月份的计算

huangapple
go评论85阅读模式
英文:

the calculation of the month

问题

  1. var defaultmonth = int.parse(DateFormat('yyyyMM').format(DateTime.now()));
  3. @override
  4. void minus() {
  5.   setState(() {
  6.     if (defaultmonth != DateTime.now().year - 1) {
  7.       defaultmonth--;
  8.     }
  9.   });
  10. }
  12. @override
  13. void add() {
  14.   setState(() {
  15.     if (defaultmonth != DateTime.now().year + 1) {
  16.       defaultmonth++;
  17.     }
  18.   });
  19. }

我想使用这个方法来更改月份。但如果我在202301运行'mius'，我希望它变成202212而不是202300。有人可以帮助我吗？

英文: 
  1. var defaultmonth = int.parse(DateFormat('yyyyMM').format(DateTime.now()));
  3. @override
  4. void minus() {
  5.   setState(() {
  6.       if (defaultmonth != DateTime.now().year - 1) {
  7.         defaultmonth--;
  8.       }
  9.   });
  10. }
  12. @override
  13. void add() {
  14.   setState(() {
  15.       if (defaultmonth != DateTime.now().year + 1) {
  16.         defaultmonth++;
  17.       }
  18.   });
  19. }

I want to change the moon using this method. But if I run 'mius' on 202301, I want it to be 202212 instead of 202300. Is there anyone who can help me?

答案1

得分: 0

Here is the translated code:

  1. import 'package:flutter/material.dart';
  2. import 'package:intl/intl.dart';
  4. class PageTestWidget extends StatefulWidget {
  5.   const PageTestWidget({Key? key}) : super(key: key);
  7.   @override
  8.   State<PageTestWidget> createState() => _PageTestWidgetState();
  9. }
  11. class _PageTestWidgetState extends State<PageTestWidget> {
  12.   var date = DateTime.now();
  14.   void minus() {
  15.     setState(() {
  16.       date = date.copyWith(month: date.month - 1);
  17.     });
  18.   }
  20.   void add() {
  21.     setState(() {
  22.       date = date.copyWith(month: date.month + 1);
  23.     });
  24.   }
  26.   @override
  27.   Widget build(BuildContext context) {
  28.     return Scaffold(
  29.       appBar: AppBar(title: Text('Demo')),
  30.       body: Column(
  31.         children: [
  32.           const Row(),
  33.           Text(DateFormat('yyyyMM').format(date)),
  34.           const SizedBox(height: 20),
  35.           Row(
  36.             children: [
  37.               Expanded(
  38.                 child: TextButton(onPressed: minus, child: const Text('minus')),
  39.               ),
  40.               Expanded(
  41.                 child: TextButton(onPressed: add, child: const Text('add')),
  42.               ),
  43.             ],
  44.           )
  45.         ],
  46.       ),
  47.     );
  48.   }
  49. }

Is there anything else you need?

英文: 
  1. import &#39;package:flutter/Material.dart&#39;;
  2. import &#39;package:intl/intl.dart&#39;;
  6. class PageTestWidget extends StatefulWidget {
  7.   const PageTestWidget({Key? key}) : super(key: key);
  9.   @override
  10.   State&lt;PageTestWidget&gt; createState() =&gt; _PageTestWidgetState();
  11. }
  13. class _PageTestWidgetState extends State&lt;PageTestWidget&gt; {
  14.   var date = DateTime.now();
  16.   void minus() {
  17.     setState(() {
  18.       date = date.copyWith(month: date.month - 1);
  19.     });
  20.   }
  22.   void add() {
  23.     setState(() {
  24.       date = date.copyWith(month: date.month + 1);
  25.     });
  26.   }
  28.   @override
  29.   Widget build(BuildContext context) {
  30.     return Scaffold(
  31.       appBar:  AppBar(title: Text(&#39;Demo&#39;)),
  32.       body: Column(
  33.         children: [
  34.           const Row(),
  35.           Text(DateFormat(&#39;yyyyMM&#39;).format(date)),
  36.           const SizedBox(height: 20),
  37.           Row(
  38.             children: [
  39.               Expanded(
  40.                   child:
  41.                       TextButton(onPressed: minus, child: const Text(&#39;minus&#39;))),
  42.               Expanded(
  43.                   child: TextButton(onPressed: add, child: const Text(&#39;add&#39;))),
  44.             ],
  45.           )
  46.         ],
  47.       ),
  48.     );
  49.   }
  50. }

答案2

得分: 0

我猜你让你的代码变得复杂了：

  1. var defaultmonth = int.parse(DateFormat('yyyyMM').format(DateTime.now()));
  3. @override
  4. void minus() {
  5.   setState(() {
  6.     if (defaultmonth != DateTime.now().year - 1) {
  7.       defaultmonth--;
  8.     }
  9.   });
  10. }
  12. @override
  13. void add() {
  14.   setState(() {
  15.     if (defaultmonth != DateTime.now().year + 1) {
  16.       defaultmonth++;
  17.     }
  18.   });
  19. }

通常，月份的计算与普通的整数计算不同，所以不要使用整数进行计算，而是使用DateTime对象进行计算。

示例：

  1. DateTime defaultmonth = DateTime.now();
  2. var finalDefaultmonth;
  4. @override
  5. void minus() {
  6.   setState(() {
  7.     if (defaultmonth.year != DateTime.now().year - 1 || defaultmonth.month != 1) {
  8.       DateTime newDateTime = DateTime(defaultmonth.year, defaultmonth.month - 1);
  9.       finalDefaultmonth = DateFormat('yyyyMM').format(newDateTime);
  10.     }
  11.   });
  12. }
英文:

I guess you made your code complicated:

  1. var defaultmonth = int.parse(DateFormat(&#39;yyyyMM&#39;).format(DateTime.now()));
  3. @override
  4. void minus() {
  5.   setState(() {
  6.       if (defaultmonth != DateTime.now().year - 1) {
  7.         defaultmonth--;
  8.       }
  9.   });
  10. }
  12. @override
  13. void add() {
  14.   setState(() {
  15.       if (defaultmonth != DateTime.now().year + 1) {
  16.         defaultmonth++;
  17.       }
  18.   });
  19. }

Generally the month calculations are different from normal integer calculations so Instead of making calculations from integers you do the calculations on DateTime objects.

Example:

  1. DateTime defaultmonth = DateTime.now();
  2. var finalDefaultmonth;
  3. @override
  4. void minus() {
  5.   setState(() {
  6.     if (defaultmonth.year != DateTime.now().year - 1 || currentDateTime.month != 1) {
  7.       DateTime newDateTime = DateTime(currentDateTime.year, currentDateTime.month - 1);
  8.       finalDefaultmonth = DateFormat(&#39;yyyyMM&#39;).format(newDateTime);
  9.     }
  10.   });
  11. }

huangapple
  • 本文由 发表于 2023年5月29日 23:52:52
  • 转载请务必保留本文链接：https://go.coder-hub.com/76358724.html
  • dart
  • flutter
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