How I give space between 4 digits ?

Want help to solve issue

CodePudding user response：

Try below code hope its helpful to you.

Your Widget:

TextFormField(
    inputFormatters: [
      FilteringTextInputFormatter.digitsOnly,
      CardNumberFormatter(),
    ],
    textInputAction: TextInputAction.done,
    keyboardType: TextInputType.number,
    decoration: InputDecoration(
      prefixIcon: Padding(
        padding: const EdgeInsets.all(8.0),
        child: Image.network(
          'https://upload.wikimedia.org/wikipedia/commons/thumb/2/2a/Mastercard-logo.svg/800px-Mastercard-logo.svg.png',
          height: 30,
          width: 30,
        ),
      ),
      suffixIcon: Padding(
        padding: const EdgeInsets.all(8.0),
        child: Text(
          'Change',
          style: TextStyle(color: Colors.green),
        ),
      ),
      border: OutlineInputBorder(),
      hintText: 'XXXX XXXX XXXX XXXX',
      labelText: 'Card Number',
    ),
    maxLength: 19,
    onChanged: (value) {},
  ),

Create class for seprate the digits

class CardNumberFormatter extends TextInputFormatter {
  @override
  TextEditingValue formatEditUpdate(
    TextEditingValue previousValue,
    TextEditingValue nextValue,
  ) {
    var inputText = nextValue.text;

    if (nextValue.selection.baseOffset == 0) {
      return nextValue;
    }

    var bufferString = new StringBuffer();
    for (int i = 0; i < inputText.length; i  ) {
      bufferString.write(inputText[i]);
      var nonZeroIndexValue = i   1;
      if (nonZeroIndexValue % 4 == 0 && nonZeroIndexValue != inputText.length) {
        bufferString.write(' ');
      }
    }

    var string = bufferString.toString();
    return nextValue.copyWith(
      text: string,
      selection: new TextSelection.collapsed(
        offset: string.length,
      ),
    );
  }
}

Full Example:

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

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      home: Scaffold(
        body: Center(
          child: MyWidget(),
        ),
      ),
    );
  }
}

class MyWidget extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Container(
      margin: EdgeInsets.symmetric(
        horizontal: 20,
      ),
      child: TextFormField(
        inputFormatters: [
          FilteringTextInputFormatter.digitsOnly,
          CardNumberFormatter(),
        ],
        textInputAction: TextInputAction.done,
        keyboardType: TextInputType.number,
        decoration: InputDecoration(
          prefixIcon: Padding(
            padding: const EdgeInsets.all(8.0),
            child: Image.network(
              'https://upload.wikimedia.org/wikipedia/commons/thumb/2/2a/Mastercard-logo.svg/800px-Mastercard-logo.svg.png',
              height: 30,
              width: 30,
            ),
          ),
          suffixIcon: Padding(
            padding: const EdgeInsets.all(8.0),
            child: Text(
              'Change',
              style: TextStyle(color: Colors.green),
            ),
          ),
          border: OutlineInputBorder(),
          hintText: 'XXXX XXXX XXXX XXXX',
          labelText: 'Card Number',
        ),
        maxLength: 19,
        onChanged: (value) {},
      ),
    );
  }
}

class CardNumberFormatter extends TextInputFormatter {
  @override
  TextEditingValue formatEditUpdate(
    TextEditingValue previousValue,
    TextEditingValue nextValue,
  ) {
    var inputText = nextValue.text;

    if (nextValue.selection.baseOffset == 0) {
      return nextValue;
    }

    var bufferString = new StringBuffer();
    for (int i = 0; i < inputText.length; i  ) {
      bufferString.write(inputText[i]);
      var nonZeroIndexValue = i   1;
      if (nonZeroIndexValue % 4 == 0 && nonZeroIndexValue != inputText.length) {
        bufferString.write(' ');
      }
    }

    var string = bufferString.toString();
    return nextValue.copyWith(
      text: string,
      selection: new TextSelection.collapsed(
        offset: string.length,
      ),
    );
  }
}

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