为什么我不能在日期时间 Flutter 项目中添加偏移时间？

Question

I tried to add offset hours to my datetime object now, but it doesn't show the added time that is actual time. It is my flutter project in android studio.

    void getTime() async {
    Response response = await
    get('http://worldtimeapi.org/api/timezone/Asia/Karachi');
    Map data = jsonDecode(response.body);
    String datetime = data['datetime'];
    String offset = data['utc_offset'].substring(1,3);

    print(offset);
    DateTime now = DateTime.parse(datetime);
    now.add(Duration(hours: int.parse('offset')));
    print(now);
    }
    @override
    void initState() {
    super.initState();
    getTime();
    }

This is the result I got: Screenshot of the output

Answer 1

You have two problems in your code:

1. You should pass offset to int.parse instead of 'offset'
2. add is an immutable operation on a DateTime object. It does not change the DataTime object but returns a new one.

Try this instead:

DateTime dateTimeAfterOffset = DateTime.parse(datetime).add(
  Duration(
    hours: int.parse(offset),
  ),
);
```

Answer 2

I found the solution. Yayyy!

  void getTime() async {

    //Make the request
    Response response = await get('http://worldtimeapi.org/api/timezone/Asia/Karachi');
    Map data = jsonDecode(response.body);
    print(data);


    //Get properties from data
    String datetime = data['datetime'];
    String offset = data['utc_offset'].substring(1,3);
    //print(datetime);
    print(offset);

    //create DateTime Object
    DateTime now = DateTime.parse(datetime);
    now = now.add(Duration(hours: int.parse(offset)));
    print(now);
  }

  @override
  void initState() {

    super.initState();
    getTime();
  }