颤动输入中只允许两位小数吗？

Question

我只想要flutter输入的小数点后两位数。用户不能在小数点后添加超过两位数。

Answer 1

给你！希望对您有所帮助:)

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;
  }
}

Answer 2

我扩展了功能...我希望你能觉得它有用。请告诉我您是否可以进一步改进。

import 'package:flutter/services.dart';
import 'dart:math' as math;

class DecimalTextInputFormatter extends TextInputFormatter {
  DecimalTextInputFormatter({this.decimalRange, this.activatedNegativeValues})
      : assert(decimalRange == null || decimalRange >= 0,
            'DecimalTextInputFormatter declaretion error');

  final int decimalRange;
  final bool activatedNegativeValues;

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


if (newValue.text.contains(' ')) {
  return oldValue;
}

if (newValue.text.isEmpty) {
  return newValue;
} else if (double.tryParse(newValue.text) == null &&
    !(newValue.text.length == 1 &&
        (activatedNegativeValues == true ||
            activatedNegativeValues == null) &&
        newValue.text == '-')) {
  return oldValue;
}

if (activatedNegativeValues == false &&
    double.tryParse(newValue.text) < 0) {
  return oldValue;
}

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

  if (decimalRange == 0 && value.contains(".")) {
    truncated = oldValue.text;
    newSelection = oldValue.selection;
  }

  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;
}
}

Answer 3

使用 Regexp 的 DecimalTextInputFormatter 的较短版本：

class DecimalTextInputFormatter extends TextInputFormatter {

  DecimalTextInputFormatter({int decimalRange, bool activatedNegativeValues})
  : assert(decimalRange == null || decimalRange >= 0,
    'DecimalTextInputFormatter declaretion error') {
    String dp = (decimalRange != null && decimalRange > 0) ? "([.][0-9]{0,$decimalRange}){0,1}" : "";
    String num = "[0-9]*$dp";

    if(activatedNegativeValues) {
      _exp = new RegExp("^((((-){0,1})|((-){0,1}[0-9]$num))){0,1}$");
    }
    else {
      _exp = new RegExp("^($num){0,1}$");
    }
  }

  RegExp _exp;

  @override
  TextEditingValue formatEditUpdate(
    TextEditingValue oldValue,
    TextEditingValue newValue,
  ) {
    if(_exp.hasMatch(newValue.text)){
      return newValue;
    }
    return oldValue;
  }
}

Answer 4

@AjayKumar 的回答允许将文本输入限制为所需的小数 places.But 我的要求是避免键盘输入除数字和 dot.So 之外的其他字符，我更新了 @AjayKumar 的上述回答

import 'package:flutter/services.dart';
import 'dart:math' as math;   

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.contains('-') ||
      value.contains(' ') ||
      value.contains('..')) {
    truncated = oldValue.text;
    newSelection = oldValue.selection;
  } else 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;

} }

Answer 5

也许对你来说有点晚了，但我也进步了一点：

只允许 1 .
允许否定
开头加负号

希望对您有所帮助 ;)

import 'package:flutter/services.dart';

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

  final int decimalRange;

  @override
  TextEditingValue formatEditUpdate(TextEditingValue oldValue, TextEditingValue newValue) {
    TextEditingValue _newValue = this.sanitize(newValue);
    String text = _newValue.text;

    if (decimalRange == null) {
      return _newValue;
    }

    if (text == '.') {
      return TextEditingValue(
        text: '0.',
        selection: _newValue.selection.copyWith(baseOffset: 2, extentOffset: 2),
        composing: TextRange.empty,
      );
    }

    return this.isValid(text) ? _newValue : oldValue;
  }

  bool isValid(String text) {
    int dots = '.'.allMatches(text).length;

    if (dots == 0) {
      return true;
    }

    if (dots > 1) {
      return false;
    }

    return text.substring(text.indexOf('.') + 1).length <= decimalRange;
  }

  TextEditingValue sanitize(TextEditingValue value) {
    if (false == value.text.contains('-')) {
      return value;
    }

    String text = '-' + value.text.replaceAll('-', '');

    return TextEditingValue(text: text, selection: value.selection, composing: TextRange.empty);
  }
}

和（别忘了导入前面的class）

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

class NumberFormField extends StatelessWidget {
  final InputDecoration decoration;
  final TextEditingController controller;
  final int decimalRange;

  const NumberFormField({Key key, this.decoration, this.controller, this.decimalRange}) :super(key: key);

  @override
  Widget build(BuildContext context) {
    return TextFormField(
      decoration: this.decoration,
      controller: this.controller,
      keyboardType: TextInputType.numberWithOptions(decimal: true),
      inputFormatters: [
        WhitelistingTextInputFormatter(RegExp(r'[\d+\-\.]')),
        NumberTextInputFormatter(decimalRange: this.decimalRange),
      ],
    );
  }
}

Answer 6

并避免不必要的零...请调试此代码。

import 'dart:math' as math;

import 'package:flutter/services.dart';

class DecimalTextInputFormatter extends TextInputFormatter {
  DecimalTextInputFormatter({this.decimalRange, this.activatedNegativeValues})
      : assert(decimalRange == null || decimalRange >= 0,
            'DecimalTextInputFormatter declaretion error');

  final int decimalRange;
  final bool activatedNegativeValues;

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

    if (newValue.text.contains(' ')) {
      return oldValue;
    }

    if (newValue.text.isEmpty) {
      return newValue;
    } else if (double.tryParse(newValue.text) == null &&
        !(newValue.text.length == 1 &&
            (activatedNegativeValues == true ||
                activatedNegativeValues == null) &&
            newValue.text == '-')) {
      return oldValue;
    }

    if (activatedNegativeValues == false &&
        double.tryParse(newValue.text) < 0) {
      return oldValue;
    }

    if ((double.tryParse(oldValue.text) == 0 && !newValue.text.contains('.'))) {
      if (newValue.text.length >= oldValue.text.length) {
        return oldValue;
      }
    }

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

      if (decimalRange == 0 && value.contains(".")) {
        truncated = oldValue.text;
        newSelection = oldValue.selection;
      }

      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;
  }
}

Answer 7

这是一个适合我的解决方案

TextFormField(
    inputFormatters: [
        WhitelistingTextInputFormatter(RegExp(r'^\d+\.?\d{0,2}')),
    ],
)

如果你想允许像 (.21) 或 (.25) 这样的输入

这里有一个解决方案-

TextFormField(
    inputFormatters: [
        WhitelistingTextInputFormatter(RegExp(r'^(\d+)?\.?\d{0,2}')),
    ],
)

Answer 8

可能这是一个更简单的解决方案

inputFormatters: [
            FilteringTextInputFormatter.allow(RegExp(r'(^\d*\.?\d{0,2})'))
          ]

Answer 9

在 Flutter 版本 v1.20.0-1.0 之后。使用

TextFormField(
  keyboardType: TextInputType.numberWithOptions(decimal: true),
  inputFormatters: [
    FilteringTextInputFormatter.allow(RegExp(r'^\d+\.?\d{0,2}')),
  ],
),

Answer 10

我认为这是最简单也是唯一适合我的方法：

inputFormatters: [ LengthLimitingTextInputFormatter(2), ]

Answer 11

飞镖 2.00+

TextFormField(
  keyboardType: TextInputType.numberWithOptions(decimal: true),
  inputFormatters: [
    // Allow Decimal Number With Precision of 2 Only
    FilteringTextInputFormatter.allow(RegExp(r'^\d*\.?\d{0,2}')),
  ],

它允许像 1.、.89、8.99

这样的小数

Answer 12

Dart SDK 版本：2.13.4（稳定） Flutter 2.2.3 • 通道稳定

我在 2021 年 7 月 25 日写了这个答案，提出了一个更简单的解决方案，只使用内置 TextField 的 inputFormatters。

我试图向你们所有人保证，该字段不会接受长于 2 的浮点数（已接受：12.25 与未接受：65.536）。而且，它不会接受多个点，只接受一个点（接受：12.25 vs notAccepted：1.1.11, 1.11, .1.1, 1.1.1.1, whatever..）。

考虑到其他答案的不同之处在于，下面的代码不会以编程方式接受等于 0.1 的 .1，这实际上更加用户友好。它很简单，对我们来说很好看。您只需将下面的代码复制并粘贴到 inputFormatters: [].

如果你想同时接受0.1和.1（不仅仅是0.1），你可以注释掉FilteringTextInputFormatter.allow(RegExp(r'^\d+\.?\d*'))!

inputFormatters: [ FilteringTextInputFormatter.allow(RegExp(r'^(\d+)?\.?\d{0,2}')), FilteringTextInputFormatter.allow(RegExp(r'^\d+\.?\d*')), ]

当你想改变最大小数点时，你可以改变下面一行中的N值：

inputFormatters: [ FilteringTextInputFormatter.allow(RegExp(r'^(\d+)?\.?\d{0,N}')), FilteringTextInputFormatter.allow(RegExp(r'^\d+\.?\d*')), ]

第一个例子展示了你想限制小数点为2的情况，而N值恰好控制了这个限制。您可以在自己的代码中尝试 [:

感谢所有其他答案，希望这个答案可以帮助未来的流浪者！祝你有美好的一天[:

Answer 13

对于 Flutter 中的 TextFeild 小数点前和小数点后长度验证 class.

import 'package:flutter/cupertino.dart';
import 'package:flutter/services.dart';
import 'dart:math' as math;

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

  final int decimalRange;
  final int beforeDecimalRange;

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

    String value;

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

      if(value.contains(".")){
        if(value.split(".")[0].length > beforeDecimalRange){
          truncated = oldValue.text;
          newSelection = oldValue.selection;
        }
      }else{
        if(value.length > beforeDecimalRange){
          truncated = oldValue.text;
          newSelection = oldValue.selection;
        }
      }
    }

    if (decimalRange != null) {
      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;
  }
}

在文本字段中，前任。小数点前 9 位和小数点后 2 位允许以下代码。

inputFormatters: [ FilteringTextInputFormatter.allow(RegExp(r'^\d+\.?\d{0,2}')),
                   DecimalTextInputFormatter(decimalRange: 2, beforeDecimalRange: 9)
                 ],
keyboardType: TextInputType.numberWithOptions(decimal: true),

Answer 14

这对我有用 (Feb/2022)

将文本限制为 2 个小数点并且只有 1 个“.” （句点）

0 将自动添加到号码的开头，如果用户手动删除“.”之前的数字

PS：对答案稍作编辑

TextFormField

TextFormField(
          autofocus: false,
          keyboardType: TextInputType.number,
          controller: controller,
          inputFormatters: [
            DecimalTextInputFormatter(decimalRange: 2),
          ],
          validator: (value) {
            if (value == null || value.isEmpty) {
              return 'Please add amount.';
            }
            return null;
          },

DecimalTextInputFormatter

import 'package:flutter/services.dart';
import 'dart:math' as math;

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

  final int decimalRange;

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

    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),
      );
    } else if (value.contains(".")) {
      String tempValue = value.substring(value.indexOf(".") + 1);
      if (tempValue.contains(".")) {
        truncated = oldValue.text;
        newSelection = oldValue.selection;
      }
      if (value.indexOf(".") == 0) {
        truncated = "0" + truncated;
        newSelection = newValue.selection.copyWith(
          baseOffset: math.min(truncated.length, truncated.length + 1),
          extentOffset: math.min(truncated.length, truncated.length + 1),
        );
      }
    }
    if (value.contains(" ") || value.contains("-")) {
      truncated = oldValue.text;
      newSelection = oldValue.selection;
    }

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

颤动输入中只允许两位小数吗？

Allow only two decimal number in flutter input?

dart

flutter

flutter-layout

在 Flutter 版本 v1.20.0-1.0 之后。使用