Flutter: How to read preferences at Widget startup?

Question

I have been trying to read preferences at Widget startup but have been unable to find a solution. I wish to show the users name in a TextField (which they can change) and store it in preferences so that it is shown as soon as they go back to the page.

class _MyHomePageState extends State<MyHomePage> {   TextEditingController _controller;   :   :   Future<Null> storeName(String name) async {     SharedPreferences prefs = await SharedPreferences.getInstance();     prefs.setString("name", name);   }    @override   initState() async {     super.initState();     SharedPreferences prefs = await SharedPreferences.getInstance();     _controller = new TextEditingController(text: prefs.getString("name"));   }    @override   Widget build(BuildContext context) {   :   :   return new TextField(                decoration: new InputDecoration(                  hintText: "Name (optional)",                ),                onChanged: (String str) {                  setState(() {                    _name = str;                    storeName(str);                  });                },                controller: _controller,              )   } } 

I got the idea for using async on initState() from :
flutter timing problems on stateful widget after API call
But the async seems to cause this error on startup :

'package:flutter/src/widgets/framework.dart': Failed assertion: line 967 pos 12:  '_debugLifecycleState == _StateLifecycle.created': is not true. 

I looked for examples of FutureBuilder but cannot seem to find any which are similar to what I am trying to do.

Answer 1

I would suggest not to use the async on initState(). but you can do this in a different way by wrapping up your SharedPreferences inside another function and declaring this as async.

I have modified your code . Please check if this works. Many Thanks.

modified code:

class _MyHomePageState extends State<MyHomePage> {   TextEditingController _controller;   String _name;    Future<Null> getSharedPrefs() async {     SharedPreferences prefs = await SharedPreferences.getInstance();     _name = prefs.getString("name");     setState(() {       _controller = new TextEditingController(text: _name);     });   }    @override   void initState() {     super.initState();     _name = "";     getSharedPrefs();     }    @override   Widget build(BuildContext context) {      return new TextField(                  decoration: new InputDecoration(                    hintText: "Name (optional)",                  ),                  onChanged: (String str) {                    setState(() {                      _name = str;                      storeName(str);                  });                },                controller: _controller,     );   } } 

Let me know if this helps. Thank you.