DynamicTypeValueReceiver.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 androidx.annotation.RestrictTo;
import androidx.annotation.UiThread;
/**
* Callback for an evaluation result. This is intended to support two-step updates; first a
* notification will be sent that the evaluation result item will be updated, then the new
* evaluation result will be delivered. This allows downstream consumers to properly synchronize
* their updates if they depend on two or more evaluation result items, rather than updating
* multiple times (with potentially invalid states).
*
* <p>It is guaranteed that for any given batch evaluation result, {@link #onPreUpdate()} will be
* called on all listeners before any {@link #onData} calls are fired.
*
* @param <T> Data type.
*/
public interface DynamicTypeValueReceiver<T> {
/**
* Called when evaluation result for the expression that this callback was registered for is
* about to be updated. This allows a downstream consumer to properly synchronize updates if it
* depends on two or more evaluation result items. In that case, it should use this call to
* figure out how many of its dependencies are going to be updated, and wait for all of them to
* be updated (via {@link DynamicTypeValueReceiver#onData(T)}) before acting on the change.
*
* @hide
*/
@UiThread
@RestrictTo(RestrictTo.Scope.LIBRARY_GROUP)
void onPreUpdate();
/**
* Called when the expression that this callback was registered for has a new evaluation result.
*
* @see DynamicTypeValueReceiver#onPreUpdate()
*/
@UiThread
void onData(@NonNull T newData);
/** Called when the expression that this callback was registered for has an invalid result. */
@UiThread
void onInvalidated();
}