Expandable + filtering - crash and problems

[MFlisar]

General problem
In general, if you use expandable items and filtering together, you always lose the expandable state during filtering. This is really a problem if you want to filter and suddenly the expanded item containing the item that you want to filter out is gone because it's parent is collapsed. Additionally expanding an item while the filter is active does not respect the current active filter either it seems, I see that always all children of an item are expanded regardless of the current filter.

Crash
A side effect of this behaviour is following crash if you collapse/expand items after filtering your views.

If desired, I can give you an example code with a little library that I'm rewritting currently in kotlin which is not far yet but can reproduce this issue easily.

Exception

kotlin.TypeCastException: null cannot be cast to non-null type kotlin.collections.List<Item>
    at com.mikepenz.fastadapter.adapters.ItemFilter.publishResults(ItemFilter.kt:104)
    at android.widget.Filter$ResultsHandler.handleMessage(Filter.java:282)
    at android.os.Handler.dispatchMessage(Handler.java:106)
    at android.os.Looper.loop(Looper.java:214)
    at android.app.ActivityThread.main(ActivityThread.java:6986)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:494)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1445)

Details

•  Used library version: 5.0.0

[mikepenz]

@MFlisar the provided filter code is not optimized for cases with expandables at once. I am sure there are a few optimizations possible / needed to make ti really work well.

I am open for improvements / PRs to improve the behavior in this matter.

But it was not a priority when creating, as it is a rare and more specialized usecase.

[usandourkids525]

Add love for self and other's

[androidacy-user]

For us on 5.7.0, expanding an item after search causes search(filter) to stop working. No crashes, just calling filter() no longer does anything