{% setvar book_path %}/reference/androidx/_book.yaml{% endsetvar %} {% include "_shared/_reference-head-tags.html" %}
public abstract class LoadStateAdapter<VH extends Object>
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 extends Object> LoadStateAdapter() |
Public methods |
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boolean |
displayLoadStateAsItem(@NonNull LoadState loadState) Returns true if the LoadState should be displayed as a list item when active. |
final int |
|
final int |
getItemViewType(int position) |
int |
getStateViewType(@NonNull LoadState loadState) Override this method to use different view types per LoadState. |
final void |
onBindViewHolder(@NonNull VH holder, int position) |
abstract void |
onBindViewHolder(@NonNull VH holder, @NonNull LoadState loadState) Called to bind the passed LoadState to the ViewHolder. |
final @NonNull VH |
onCreateViewHolder(@NonNull <ERROR CLASS> parent, int viewType) |
abstract @NonNull VH |
onCreateViewHolder( Called to create a ViewHolder for the given LoadState. |
@NonNull
public final @NonNull LoadState loadState
LoadState to present in the adapter.
Changing this property will immediately notify the Adapter to change the item it's presenting.
@NonNull
public boolean displayLoadStateAsItem(@NonNull LoadState loadState)
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.
@NonNull
public int getStateViewType(@NonNull LoadState loadState)
Override this method to use different view types per LoadState.
By default, this LoadStateAdapter only uses a single view type.
@NonNull
public abstract void onBindViewHolder(@NonNull VH holder, @NonNull LoadState loadState)
Called to bind the passed LoadState to the ViewHolder.
See also | |
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getItemViewType |
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displayLoadStateAsItem |
@NonNull
public final VH onCreateViewHolder(@NonNull <ERROR CLASS> parent, int viewType)
@NonNull
public abstract VH onCreateViewHolder(
@NonNull <ERROR CLASS> parent,
@NonNull LoadState loadState
)
Called to create a ViewHolder for the given LoadState.
Parameters | |
---|---|
@NonNull <ERROR CLASS> parent |
The ViewGroup into which the new View will be added after it is bound to an adapter position. |
@NonNull LoadState loadState |
The LoadState to be initially presented by the new ViewHolder. |
See also | |
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getItemViewType |
|
displayLoadStateAsItem |