Hey guys, I was trying to use on-demand feature of...

# android

[Ali]

Hey guys,
I was trying to use on-demand feature of ViewStub and OnInflateListener to listen once the original layout is inflated.
This is my ViewStub layout `fragment_navigation_viewstub`:

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="<http://schemas.android.com/apk/res/android>"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <ViewStub
        android:id="@+id/fragmentNavigationViewStub"
        android:layout="@layout/fragment_navigation"
        android:layout_width="match_parent"
        android:inflatedId="@+id/items_list"
        android:layout_height="match_parent" />

</androidx.constraintlayout.widget.ConstraintLayout>

and this is my original layout `fragment_navigation`:

<?xml version="1.0" encoding="utf-8"?>
<androidx.recyclerview.widget.RecyclerView
    xmlns:android="<http://schemas.android.com/apk/res/android>"
    android:id="@+id/items_list"
    android:layout_width="match_parent"
    android:layout_height="match_parent"/>

and my listeneer inside the fragment:

private val binding by viewBinding { FragmentNavigationViewstubBinding.inflate(it) }

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    binding.fragmentNavigationViewStub.setOnInflateListener { _, view ->
        fragmentNavigation = FragmentNavigationBinding.bind(view)
    }
}

But I got this exception and looks like setOnInflateListener is not called
kotlin.UninitializedPropertyAccessException: lateinit property fragmentNavigation has not been initialized

[Ronald Wolvers]

Sorry, deleted my comments yet again. I think the explanation here is that you need to explicitly call inflate() on the ViewStub to have an OnInflateListener be invoked. From what I understand that's how ViewStub works.

[Ronald Wolvers]

According to https://developer.android.com/reference/android/view/ViewStub:

[Ronald Wolvers]

ViewStub stub = findViewById(R.id.stub);
View inflated = stub.inflate();

[Ali]

Thanks for your response. But I am using viewbinding

[Ronald Wolvers]

Even with view binding you will if I understood correctly still have to call inflate() on the stub. View binding does not inflate the stub specifically and so the listener is not called.

[Ali]

But I already called the inflate as you can see in the class

private val binding by viewBinding { FragmentNavigationViewstubBinding.inflate(it) }

[Ronald Wolvers]

Yes, but you are inflating the ConstraintLayout with that call and not the ViewStub

[Ronald Wolvers]

Your layout is called fragment_navigation_viewstub and so the call to FragmentNavigationViewstubBinding.inflate(it) is inflating the layout (ConstraintLayout) and not the ViewStub unless you specifically call inflate() on the ViewStub.

[Ali]

I already inflated fragment_navigation_viewstub layout not sure how can i inflate again the ViewStub 🤔

[Ronald Wolvers]

Hey, good morning, @Ali! Ah, well assuming that what I'm saying is correct, this is what you would do:

binding.fragmentNavigationViewStub.inflate()

If you call that after setting the listener, I'm quite sure your OnInflateListener will trigger. The reason is that the ViewStub needs to be inflated separately. Let me know if that works!

[Ali]

It means we need two inflate call inside this class?

[Ronald Wolvers]

That's right! That's what ViewStub is for! Lazy inflation.

[Ronald Wolvers]

That is, after reading the documentation several times because I didn't understand it either! 😆

[Ali]

I also found another way. We can also make setVisibility true to be called the OnInflateListener as per the developer doc

[Ronald Wolvers]

Yeah, that should work too! Let me know if this fixes the issue!

[Ali]

yeah I fixed my issue that way for now

[Ronald Wolvers]

That's awesome! Happy to hear it and good luck with your project 😄!

[Ali]

thanks man! Cheers