how to print Firestore timestamp as formatted date and time in flutter

问题

timestamp return aa Timestamp(seconds=1560523991, nanoseconds=286000000) in flutter firestore snapshot

I want to print it properly formatted date and time

I m using DateTime.now() to store current DateTime in firestore while creating new records and retrieving it using firestore snapshot but it returning format I notable convert to into formatted date time, for formatting I m using lib intl.dart

code for saving data

d={'amount':amount,
  'desc':desc,
  'user_id':user_id,
  'flie_ref':url.toString(),
  'date':'${user_id}${DateTime.now().day}-${DateTime.now().month}-${DateTime.now().year}',
  'timestamp':DateTime.now()

return Firestore.instance.collection('/data').add(d).then((v){return true; }).catchError((onError)=>print(onError)); });

Accessing with

FutureBuilder(
              future: Firestore.instance
                  .collection('data')
                  .where('user_id', isEqualTo:_user_id)
                  .getDocuments(),
              builder: (BuildContext context,
                  AsyncSnapshot<QuerySnapshot> snapshot) {
                if (!snapshot.hasData)
                  return Container(
                      child: Center(child: CircularProgressIndicator()));
                return ListView.builder(
                    itemCount: snapshot.data.documents.length,
                    itemBuilder: (BuildContext context, int index) {
                      return Column(
                        children: <Widget>[
   Text(DateFormat.yMMMd().add_jm().format(DateTime.parse(snapshot.data.documents[index].data['timestamp'].toString())]);
....

error throwing is Invalid date format.

I m expecting output is: 'Jan 17, 2019, 2:19 PM'

回答1:

When we push the DateTime object to Firestore, it internally converts it to it's own timestamp object and stores it.

Method to convert it back to Datetime after fetching timestamp from Firestore:

Firestore's timestamp contains a method called toDate() which can be converted to String and then that String can be passed to DateTime's parse method to convert back to DateTime

DateTime.parse(timestamp.toDate().toString())

回答2:

timestamp parameter is the time in seconds

String formatTimestamp(int timestamp) {
      var format = new DateFormat('d MMM, hh:mm a');
      var date = new DateTime.fromMillisecondsSinceEpoch(timestamp * 1000);
      return format.format(date);
    }

Please check this answer for intl date formats

Hope it helps !

回答3:

You will get a unix timestamp from firestore even if you send a DateTime to firestore.

You can parse a DateTime from Firestore with DateTime.fromMillisecondsSinceEpoch(timestamp * 1000);

The DateTime class has two option to return a sting. toIso8601String() or toString() choose the one you need. Or use eg. DateTime.now().hour; to get the our and create your own output.

For more information: Check https://api.dartlang.org/stable/2.4.0/dart-core/DateTime-class.html

回答4:

Do like so:

DateFormat.yMMMd().add_jm().format(DateTime.parse(snapshot.data.documents[index].data['timestamp'].toDate().toString())]

回答5:

Here is way!

Firestore will return TimeStamp like Timestamp(seconds=1560523991, nanoseconds=286000000).

This can be parsed as

Timestamp t = document['timeFieldName'];
DateTime d = t.toDate();
print(d.toString()); //2019-12-28 18:48:48.364

来源：https://stackoverflow.com/questions/56627888/how-to-print-firestore-timestamp-as-formatted-date-and-time-in-flutter

标签

time

Flutter

dart

google-cloud-firestore