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/*
* 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.AnyThread;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
import android.support.annotation.WorkerThread;
import java.util.concurrent.Executor;
class TiledPagedList<T> extends PagedList<T>
implements PagedStorage.Callback {
private final PositionalDataSource<T> mDataSource;
private PageResult.Receiver<T> mReceiver = new PageResult.Receiver<T>() {
// Creation thread for initial synchronous load, otherwise main thread
// Safe to access main thread only state - no other thread has reference during construction
@AnyThread
@Override
public void onPageResult(@PageResult.ResultType int type,
@NonNull PageResult<T> pageResult) {
if (pageResult.isInvalid()) {
detach();
return;
}
if (isDetached()) {
// No op, have detached
return;
}
if (mStorage.getPageCount() == 0) {
mStorage.initAndSplit(
pageResult.leadingNulls, pageResult.page, pageResult.trailingNulls,
pageResult.positionOffset, mConfig.pageSize, TiledPagedList.this);
} else {
mStorage.insertPage(pageResult.positionOffset, pageResult.page,
TiledPagedList.this);
}
if (mBoundaryCallback != null) {
boolean deferEmpty = mStorage.size() == 0;
boolean deferBegin = !deferEmpty
&& pageResult.leadingNulls == 0
&& pageResult.positionOffset == 0;
int size = size();
boolean deferEnd = !deferEmpty
&& ((type == PageResult.INIT && pageResult.trailingNulls == 0)
|| (type == PageResult.TILE
&& pageResult.positionOffset
== (size - size % mConfig.pageSize)));
deferBoundaryCallbacks(deferEmpty, deferBegin, deferEnd);
}
}
};
@WorkerThread
TiledPagedList(@NonNull PositionalDataSource<T> dataSource,
@NonNull Executor mainThreadExecutor,
@NonNull Executor backgroundThreadExecutor,
@Nullable BoundaryCallback<T> boundaryCallback,
@NonNull Config config,
int position) {
super(new PagedStorage<T>(), mainThreadExecutor, backgroundThreadExecutor,
boundaryCallback, config);
mDataSource = dataSource;
final int pageSize = mConfig.pageSize;
mLastLoad = position;
if (mDataSource.isInvalid()) {
detach();
} else {
final int firstLoadSize =
(Math.max(Math.round(mConfig.initialLoadSizeHint / pageSize), 2)) * pageSize;
final int idealStart = position - firstLoadSize / 2;
final int roundedPageStart = Math.max(0, Math.round(idealStart / pageSize) * pageSize);
mDataSource.dispatchLoadInitial(true, roundedPageStart, firstLoadSize,
pageSize, mMainThreadExecutor, mReceiver);
}
}
@Override
boolean isContiguous() {
return false;
}
@Nullable
@Override
public Object getLastKey() {
return mLastLoad;
}
@Override
protected void dispatchUpdatesSinceSnapshot(@NonNull PagedList<T> pagedListSnapshot,
@NonNull Callback callback) {
//noinspection UnnecessaryLocalVariable
final PagedStorage<T> snapshot = pagedListSnapshot.mStorage;
if (snapshot.isEmpty()
|| mStorage.size() != snapshot.size()) {
throw new IllegalArgumentException("Invalid snapshot provided - doesn't appear"
+ " to be a snapshot of this PagedList");
}
// loop through each page and signal the callback for any pages that are present now,
// but not in the snapshot.
final int pageSize = mConfig.pageSize;
final int leadingNullPages = mStorage.getLeadingNullCount() / pageSize;
final int pageCount = mStorage.getPageCount();
for (int i = 0; i < pageCount; i++) {
int pageIndex = i + leadingNullPages;
int updatedPages = 0;
// count number of consecutive pages that were added since the snapshot...
while (updatedPages < mStorage.getPageCount()
&& mStorage.hasPage(pageSize, pageIndex + updatedPages)
&& !snapshot.hasPage(pageSize, pageIndex + updatedPages)) {
updatedPages++;
}
// and signal them all at once to the callback
if (updatedPages > 0) {
callback.onChanged(pageIndex * pageSize, pageSize * updatedPages);
i += updatedPages - 1;
}
}
}
@Override
protected void loadAroundInternal(int index) {
mStorage.allocatePlaceholders(index, mConfig.prefetchDistance, mConfig.pageSize, this);
}
@Override
public void onInitialized(int count) {
notifyInserted(0, count);
}
@Override
public void onPagePrepended(int leadingNulls, int changed, int added) {
throw new IllegalStateException("Contiguous callback on TiledPagedList");
}
@Override
public void onPageAppended(int endPosition, int changed, int added) {
throw new IllegalStateException("Contiguous callback on TiledPagedList");
}
@Override
public void onPagePlaceholderInserted(final int pageIndex) {
// placeholder means initialize a load
mBackgroundThreadExecutor.execute(new Runnable() {
@Override
public void run() {
if (isDetached()) {
return;
}
final int pageSize = mConfig.pageSize;
if (mDataSource.isInvalid()) {
detach();
} else {
int startPosition = pageIndex * pageSize;
int count = Math.min(pageSize, mStorage.size() - startPosition);
mDataSource.dispatchLoadRange(
startPosition, count, mMainThreadExecutor, mReceiver);
}
}
});
}
@Override
public void onPageInserted(int start, int count) {
notifyChanged(start, count);
}
}
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