Random function does not giving proper value when used for date time in flutter-CodePudding

I have created a function that generates ExpenseModel's objects,

While creating an object and setting the date, I used randomly month and day and gave 2022 as a fixed year.

but even though it generates 2021 as well as I have given a random range of 28 but generated 31 also...

Can't figure out where I am doing mistakes...

here is my code

void createexpenses() {
    expensies.clear();
    for (int x = 1; x <= 50; x  ) {
      expensies.add(ExpenseModel(
          category: categories[Random().nextInt(6)],
          amount: Random().nextInt(100),
          date: DateTime(2022, Random().nextInt(12), Random().nextInt(28))));
      //here i have given fixed year 2022,and day upto 28
      

    }

here is my expense mode


class ExpenseModel
{
  String category;
  int amount;
  DateTime date;

  ExpenseModel({required this.category,required this.amount,required this.date});
}

this is my code where I display this expenses...

Widget build(BuildContext context) {
    createexpenses(); //creating 50 objects of ExpenseModel
    return Scaffold(
      body: SafeArea(
        child: Padding(
          padding: const EdgeInsets.symmetric(horizontal: 10.0),
          child: Column(
            children: [
              StatusWidget(amount:totalexpense),
              SizedBox(
                height: 10,
              ),
              Expanded(
                  child: ListView.builder(
                      itemCount: expensies.length,
                      itemBuilder: (context, index) {
                        final data = expensies[index];
                        return Padding(
                          padding: const EdgeInsets.only(bottom: 8.0),
                          child: ExpenseTile(data: data),
                        );
                      }))
            ],
          ),
        ),
      ),
    );
  }

this is code of expense tile


class ExpenseTile extends StatelessWidget {

  ExpenseModel data;
  ExpenseTile({Key? key,required this.data}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Container(
      padding: EdgeInsets.symmetric(vertical: 15),
      decoration: BoxDecoration(
        borderRadius: BorderRadius.circular(20),
        color: Colors.grey[200],

      ),
      child: ListTile(
        title: Text(data.category.toString()),
        trailing: Container(
          decoration: BoxDecoration(
            color: Colors.grey[300],
            borderRadius: BorderRadius.circular(20),

          ),
            padding: EdgeInsets.all(10),
            child: Text(data.amount.toDouble().toString(),style: TextStyle(fontSize: 20,fontWeight: FontWeight.bold),)),
        subtitle: Text(DateFormat("dd-MM-yyyy").format(data.date)),
        leading: CircleAvatar(child: Text(data.category.substring(0,1)),),
      ),
    );
  }
}

CodePudding user response：

Random.nextInt() Generates a non-negative random integer uniformly distributed in the range from 0, inclusive, to [max], exclusive. So in your case your month random have 0-11, and when you enter 0 in month, DateTime class reduces year by 1 and sets month to 12. Same for days, if you get 0, month -1 and day will be last possible day of the month you got.