面对按钮 onclick 后通过 TextField 发生重复值的问题

Question

I'm facing a problem when I add in a text value into my TextField it immediately gets duplicated once I save it and redirect it back to the Home screen through the save button onclick.

The video link for a better view of the error:

https://youtu.be/jtujDoXzL7o

The entire code:

import 'package:flutter/material.dart';
import 'package:shared_preferences/shared_preferences.dart';

TextEditingController _notesController1 = new TextEditingController();
TextEditingController _notesController2 = new TextEditingController();
final data = [];

void main() => runApp(MaterialApp(
      debugShowCheckedModeBanner: false,
      home: Home(),
    ));

class Home extends StatefulWidget {
  @override
  _HomeState createState() => _HomeState();
}

class _HomeState extends State<Home> {
  @override
  Widget build(BuildContext context) {
    return (Scaffold(
      backgroundColor: Colors.blueGrey[700],
      appBar: AppBar(
        automaticallyImplyLeading: false,
        title: Text(
          'Glass',
          style: TextStyle(
            fontSize: 20.0,
            letterSpacing: 1.0,
            color: Colors.white,
            fontFamily: 'Montserrat',
          ),
        ),
        centerTitle: true,
        backgroundColor: Colors.blueGrey[700],
      ),
      body: ListView.builder(
        padding: const EdgeInsets.only(top: 10.0),
        itemCount: data.length,
        itemBuilder: (context, index) {
        return GestureDetector(
          child:Card(
            child:Padding(
            padding: const EdgeInsets.only(top: 12.0, bottom: 10, left: 10.0, right: 10.0),
          child: ListTile(
            dense: true,
            onTap:() {},
            title: Text(
              data[index],
              overflow: TextOverflow.ellipsis,
            ),
          ), 
          ),
          ),
        );
       },
      ), 
      floatingActionButton: FloatingActionButton(
              elevation: 9.0,
        child: Icon(Icons.add),
        onPressed: () async {
          await Navigator.push(
            context, MaterialPageRoute(builder: (context) => SharedPreference1()));
        },
        backgroundColor: Colors.blueGrey[300],
      ),
      floatingActionButtonLocation: FloatingActionButtonLocation.centerFloat,
    ));
  }
}

Future<bool> saveData(String nameKey, String value) async {
    SharedPreferences preferences = await SharedPreferences.getInstance();
    return await preferences.setString(nameKey, value);
  }
Future<String> loadData(String nameKey) async {
    SharedPreferences preferences = await SharedPreferences.getInstance();
    return preferences.getString(nameKey);
  }

class Hero extends State<SharedPreference1> {
  Widget buildSaveButton(context) {
  return Container(
    color: Colors.blueGrey[700],
    margin: EdgeInsets.only(top:340.0),
    child: RaisedButton.icon(
      elevation: 9.0,
      icon: Icon(Icons.save),
      label: Text('Save'),
      color: Colors.white,
      onPressed: () async {
        await saveData("_key_name", _notesController1.text);
        await setData();
        print(data);
        Navigator.push(context, MaterialPageRoute(builder: (context) => Home()));
              },
            ),
          ); 
        }      
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Container(
        height: MediaQuery.of(context).size.height,
        width: MediaQuery.of(context).size.width,
        color: Colors.blueGrey[700],
        child: SafeArea(
          child: SingleChildScrollView(
            child: Column(
              children: <Widget>[
                buildHeading(context),
                buildNotesText(),
                buildSaveButton(context),
              ],
            ),
          ),
        ),
      ),
    );
  }
  @override
  void initState() {
    super.initState();
    setData();
  }

  setData() {
    loadData("_key_name").then((value) {
      setState(() {
        if(value==null){
          print("Value not available.");
        }
        else{
          data.add(value);
        }
        
      });
    });
  }

}

Widget buildHeading(context) {
  return Material(
    color: Colors.blueGrey[700],
    child: Padding(
      padding: const EdgeInsets.only(left: 20.0, top: 10.0),
      child: Row(
        children: <Widget>[
          Expanded(
            child: TextField(
              maxLines: 1,
              controller: _notesController1,
              decoration: InputDecoration(
                border: InputBorder.none,
                hintText: 'Note Title',
              ),
              style: TextStyle(
                fontSize: 20, 
                color: Colors.white, 
                fontFamily: 'Montserrat',
                ),
            ),
          ),
          FlatButton(
            child: Icon(Icons.close, color: Colors.white, size: 27),
            onPressed: () {
              Navigator.of(context).pop();
            },
          )
        ],
      ),
    ),
  );
}

Widget buildNotesText() {
  return Material(
    color: Colors.blueGrey[700],
    child: Padding(
      padding: const EdgeInsets.all(20.0),
      child: TextField(
        maxLines: null,
        controller: _notesController2,
        decoration: InputDecoration(
          border: InputBorder.none,
          hintText: 'Create Note Here',
        ),
        cursorColor: Colors.white,
        autofocus: true,
        style: TextStyle(color: Colors.white,fontSize: 18,fontFamily: 'Montserrat'),
      ),
    ),
  );
}

class SharedPreference1 extends StatefulWidget {
  SharedPreference1() : super(); 
  @override
  Hero createState() => Hero();
}

The buildHeading widget is where the title of the notes will be inputted.

The Hero class is where the save button is made which will then save the value to the list and immediately be displayed to the Home screen which is the Home/_HomeState class.

Answer 1

You're calling setData on initState for Hero widget, that's the reason why you see duplicated values. The value on SharedPreferences will be added to data every time you open Hero widget.

Don't see this call makes sense as you want to call this method when onPressed is executed and you're already doing it.