TimeGateway.java
/*
* Copyright 2022 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 androidx.wear.protolayout.expression.pipeline;
import androidx.annotation.NonNull;
import java.util.concurrent.Executor;
/**
* Controls evaluation triggering of time-related expressions.
*
* <p>Can be optionally provided to {@link DynamicTypeEvaluator} in order to have fine control of
* how time-related expressions are triggered for re-evaluation.
*/
public interface TimeGateway {
/** Callback for {@link TimeGateway} triggers. */
interface TimeCallback {
/**
* Called just before an update happens. All onPreUpdate calls will be made before any
* onUpdate calls fire.
*
* <p>Will be called on the same executor passed to {@link TimeGateway#registerForUpdates}.
*
* <p>It is up to the caller to ensure synchronization between {@link #onPreUpdate()} and
* {@link #onData()} calls (both called on the {@link Executor} provided to {@link
* #registerForUpdates}), e.g. by providing a single-threaded ordered {@link Executor}. If
* not synchronized, it's possible that {@link #onData()} will be invoked before {@link
* #onPreUpdate()} on the same time tick.
*/
void onPreUpdate();
/**
* Notifies that the current time has changed.
*
* <p>Will be called on the same executor passed to {@link TimeGateway#registerForUpdates}.
*
* <p>It is up to the caller to ensure synchronization between {@link #onPreUpdate()} and
* {@link #onData()} calls (both called on the {@link Executor} provided to {@link
* #registerForUpdates}), e.g. by providing a single-threaded ordered {@link Executor}. If
* not synchronized, it's possible that {@link #onData()} will be invoked before {@link
* #onPreUpdate()} on the same time tick.
*/
void onData();
}
/**
* Register for time updates. All callbacks will be called on the provided executor.
*
* <p>It is up to the caller to ensure synchronization between {@link
* TimeCallback#onPreUpdate()} and {@link TimeCallback#onData()} calls (both called on the
* provided {@link Executor}), e.g. by providing a single-threaded ordered {@link Executor}. If
* not synchronized, it's possible that {@link TimeCallback#onData()} will be invoked before
* {@link TimeCallback#onPreUpdate()} on the same time tick.
*/
void registerForUpdates(@NonNull Executor executor, @NonNull TimeCallback callback);
/** Unregister for time updates. */
void unregisterForUpdates(@NonNull TimeCallback callback);
}