Develop Reference

Check for network status update while application killed

My scenario is the following:
I'm working on a chat application and I would like to implement some type synchronization service that starts itself when device recovers network connection. Anytime device has network connection again, unsent messages are going to be automatically sent. With independence of application state (foregorund, background or killed).
Options tried:
1. Broadcast Receiver with android.net.conn.CONNECTIVITY_CHANGE
This scenario only works when the application is active (Foreground or Backround) but stops working when app is killed.
2. Foreground service
A notification is going to be shown all the time which is not ideal. Also I want to avoid draining users' battery.
3. AndroidX.Work.Worker
PeriodicWorkRequest networkCheckingPeriodicWork = PeriodicWorkRequest.Builder.
From<ConnectivityChangeWroker>(repeatInterval:30, repeatIntervalTimeUnit: Java.Util.Concurrent.TimeUnit.Minutes, flexInterval:25, flexIntervalTimeUnit:Java.Util.Concurrent.TimeUnit.Minutes)
.SetConstraints(new Constraints.Builder().SetRequiredNetworkType(AndroidX.Work.NetworkType.Connected)
.SetRequiredNetworkType(AndroidX.Work.NetworkType.Unmetered).Build()).Build();
WorkManager.Instance.EnqueueUniquePeriodicWork("", ExistingPeriodicWorkPolicy.Replace, networkCheckingPeriodicWork);
public class ConnectivityChangeWroker : AndroidX.Work.Worker
{
public ConnectivityChangeWroker(Context context, WorkerParameters workerParameters) : base(context, workerParameters)
{
}
public override Result DoWork()
{
try
{
//Start synch service
return Result.InvokeSuccess();
}
catch (Exception)
{
return Result.InvokeFailure();
}
}
}
But in this case, I'm not achieving the desired behaviour. For my undestanding, I just set a periodic work that checks for network connection, and if there is one, runs DoWork() method.
-- EDIT --
4.JobService
Java.Lang.Class javaClass = Java.Lang.Class.FromType(typeof(ConnectivityChangeJob));
ComponentName component = new ComponentName(Application.Context, javaClass);
JobInfo jobInfo = new JobInfo.Builder(1, component)
.SetRequiredNetworkType(Android.App.Job.NetworkType.Any)
.SetOverrideDeadline(5000)
.SetPersisted(true)
.Build();
JobScheduler jobScheduler = (JobScheduler)GetSystemService(JobSchedulerService);
jobScheduler.Schedule(jobInfo);
[Service(Name = "Extintores.ConnectivityChangeJob", Permission = "android.permission.BIND_JOB_SERVICE")]
public class ConnectivityChangeJob : JobService
{
private Intent startServiceIntent;
public ConnectivityChangeJob()
{
}
public override bool OnStartJob(JobParameters jobParams)
{
//Start synchService
return true;
}
public override bool OnStopJob(JobParameters jobParams)
{
return true; //Reschedule the job
}
}
But in this case, OnStartJob is only fired the first time the applicatio is opened and, apparently, never again.
Is there any way I can achieve what I'm aming for?
-- EDIT --
I want to achieve the same bahaviour as applications as WhatsApp. When it detects network connection again, automatically all unsent messages are going to be send.

I guess the AndroidX.Work.Worker is the best option.
In DoWork you should update databases and send requests.
Besides worker supports long-running workers
Example DownloadWorker:
class DownloadWorker(context: Context, parameters: WorkerParameters) :
CoroutineWorker(context, parameters) {
private val notificationManager =
context.getSystemService(Context.NOTIFICATION_SERVICE) as
NotificationManager
override suspend fun doWork(): Result {
val inputUrl = inputData.getString(KEY_INPUT_URL)
?: return Result.failure()
val outputFile = inputData.getString(KEY_OUTPUT_FILE_NAME)
?: return Result.failure()
// Mark the Worker as important
val progress = "Starting Download"
setForeground(createForegroundInfo(progress))
download(inputUrl, outputFile)
return Result.success()
}
private fun download(inputUrl: String, outputFile: String) {
// Downloads a file and updates bytes read
// Calls setForeground() periodically when it needs to update
// the ongoing Notification
}
// Creates an instance of ForegroundInfo which can be used to update the
// ongoing notification.
private fun createForegroundInfo(progress: String): ForegroundInfo {
val id = applicationContext.getString(R.string.notification_channel_id)
val title = applicationContext.getString(R.string.notification_title)
val cancel = applicationContext.getString(R.string.cancel_download)
// This PendingIntent can be used to cancel the worker
val intent = WorkManager.getInstance(applicationContext)
.createCancelPendingIntent(getId())
// Create a Notification channel if necessary
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
createChannel()
}
val notification = NotificationCompat.Builder(applicationContext, id)
.setContentTitle(title)
.setTicker(title)
.setContentText(progress)
.setSmallIcon(R.drawable.ic_work_notification)
.setOngoing(true)
// Add the cancel action to the notification which can
// be used to cancel the worker
.addAction(android.R.drawable.ic_delete, cancel, intent)
.build()
return ForegroundInfo(notificationId, notification)
}
#RequiresApi(Build.VERSION_CODES.O)
private fun createChannel() {
// Create a Notification channel
}
companion object {
const val KEY_INPUT_URL = "KEY_INPUT_URL"
const val KEY_OUTPUT_FILE_NAME = "KEY_OUTPUT_FILE_NAME"
}
}

Android timer when phone is idle

I am trying to create an Android app which plays a sound every few seconds. I want this to work even when the phone is idle. At the moment everything works fine even when the phone screen is off. But after about a minute, the timer stops working. As soon as the screen is turned back on, the missed sounds are played in quick succession. I struggle to find the right terms and concepts to properly find a solution with Google.
When I first encountered this issue, I made sure that my service was running in the background. As it seems, the service is also enabled in the background because everything works fine as long as the screen is not turned off.
Code for running the service in the background:
override fun onStartCommand(intent: Intent, flags: Int, startId: Int): Int {
timer.scheduleAtFixedRate(TimeTask(), 0, 100);
return START_STICKY
}
private inner class TimeTask() : TimerTask() {
override fun run() {
sendBroadcast(Intent(TIMER_UPDATED))
}
}
Since this didn't work, I tried to make the service a foreground service. But this didn't work either. (I tried to do it as shown here)
Code for running the service in foreground:
private fun runInBackground() {
val channelId =
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
createNotificationChannel("service", "something")
} else {
""
}
val notification: Notification = NotificationCompat.Builder(this, channelId)
.setContentTitle("title")
.setContentText("text")
.setSmallIcon(R.drawable.alert_dark_frame)
.build()
startForeground(1, notification)
}
#RequiresApi(Build.VERSION_CODES.O)
private fun createNotificationChannel(channelId: String, channelName: String): String{
val channel = NotificationChannel(channelId, channelName, NotificationManager.IMPORTANCE_NONE)
channel.lightColor = Color.BLUE
channel.lockscreenVisibility = Notification.VISIBILITY_PRIVATE
(getSystemService(Context.NOTIFICATION_SERVICE) as NotificationManager)
.createNotificationChannel(channel)
return channelId
}
I read something about scheduling tasks in Android. And found the AlarmManager, but I don't think this would really work the way I want it to because I would have to schedule an alarm for every 100ms. The official doc also states that this shouldn't be used in that way and that "handlers" are more suited, but I struggle to understand how I could replace my current timer with such a handler. I have tried to implement something, but failed.
val updateHandler = Handler()
val runnable = Runnable {
// some action
}
updateHandler.looper(runnable, 100)

Finally solved my problem. Something that I didn't understand before was a "wakelock". It looks something like this:
val wakeLock: PowerManager.WakeLock = (getSystemService(Context.POWER_SERVICE) as PowerManager).run {
newWakeLock(PowerManager.PARTIAL_WAKE_LOCK, "ShuttleRun::DefaultWakeLock").apply {
acquire(30*60*1000L)
}
}
It basically just keeps the device awake, which doesn't mean that the screen is turned on, but rather that the service can run in the background without being disturbed.

JobScheduler - How to skip first job run of periodic job?

in my app i have set a periodic job that is set to run every 30 minutes.
The first job run occurs right when I do schedule that periodic job, which is not wanted in my case.
What I want is to skip the first run so that it will run for the first time after 30+ minutes.
My two thoughts on how to approach this was to either have it not run at all for the first 30 minutes somehow (some kind of delay), or mark the first job run as done before even having the chance to start.
Unfortunately I have not found any method in JobInfo that would allow me to do any of those.
Another workaround that would fulfill my needs would be to somehow limit the jobs to only occur while app is in the background. It does not entirely solve the issue but it could serve as a workaround in my case.
Following is my current code for scheduling the periodic job:
private void scheduleJob() {
ComponentName componentName = new ComponentName(this, myRecurringTask.class);
JobInfo info = new JobInfo.Builder(JOB_ID, componentName)
.setRequiredNetworkType(JobInfo.NETWORK_TYPE_ANY)
.setPersisted(true)
.setPeriodic(1800000)
.build();
JobScheduler scheduler = (JobScheduler) getSystemService(JOB_SCHEDULER_SERVICE);
scheduler.schedule(info);
}
I hope someone has run into the same situation and can help me resolve it... Thank you!

Use WorkManager for scheduling backgound work, see introduction here.
1. Add Dependency:
implementation "androidx.work:work-runtime-ktx:2.4.0"
2. Create Worker Class:
class DataRefresher(context: Context, params: WorkerParameters) : CoroutineWorker(context, params) {
override suspend fun doWork(): Result { //will run on background thread
//your logic
return try {
//your logic
Result.success()
} catch (e: HttpException) {
Result.retry()
}
}
}
3. Create Application Class:
class DevBytesApplication : Application() {
private val backgroundScope = CoroutineScope(Dispatchers.Default) //standard background thread
override fun onCreate() { //called when app launches, same as Activity
super.onCreate()
initWork()
}
private fun initWork() {
backgroundScope.launch { //run in background, not affecting ui
setupDataRefreshingWork()
}
}
#SuppressLint("IdleBatteryChargingConstraints")
private fun setupDataRefreshingWork() {
val constraints = Constraints.Builder()
.setRequiredNetworkType(NetworkType.UNMETERED) //when using wifi
.setRequiresBatteryNotLow(true)
.setRequiresCharging(true)
.setRequiresDeviceIdle(true) //when not running heavy task
.build()
val repeatingRequest = PeriodicWorkRequestBuilder<DataRefresher>(1, TimeUnit.DAYS) //【15 minutes is minimum!!】
.setConstraints(constraints)
.setInitialDelay(30, TimeUnit.MINUTES) //【initial delay!!】
.build()
WorkManager.getInstance(this).enqueueUniquePeriodicWork(
DataRefresher::class.java.simpleName, //work name
ExistingPeriodicWorkPolicy.KEEP, //if new work comes in with same name, discard it
repeatingRequest
)
}
}
4. Setup AndroidManifest:
<manifest
xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.devbytestest">
<application
android:name=".DevBytesApplication" //【here, must!!!】
...
</application>
</manifest>

Android Kotlin future notification with worker with method from main activity

I want to schedule my MainActivty to perform checks on its data periodically without showing UI to the user. When a condition is true, I want to show a notification.
Furthermore, I need to check for this notification only once per day, without an exact timing and I want this check to remain scheduled even if the device is rebooted /after poweron.
Looks like the worker model with TimeUnit.ONE_DAY is the best fit for me (Here I am setting the interval at one minute so I don't need to wait for one day to test).
I create in "onCreate" method the Periodic Request Builder and the enqueue the request in the work manager.
Outside onCreate method I define the sendNotification method and provide my class implementatio on Notification Worker, where I define the action to be performed when the woker callback is fired.
In main class I have:
class MainActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
[...]
val CheckRequest = PeriodicWorkRequestBuilder<NotificationWorker>(1, TimeUnit.MINUTES).build()
WorkManager.getInstance(context).enqueue(CheckRequest)
}
fun sendNotification(){
with(NotificationManagerCompat.from(this)) {
notify(notificationId, builder.build())
}
class NotificationWorker(appContext: Context, workerParams: WorkerParameters):
Worker(appContext, workerParams) {
override fun doWork(): Result {
// Do the work here--in this case, upload the images.
MainActivity().sendNotification()
// Indicate whether the work finished successfully with the Result
return Result.success()
}
}
}
My Issue is that I encounter the following error
java.util.concurrent.ExecutionException: java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare()
I think that what's happening is that I am calling a method from the super class of the worker when the UI is not active, so the app context etc is not availlable to the called method.
Any hin on this point would be gladly appreciated.
Kind regards,

After reopening application, multiple instances of a service are created

I am trying to create an application to update a persistent notification even while the app is closed. Right now, I'm using a service that is started in MainActivity's onCreate():
serviceIntent = Intent(this, PersistentService::class.java)
val stopped = stopService(serviceIntent)
println("[123] stopped: $stopped")
if(Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
startForegroundService(serviceIntent)
} else {
startService(serviceIntent)
}
This works perfectly to start it. However, when I reopen and close the app, even though stopped: true is printed, the previous service is still running and the previous service's stopService() was not called.
Stripped down version of the PersistentService class:
var timesStarted = 0
var lastService: PersistentService? = null
class PersistentService: Service(){
private var timer: Timer? = null
private var task: AsyncTask<*, *, *>? = null
override fun onBind(intent: Intent?): IBinder? {
return null
}
override fun onStartCommand(intent: Intent?, flags: Int, startId: Int): Int {
timesStarted++
println("[123]starting persistent service. timesStarted: $timesStarted lastService===this: ${lastService===this} lastService==this: ${lastService==this} lastService: $lastService")
println("[123] hashCode: ${hashCode()}")
lastService = this
if(timer == null){
timer = Timer()
}
setToLoadingNotification()
timer?.scheduleAtFixedRate(object : TimerTask(){
override fun run(){
println("[123]Updating hashCode: ${this#PersistentService.hashCode()}")
if(task?.status == AsyncTask.Status.RUNNING){
// send notification saying last request timed out
}
task?.cancel(true)
task = DataUpdaterTask(DatabaseDataRequester { GlobalData.connectionProperties }) { dataRequest ->
// send notification based on dataRequest value
}.execute()
}
}, 1000L, UPDATE_PERIOD)
return START_STICKY
}
private fun notify(notification: Notification){
getManager().notify(NOTIFICATION_ID, notification)
startForeground(NOTIFICATION_ID, notification)
}
private fun getBuilder(): Notification.Builder {
if(Build.VERSION.SDK_INT >= Build.VERSION_CODES.O){
return Notification.Builder(this, NotificationChannels.PERSISTENT_STATUS.id)
}
return Notification.Builder(this)
}
private fun getManager() = getSystemService(Context.NOTIFICATION_SERVICE) as NotificationManager
override fun stopService(name: Intent?): Boolean {
println("[123]Stopping persistent service")
timer?.cancel() // stop the timer from calling the code any more times
task?.cancel(true) // stop the code from running if it's running
// getManager().cancel(NOTIFICATION_ID)
return super.stopService(name)
}
}
Here is the output
[123] stopped: false
[123]starting persistent service. timesStarted: 1 lastService===this: false lastService==this: false lastService: null
[123] hashCode: 4008007
[123]Updating hashCode: 4008007
[123]Got successful data request
[123]Updating hashCode: 4008007
[123]Got successful data request
// *close and reopen the app*
[123] stopped: true
[123]starting persistent service. timesStarted: 2 lastService===this: false lastService==this: false lastService: me.retrodaredevil.solarthing.android.PersistentService#3d2847
[123] hashCode: 7823272
[123]Updating hashCode: 7823272
[123]Got successful data request
[123]Updating hashCode: 4008007
[123]Got successful data request
[123]Updating hashCode: 7823272
[123]Got successful data request
As you can see from the output, both services are running at the same time. The hashcode shows that they are not the same object so it wouldn't matter if I put my code in the onCreate() instead of onStartCommand() (I already tested this anyway)
It would be helpful if anyone could point me in the right direction. I am new to android development and I had trouble finding the correct way to do this. I'm not even sure if what I'm doing right now is the best way to update the notification.

and the previous service's stopService() was not called.
stopService() is not a lifecycle method of a Service. Perhaps you are thinking of onDestroy().
the previous service is still running
No, the previous service instance was stopped. You just leaked the Timer, because you did not cancel the Timer in onDestroy().
So, override onDestroy(), put your cancel() calls in there, get rid of the rest of stopService(), and you should be in better shape.