颤振输入中只允许两个十进制数?

问题描述

I want only two digits after the decimal point in the flutter input.User can't add more than two digits after the decimal point.

解决方案

Here you go!Hope it helps :)

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

import 'dart:math' as math;

void main() {
  runApp(new MaterialApp(home: new MyApp()));
}

class MyApp extends StatefulWidget {
  @override
  _MyAppState createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text("Flutter"),
      ),
      body: Form(
        child: ListView(
          children: <Widget>[
            TextFormField(
              inputFormatters: [DecimalTextInputFormatter(decimalRange: 2)],
              keyboardType: TextInputType.numberWithOptions(decimal: true),
            )
          ],
        ),
      ),
    );
  }
}

class DecimalTextInputFormatter extends TextInputFormatter {
  DecimalTextInputFormatter({this.decimalRange})
      : assert(decimalRange == null || decimalRange > 0);

  final int decimalRange;

  @override
  TextEditingValue formatEditUpdate(
    TextEditingValue oldValue, // unused.
    TextEditingValue newValue,
  ) {
    TextSelection newSelection = newValue.selection;
    String truncated = newValue.text;

    if (decimalRange != null) {
      String value = newValue.text;

      if (value.contains(".") &&
          value.substring(value.indexOf(".") + 1).length > decimalRange) {
        truncated = oldValue.text;
        newSelection = oldValue.selection;
      } else if (value == ".") {
        truncated = "0.";

        newSelection = newValue.selection.copyWith(
          baseOffset: math.min(truncated.length, truncated.length + 1),
          extentOffset: math.min(truncated.length, truncated.length + 1),
        );
      }

      return TextEditingValue(
        text: truncated,
        selection: newSelection,
        composing: TextRange.empty,
      );
    }
    return newValue;
  }
}

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