TimLariviere
commented
1 year ago Thanks for the report! I managed to reproduce with the example given 👍
What's happening in your case is that Fabulous expects your items to be a stable reference value (aka mutable list) instead of a non-mutable one (like F# list type where a new list instance is created with each mutation).
If the reference changes, Fabulous will consider the whole list needs to be reloaded and will lose the DataTemplates that were created previously -- causing the crash on Android after reaching the limit of .NET MAUI.
A workaround would be to change the Model type:
type Model = { Items: ObservableCollection<Item> }Note: I'm using ObservableCollection instead of any System.Collections.IList type, because .NET MAUI expects the collection to raise events when adding/removing items which ObservableCollection do
Then, you can still add and remove items like usual.
let init () =
let items = ObservableCollection<Item>()
items.Add(Item.create())
{ Items = items }, Cmd.none
let update msg model =
match msg with
| Add ->
model.Items.Add(Item.create())
model, Cmd.none
| RemoveLast ->
if model.Items.Count > 0 then
model.Items.RemoveAt(model.Items.Count - 1)
model, Cmd.noneThis approach will work, though it has some drawbacks because of the mutated collection (especially if you want clean separation between states).
Virtualized collection widgets like ListView are very tricky to work with in Fabulous, and can easily crash. I'm not really satisfied with our implementation.
heldap
Code:
On Windows Machine target, whether I click Add or Remove, the app crash: it seems that any attempt to modify ListView's items results in a crash (Win32 exception)
Here is the log:
On Android, with both emulator (Android 10.0, API 29) and my phone (Android 6.0 API 23); after a while adding and removing items, I get a System.Exception:'ItemTemplate count has exceeded the limit of 23 Please make sure to reuse DataTemplate objects