| /* |
| * Copyright (C) 2017 The Android Open Source Project |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| package android.arch.paging; |
| |
| import android.arch.core.executor.AppToolkitTaskExecutor; |
| import android.arch.lifecycle.ComputableLiveData; |
| import android.arch.lifecycle.LiveData; |
| import android.support.annotation.Nullable; |
| import android.support.annotation.WorkerThread; |
| |
| /** |
| * Provides a {@code LiveData<PagedList>}, given a means to construct a DataSource. |
| * <p> |
| * Return type for data-loading system of an application or library to produce a |
| * {@code LiveData<PagedList>}, while leaving the details of the paging mechanism up to the |
| * consumer. |
| * |
| * @param <Key> Tyep of input valued used to load data from the DataSource. Must be integer if |
| * you're using TiledDataSource. |
| * @param <Value> Data type produced by the DataSource, and held by the PagedLists. |
| * |
| * @see DataSource |
| * @see PagedList |
| */ |
| public abstract class LivePagedListProvider<Key, Value> { |
| |
| /** |
| * Construct a new data source to be wrapped in a new PagedList, which will be returned |
| * through the LiveData. |
| * |
| * @return The data source. |
| */ |
| @WorkerThread |
| protected abstract DataSource<Key, Value> createDataSource(); |
| |
| /** |
| * Creates a LiveData of PagedLists, given the page size. |
| * <p> |
| * This LiveData can be passed to a {@link PagedListAdapter} to be displayed with a |
| * {@link android.support.v7.widget.RecyclerView}. |
| * |
| * @param initialLoadKey Initial key used to load initial data from the data source. |
| * @param pageSize Page size defining how many items are loaded from a data source at a time. |
| * Recommended to be multiple times the size of item displayed at once. |
| * |
| * @return The LiveData of PagedLists. |
| */ |
| public LiveData<PagedList<Value>> create(@Nullable Key initialLoadKey, int pageSize) { |
| return create(initialLoadKey, |
| new PagedList.Config.Builder() |
| .setPageSize(pageSize) |
| .build()); |
| } |
| |
| /** |
| * Creates a LiveData of PagedLists, given the PagedList.Config. |
| * <p> |
| * This LiveData can be passed to a {@link PagedListAdapter} to be displayed with a |
| * {@link android.support.v7.widget.RecyclerView}. |
| * |
| * @param initialLoadKey Initial key to pass to the data source to initialize data with. |
| * @param config PagedList.Config to use with created PagedLists. This specifies how the |
| * lists will load data. |
| * |
| * @return The LiveData of PagedLists. |
| */ |
| public LiveData<PagedList<Value>> create(@Nullable final Key initialLoadKey, |
| final PagedList.Config config) { |
| return new ComputableLiveData<PagedList<Value>>() { |
| @Nullable |
| private PagedList<Value> mList; |
| @Nullable |
| private DataSource<Key, Value> mDataSource; |
| |
| private final DataSource.InvalidatedCallback mCallback = |
| new DataSource.InvalidatedCallback() { |
| @Override |
| public void onInvalidated() { |
| invalidate(); |
| } |
| }; |
| |
| @Override |
| protected PagedList<Value> compute() { |
| @Nullable Key initializeKey; |
| if (mList == null || mDataSource == null) { |
| initializeKey = initialLoadKey; |
| } else if (mList.size() == 0) { |
| initializeKey = null; |
| } else { |
| if (mDataSource.isContiguous() && mDataSource instanceof KeyedDataSource) { |
| KeyedDataSource<Key, Value> keyedDataSource = |
| (KeyedDataSource<Key, Value>) mDataSource; |
| initializeKey = keyedDataSource.getKey(mList.getLastItem()); |
| } else { |
| initializeKey = (Key) ((Integer) mList.getLastLoad()); |
| } |
| } |
| |
| do { |
| if (mDataSource != null) { |
| mDataSource.removeInvalidatedCallback(mCallback); |
| } |
| |
| mDataSource = createDataSource(); |
| mDataSource.addInvalidatedCallback(mCallback); |
| |
| mList = new PagedList.Builder<Key, Value>() |
| .setDataSource(mDataSource) |
| .setMainThreadExecutor(AppToolkitTaskExecutor.getMainThreadExecutor()) |
| .setBackgroundThreadExecutor( |
| AppToolkitTaskExecutor.getIOThreadExecutor()) |
| .setConfig(config) |
| .setInitialKey(initializeKey) |
| .build(); |
| } while (mList.isDetached()); |
| return mList; |
| } |
| }.getLiveData(); |
| } |
| } |