import 'package:flutter/material.dart';
    import 'package:flutter_application_1/pages/home_page.dart';
    import 'package:flutter_application_1/utils/routes.dart';
    
    class LoginPage extends StatefulWidget {
      const LoginPage({Key? key}) : super(key: key);
    
      @override
      State<LoginPage> createState() => _LoginPageState();
    }
    
    class _LoginPageState extends State<LoginPage> {
      @override
      Widget build(BuildContext context) {
        String x = '';
        return Material(
            // wrap column with singlechildscrollview widget
            child: SingleChildScrollView(
          child: Column(
            children: [
              SizedBox(
                height: 28,
              ),
              Image.asset(
                "assets/images/login_image.png",
                fit: BoxFit.contain,
              ),
              SizedBox(
                height: 20.0,
              ),
              Text("Welcome $x",
                  style: TextStyle(fontSize: 24, fontWeight: FontWeight.bold)),
              SizedBox(
                height: 20,
              ),
              // wrapping a column with Padding
              Padding(
                padding:
                    const EdgeInsets.symmetric(vertical: 16.0, horizontal: 32.0),
                child: Column(
                  children: [
                    TextFormField(
                      decoration: InputDecoration(
                          hintText: "Enter Username", labelText: "Username"),
                      onChanged: (value) {
                        x = value;
                        setState(() {});
                      },
                    ),
                    TextFormField(
                      obscureText: true,
                      decoration: InputDecoration(
                          hintText: "Enter Password", labelText: "Password"),
                    ),
                    SizedBox(
                      height: 30,
                    ),
                    ElevatedButton(
                      child: Text("Login"),
                      style: TextButton.styleFrom(minimumSize: Size(150, 40)),
                      onPressed: () {
                        print("hello");
                      },
                    )
                  ],
                ),
              ),
            ],
          ),
        ));
      }
    }
    

I'm new to flutter and as I was learning about stateful widget. I'm facing this problem.setstate() is not working in flutter, the compiler is showing no error. Basically I want that when someone enter string in username textfield then the value should be appended along with "welcome".

CodePudding user response：

Try to declare your state variable outside the build method.

class _LoginPageState extends State<LoginPage> {
      String x = '';

      @override
      Widget build(BuildContext context) {
       .....
}

CodePudding user response：

The problem is that you assign your String x = ''; inside the build function and it always assigns the empty string when the widget rebuilds.

Just assign the variable outside the build function.

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

  @override
  State<LoginPage> createState() => _LoginPageState();
}

class _LoginPageState extends State<LoginPage> {
  String x = '';
  @override
  Widget build(BuildContext context) {
    return Material(
        // wrap column with singlechildscrollview widget
        child: SingleChildScrollView(
      child: Column(
        children: [
          SizedBox(
            height: 28,
          ),
          Image.asset(
            "assets/images/login_image.png",
            fit: BoxFit.contain,
          ),
          SizedBox(
            height: 20.0,
          ),
          Text("Welcome $x",
              style: TextStyle(fontSize: 24, fontWeight: FontWeight.bold)),
          SizedBox(
            height: 20,
          ),
          // wrapping a column with Padding
          Padding(
            padding:
                const EdgeInsets.symmetric(vertical: 16.0, horizontal: 32.0),
            child: Column(
              children: [
                TextFormField(
                  decoration: InputDecoration(
                      hintText: "Enter Username", labelText: "Username"),
                  onChanged: (value) {
                    x = value;
                    print(value);
                    setState(() {});
                  },
                ),
                TextFormField(
                  obscureText: true,
                  decoration: InputDecoration(
                      hintText: "Enter Password", labelText: "Password"),
                ),
                SizedBox(
                  height: 30,
                ),
                ElevatedButton(
                  child: Text("Login"),
                  style: TextButton.styleFrom(minimumSize: Size(150, 40)),
                  onPressed: () {
                    print("hello");
                  },
                )
              ],
            ),
          ),
        ],
      ),
    ));
  }
}