PageKeyedDataSource.LoadCallback

public abstract class PageKeyedDataSource.LoadCallback<Key extends Object, Value extends Object>


Callback for loadBefore and loadAfter to return data.

A callback can be called only once, and will throw if called again.

It is always valid for a DataSource loading method that takes a callback to stash the callback and call it later. This enables DataSources to be fully asynchronous, and to handle temporary, recoverable error states (such as a network error that can be retried).

Parameters
<Key extends Object>

Type of data used to query pages.

<Value extends Object>

Type of items being loaded.

Summary

Public constructors

<Key extends Object, Value extends Object> LoadCallback()

Public methods

abstract void
onResult(@NonNull List<@NonNull Value> data, @Nullable Key adjacentPageKey)

Called to pass loaded data from a DataSource.

Public constructors

LoadCallback

public final <Key extends Object, Value extends Object> LoadCallback()
Parameters
<Key extends Object>

Type of data used to query pages.

<Value extends Object>

Type of items being loaded.

Public methods

onResult

@NonNull
public abstract void onResult(@NonNull List<@NonNull Value> data, @Nullable Key adjacentPageKey)

Called to pass loaded data from a DataSource.

Call this method from your PageKeyedDataSource's loadBefore and loadAfter methods to return data.

It is always valid to pass a different amount of data than what is requested. Pass an empty list if there is no more data to load.

Pass the key for the subsequent page to load to adjacentPageKey. For example, if you've loaded a page in loadBefore, pass the key for the previous page, or null if the loaded page is the first. If in loadAfter, pass the key for the next page, or null if the loaded page is the last.

Parameters
@NonNull List<@NonNull Value> data

List of items loaded from the PageKeyedDataSource.

@Nullable Key adjacentPageKey

Key for subsequent page load (previous page in loadBefore / next page in loadAfter), or null if there are no more pages to load in the current load direction.