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/*
* Copyright 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.support.v7.recyclerview.extensions;
import android.os.Handler;
import android.os.Looper;
import android.support.annotation.NonNull;
import android.support.annotation.RestrictTo;
import android.support.v7.util.DiffUtil;
import java.util.concurrent.Executor;
import java.util.concurrent.Executors;
/**
* Configuration object for {@link ListAdapter}, {@link ListAdapterHelper}, and similar
* background-thread list diffing adapter logic.
* <p>
* At minimum, defines item diffing behavior with a {@link DiffUtil.ItemCallback}, used to compute
* item differences to pass to a RecyclerView adapter.
*
* @param <T> Type of items in the lists, and being compared.
*/
public final class ListAdapterConfig<T> {
@NonNull
private final Executor mMainThreadExecutor;
@NonNull
private final Executor mBackgroundThreadExecutor;
@NonNull
private final DiffUtil.ItemCallback<T> mDiffCallback;
private ListAdapterConfig(
@NonNull Executor mainThreadExecutor,
@NonNull Executor backgroundThreadExecutor,
@NonNull DiffUtil.ItemCallback<T> diffCallback) {
mMainThreadExecutor = mainThreadExecutor;
mBackgroundThreadExecutor = backgroundThreadExecutor;
mDiffCallback = diffCallback;
}
/** @hide */
@SuppressWarnings("WeakerAccess")
@RestrictTo(RestrictTo.Scope.LIBRARY_GROUP)
@NonNull
public Executor getMainThreadExecutor() {
return mMainThreadExecutor;
}
/** @hide */
@SuppressWarnings("WeakerAccess")
@RestrictTo(RestrictTo.Scope.LIBRARY_GROUP)
@NonNull
public Executor getBackgroundThreadExecutor() {
return mBackgroundThreadExecutor;
}
@SuppressWarnings("WeakerAccess")
@NonNull
public DiffUtil.ItemCallback<T> getDiffCallback() {
return mDiffCallback;
}
/**
* Builder class for {@link ListAdapterConfig}.
*
* @param <T>
*/
public static class Builder<T> {
private Executor mMainThreadExecutor;
private Executor mBackgroundThreadExecutor;
private final DiffUtil.ItemCallback<T> mDiffCallback;
public Builder(@NonNull DiffUtil.ItemCallback<T> diffCallback) {
mDiffCallback = diffCallback;
}
/**
* If provided, defines the main thread executor used to dispatch adapter update
* notifications on the main thread.
* <p>
* If not provided, it will default to the main thread.
*
* @param executor The executor which can run tasks in the UI thread.
* @return this
*
* @hide
*/
@RestrictTo(RestrictTo.Scope.LIBRARY_GROUP)
@NonNull
public Builder<T> setMainThreadExecutor(Executor executor) {
mMainThreadExecutor = executor;
return this;
}
/**
* If provided, defines the background executor used to calculate the diff between an old
* and a new list.
* <p>
* If not provided, defaults to two thread pool executor, shared by all ListAdapterConfigs.
*
* @param executor The background executor to run list diffing.
* @return this
*/
@SuppressWarnings({"unused", "WeakerAccess"})
@NonNull
public Builder<T> setBackgroundThreadExecutor(Executor executor) {
mBackgroundThreadExecutor = executor;
return this;
}
private static class MainThreadExecutor implements Executor {
final Handler mHandler = new Handler(Looper.getMainLooper());
@Override
public void execute(@NonNull Runnable command) {
mHandler.post(command);
}
}
/**
* Creates a {@link ListAdapterHelper} with the given parameters.
*
* @return A new ListAdapterConfig.
*/
@NonNull
public ListAdapterConfig<T> build() {
if (mMainThreadExecutor == null) {
mMainThreadExecutor = sMainThreadExecutor;
}
if (mBackgroundThreadExecutor == null) {
synchronized (sExecutorLock) {
if (sDiffExecutor == null) {
sDiffExecutor = Executors.newFixedThreadPool(2);
}
}
mBackgroundThreadExecutor = sDiffExecutor;
}
return new ListAdapterConfig<>(
mMainThreadExecutor,
mBackgroundThreadExecutor,
mDiffCallback);
}
// TODO: remove the below once supportlib has its own appropriate executors
private static final Object sExecutorLock = new Object();
private static Executor sDiffExecutor = null;
// TODO: use MainThreadExecutor from supportlib once one exists
private static final Executor sMainThreadExecutor = new MainThreadExecutor();
}
}
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