Implementing ConcatAdapter In Android

TL;DR

Let’s say the designer team give you a design as above screenshot. The first idea is using RecyclerView with multiple view types inside, but it will be a lot of view types that you need to manage.

Sine recyclerview:1.2.0-alpha04, ConcatAdapter is introduced that presents the contents of multiple adapters in sequence.

Integration

Add the dependencies for the artifacts you need in the build.gradle file for your app or module:

dependencies {
    implementation "androidx.recyclerview:recyclerview:1.2.0-alpha04"
}

For example, we need to show a header layout as user info, a note, then a list of photos. We will create three different adapters:

HeaderAdapter
NoteAdapter
GalleryAdapter

We can merge these three adapters by using constructor or just add one by one:

val concatAdapter = ConcatAdapter()
concatAdapter.addAdapter(characterAdapter)
concatAdapter.addAdapter(noteAdapter)
concatAdapter.addAdapter(galleryAdapter)
with(rvData) {
    adapter = concatAdapter
}

In main layout, we will add a recyclerView:

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <androidx.recyclerview.widget.RecyclerView
        android:id="@+id/rvData"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        app:layoutManager="androidx.recyclerview.widget.LinearLayoutManager" />

</FrameLayout>

Keynote

1. By default, each added adapter will have its own isolated pool of RecyclerView.ViewHolders, with no re-use in between added adapters.

If your RecyclerView.Adapters share the same view types, and can support sharing RecyclerView.ViewHolder s between added adapters, provide a config like this:

val config = ConcatAdapter.Config.Builder().setIsolateViewTypes(true)
    .build()
val concatAdapter = ConcatAdapter(config)

2. We can remove an adapter by:

concatAdapter.removeAdapter(noteAdapter)

Conclusion

It’s an alpha version of development, there may be changed or removed in next version, so consider to use.

You can find the sample code here.

Happy coding!