{% setvar book_path %}/reference/kotlin/androidx/_book.yaml{% endsetvar %} {% include "_shared/_reference-head-tags.html" %}

LoadStateAdapter

{% setvar page_path %}androidx/paging/LoadStateAdapter.html{% endsetvar %} {% setvar can_switch %}1{% endsetvar %} {% include "reference/_kotlin_switcher2.md" %}

abstract class LoadStateAdapter<VH : Any?>


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 RecyclerView.Adapter.getItemViewType 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 androidx.recyclerview.widget.ConcatAdapter directly to concatenate Adapters.

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 properties

LoadState

LoadState to present in the adapter.

Public constructors

<VH : Any?> LoadStateAdapter()

Public functions

open Boolean

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

Int
Int
getItemViewType(position: Int)
open Int

Override this method to use different view types per LoadState.

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

Called to bind the passed LoadState to the ViewHolder.

VH
onCreateViewHolder(parent: <ERROR CLASS>, viewType: Int)
abstract VH

Called to create a ViewHolder for the given LoadState.

Public properties

loadState

val loadStateLoadState

LoadState to present in the adapter.

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

Public constructors

LoadStateAdapter

<VH : Any?> 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

fun getItemCount(): Int

getItemViewType

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

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

onBindViewHolder

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

Called to bind the passed LoadState to the ViewHolder.

Parameters
loadState: LoadState

LoadState to display.

See also
getItemViewType
displayLoadStateAsItem

onCreateViewHolder

fun onCreateViewHolder(parent: <ERROR CLASS>, viewType: Int): VH

onCreateViewHolder

abstract fun onCreateViewHolder(parent: <ERROR CLASS>, loadState: LoadState): VH

Called to create a ViewHolder for the given LoadState.

Parameters
parent: <ERROR CLASS>

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.

See also
getItemViewType
displayLoadStateAsItem