Question 177757 in Flutter Question posted in
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How much is the Flutter cost this month?

var defaultmonth = int.parse(DateFormat('yyyyMM').format(DateTime.now()));

@override
void minus() {
  setState(() {
      if (defaultmonth != DateTime.now().year - 1) {
        defaultmonth--;
      }
  });
}

@override
void add() {
  setState(() {
      if (defaultmonth != DateTime.now().year + 1) {
        defaultmonth++;
      }
  });
}

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?

Tags:

2

Answers


  1. 0 
    import 'package:flutter/Material.dart';
import 'package:intl/intl.dart';



class PageTestWidget extends StatefulWidget {
  const PageTestWidget({Key? key}) : super(key: key);

  @override
  State<PageTestWidget> createState() => _PageTestWidgetState();
}

class _PageTestWidgetState extends State<PageTestWidget> {
  var date = DateTime.now();

  void minus() {
    setState(() {
      date = date.copyWith(month: date.month - 1);
    });
  }

  void add() {
    setState(() {
      date = date.copyWith(month: date.month + 1);
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar:  AppBar(title: Text('Demo')),
      body: Column(
        children: [
          const Row(),
          Text(DateFormat('yyyyMM').format(date)),
          const SizedBox(height: 20),
          Row(
            children: [
              Expanded(
                  child:
                      TextButton(onPressed: minus, child: const Text('minus'))),
              Expanded(
                  child: TextButton(onPressed: add, child: const Text('add'))),
            ],
          )
        ],
      ),
    );
  }
}
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  2. 0

    I guess you made your code complicated:

    var defaultmonth = int.parse(DateFormat('yyyyMM').format(DateTime.now()));

@override
void minus() {
  setState(() {
      if (defaultmonth != DateTime.now().year - 1) {
        defaultmonth--;
      }
  });
}

@override
void add() {
  setState(() {
      if (defaultmonth != DateTime.now().year + 1) {
        defaultmonth++;
      }
  });
}

    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:

    DateTime defaultmonth = DateTime.now();
var finalDefaultmonth;
@override
void minus() {
  setState(() {
    if (defaultmonth.year != DateTime.now().year - 1 || currentDateTime.month != 1) {
      DateTime newDateTime = DateTime(currentDateTime.year, currentDateTime.month - 1);
      finalDefaultmonth = DateFormat('yyyyMM').format(newDateTime);
    }
  });
}
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