RxRemoteMediator

Kotlin |Java

public abstract class RxRemoteMediator<Key extends Object, Value extends Object> extends RemoteMediator

Object
↳	RemoteMediator
	↳	RxRemoteMediator

RxJava2 compatibility wrapper around RemoteMediator's suspending APIs.

Summary

Public constructors
`<Key extends Object, Value extends Object> RxRemoteMediator()`

Public methods
`final @NonNull RemoteMediator.InitializeAction`	`initialize()` Callback fired during initialization of a `PagingData` stream, before initial load.
`@NonNull Single<@NonNull RemoteMediator.InitializeAction>`	`initializeSingle()` Callback fired during initialization of a `PagingData` stream, before initial load.
`final @NonNull RemoteMediator.MediatorResult`	`load( @NonNull LoadType loadType, @NonNull PagingState<@NonNull Key, @NonNull Value> state )` Callback triggered when Paging needs to request more data from a remote source due to any of the following events:
`abstract @NonNull Single<@NonNull RemoteMediator.MediatorResult>`	`loadSingle( @NonNull LoadType loadType, @NonNull PagingState<@NonNull Key, @NonNull Value> state )` Implement this method to load additional remote data, which will then be stored for the `PagingSource` to access.

Public constructors

RxRemoteMediator

@NonNull
public final <Key extends Object, Value extends Object> RxRemoteMediator()

Public methods

initialize

@NonNull
public final RemoteMediator.InitializeAction initialize()

Callback fired during initialization of a PagingData stream, before initial load.

This function runs to completion before any loading is performed.

Returns

Returns
`RemoteMediator.InitializeAction`	`InitializeAction` used to control whether `load` with load type `REFRESH` will be immediately dispatched when the first `PagingData` is submitted: `LAUNCH_INITIAL_REFRESH` to immediately dispatch `load` asynchronously with load type `REFRESH`, to update paginated content when the stream is initialized. Note: This also prevents `RemoteMediator` from triggering `PREPEND` or `APPEND` until `REFRESH` succeeds. SKIP_INITIAL_REFRESH to wait for a refresh request from the UI before dispatching `load` asynchronously with load type `REFRESH`.

RemoteMediator.InitializeAction

InitializeAction used to control whether load with load type REFRESH will be immediately dispatched when the first PagingData is submitted:

LAUNCH_INITIAL_REFRESH to immediately dispatch load asynchronously with load type REFRESH, to update paginated content when the stream is initialized. Note: This also prevents RemoteMediator from triggering PREPEND or APPEND until REFRESH succeeds.
SKIP_INITIAL_REFRESH to wait for a refresh request from the UI before dispatching load asynchronously with load type REFRESH.

initializeSingle

@NonNull
public Single<@NonNull RemoteMediator.InitializeAction> initializeSingle()

Callback fired during initialization of a PagingData stream, before initial load.

This function runs to completion before any loading is performed.

Returns

Returns
`Single<@NonNull RemoteMediator.InitializeAction>`	`InitializeAction` indicating the action to take after initialization: `LAUNCH_INITIAL_REFRESH` to immediately dispatch a `load` asynchronously with load type `LoadType.REFRESH`, to update paginated content when the stream is initialized. Note: This also prevents `RemoteMediator` from triggering `PREPEND` or `APPEND` until `REFRESH` succeeds. `SKIP_INITIAL_REFRESH` to wait for a refresh request from the UI before dispatching a `load` with load type `LoadType.REFRESH`.

Single<@NonNull RemoteMediator.InitializeAction>

InitializeAction indicating the action to take after initialization:

LAUNCH_INITIAL_REFRESH to immediately dispatch a load asynchronously with load type LoadType.REFRESH, to update paginated content when the stream is initialized. Note: This also prevents RemoteMediator from triggering PREPEND or APPEND until REFRESH succeeds.
SKIP_INITIAL_REFRESH to wait for a refresh request from the UI before dispatching a load with load type LoadType.REFRESH.

load

@NonNull
public final RemoteMediator.MediatorResult load(
    @NonNull LoadType loadType,
    @NonNull PagingState<@NonNull Key, @NonNull Value> state
)

Callback triggered when Paging needs to request more data from a remote source due to any of the following events:

Stream initialization if initialize returns LAUNCH_INITIAL_REFRESH
REFRESH signal driven from UI
PagingSource returns a LoadResult which signals a boundary condition, i.e., the most recent LoadResult.Page in the PREPEND or APPEND direction has LoadResult.Page.prevKey or LoadResult.Page.nextKey set to null respectively.

It is the responsibility of this method to update the backing dataset and trigger PagingSource.invalidate to allow androidx.paging.PagingDataAdapter to pick up new items found by load.

The runtime and result of this method defines the remote LoadState behavior sent to the UI via CombinedLoadStates.

This method is never called concurrently unlessPager.flow has multiple collectors. Note that Paging might cancel calls to this function if it is currently executing a PREPEND or APPEND and a REFRESH is requested. In that case, REFRESH has higher priority and will be executed after the previous call is cancelled. If the load call with REFRESH returns an error, Paging will call load with the previously cancelled APPEND or PREPEND request. If REFRESH succeeds, it won't make the APPEND or PREPEND requests unless they are necessary again after the REFRESH is applied to the UI.

Parameters

Parameters
`@NonNull LoadType loadType`	`LoadType` of the condition which triggered this callback. `PREPEND` indicates the end of pagination in the `PREPEND` direction was reached. This occurs when `PagingSource.load` returns a LoadResult.Page with LoadResult.Page.prevKey == `null`. `APPEND` indicates the end of pagination in the `APPEND` direction was reached. This occurs when `PagingSource.load` returns a LoadResult.Page with LoadResult.Page.nextKey == `null`. `REFRESH` indicates this method was triggered due to a requested refresh. Generally, this means that a request to load remote data and replace all local data was made. This can happen when: Stream initialization if `initialize` returns `LAUNCH_INITIAL_REFRESH` An explicit call to refresh driven by the UI
`@NonNull PagingState<@NonNull Key, @NonNull Value> state`	A copy of the state including the list of pages currently held in memory of the currently presented `PagingData` at the time of starting the load. E.g. for load(loadType = APPEND), you can use the page or item at the end as input for what to load from the network.

@NonNull LoadType loadType

LoadType of the condition which triggered this callback.

PREPEND indicates the end of pagination in the PREPEND direction was reached. This occurs when PagingSource.load returns a LoadResult.Page with LoadResult.Page.prevKey == null.
APPEND indicates the end of pagination in the APPEND direction was reached. This occurs when PagingSource.load returns a LoadResult.Page with LoadResult.Page.nextKey == null.
REFRESH indicates this method was triggered due to a requested refresh. Generally, this means that a request to load remote data and replace all local data was made. This can happen when:

Stream initialization if initialize returns LAUNCH_INITIAL_REFRESH
An explicit call to refresh driven by the UI

@NonNull PagingState<@NonNull Key, @NonNull Value> state

A copy of the state including the list of pages currently held in memory of the currently presented PagingData at the time of starting the load. E.g. for load(loadType = APPEND), you can use the page or item at the end as input for what to load from the network.

Returns
`RemoteMediator.MediatorResult`	`MediatorResult` signifying what `LoadState` to be passed to the UI, and whether there's more data available.

loadSingle

@NonNull
public abstract Single<@NonNull RemoteMediator.MediatorResult> loadSingle(
    @NonNull LoadType loadType,
    @NonNull PagingState<@NonNull Key, @NonNull Value> state
)

Implement this method to load additional remote data, which will then be stored for the PagingSource to access. These loads take one of two forms:

type == LoadType.PREPEND / LoadType.APPEND The PagingSource has loaded a 'boundary' page, with a null adjacent key. This means this method should load additional remote data to append / prepend as appropriate, and store it locally.
type == LoadType.REFRESH The app (or initialize) has requested a remote refresh of data. This means the method should generally load remote data, and replace all local data.

The runtime of this method defines loading state behavior in boundary conditions, which affects e.g., LoadState callbacks registered to androidx.paging.PagingDataAdapter.

NOTE: A PagingSource.load request which is fulfilled by a page that hits a boundary condition in either direction will trigger this callback with LoadType.PREPEND or LoadType.APPEND or both. LoadType.REFRESH occurs as a result of initialize.

Parameters

Parameters
`@NonNull LoadType loadType`	`LoadType` of the boundary condition which triggered this callback. `LoadType.PREPEND` indicates a boundary condition at the front of the list. `LoadType.APPEND` indicates a boundary condition at the end of the list. `LoadType.REFRESH` indicates this callback was triggered as the result of a requested refresh - either driven by the UI, or by `initialize`.
`@NonNull PagingState<@NonNull Key, @NonNull Value> state`	A copy of the state including the list of pages currently held in memory of the currently presented `PagingData` at the time of starting the load. E.g. for load(loadType = END), you can use the page or item at the end as input for what to load from the network.

@NonNull LoadType loadType

LoadType of the boundary condition which triggered this callback.

LoadType.PREPEND indicates a boundary condition at the front of the list.
LoadType.APPEND indicates a boundary condition at the end of the list.
LoadType.REFRESH indicates this callback was triggered as the result of a requested refresh - either driven by the UI, or by initialize.

@NonNull PagingState<@NonNull Key, @NonNull Value> state

A copy of the state including the list of pages currently held in memory of the currently presented PagingData at the time of starting the load. E.g. for load(loadType = END), you can use the page or item at the end as input for what to load from the network.

Returns
`Single<@NonNull RemoteMediator.MediatorResult>`	`MediatorResult` signifying what `LoadState` to be passed to the UI, and whether there's more data available.