demo_date_picker.dart

import 'package:flutter/material.dart';

import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:flutter/rendering.dart';
import 'package:intl/intl.dart';

class DatePicker extends StatefulWidget {
  @override
  _DatePickerState createState() => _DatePickerState();
}

class _DatePickerState extends State<DatePicker> {
  var fsconnect = FirebaseFirestore.instance;

  DateTime selectedDate = DateTime.now();
  var formatter = new DateFormat('dd-MM-yyyy');

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      backgroundColor: Colors.black,
      appBar: AppBar(
        backgroundColor: Colors.black26,
        title: Text(
          'Date Picker',
        ),
      ),
      body: SafeArea(
        child: GestureDetector(
          onTap: () async {
            DateTime date = await _selectDate(context);
            fsconnect.collection("WorkoutDateWise").add({
              "date": formatter
                  .format(date)
                  .toString(),
            }).then((value) => print(value.id));
          },
          child: Card(
            child: Text("hsdb  sjfjdskjbf sb hfbjh bdfjbj"),
          ),
        ),
      ),
    );
  }

  bool _decideWhichDayToEnable(DateTime day) {
    if ((day.isAfter(DateTime.now().subtract(Duration(days: 1))) &&
        day.isBefore(DateTime.now().add(Duration(days: 10))))) {
      return true;
    }
    return false;
  }

  Future<DateTime> _selectDate(BuildContext context) async {
    final DateTime picked = await showDatePicker(
      context: context,
      initialDate: selectedDate, // Refer step 1
      firstDate: DateTime(2000),
      lastDate: DateTime(2025),
      selectableDayPredicate: _decideWhichDayToEnable,
    );
    if (picked != null && picked != selectedDate) {
      selectedDate = picked;
      print(formatter.format(selectedDate));
    }
    return selectedDate;
  }
}