WindowInfoTrackerImpl.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.Context
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 [WindowInfoTracker] that provides the [WindowLayoutInfo] and
* [WindowMetrics] for the given [Activity].
*
* @param windowMetricsCalculator a helper to calculate the [WindowMetrics] for the [Activity].
* @param windowBackend a helper to provide the [WindowLayoutInfo].
*/
internal class WindowInfoTrackerImpl(
private val windowMetricsCalculator: WindowMetricsCalculator,
private val windowBackend: WindowBackend
) : WindowInfoTracker {
/**
* A [Flow] of window layout changes in the current visual [Context].
*
* @see Activity.onAttachedToWindow
*/
override fun windowLayoutInfo(activity: Activity): Flow<WindowLayoutInfo> {
// 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
}
}