com.google.android.agera.rvadapter

Class RepositoryPresenter<T>

java.lang.Object

com.google.android.agera.rvadapter.RepositoryPresenter<T>

public abstract class RepositoryPresenter<T>
extends java.lang.Object

Contains logic to present the content of a Repository.

Constructor Summary

Constructors

Constructor and Description
RepositoryPresenter()

Method Summary

Modifier and Type	Method and Description
abstract void	bind(T data, int index, android.support.v7.widget.RecyclerView.ViewHolder holder) Binds the index-th item to present the data into the item view held in the given holder.
abstract int	getItemCount(T data) Returns the number of adapter items needed to present the data.
long	getItemId(T data, int index) Returns the stable ID for the index-th item to present the data.
abstract int	getLayoutResId(T data, int index) Returns the layout resource ID to inflate the view for the index-th item to present the data.
boolean	getUpdates(T oldData, T newData, android.support.v7.util.ListUpdateCallback listUpdateCallback) Produces a sequence of fine-grained events (addition, removal, changing and moving of individual items) to the given listUpdateCallback capturing the changes of data to be presented by this RepositoryPresenter, in response to an update.
void	recycle(android.support.v7.widget.RecyclerView.ViewHolder holder) Called when the given holder is recycled.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

RepositoryPresenter

public RepositoryPresenter()

Method Detail

getItemCount

public abstract int getItemCount(@NonNull
                                 T data)

Returns the number of adapter items needed to present the data. This method may be called very frequently; implementation should be very lightweight.

getItemId

public long getItemId(@NonNull
                      T data,
                      int index)

Returns the stable ID for the index-th item to present the data. Called only if stable IDs are enabled with RepositoryAdapter.setHasStableIds(true), and therefore this method is optional with a default implementation of returning RecyclerView.NO_ID. If stable IDs are enabled, this ID and the item's layout resource ID should together uniquely identify this item in the whole RecyclerView throughout all changes.

Parameters:

index - The item index between 0 (incl.) and getItemCount(T) (excl.).

getLayoutResId

@LayoutRes
public abstract int getLayoutResId(@NonNull
                                              T data,
                                              int index)

Returns the layout resource ID to inflate the view for the index-th item to present the data.

Parameters:

index - The item index between 0 (incl.) and getItemCount(T) (excl.).

bind

public abstract void bind(@NonNull
                          T data,
                          int index,
                          @NonNull
                          android.support.v7.widget.RecyclerView.ViewHolder holder)

Binds the index-th item to present the data into the item view held in the given holder. The view is inflated from the layout resource specified by getLayoutResId(T, int), but may have been previously bound to a different index, different data, and/or with a different presenter. Therefore, implementation should take care of resetting the view state.

Parameters:

index - The item index between 0 (incl.) and getItemCount(T) (excl.).

holder - The view holder that holds the view. If a subclass of RepositoryAdapter is used, which returns a custom view holder for this item's layout resource ID, then this object will be of that custom type.

recycle

public void recycle(@NonNull
                    android.support.v7.widget.RecyclerView.ViewHolder holder)

Called when the given holder is recycled.

Parameters:

holder - The view holder that holds the view. If a subclass of RepositoryAdapter is used, which returns a custom view holder for this item's layout resource ID, then this object will be of that custom type.

getUpdates

public boolean getUpdates(@NonNull
                          T oldData,
                          @NonNull
                          T newData,
                          @NonNull
                          android.support.v7.util.ListUpdateCallback listUpdateCallback)

Produces a sequence of fine-grained events (addition, removal, changing and moving of individual items) to the given listUpdateCallback capturing the changes of data to be presented by this RepositoryPresenter, in response to an update. Implementation should do either of the following:

• Produce and dispatch the fine-grained events that accurately describe the changes, and then return true;
• Refuse to produce the fine-grained events by returning false. This is the base implementation.

While a RepositoryAdapter is in use (for example, attached to a RecyclerView), when it receives an update from a presented Repository, the associated RepositoryPresenter will be asked to produce a sequence of fine-grained events capturing the update; when the RepositoryAdapter receives an update from one of the additional observables, then all RepositoryPresenters will be asked. If all affected RepositoryPresenters produced fine-grained events, then RepositoryAdapter will apply the new data and notify the RecyclerView of the aggregated sequence of events; otherwise the adapter will call RecyclerView.Adapter.notifyDataSetChanged(), and pause all update processing (both data and events) until fresh data is needed, hinted by the next call to RepositoryAdapter.getItemCount().

Notes for implementation:

• If the update comes from the paired repository, then oldData is the previously presented repository value, and newData is the value newly obtained from the repository. The new value has not been applied and is not exposed through the adapter. Note that repositories are allowed to dispatch updates while maintaining oldData.equals(newData) or even oldData == newData, depending on the repository implementation.
• If the update comes from an additional observable, then it is guaranteed that oldData == newData, because the value is not reloaded from the repository.
• A RepositoryPresenter may not have a chance to produce fine-grained events in response to an update. This can happen when an earlier presenter returns false from this method, or the adapter is not in use (for example, not attached to any RecyclerView).
• RepositoryAdapter guarantees that, if this method is not called, then getItemCount(T) will be called before this RepositoryPresenter is asked to present any item from the new data. getItemCount(T) may be called again when there is a chance that the last data passed into the method may not be the latest.
• A RepositoryPresenter presenting a static item (added with RepositoryAdapter.Builder.addItem(T, com.google.android.agera.rvadapter.RepositoryPresenter<T>)) will not be able to produce any events for any item views presented for the static item.

Parameters:

oldData - The data previously presented by this RepositoryPresenter.

newData - The data to be presented by this RepositoryPresenter following the update.

listUpdateCallback - A callback to record the sequence of fine-grained events to be dispatched via the RepositoryAdapter to the RecyclerView. To be used within this method call only. Positions and counts are relative to this presenter.

Returns:

Whether the sequence of calls to listUpdateCallback during the execution of this method has completely and accurately described all changes.