Runnable.kt
/*
* 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.core.util
import java.util.concurrent.atomic.AtomicBoolean
import kotlin.coroutines.Continuation
import kotlin.coroutines.resume
/**
* Returns a [Runnable] that will resume this [Continuation] when an operation completes and
* the returned [Runnable]'s [Runnable.run] method is called.
*
* Useful for writing `suspend` bindings to async Jetpack library methods that accept [Runnable]
* as a completion callback for a one-time operation:
*
* ```
* public suspend fun FancinessManager.setFanciness(
* fanciness: Float
* ): Unit = suspendCancellableCoroutine<Unit> { continuation ->
*
* // Any Android API that supports cancellation should be configured to propagate
* // coroutine cancellation as follows:
* val canceller = CancellationSignal()
* continuation.invokeOnCancellation { canceller.cancel() }
*
* // Invoke the FancinessManager#setFanciness method as follows:
* queryAsync(
* fanciness,
* canceller,
* // Use a direct executor to avoid extra dispatch. Resuming the continuation will
* // handle getting to the right thread or pool via the ContinuationInterceptor.
* Runnable::run,
* continuation.asRunnable()
* )
* }
* ```
*/
public fun Continuation<Unit>.asRunnable(): Runnable = ContinuationRunnable(this)
private class ContinuationRunnable(
private val continuation: Continuation<Unit>
) : Runnable, AtomicBoolean(false) {
override fun run() {
// Do not attempt to resume more than once, even if the caller of the returned
// Runnable is buggy and tries anyway.
if (compareAndSet(false, true)) {
continuation.resume(Unit)
}
}
override fun toString() = "ContinuationRunnable(ran = ${get()})"
}