How to only display the year in datepicker for Flutter?

Afaik, you can't use datePicker to only select the year. But you can do it by using dialog and a YearPicker widget.

Here a sample code to show dialog with a YearPicker (read the comment):

showDialog(
      context: context,
      builder: (BuildContext context) {
        return AlertDialog(
          title: Text("Select Year"),
          content: Container( // Need to use container to add size constraint.
            width: 300,
            height: 300,
            child: YearPicker(
              firstDate: DateTime(DateTime.now().year - 100, 1),
              lastDate: DateTime(DateTime.now().year + 100, 1),
              initialDate: DateTime.now(),
              // save the selected date to _selectedDate DateTime variable.
              // It's used to set the previous selected date when
              // re-showing the dialog.
              selectedDate: _selectedDate,
              onChanged: (DateTime dateTime) {
                // close the dialog when year is selected.
                Navigator.pop(context);

                // Do something with the dateTime selected.
                // Remember that you need to use dateTime.year to get the year
              },
            ),
          ),
        );
      },
    );

You can use this snippet to select a year, it's a custom year picker using Alert dialog.

  // Call this in the select year button.
  void _pickYear(BuildContext context) {
    showDialog(
      context: context,
      builder: (context) {
        final Size size = MediaQuery.of(context).size;
        return AlertDialog(
          title: Text('Select a Year'),
          // Changing default contentPadding to make the content looks better

          contentPadding: const EdgeInsets.all(10),
          content: SizedBox(
            // Giving some size to the dialog so the gridview know its bounds

            height: size.height / 3,
            width: size.width,
            //  Creating a grid view with 3 elements per line.
            child: GridView.count(
              crossAxisCount: 3,
              children: [
                // Generating a list of 123 years starting from 2022
                // Change it depending on your needs.
                ...List.generate(
                  123,
                  (index) => InkWell(
                    onTap: () {
                      // The action you want to happen when you select the year below,

                      // Quitting the dialog through navigator.
                      Navigator.pop(context);
                    },
                    // This part is up to you, it's only ui elements
                    child: Padding(
                      padding: const EdgeInsets.all(8.0),
                      child: Chip(
                        label: Container(
                          padding: const EdgeInsets.all(5),
                          child: Text(
                            // Showing the year text, it starts from 2022 and ends in 1900 (you can modify this as you like)
                            (2022 - index).toString(),
                          ),
                        ),
                      ),
                    ),
                  ),
                ),
              ],
            ),
          ),
        );
      },
    );
  }