Flutter countdown not counting down-CodePudding

I'm kind of new to the flutter programming so I'm trying to create some basic things to learn. Currently, I'm trying to create a list of countdowns to a specific date. Nothing fancy, the dates are retrieved through firestore and then shown in a list. However, I encountered a small issue:

All the dates start at the same hour, for now, this is 00:00:00, which means they should have the same seconds in the countdown at all times. This was not the case. I posted this question earlier this week and the issue was that I always used a new value for DateTime.now() so I 'solved' that part by creating a new variable in the main widget and passing it to the countdown. I used milliseconds and microseconds in this example because everything loads faster. But as you can see, now the mill/micro/seconds are nicely aligned (image from mobile), but it's not counting down anymore. So I'm reposting but now with a verifiable example in dartpad which can be found here. This code should be usable as well to replicate the problem on your local machine.

If I reload the app, it updates because the currentTime gets a new value of course.

Is anybody that could help me in the right direction?

CodePudding user response：

Once you are passing the currentTime it stays the same. Because the currentTime is initialized only once.

  DateTime currentTime = DateTime.now();

And used

CountdownWidget(
    startDate: DateTime(2023, 1), currentTime: currentTime),

The currentTime value never get changes including the CountdownWidget widget. Therefore the UI doesnt update.

You can change the value of CountdownWidget from parent widget and pass the instance CountdownWidget, the current way.

Solution 1: The solution will be

class _MyHomePageState extends State<MyHomePage> {
  DateTime currentTime = DateTime.now();

  @override
  void initState() {
    super.initState();
    Timer.periodic(Duration(seconds: 1), (timer) {
      currentTime = DateTime.now();
      setState(() {});
    });
  }

It is changing the currentTime on every second and passing the value, then updating the parent widget.

Solution 0:

Another solution will be handling the update on CountdownWidget

class CountdownWidgetState extends State<CountdownWidget> {
  Timer? timer;

  late DateTime currentTime = widget.currentTime;
  @override
  void initState() {
    super.initState();

    timer = Timer.periodic(const Duration(microseconds: 1), (timer) {
      currentTime = DateTime.now();
      setState(() {});
    });
  }