{% setvar book_path %}/reference/kotlin/androidx/_book.yaml{% endsetvar %} {% include "_shared/_reference-head-tags.html" %}
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) }
Public constructors |
|
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<VH : Any?> LoadStateAdapter() |
Public functions |
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open Boolean |
displayLoadStateAsItem(loadState: LoadState) Returns true if the LoadState should be displayed as a list item when active. |
Int |
|
Int |
getItemViewType(position: Int) |
open Int |
getStateViewType(loadState: LoadState) 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 |
onCreateViewHolder(parent: <ERROR CLASS>, loadState: LoadState) Called to create a ViewHolder for the given LoadState. |
val loadState: LoadState
LoadState to present in the adapter.
Changing this property will immediately notify the Adapter to change the item it's presenting.
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.
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.
abstract fun onBindViewHolder(holder: VH, loadState: LoadState): Unit
Called to bind the passed LoadState to the ViewHolder.
Parameters | |
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loadState: LoadState |
LoadState to display. |
See also | |
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getItemViewType |
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displayLoadStateAsItem |
abstract fun onCreateViewHolder(parent: <ERROR CLASS>, loadState: LoadState): VH
Called to create a ViewHolder for the given LoadState.
Parameters | |
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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 | |
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getItemViewType |
|
displayLoadStateAsItem |