| /* |
| * 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.support.annotation.NonNull; |
| import android.support.annotation.Nullable; |
| import android.support.annotation.RestrictTo; |
| |
| import java.util.ArrayList; |
| import java.util.List; |
| |
| /** @hide */ |
| @RestrictTo(RestrictTo.Scope.LIBRARY_GROUP) |
| class PageArrayList<T> extends PagedList<T> { |
| // partial list of pages, doesn't include pages below the lowest accessed, or above the highest |
| final ArrayList<List<T>> mPages; |
| |
| // to access page at index N, do mPages.get(N - mPageIndexOffset), but do bounds checking first! |
| int mPageIndexOffset; |
| |
| final int mPageSize; |
| final int mCount; |
| final int mMaxPageCount; |
| |
| PageArrayList(int pageSize, int count) { |
| mPages = new ArrayList<>(); |
| mPageSize = pageSize; |
| mCount = count; |
| mMaxPageCount = (mCount + mPageSize - 1) / mPageSize; |
| } |
| |
| private PageArrayList(PageArrayList<T> other) { |
| mPages = other.isImmutable() ? other.mPages : new ArrayList<>(other.mPages); |
| mPageIndexOffset = other.mPageIndexOffset; |
| mPageSize = other.mPageSize; |
| mCount = other.size(); |
| mMaxPageCount = other.mMaxPageCount; |
| } |
| |
| @Override |
| public T get(int index) { |
| if (index < 0 || index >= mCount) { |
| throw new IllegalArgumentException(); |
| } |
| |
| int localPageIndex = getLocalPageIndex(index); |
| |
| List<T> page = getPage(localPageIndex); |
| |
| if (page == null) { |
| // page empty |
| return null; |
| } |
| |
| return page.get(index % mPageSize); |
| } |
| |
| @Nullable |
| private List<T> getPage(int localPageIndex) { |
| if (localPageIndex < 0 || localPageIndex >= mPages.size()) { |
| // page not present |
| return null; |
| } |
| |
| return mPages.get(localPageIndex); |
| } |
| |
| private int getLocalPageIndex(int index) { |
| return index / mPageSize - mPageIndexOffset; |
| } |
| |
| @Override |
| public void loadAround(int index) { |
| // do nothing - immutable, so no fetching will be done |
| } |
| |
| @Override |
| public int size() { |
| return mCount; |
| } |
| |
| @Override |
| public boolean isImmutable() { |
| return true; |
| } |
| |
| boolean hasPage(int pageIndex) { |
| final int localPageIndex = pageIndex - mPageIndexOffset; |
| List<T> page = getPage(localPageIndex); |
| return page != null && page.size() != 0; |
| } |
| |
| @Override |
| public PagedList<T> snapshot() { |
| if (isImmutable()) { |
| return this; |
| } |
| return new PageArrayList<>(this); |
| } |
| |
| @Override |
| boolean isContiguous() { |
| return false; |
| } |
| |
| @Override |
| public void addCallback(@Nullable PagedList<T> previousSnapshot, @NonNull Callback callback) { |
| // no op, immutable |
| } |
| |
| @Override |
| public void removeCallback(Callback callback) { |
| // no op, immutable |
| } |
| } |