No instance(s) of type variable(s) Y exist so that Calendar conforms to LiveData

Question

I want my LiveData<Calendar> instance to change everytime List of Alarms change. I have following code:

private LiveData<Calendar> nextAlarm;

public MyViewModel(@NonNull Application app) {

    nextAlarm = Transformations.switchMap(alarmRepo.getAlarms(), alarms -> {
        Calendar nearest = null;
        // ... some necessary computation here (iterating through alarms):
        // foreach alarms, find nearest one, create new Calendar according to day and time saved in database
        return nearest;
    });

Error I see:

No instance(s) of type variable(s) Y exist so that Calendar conforms

Can somebody help me out here? How can I return new Calendar instance in SwitchMapFunction?

to LiveData

Please add more code, e.g. the imports you are using. Specifically: What is `LiveData`, what is `Calendar`, how are they related to each other. — Smutje, May 20 '19 at 06:37
There is a lot of computation, but I can say that Calendar is new object created from specific alarm's day and time. — Tom11, May 20 '19 at 06:42
`switchMap` returns `LiveData`, not `` - your `nearest` is not a `LiveData` object — pskink, May 20 '19 at 06:43
OK, but how can I return `LiveData`? I cannot create it, since it is abstract class. — Tom11, May 20 '19 at 06:55
I solved this with @HelloBird answer - I used `Transformations.map()`. Thank you all. — Tom11, May 20 '19 at 07:29

score 2 · Accepted Answer · answered May 20 '19 at 07:08

2

I think you need use Transformation.map() function instead of Transformation.switchMap()

answered May 20 '19 at 07:08

HelloBird

69
5

One question - do `Transformations.map()` keep `Observers` working? – Tom11 May 20 '19 at 07:30
sorry, i don't understand,you want know Is observer will be called when alarms list changed? – HelloBird May 20 '19 at 07:40
Yes, I want to know if it will keep the observers connected to this livedata. – Tom11 May 20 '19 at 11:15
Yes, it will keep the observers connected to this livedata when observers active – HelloBird May 21 '19 at 01:20

No instance(s) of type variable(s) Y exist so that Calendar conforms to LiveData

1 Answers1