onPressed: () {
470 Navigator.of(context).pop();
471 if (onPressed != null) {
472 onPressed();
473 }
474 },
475 ),
476 ],
477 );
478 },
479 );
480 }
481 }
482When debug parameter in function Parse().initialize is true, allows displaying Parse API calls on the console. This configuration can help you debug the code. It is prudent to disable debug in the release version.
2 - Connect Template to Back4app Project
Find your Application Id and Client Key credentials navigating to your app Dashboard at Back4App Website.
Update your code in main.dart with the values of your project’s ApplicationId and ClientKey in Back4app.
- keyApplicationId = App Id
- keyClientKey = Client Key
Run the project, and the app will load as shown in the image.
3 - Code for get current user on Session
The User Login or SignUp function creates a Session object, which points to the User logged in and stores in your local storage a valid user session.
Calls to methods currentUser will successfully retrieve your ParseUser data and sessionToken for Session object.
Search for the function hasUserLogged in the file main.dart.
Replace the code inside hasUserLogged with:
1 ParseUser? currentUser = await ParseUser.currentUser() as ParseUser?;
2 if (currentUser == null) {
3 return false;
4 }
5 //Checks whether the user's session token is valid
6 final ParseResponse? parseResponse =
7 await ParseUser.getCurrentUserFromServer(currentUser.sessionToken!);
8
9 if (parseResponse?.success == null || !parseResponse!.success) {
10 //Invalid session. Logout
11 await currentUser.logout();
12 return false;
13 } else {
14 return true;
15 }To build this function, follow these steps:
- Call the ParseUser.currentUser() function, which will return a ParseUser object from local storage.
- IfParseUser is null, we do not have any users with an active session in the app.
- IfParseUser is not null, we have a user with an active session in our app.
- The user’s session needs to be validated on the Parse Server, as it has a lifetime.
- If the token is not valid, it is necessary to call the logout function to clear the current session and the user needs to log in again.
The complete function should look like this:
1 Future<bool> hasUserLogged() async {
2 ParseUser? currentUser = await ParseUser.currentUser() as ParseUser?;
3 if (currentUser == null) {
4 return false;
5 }
6 //Checks whether the user's session token is valid
7 final ParseResponse? parseResponse =
8 await ParseUser.getCurrentUserFromServer(currentUser.sessionToken!);
9
10 if (parseResponse?.success == null || !parseResponse!.success) {
11 //Invalid session. Logout
12 await currentUser.logout();
13 return false;
14 } else {
15 return true;
16 }
17 }Look for the function getUser in the file main.dart.
Replace the code inside getUser with:
1 currentUser = await ParseUser.currentUser() as ParseUser?;
2 return currentUser;To build this function, follow these steps:
- Call the ParseUser.currentUser() function, which will return a ParseUser object from local storage.
The complete function should look like this:
1 Future<ParseUser> getUser() async {
2 currentUser = await ParseUser.currentUser() as ParseUser?;
3 return currentUser;
4 }To test it, click on theRunbutton in Android Studio/VSCode.
SignUp or Login and the next screen will display the username of the logged in user.
Quit the application and run again.
If a valid user session is identified, the screen with the user’s username will be displayed.
It’s done!
At the end of this guide, you can get current user on Session of your app using Parse Server core features through Back4App!