Error when selecting a dropdown item in Flutter
To complete the rmtmckenzie answer, here is the code you should put in your FeedCategory object:
bool operator ==(o) => o is FeedCategory && o.name == name; int get hashCode => name.hashCode;
Edit: A link that explains what hashCode is made for in Flutter
I think I've figured out your issue. It stems from how you're using FutureBuilder.
This is what I think is going on:
- Your app is runs. It does the call to getFeedCategories()
The future completes, and the list is built, etc with the following items:
obj 123 ==> FeedCategory(Prueba),
obj 345 ==> FeedCategory(Categories 2)
You select the item from the dropdown, setState() is called
Your _feedCategory is now equal to
obj 123 ==> FeedCategory(Prueba)
Widget is rebuilt. It does another call to getFeedCategories()
Future completes, list is built etc with the following items
obj 567 ==> FeedCategory(Prueba),
obj 789 ==> FeedCategory(Categories 2)
- The Dropdown tests
items.where((DropdownMenuItem item) => item.value == value).length == 1, but length == 0 because
obj 123 ==> FeedCategory(Prueba)is not found.
There are a couple of solutions to your problem. One would be to add an equals operator to your
FeedCategory class that compares the category and/or id.
Another would be to separate the Future used in the futurebuilder from the part that changes - you could do this either by keeping the future as a member variable (maybe instantiate it in initState?), or by making the inner part of the builder into it's own Stateful widget (in which case you could probably make ManageFeedSource a StatelessWidget). I'd recommend the last option.
Let me know if that doesn't solve your issue, but I'm pretty sure that's the reason it's doing what it's doing.