Using T in a baseFragment, will result in using that function to need a 'Nothing" instead of Fragment

Question

This is my method:

abstract class BaseFragmentKey<T : Fragment> : Parcelable {
     fun newFragment(): T {
        val fragment = createFragment()
        val bundle = Bundle()
        bundle.putParcelable("KEY", this)
        fragment.arguments = bundle
        return fragment
    }

    protected abstract fun createFragment(): T

    @CallSuper
    open fun updateExistingFragment(fragment: T): T {
        return fragment
    }
}

But when I try to call with a Fragment:

   newFragment = newKey.updateExistingFragment(existingFragment)

It says before compiling that Type mismatch. Required Nothing, found Fragment. If I do existingFragment as Nothing it crashes cause I cannot cast to null.

How can I fix this?

neyKey is a : BaseFragmentKey (I already attached it's code) — rosu alin, Aug 22 '19 at 13:28
but you cannot just instantiate `BaseFragmentKey` you have to at least set type parameter `T`. That's why I'm asking — Andrei Tanana, Aug 22 '19 at 13:40
Attached pic from where I call updateExistingFragment. Item that I try, is Fragment — rosu alin, Aug 22 '19 at 13:53
the problem in wildcard in `stateChange.getNewState>`. It should be for example `stateChange.getNewState>` — Andrei Tanana, Aug 22 '19 at 14:00
You are totally right, changing from there the * to Fragment works, thanks a lot!!! If you make an answer regarding this, I will accept it, so the credit and points can go to you — rosu alin, Aug 22 '19 at 14:10

score 1 · Accepted Answer · answered Aug 22 '19 at 14:13

1

The problem in wildcard in stateChange.getNewState<BaseFragmentKey<*>>. It should be for example stateChange.getNewState<BaseFragmentKey<Fragment>>

answered Aug 22 '19 at 14:13

Andrei Tanana

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Using T in a baseFragment, will result in using that function to need a 'Nothing" instead of Fragment

1 Answers1