Paging Adapter

In Android development, a PagingAdapter is part of the Paging library, which is a component of Jetpack designed to handle large datasets in a RecyclerView efficiently. The Paging library helps load data incrementally, reducing memory consumption and improving the responsiveness of the application. In onelib, there is already a base for the paging adapter and there is an extension function to handle the state of LoadState. For example

Usage

class TestPagingAdapter : BasePagingRecyclerAdapter<Movie, TestPagingAdapter.ViewHolder>() {

    override fun getViewBinding(parent: ViewGroup, viewType: Int): ViewBinding {
        return ItemRecyclerBinding.inflate(LayoutInflater.from(parent.context), parent, false)
    }

    override fun onCreateViewHolder(
        parent: ViewGroup,
        viewType: Int
    ): ViewHolder {
        return ViewHolder(getViewBinding(parent, viewType))
    }

    inner class ViewHolder(binding: ViewBinding) : BaseAsyncItemViewHolder<Movie>(binding) {
        override fun bind(data: Movie) {
            with(binding as ItemRecyclerBinding) {
                tvTitle.text = data.title
            }
        }
    }

}

And if you need the load state to take the loading down from the content, you can create a new xml file and create a class to handle the state. For example

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout 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="wrap_content"
    android:paddingTop="18dp">

    <ProgressBar
        android:id="@+id/progress_bar"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:indeterminateTint="@color/black"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <TextView
        android:id="@+id/tv_error"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginHorizontal="@dimen/dimen_20dp"
        android:gravity="center"
        android:text="@string/error"
        android:textColor="@color/black"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <androidx.appcompat.widget.AppCompatButton
        android:id="@+id/btn_retry"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Retry"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        android:textAllCaps="false"
        android:textSize="14sp"
        android:textColor="@color/white"
        app:layout_constraintTop_toBottomOf="@id/tv_error"
        android:layout_marginTop="10dp"
        android:backgroundTint="@color/black"/>

</androidx.constraintlayout.widget.ConstraintLayout>

class TestLoadStateAdapter(
    private val retry: () -> Unit
) : LoadStateAdapter<TestLoadStateAdapter.ViewHolder>() {
    override fun onBindViewHolder(holder: TestLoadStateAdapter.ViewHolder, loadState: LoadState) {
        holder.bind(loadState)
    }

    override fun onCreateViewHolder(
        parent: ViewGroup,
        loadState: LoadState
    ): TestLoadStateAdapter.ViewHolder {
        return ViewHolder(
            LayoutLoadStateAdapterBinding.inflate(
                parent.context.layoutInflater,
                parent,
                false
            )
        )
    }

    inner class ViewHolder(
        private val binding: LayoutLoadStateAdapterBinding
    ) : RecyclerView.ViewHolder(binding.root) {
        fun bind(loadState: LoadState) = with(binding) {
            if (loadState is LoadState.Error) tvError.text = loadState.error.message
            progressBar.isVisible = loadState is LoadState.Loading
            tvError.isVisible = loadState is LoadState.Error
            btnRetry.isVisible = loadState is LoadState.Error

            btnRetry.onClick {
                retry.invoke()
            }
        }
    }

Then, you can implement it in an Activity or Fragment. For example

// submit data into adapter
viewModel.paging.observe(this) {
    mAdapter.submitData(lifecycle, it)
}

// handle loading or error
binding.rvMovie.apply {
    adapter = mAdapter.withLoadStateHeaderAndFooter(
        header = TestLoadStateAdapter { mAdapter.retry() },
        footer = TestLoadStateAdapter { mAdapter.retry() }
    )
}

// handle state
mAdapter.loadStateListener(
    notLoading = { binding.stateView.showContent() },
    loading = { binding.stateView.showLoading() },
    endOfPaging = { binding.stateView.showContent() }
)

Result