YANGANANDY上计算3个彼此依赖的文本字段，例如Flutter

Question

因此，我的财务应用程序中有这三个字段，名为金额，费率和总数。我使用控制器来获取值。通常是用户给出的费率。我希望金额字段动态更改给定的速率，反之亦然。 金额=总/费率 总计=金额*费率 我希望值以用户类型为变化。任何帮助都非常感谢

Answer 1

也许不是最好的/最简洁的代码，但它有效：

import 'package:flutter/material.dart';

class Test extends StatefulWidget {
  const Test({super.key});

  @override
  State<StatefulWidget> createState() => _TestState();
}

class _TestState extends State<Test> {
  final TextEditingController amountController = TextEditingController();
  final TextEditingController rateController = TextEditingController();
  final TextEditingController totalController = TextEditingController();
  double amount = 0;
  double rate = 0;
  double total = 0;

  @override
  void initState() {
    super.initState();
  }

  @override
  void dispose() {
    amountController.dispose();
    rateController.dispose();
    totalController.dispose();
    super.dispose();
  }

  onChangedAmount(String? value) {
    try {
      amount = double.parse(value ?? amount.toString());
      totalController.text = (amount * rate).toString();
    } catch (e) {
      debugPrint('Error when parsing amount value: $value, error: $e');
    }
  }

  onChangedRate(String? value) {
    try {
      rate = double.parse(value ?? rate.toString());
      totalController.text = (amount * rate).toString();
    } catch (e) {
      debugPrint('Error when parsing rate value: $value, error: $e');
    }
  }

  onChangedTotal(String? value) {
    try {
      total = double.parse(value ?? total.toString());
      amountController.text = (total / rate).toString();
    } catch (e) {
      debugPrint('Error when parsing total value: $value, error: $e');
    }
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(),
      body: Padding(
        padding: const EdgeInsets.symmetric(vertical: 10, horizontal: 25),
        child: Column(
          children: [
            TextField(
              controller: amountController,
              decoration: InputDecoration(labelText: "Amount"),
              onChanged: onChangedAmount,
            ),
            SizedBox(height: 10),
            TextField(
              controller: rateController,
              decoration: InputDecoration(labelText: "Rate"),
              onChanged: onChangedRate,
            ),
            SizedBox(height: 10),
            TextField(
              controller: totalController,
              decoration: InputDecoration(labelText: "Total"),
              onChanged: onChangedTotal,
            ),
          ],
        ),
      ),
    );
  }
}

您还应改进代码（速率！= 0之前，将输入限制为数字等...）。