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/*
* Copyright (C) 2019 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 com.android.permissioncontroller.permission.data
import android.os.Binder
import com.android.permissioncontroller.permission.utils.IPC
import kotlinx.coroutines.Dispatchers.Main
import kotlinx.coroutines.GlobalScope
import kotlinx.coroutines.Job
import kotlinx.coroutines.launch
/**
* A LiveData which loads its data in a background AsyncTask. It will cancel current tasks, if new
* requests come during execution
*
* @param isStaticVal Whether or not this LiveData value is expected to change
* @param alwaysUpdateOnActive Whether or not this LiveData should update upon going active
*/
abstract class SmartAsyncMediatorLiveData<T>(
isStaticVal: Boolean = false,
private val alwaysUpdateOnActive: Boolean = true
) : SmartUpdateMediatorLiveData<T>(isStaticVal) {
private var currentJob: Job? = null
@Volatile private var jobQueued = false
@Volatile private var jobRunning = false
/**
* The main function which will load data. It should periodically check isCancelled to see if it
* should stop working. If data is loaded, it should call "postValue".
*/
abstract suspend fun loadDataAndPostValue(job: Job)
override fun onUpdate() {
updateAsync()
}
open fun updateAsync() {
if (jobRunning) {
jobQueued = true
return
} else {
jobRunning = true
}
GlobalScope.launch(IPC) {
currentJob = coroutineContext[Job]
loadDataAndPostValue(currentJob!!)
// TODO ntmyren: generalize this command to the IPC dispatcher
Binder.flushPendingCommands()
jobRunning = false
if (jobQueued) {
jobQueued = false
GlobalScope.launch(Main.immediate) { updateAsync() }
}
}
}
override fun onActive() {
super.onActive()
if (alwaysUpdateOnActive) {
updateAsync()
}
}
override fun onInactive() {
cancelJobIfRunning()
jobQueued = false
super.onInactive()
}
private fun cancelJobIfRunning() {
currentJob?.let { job ->
if (job.isActive) {
job.cancel()
}
}
}
}
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