WindowInfoRepositoryImpl.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
import android.app.Activity
import android.content.ComponentCallbacks
import android.content.Context
import android.content.res.Configuration
import androidx.core.util.Consumer
import kotlinx.coroutines.channels.BufferOverflow.DROP_OLDEST
import kotlinx.coroutines.channels.Channel
import kotlinx.coroutines.flow.Flow
import kotlinx.coroutines.flow.flow
/**
* An implementation of [WindowInfoRepository] that provides the [WindowLayoutInfo] and
* [WindowMetrics] for the given [Activity].
*
* @param activity that the provided window is based on.
* @param windowMetricsCalculator a helper to calculate the [WindowMetrics] for the [Activity].
* @param windowBackend a helper to provide the [WindowLayoutInfo].
*/
internal class WindowInfoRepositoryImpl(
private val activity: Activity,
private val windowMetricsCalculator: WindowMetricsCalculator,
private val windowBackend: WindowBackend
) : WindowInfoRepository {
/**
* Returns the [WindowMetrics] according to the current system state.
*
*
* The metrics describe the size of the area the window would occupy with
* [MATCH_PARENT][android.view.WindowManager.LayoutParams.MATCH_PARENT] width and height
* and any combination of flags that would allow the window to extend behind display cutouts.
*
*
* The value of this is based on the **current** windowing state of the system. For
* example, for activities in multi-window mode, the metrics returned are based on the
* current bounds that the user has selected for the [Activity][android.app.Activity]'s
* window.
*
* @see android.view.WindowManager.getCurrentWindowMetrics
*/
override val currentWindowMetrics: Flow<WindowMetrics>
get() {
return configurationChanged {
windowMetricsCalculator.computeCurrentWindowMetrics(activity)
}
}
private fun <T> configurationChanged(producer: () -> T): Flow<T> {
return flow {
val channel = Channel<T>(
capacity = BUFFER_CAPACITY,
onBufferOverflow = DROP_OLDEST
)
val publish: () -> Unit = { channel.trySend(producer()) }
val configChangeObserver = object : ComponentCallbacks {
override fun onConfigurationChanged(newConfig: Configuration) {
publish()
}
override fun onLowMemory() {
}
}
publish()
activity.registerComponentCallbacks(configChangeObserver)
try {
for (item in channel) {
emit(item)
}
} finally {
activity.unregisterComponentCallbacks(configChangeObserver)
}
}
}
/**
* A [Flow] of window layout changes in the current visual [Context].
*
* @see Activity.onAttachedToWindow
*/
override val windowLayoutInfo: Flow<WindowLayoutInfo>
get() {
// TODO(b/191386826) migrate to callbackFlow once the API is stable
return flow {
val channel = Channel<WindowLayoutInfo>(
capacity = BUFFER_CAPACITY,
onBufferOverflow = DROP_OLDEST
)
val listener = Consumer<WindowLayoutInfo> { info -> channel.trySend(info) }
windowBackend.registerLayoutChangeCallback(activity, Runnable::run, listener)
try {
for (item in channel) {
emit(item)
}
} finally {
windowBackend.unregisterLayoutChangeCallback(listener)
}
}
}
internal companion object {
private const val BUFFER_CAPACITY = 10
}
}