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LoadStateAdapter

abstract class LoadStateAdapter<VH : RecyclerView.ViewHolder> : RecyclerView.Adapter

kotlin.Any
   ↳ androidx.recyclerview.widget.RecyclerView.Adapter
     ↳ androidx.paging.LoadStateAdapter

Adapter for displaying a RecyclerView item based on LoadState, such as a loading spinner, or a retry error button.

By default will use one shared view type for all items.

By default, both LoadState.Loading and LoadState.Error are presented as adapter items, other states are not. To configure this, override displayLoadStateAsItem.

To present this Adapter as a header and or footer alongside your PagingDataAdapter, see PagingDataAdapter.withLoadStateHeaderAndFooter, or use ConcatAdapter directly to concatenate Adapters.

import androidx.paging.LoadState
import androidx.paging.LoadStateAdapter
import androidx.recyclerview.widget.RecyclerView

class LoadStateViewHolder(
    parent: ViewGroup,
    retry: () -> Unit
) : RecyclerView.ViewHolder(
    LayoutInflater.from(parent.context)
        .inflate(R.layout.load_state_item, parent, false)
) {
    private val progressBar: ProgressBar = itemView.findViewById(R.id.progress_bar)
    private val errorMsg: TextView = itemView.findViewById(R.id.error_msg)
    private val retry: Button = itemView.findViewById<Button>(R.id.retry_button)
        .also { it.setOnClickListener { retry.invoke() } }

    fun bind(loadState: LoadState) {
        if (loadState is LoadState.Error) {
            errorMsg.text = loadState.error.localizedMessage
        }
        progressBar.visibility = toVisibility(loadState is LoadState.Loading)
        retry.visibility = toVisibility(loadState !is LoadState.Loading)
        errorMsg.visibility = toVisibility(loadState !is LoadState.Loading)
    }

    private fun toVisibility(constraint: Boolean): Int = if (constraint) {
        View.VISIBLE
    } else {
        View.GONE
    }
}

/**
 * Adapter which displays a loading spinner when `state = LoadState.Loading`, and an error
 * message and retry button when `state is LoadState.Error`.
 */
class MyLoadStateAdapter(
    private val retry: () -> Unit
) : LoadStateAdapter<LoadStateViewHolder>() {

    override fun onCreateViewHolder(parent: ViewGroup, loadState: LoadState) =
        LoadStateViewHolder(parent, retry)

    override fun onBindViewHolder(holder: LoadStateViewHolder, loadState: LoadState) =
        holder.bind(loadState)
}
See also
withLoadStateHeaderAndFooter
withLoadStateHeader
withLoadStateFooter

Summary

Public constructors

Public functions

open Boolean

Returns true if the LoadState should be displayed as a list item when active.

final Int
final Int
getItemViewType(position: Int)
open Int

Override this method to use different view types per LoadState.

abstract Unit
onBindViewHolder(holder: VH, loadState: LoadState)

Called to bind the passed LoadState to the ViewHolder.

final Unit
onBindViewHolder(holder: VH, position: Int)
abstract VH
onCreateViewHolder(parent: ViewGroup, loadState: LoadState)

Called to create a ViewHolder for the given LoadState.

final VH
onCreateViewHolder(parent: ViewGroup, viewType: Int)

Public properties

LoadState

LoadState to present in the adapter.

Inherited functions

From androidx.recyclerview.widget.RecyclerView.Adapter

Public constructors

LoadStateAdapter

<VH : RecyclerView.ViewHolder> LoadStateAdapter()

Public functions

displayLoadStateAsItem

open fun displayLoadStateAsItem(loadState: LoadState): Boolean

Returns true if the LoadState should be displayed as a list item when active.

By default, LoadState.Loading and LoadState.Error present as list items, others do not.

getItemCount

final fun getItemCount(): Int

getItemViewType

final fun getItemViewType(position: Int): Int

getStateViewType

open fun getStateViewType(loadState: LoadState): Int

Override this method to use different view types per LoadState.

By default, this LoadStateAdapter only uses a single view type.

onBindViewHolder

abstract fun onBindViewHolder(holder: VH, loadState: LoadState): Unit

Called to bind the passed LoadState to the ViewHolder.

Parameters
loadState: LoadState

LoadState to display.

onBindViewHolder

final fun onBindViewHolder(holder: VH, position: Int): Unit

onCreateViewHolder

abstract fun onCreateViewHolder(parent: ViewGroup, loadState: LoadState): VH

Called to create a ViewHolder for the given LoadState.

Parameters
parent: ViewGroup

The ViewGroup into which the new View will be added after it is bound to an adapter position.

loadState: LoadState

The LoadState to be initially presented by the new ViewHolder.

onCreateViewHolder

final fun onCreateViewHolder(parent: ViewGroup, viewType: Int): VH

Public properties

loadState

var loadStateLoadState

LoadState to present in the adapter.

Changing this property will immediately notify the Adapter to change the item it's presenting.