Flutter：如何在textformfield中加下划线

Question

I'm trying to make it such that the user can enter his pin, and the pin is supposed to be 4 digits long. Now, the 4 digits that he can enter should be underscored in the text form field (even before he enters the pin), somewhat like ____ .

So something like this:

Basically just a normal input field that has the 4 underscores. Is there anyway I can do this in textformfield?

Thanks in advance!

Answer 1

I have tried this on Android Kotlin by using TextWatcher , and I think this could be done by this link below: Here's a reference !

Answer 2

Try This: https://api.flutter.dev/flutter/material/UnderlineInputBorder-class.html

Full Code:

import 'package:flutter/material.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: MyHomePage(),
    );
  }
}

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

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  Widget build(BuildContext context) {
    return Scaffold(
        appBar: AppBar(
          title: Text('TextField Input Decoration Demo'),
        ),
        body: new SafeArea(
            top: true,
            bottom: true,
            child: Column(
              children: [
                Padding(
                    padding: EdgeInsets.all(20),
                    child: Row(
                      children: [
                        Container(
                            width: 40,
                            child: TextFormField(
                              style: TextStyle(fontSize: 50),
                              textInputAction: TextInputAction.next,
                              decoration: const InputDecoration(
                                enabledBorder: UnderlineInputBorder(
                                    borderSide: BorderSide(
                                  color: Colors.black,
                                  width: 10.0,
                                )),
                                focusedBorder: UnderlineInputBorder(
                                  borderSide: BorderSide(
                                    color: Colors.black,
                                    width: 10.0,
                                  ),
                                ),
                              ),
                            )),
                        SizedBox(width: 5),
                        Container(
                            width: 40,
                            child: TextFormField(
                              style: TextStyle(fontSize: 50),
                              textInputAction: TextInputAction.next,
                              decoration: const InputDecoration(
                                enabledBorder: UnderlineInputBorder(
                                    borderSide: BorderSide(
                                  color: Colors.black,
                                  width: 10.0,
                                )),
                                focusedBorder: UnderlineInputBorder(
                                  borderSide: BorderSide(
                                    color: Colors.black,
                                    width: 10.0,
                                  ),
                                ),
                              ),
                            )),
                        SizedBox(width: 5),
                        Container(
                            width: 40,
                            child: TextFormField(
                              style: TextStyle(fontSize: 50),
                              textInputAction: TextInputAction.next,
                              decoration: const InputDecoration(
                                enabledBorder: UnderlineInputBorder(
                                    borderSide: BorderSide(
                                  color: Colors.black,
                                  width: 10.0,
                                )),
                                focusedBorder: UnderlineInputBorder(
                                  borderSide: BorderSide(
                                    color: Colors.black,
                                    width: 10.0,
                                  ),
                                ),
                              ),
                            )),
                        SizedBox(width: 5),
                        Container(
                            width: 40,
                            child: TextFormField(
                              style: TextStyle(fontSize: 50),
                              textInputAction: TextInputAction.next,
                              decoration: const InputDecoration(
                                enabledBorder: UnderlineInputBorder(
                                    borderSide: BorderSide(
                                  color: Colors.black,
                                  width: 10.0,
                                )),
                                focusedBorder: UnderlineInputBorder(
                                  borderSide: BorderSide(
                                    color: Colors.black,
                                    width: 10.0,
                                  ),
                                ),
                              ),
                            )),
                      ],
                    )),
                new Divider(
                  color: Colors.black,
                ),
              ],
            )));
  }
}