Foreach loop with Widgets

I use the ‘Sticky Headers’ package and have to dynamically create a new header using a dataset.

Now I have been helped a bit by others by walking through my dataset so that I have grouped it per day only I can’t manage to show this in sticky headers …

Dataset from API:

[
  {
    "time": "2020-06-16T10:31:12.000Z",
    "message": "P2 BGM-01 HV buiten materieel (Gas lekkage) Franckstraat Arnhem 073631"
  },
  {
    "time": "2020-06-16T10:29:35.000Z",
    "message": "A1 Brahmslaan 3862TD Nijkerk 73278"
  },
  {
    "time": "2020-06-16T10:29:35.000Z",
    "message": "A2 NS Station Rheden Dr. Langemijerweg 6991EV Rheden 73286"
  },
  {
    "time": "2020-06-15T09:41:18.000Z",
    "message": "A2 VWS Utrechtseweg 6871DR Renkum 74636"
  },
  {
    "time": "2020-06-14T09:40:58.000Z",
    "message": "B2 5623EJ : Michelangelolaan Eindhoven Obj: ziekenhuizen 8610 Ca CATH route 522 PAAZ Rit: 66570"
  }
]

Data after this loop:

var groupByDate = groupBy(dataSet, (obj) => obj.tijd.substring(0, 10));
  groupByDate.forEach((date, list) {
    print('${date}:');

    list.forEach((listItem) {
     print('${listItem.tijd}, ${listItem.melding}');
    });
    print('\n');
  });

Data:

I/flutter ( 5991): 2020-06-22:
I/flutter ( 5991): 2020-06-22T09:42:52.000Z, B1 LUMC (C4-S/T) Hart Catheterisatie Einthovenweg LEIDEN : 16171
I/flutter ( 5991): 2020-06-22T09:42:09.000Z, P 2 BDH-05 Dier op hoogte Reepstraat SGRAVH 157750
I/flutter ( 5991): 2020-06-22T09:41:46.000Z, A2 10185 Rit 70880 VWS Heiloo Rosendaal Heiloo
I/flutter ( 5991):
I/flutter ( 5991): 2020-06-21:
I/flutter ( 5991): 2020-06-21T09:40:58.000Z, B2 5623EJ : Michelangelolaan Eindhoven Obj: ziekenhuizen 8610 Ca CATH route 522 PAAZ Rit: 66570
I/chatty ( 5991): uid=10134(com.mundaro.p2000scannerdemo) Thread-2 identical 2 lines
I/flutter ( 5991): 2020-06-21T09:40:58.000Z, B2 5623EJ : Michelangelolaan Eindhoven Obj: ziekenhuizen 8610 Ca CATH route 522 PAAZ Rit: 66570
I/flutter ( 5991):
I/flutter ( 5991): 2020-06-20:
I/flutter ( 5991): 2020-06-20T09:40:58.000Z, B2 5623EJ : Michelangelolaan Eindhoven Obj: ziekenhuizen 8610 Ca CATH route 522 PAAZ Rit: 66570

Now I would like to show it as below but after a lot of fiddling I can’t get it done. Really feel it is very simple but maybe someone can help me?