ExtensionWindowLayoutInfoBackend.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.layout.adapter.extensions
import android.app.Activity
import android.content.Context
import androidx.annotation.GuardedBy
import androidx.annotation.UiContext
import androidx.annotation.VisibleForTesting
import androidx.core.util.Consumer
import androidx.window.core.ConsumerAdapter
import androidx.window.core.ExtensionsUtil
import androidx.window.extensions.WindowExtensions
import androidx.window.extensions.core.util.function.Consumer as OEMConsumer
import androidx.window.extensions.layout.WindowLayoutComponent
import androidx.window.extensions.layout.WindowLayoutInfo as OEMWindowLayoutInfo
import androidx.window.layout.WindowLayoutInfo
import androidx.window.layout.adapter.WindowBackend
import androidx.window.layout.adapter.extensions.ExtensionsWindowLayoutInfoAdapter.translate
import java.util.concurrent.Executor
import java.util.concurrent.locks.ReentrantLock
import kotlin.concurrent.withLock
/**
* A wrapper around [WindowLayoutComponent] that ensures
* [WindowLayoutComponent.addWindowLayoutInfoListener] is called at most once per context while
* there are active listeners. Context has to be an [Activity] or a [UiContext] created with
* [Context#createWindowContext] or InputMethodService.
*/
internal class ExtensionWindowLayoutInfoBackend(
private val component: WindowLayoutComponent,
private val consumerAdapter: ConsumerAdapter
) : WindowBackend {
private val extensionWindowBackendLock = ReentrantLock()
@GuardedBy("lock")
private val contextToListeners = mutableMapOf<Context, MulticastConsumer>()
@GuardedBy("lock")
private val listenerToContext = mutableMapOf<Consumer<WindowLayoutInfo>, Context>()
@GuardedBy("lock")
private val consumerToToken = mutableMapOf<MulticastConsumer, ConsumerAdapter.Subscription>()
/**
* The mapping from [MulticastConsumer] to Extensions Core version [Consumer]. This is used
* to translate [MulticastConsumer] to Extensions APIs after
* [WindowExtensions.VENDOR_API_LEVEL_2].
*
* @see WindowLayoutComponent.addWindowLayoutInfoListener
* @see WindowLayoutComponent.removeWindowLayoutInfoListener
*/
@GuardedBy("lock")
private val consumerToOemConsumer =
mutableMapOf<MulticastConsumer, OEMConsumer<OEMWindowLayoutInfo>>()
/**
* Registers a listener to consume new values of [WindowLayoutInfo]. If there was a listener
* registered for a given [Context] then the new listener will receive a replay of the last
* known value.
* @param context the host of a [android.view.Window] or an area on the screen. Has to be an
* [Activity] or a [UiContext] created with [Context#createWindowContext] or InputMethodService.
* @param executor an executor from the parent interface
* @param callback the listener that will receive new values
*/
@OptIn(androidx.window.core.ExperimentalWindowApi::class)
override fun registerLayoutChangeCallback(
@UiContext context: Context,
executor: Executor,
callback: Consumer<WindowLayoutInfo>
) {
extensionWindowBackendLock.withLock {
contextToListeners[context]?.let { listener ->
listener.addListener(callback)
listenerToContext[callback] = context
} ?: run {
val consumer = MulticastConsumer(context)
contextToListeners[context] = consumer
listenerToContext[callback] = context
consumer.addListener(callback)
if (ExtensionsUtil.safeVendorApiLevel < WindowExtensions.VENDOR_API_LEVEL_2) {
val consumeWindowLayoutInfo: (OEMWindowLayoutInfo) -> Unit = { value ->
consumer.accept(value)
}
// The registrations above maintain 1-many mapping of Context-Listeners across
// different subscription implementations.
val disposableToken = if (context is Activity) {
consumerAdapter.createSubscription(
component,
OEMWindowLayoutInfo::class,
"addWindowLayoutInfoListener",
"removeWindowLayoutInfoListener",
context,
consumeWindowLayoutInfo
)
} else {
// Prior to WM Extensions v2 addWindowLayoutInfoListener only
// supports Activities. Return empty WindowLayoutInfo if the
// provided Context is not an Activity.
consumer.accept(OEMWindowLayoutInfo(emptyList()))
return@registerLayoutChangeCallback
}
consumerToToken[consumer] = disposableToken
} else {
val oemConsumer = OEMConsumer<OEMWindowLayoutInfo> { info ->
consumer.accept(info)
}
consumerToOemConsumer[consumer] = oemConsumer
component.addWindowLayoutInfoListener(context,
oemConsumer)
}
}
}
}
/**
* Unregisters a listener, if this is the last listener for a [UiContext] then the listener is
* removed from the [WindowLayoutComponent]. Calling with the same listener multiple times in a
* row does not have an effect.
* @param callback a listener that may have been registered
*/
override fun unregisterLayoutChangeCallback(callback: Consumer<WindowLayoutInfo>) {
extensionWindowBackendLock.withLock {
val context = listenerToContext[callback] ?: return
val multicastListener = contextToListeners[context] ?: return
multicastListener.removeListener(callback)
listenerToContext.remove(callback)
if (multicastListener.isEmpty()) {
contextToListeners.remove(context)
if (ExtensionsUtil.safeVendorApiLevel < WindowExtensions.VENDOR_API_LEVEL_2) {
consumerToToken.remove(multicastListener)?.dispose()
} else {
val oemConsumer = consumerToOemConsumer.remove(multicastListener)
if (oemConsumer != null) {
component.removeWindowLayoutInfoListener(oemConsumer)
}
}
}
}
}
/**
* Returns {@code true} if all the collections are empty, {@code false} otherwise
*/
@VisibleForTesting
fun hasRegisteredListeners(): Boolean {
return !(contextToListeners.isEmpty() && listenerToContext.isEmpty() &&
consumerToToken.isEmpty())
}
/**
* A class that implements [Consumer] by aggregating multiple instances of [Consumer]
* and multicasting each value that is consumed. [MulticastConsumer] also replays the last known
* value whenever a new consumer registers.
*/
private class MulticastConsumer(
private val context: Context
) : Consumer<OEMWindowLayoutInfo> {
private val multicastConsumerLock = ReentrantLock()
@GuardedBy("lock")
private var lastKnownValue: WindowLayoutInfo? = null
@GuardedBy("lock")
private val registeredListeners = mutableSetOf<Consumer<WindowLayoutInfo>>()
override fun accept(value: OEMWindowLayoutInfo) {
multicastConsumerLock.withLock {
lastKnownValue = translate(context, value)
registeredListeners.forEach { consumer -> consumer.accept(lastKnownValue) }
}
}
fun addListener(listener: Consumer<WindowLayoutInfo>) {
multicastConsumerLock.withLock {
lastKnownValue?.let { value -> listener.accept(value) }
registeredListeners.add(listener)
}
}
fun removeListener(listener: Consumer<WindowLayoutInfo>) {
multicastConsumerLock.withLock {
registeredListeners.remove(listener)
}
}
fun isEmpty(): Boolean {
return registeredListeners.isEmpty()
}
}
}