This is a similar question to How to check if a service is running on Android? but since the question is old and the answers provided there are deprecated or not working properly. Thus the separate question.
I have an implementation, that fires a Service on Boot Complete, but I also want to start the service in onCreate of MainActivity, in case the service was not started before.
here are what I have tried:
1. Fetch Static Boolean to get the state of the Service as demonstrated below.
MyService.kt
class MyService : Service() {
override fun onCreate() {
super.onCreate()
isServiceStarted = true
}
override fun onDestroy() {
super.onDestroy()
isServiceStarted = false
}
companion object {
var isServiceStarted = false
}
}
MainActivity.kt
class MainActivity : AppCompatActivity(){
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
val serviceStarted = MyService.isServiceStarted
if (!serviceStarted) {
val startMyService = Intent(this, MyService::class.java)
ContextCompat.startForegroundService(this, startMyService)
}
}
}
but I soon discovered that onDestroy is not always called when a Service is destroyed, thereby leaving my static boolean variable (isServiceStarted) to be true, when in reality it has been destroyed.
2.A function to check
fun isMyServiceRunning(serviceClass : Class<*> ) : Boolean{
var manager = getSystemService(Context.ACTIVITY_SERVICE) as ActivityManager
for (service in manager.getRunningServices(Integer.MAX_VALUE)) {
if (serviceClass.name.equals(service.service.className)) {
return true
}
}
return false
}
The Call
isMyServiceRunning(MyService::class.java)
Problems with this approach include:
- getRunningServices is deprecated since Android O (API 27),
- It is resource consuming and inefficient to loop through running services like that and because the docs say:
Note: this method is only intended for debugging or implementing service management type user interfaces.
It's not meant for control flow!
What is an Elegant/Efficient way to check if a Service is already running?
If service is in the application process just use the static field inside service (companion object) or bind to service.
If the service runs in remote process use Messanger if you want to have a synchronized communication or AIDL when you want to care about threads.
Related
So, I'm trying to collect data from flows in my Foreground service (LifecycleService) in onCreate(), but after the first callback, it is not giving new data.
The code is :
override fun onCreate() {
super.onCreate()
lifecycleScope.launchWhenStarted {
repeatOnLifecycle(Lifecycle.State.STARTED) {
observeCoinsPrices()
}
}
}
I couldn't get lifecycleScope.launch to work in the LifecycleService.onCreate method without it freezing the app, so what I did instead was moved the collector into a method that I use to start the service, assign the Job into a property so I can cancel it when the Service is destroyed.
import kotlinx.coroutines.Job
//...
class MyService : LifecycleService() {
//...
private lateinit var myJob: Job
// my custom method for starting The Foreground service
fun startTheService() {
// call startForeground()
//...
myJob = lifecycleScope.launch {
collectFromFlow()
}
}
override fun onDestroy() {
myJob.cancel()
}
}
In my case, I was wanting to update text in the foreground notification every time a value was emitted to my Flow collector.
Because Flow used in observeCoinsPrices() not replay the latest value (replay < 1). You should change Flow logic
I am developing an app in which several Activitis bound to a sevice once they become visible to the user. During start up, each Activity needs to:
check some status flag of the service, based on which some UI elements are configured
check wether an adapters is enabled whose reference is inside the service
execute some functions of the Service
Since the applications should not get updates in the background, I bind to the service at onStart() and unbind at onStop(). I.e. in have something like this:
override fun onStart() {
super.onStart()
Intent(context, MyService::class.java).also { intent ->
bindService(intent, serviceCallback, Context.BIND_AUTO_CREATE)
}
}
Now I want to perform the above mentionned actions inside onResume.
override fun onResume() {
super.onResume()
// check flags
// check adapter status
// excute functions of service
}
The problem is that binding to a service is asynchronous and I do not have a valid reference to the Service's binder inside onResume(). Consequently, the app will crash with a nullpointer exception.
Approach 1: Using lateinit
I tried solving this problem using the lateinit keyword. I.e. I define the reference to the binder as
private lateinit var myBinder: MyService.LocalBinder
Problem: I cannot guarantee that the binder is initialized as it is asynchronous. Thus, the app will crash.
Approach 2: Waiting for callback in while loop
In my service callback, I set a flag as follows:
val serviceCallback = object : ServiceConnection {
override fun onServiceConnected(className: ComponentName, service: IBinder) {
myBinder = service as MyService.LocalBinder
isServiceBounded = true
}
override fun onServiceDisconnected(arg0: ComponentName) {
isServiceBounded = false
myBinder = null
}
}
Then inside onResume, I block the Activity until the flag is true
override fun onResume() {
super.onResume()
while(!isServiceBounded){
// block and wait
}
}
Problem: Doesn't work either. The app will stop responding and crashes.
Approach 3: Using suspended functions and Kotlin coroutines
A suspended function will not continue unless it has received a return value. This, I can use it to wait for an event. So I tried something like this:
override fun onStart() {
super.onStart()
CoroutineScope(Dispatchers.Main).launch {
bindServiceAndWait(this#Activityname)
}
}
suspend fun bindServiceAndWait(context: Context): Boolean{
Intent(context, MyService::class.java).also { intent ->
bindService(intent, serviceCallback, Context.BIND_AUTO_CREATE)
}
return isServiceBounded // This is the flag from the callback
}
Problem: This suspended function does not actually wait for the callback. It just returns the current value of isServiceBounded.
I found a similar solution here, but I do not quite understand this solution as it has a global service callback (ServiceConnection) as well as a local one inside the suspended function. Also, I don't understand how to I could unbound in this provided example.
What is the proper way of doing this?
you simply can't ensure that service will be bounded until onResume gets called. why won't you introduce flag isResumed, set it in onResume (unset in onPause) and line below check if (isResumed && isServiceBounded).... yes, there is a chance that isServiceBounded = false in onResume, so same if check put in onServiceConnected
In Android Oreo, I want to create a service that periodically updates data from the network.
class NetworkJobService : JobService() {
override fun onStopJob(p0: JobParameters?): Boolean {
jobFinished(p0,true)
return true
}
override fun onStartJob(p0: JobParameters?): Boolean {
//Average working time 3 to 5 minutes
NetworkConnect.connect()
.subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread())
.doFinally {
jobFinished(p0,true)
}
.subscribe({result->
// Writes the parameters to the cache with the current time.
Cache.write("result : $result")
},{e->
// Writes the parameters to the cache with the current time.
Cache.write(e)
})
return true
}
}
This service is registered in the schedule when you run MainActivity.
class MainActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
jobSchedule()
button.setOnClickListener { readLog() }
}
val interval = 1000 * 60 * 15L
private fun jobSchedule(){
val jobScheduler = getSystemService(Context.JOB_SCHEDULER_SERVICE) as JobScheduler
val jobInfo = JobInfo.Builder(3,
ComponentName(this, NetworkJobService::class.java))
.setRequiredNetworkType(JobInfo.NETWORK_TYPE_ANY)
.setPeriodic(interval)
.build()
jobScheduler.schedule(jobInfo)
}
private fun readLog(){
//The log file is read line by line.
Cache.read()
.reversed()
.toObservable()
.subscribe({ text->
Log.i("Service Log",text)
},{
})
}
}
However, when I read the log file and checked the results, the service was running only when the MainActivity was running. In other words, it was not being rescheduled.
1) Run the activity and just turn off the device's screen
2) Run the activity and press the Home button to return to the launcher.
3) When the service is terminated and the app is deleted in the multitasking window
The most I wanted was to work in case 3), but in any of the above, the services I wanted were not rescheduled.
What have I missed?
While working with background threads in Oreo when the app is in killed you need to start the services as foreground service. Here is the details of the same. Essentially, show a notification to make the user aware that your app is trying to doing something in the background.
Hope it helps you.
Sometimes my app is forced to quit and then later Android restarts it just to run a scheduled job. I can't find a callback that would correspond to this scenario: that my app got killed in the meantime, so I have to restore all my retained state.
I want to avoid a proliferation of entry points where I have to re-check whether everything is still in place. I already have onUpdate() for a widget, onCreate() for the main activity, onResume() for a view fragment, and onStartJob() for the scheduled job. Any of them could be the first thing to be called after the app is killed, so in all these places I have to repeat the initialization code.
Is there a single point where I can register a callback that will re-initialize my app state?
To be specific, I have a JobService:
class RefreshImageService : JobService() {
override fun onStartJob(params: JobParameters): Boolean {
MyLog.i("RefreshImageService start job")
updateWidgetAndScheduleNext(applicationContext)
return true
}
override fun onStopJob(params: JobParameters): Boolean {
MyLog.i("RefreshImageService stop job")
return true
}
}
The updateWidgetAndScheduleNext() call involves some state I have:
private data class TimestampedBitmap(val bitmap : Bitmap, val timestamp : Long)
private var tsBitmap: TimestampedBitmap? = null
To compute the timestamp, I have to call into further code that has its own state; that other code is called form all the entry points I mentioned. I'd like to centralize my initialization code, if possible.
My sample app uses targetSdkVersion 26.
I have a simple service, which is both started and bounded with the following code snippet:
val intent = BoundServiceTest.buildIntent(applicationContext)
applicationContext.startService(intent)
applicationContext.bindService(intent, serviceConnection, BIND_AUTO_CREATE)
Please be aware that I use a global application Context for binding, not an Activity Context.
The service itself does only imlements some basic logging:
class BoundServiceTest : Service() {
companion object {
private val TAG = "BoundServiceTest"
fun buildIntent(context: Context): Intent {
return Intent(context, BoundServiceTest::class.java)
}
}
private val binder = Binder()
override fun onBind(p0: Intent?): IBinder {
Log.d(TAG, "onBind")
return binder
}
override fun onUnbind(intent: Intent?): Boolean {
Log.d(TAG, "onUnbind")
return super.onUnbind(intent)
}
override fun onCreate() {
super.onCreate()
Log.d(TAG, "onCreate")
}
override fun onStartCommand(intent: Intent?, flags: Int, startId: Int): Int {
Log.d(TAG, "onStartCommand: startId = " + startId)
return START_STICKY
}
override fun onDestroy() {
Log.d(TAG, "onDestroy")
super.onDestroy()
}
}
Basically I am not sure, if Android O applies the Background execution limits or not, since basically the documentation states (Background Service Limitations):
Bound services are not affected
These rules do not affect bound services in any way. If your app
defines a bound service, other components can bind to that service
whether or not your app is in the foreground.
But it seems that the OS isn't quite sure as well regarding the Logcat:
de.continental.android.androidoservicetest D/BoundServiceTest: onCreate
de.continental.android.androidoservicetest D/BoundServiceTest: onStartCommand: startId = 1
de.continental.android.androidoservicetest D/BoundServiceTest: onBind
? W/ActivityManager: Stopping service due to app idle: u0a141 -1m9s733ms de.continental.android.androidoservicetest/.BoundServiceTest
I/RunningState: Unknown non-service process: de.continental.android.androidoservicetest #14943
I/chatty: uid=1000(system) RunningState:Ba identical 1 line
I/RunningState: Unknown non-service process: de.continental.android.androidoservicetest #14943
The ActivityManager log message indicates that the service shall be stopped (regardless that it is a bound one), but the OS doesn't stop my service: The log messages for calling onDestroy method are not displayed, compared to a simple started Service without binding.
How is this scenario (started and bound service) handled in Android O? Or do I encounter a bug?