PageKeyedDataSource

public <Key extends Object, Value extends Object> PageKeyedDataSource()

public abstract void loadAfter(
    @NonNull PageKeyedDataSource.LoadParams<@NonNull Key> params,
    @NonNull PageKeyedDataSource.LoadCallback<@NonNull Key, @NonNull Value> callback
)

Append page with the key specified by LoadParams.key.

It's valid to return a different list size than the page size if it's easier, e.g. if your backend defines page sizes. It is generally preferred to increase the number loaded than reduce.

Data may be passed synchronously during the load method, or deferred and called at a later time. Further loads going down will be blocked until the callback is called.

If data cannot be loaded (for example, if the request is invalid, or the data would be stale and inconsistent), it is valid to call invalidate to invalidate the data source, and prevent further loading.

public abstract void loadBefore(
    @NonNull PageKeyedDataSource.LoadParams<@NonNull Key> params,
    @NonNull PageKeyedDataSource.LoadCallback<@NonNull Key, @NonNull Value> callback
)

Prepend page with the key specified by LoadParams.key.

It's valid to return a different list size than the page size if it's easier, e.g. if your backend defines page sizes. It is generally preferred to increase the number loaded than reduce.

Data may be passed synchronously during the load method, or deferred and called at a later time. Further loads going down will be blocked until the callback is called.

If data cannot be loaded (for example, if the request is invalid, or the data would be stale and inconsistent), it is valid to call invalidate to invalidate the data source, and prevent further loading.

public abstract void loadInitial(
    @NonNull PageKeyedDataSource.LoadInitialParams<@NonNull Key> params,
    @NonNull PageKeyedDataSource.LoadInitialCallback<@NonNull Key, @NonNull Value> callback
)

Load initial data.

This method is called first to initialize a PagedList with data. If it's possible to count the items that can be loaded by the DataSource, it's recommended to pass the loaded data to the callback via the three-parameter LoadInitialCallback.onResult. This enables PagedLists presenting data from this source to display placeholders to represent unloaded items.

LoadInitialParams.requestedLoadSize is a hint, not a requirement, so it may be may be altered or ignored.

public final @NonNull PageKeyedDataSource<@NonNull Key, @NonNull ToValue> <ToValue extends Object> map(
    @NonNull Function<@NonNull Value, @NonNull ToValue> function
)

Applies the given function to each value emitted by the DataSource.

Same as mapByPage, but operates on individual items.

public final @NonNull PageKeyedDataSource<@NonNull Key, @NonNull ToValue> <ToValue extends Object> map(
    @NonNull Function1<@NonNull Value, @NonNull ToValue> function
)

Applies the given function to each value emitted by the DataSource.

An overload of map that accepts a kotlin function type.

Same as mapByPage, but operates on individual items.

public final @NonNull PageKeyedDataSource<@NonNull Key, @NonNull ToValue> <ToValue extends Object> mapByPage(
    @NonNull Function<@NonNull List<@NonNull Value>, @NonNull List<@NonNull ToValue>> function
)

Applies the given function to each value emitted by the DataSource.

Same as map, but allows for batch conversions.

public final @NonNull PageKeyedDataSource<@NonNull Key, @NonNull ToValue> <ToValue extends Object> mapByPage(
    @NonNull Function1<@NonNull List<@NonNull Value>, @NonNull List<@NonNull ToValue>> function
)

Applies the given function to each value emitted by the DataSource.

An overload of mapByPage that accepts a kotlin function type.

Same as map, but allows for batch conversions.