WindowInfoRepositoryCallbackAdapter.kt
/*
* Copyright 2021 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.window.java.layout
import androidx.core.util.Consumer
import androidx.window.layout.WindowInfoRepository
import androidx.window.layout.WindowLayoutInfo
import androidx.window.layout.WindowMetrics
import kotlinx.coroutines.CoroutineScope
import kotlinx.coroutines.Job
import kotlinx.coroutines.asCoroutineDispatcher
import kotlinx.coroutines.flow.Flow
import kotlinx.coroutines.flow.collect
import kotlinx.coroutines.launch
import java.util.concurrent.Executor
import java.util.concurrent.locks.ReentrantLock
import kotlin.concurrent.withLock
/**
* An adapted interface for [WindowInfoRepository] that allows listening for events via a callback
* shaped API.
*/
class WindowInfoRepositoryCallbackAdapter(
private val repository: WindowInfoRepository
) : WindowInfoRepository by repository {
/**
* A [ReentrantLock] to protect against concurrent access to [consumerToJobMap].
*/
private val lock = ReentrantLock()
private val consumerToJobMap = mutableMapOf<Consumer<*>, Job>()
/**
* Register a listener to consume [WindowMetrics] values. If the same consumer is registered
* twice then this method is a no-op.
* @see WindowInfoRepository.currentWindowMetrics
*/
fun addCurrentWindowMetricsListener(executor: Executor, consumer: Consumer<WindowMetrics>) {
addListener(executor, consumer, repository.currentWindowMetrics)
}
/**
* Remove a listener to stop consuming [WindowMetrics] values. If the listener has already
* been removed then this is a no-op.
* @see WindowInfoRepository.currentWindowMetrics
*/
fun removeCurrentWindowMetricsListener(consumer: Consumer<WindowMetrics>) {
removeListener(consumer)
}
/**
* Register a listener to consume [WindowLayoutInfo] values. If the same consumer is
* registered twice then this method is a no-op.
* @see WindowInfoRepository.windowLayoutInfo
*/
fun addWindowLayoutInfoListener(
executor: Executor,
consumer: Consumer<WindowLayoutInfo>
) {
addListener(executor, consumer, repository.windowLayoutInfo)
}
/**
* Remove a listener to stop consuming [WindowLayoutInfo] values. If the listener has already
* been removed then this is a no-op.
* @see WindowInfoRepository.windowLayoutInfo
*/
fun removeWindowLayoutInfoListener(consumer: Consumer<WindowLayoutInfo>) {
removeListener(consumer)
}
/**
* Generic method for registering a [Consumer] to collect the values from a [Flow].
* Registering the same [Consumer] is a no-op.
*/
private fun <T> addListener(executor: Executor, consumer: Consumer<T>, flow: Flow<T>) {
lock.withLock {
if (consumerToJobMap[consumer] == null) {
val scope = CoroutineScope(executor.asCoroutineDispatcher())
consumerToJobMap[consumer] = scope.launch {
flow.collect { consumer.accept(it) }
}
}
}
}
/**
* Generic method for canceling a [Job] related to a consumer. Canceling twice in a row is a
* no-op.
*/
private fun removeListener(consumer: Consumer<*>) {
lock.withLock {
consumerToJobMap[consumer]?.cancel()
consumerToJobMap.remove(consumer)
}
}
}