rxJava and app lifecycle error

Question

I use rxjava to read from the room database on the Schedulers.io thread. I've noticed that when my app is killed and reopened it always crashes with

Cannot access database on the main thread since it may potentially lock the UI for a long period of time.

I use MVVM architecture with Dagger and instantiate view model with lazy

private val viewModel by lazy { ViewModelProviders.of(this, viewModelFactory).get(StudentsListViewModel::class.java) }

All my requests to database look like this:

compositeDisposable.add(viewModel.students
                .subscribeOn(Schedulers.io())
                .observeOn(AndroidSchedulers.mainThread())
                .doOnNext {
                    <I do things here>
                }
                .doOnError { it.printStackTrace() }
                .subscribe()
        )

I kill disposable onDestroy with

compositeDisposable.apply {
            clear()
            dispose()
        }

So, why is it crushing on recreate and what is it trying to do on the main thread?

My ModelView class:

class StudentsListViewModel@Inject
constructor(private val studioRepository: StudioRepository): ViewModel() {

val students: Flowable<List<Student>> = studioRepository.students

fun getStudentById(studentId: Int): Maybe<Student> {
    return studioRepository.getStudentById(studentId)
}

fun insertStudent(student: Student): Unit = studioRepository.insertStudent(student)
fun insertStudentFlat(student: Student) = studioRepository.insertStudentFlat(student)

fun updateStudent(student: Student) {
    studioRepository.updateStudent(student)
}

fun deleteAllStudents() {
    studioRepository.deleteAllStudents()
}

fun getStudentsNames(): Flowable<List<String>> = studioRepository.studentNames

val studentsCount: Flowable<Int> = studioRepository.studentsCount

fun getTicketById(ticketId: Int): Maybe<Ticket> {
    return studioRepository.getTicketById(ticketId)
}

fun getTicketByIdFlat(ticketId: Int): Ticket {
    return studioRepository.getTicketByIdFlat(ticketId)
}

fun updateTicket(ticket: Ticket) = studioRepository.updateTicket(ticket)

val activeTicketsStudentIds: Flowable<List<Int>> = studioRepository.activeTicketsStudentIds

fun getClassesByIdFlat(values: List<Int>): List<YClass> = studioRepository.getYclassesByIdFlat(values)

private fun getStudent(studentId: Int): Maybe<Student> = studioRepository.getStudentById(studentId)

private fun getAllActiveTicketsForAStudent(studentId: Int): Maybe<List<Ticket>> = studioRepository.getAllActiveTicketsForAStudent(studentId)

fun archiveStudentByIdAndDeactivateHisTickets(id: Int) {
    getStudent(id)
            .subscribeOn(Schedulers.io())
            .observeOn(Schedulers.io())
            .doOnSuccess {
                it.isArchived = true
                studioRepository.updateStudent(it)
                getAllActiveTicketsForAStudent(id)
                        .subscribeOn(Schedulers.io())
                        .observeOn(Schedulers.io())
                        .doOnSuccess { list ->
                            list.forEach {
                                it.actual = false
                                updateTicket(it)
                            }
                        }
                        ?.subscribe()
            }
            .doOnError {
                it.printStackTrace()
            }
            .subscribe()
}

}

08-03 22:17:45.601 7776-7776/com.labfoodandfriends.nikitagudkovs.jlogOpenClasses E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.labfoodandfriends.nikitagudkovs.jlogOpenClasses, PID: 7776
    java.lang.RuntimeException: **Unable to start activity** ComponentInfo{com.labfoodandfriends.nikitagudkovs.jlogOpenClasses/com.labfoodandfriends.nikitagudkovs.jlog.activity.students.StudentsActivity}: java.lang.RuntimeException: java.lang.IllegalStateException: Cannot access database on the main thread since it may potentially lock the UI for a long period of time.
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2778)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2856)
        at android.app.ActivityThread.-wrap11(Unknown Source:0)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1589)
        at android.os.Handler.dispatchMessage(Handler.java:106)
        at android.os.Looper.loop(Looper.java:164)
        at android.app.ActivityThread.main(ActivityThread.java:6494)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807)
     Caused by: java.lang.RuntimeException: java.lang.IllegalStateException: Cannot access database on the main thread since it may potentially lock the UI for a long period of time.
        at com.labfoodandfriends.nikitagudkovs.jlog.factory.AppViewModelFactory.create(AppViewModelFactory.java:55)
        at android.arch.lifecycle.ViewModelProvider.get(ViewModelProvider.java:134)
        at android.arch.lifecycle.ViewModelProvider.get(ViewModelProvider.java:102)
        at com.labfoodandfriends.nikitagudkovs.jlog.activity.students.StudentsActivity$viewModel$2.invoke(StudentsActivity.kt:83)
        at com.labfoodandfriends.nikitagudkovs.jlog.activity.students.StudentsActivity$viewModel$2.invoke(StudentsActivity.kt:69)
        at kotlin.SynchronizedLazyImpl.getValue(LazyJVM.kt:74)
        at com.labfoodandfriends.nikitagudkovs.jlog.activity.students.StudentsActivity.getViewModel(Unknown Source:7)
        at com.labfoodandfriends.nikitagudkovs.jlog.activity.students.StudentsActivity.observeStudents(StudentsActivity.kt:136)
        at com.labfoodandfriends.nikitagudkovs.jlog.activity.students.StudentsActivity.onCreate(StudentsActivity.kt:103)
        at android.app.Activity.performCreate(Activity.java:7009)
        at android.app.Activity.performCreate(Activity.java:7000)
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1214)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2731)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2856) 
        at android.app.ActivityThread.-wrap11(Unknown Source:0) 
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1589) 
        at android.os.Handler.dispatchMessage(Handler.java:106) 
        at android.os.Looper.loop(Looper.java:164) 
        at android.app.ActivityThread.main(ActivityThread.java:6494) 
        at java.lang.reflect.Method.invoke(Native Method) 
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438) 
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807) 
     Caused by: java.lang.IllegalStateException: Cannot access database on the main thread since it may potentially lock the UI for a long period of time.
        at android.arch.persistence.room.RoomDatabase.assertNotMainThread(RoomDatabase.java:204)
        at android.arch.persistence.room.RoomDatabase.query(RoomDatabase.java:232)
        at com.labfoodandfriends.nikitagudkovs.jlog.database.dao.StudentDAO_Impl.getStudents(StudentDAO_Impl.java:272)
        at com.labfoodandfriends.nikitagudkovs.jlog.repository.StudioRepositoryImpl.<init>(StudioRepositoryImpl.kt:50)
        at com.labfoodandfriends.nikitagudkovs.jlog.di.AppModule.provideStudioRepository(AppModule.kt:26)
        at com.labfoodandfriends.nikitagudkovs.jlog.di.AppModule_ProvideStudioRepositoryFactory.get(AppModule_ProvideStudioRepositoryFactory.java:24)
        at com.labfoodandfriends.nikitagudkovs.jlog.di.AppModule_ProvideStudioRepositoryFactory.get(AppModule_ProvideStudioRepositoryFactory.java:10)
        at dagger.internal.DoubleCheck.get(DoubleCheck.java:47)
        at com.labfoodandfriends.nikitagudkovs.jlog.activity.students.StudentsListViewModel_Factory.get(StudentsListViewModel_Factory.java:17)
        at com.labfoodandfriends.nikitagudkovs.jlog.activity.students.StudentsListViewModel_Factory.get(StudentsListViewModel_Factory.java:8)
        at com.labfoodandfriends.nikitagudkovs.jlog.factory.AppViewModelFactory.create(AppViewModelFactory.java:53)

After allowing main thread operations in database setup problem was solved. But this is obviously not the way I want tot solve it. — Tuesday Four AM, Aug 04 '18 at 14:17
do you have this code somewhere on github so that to try t out? — Anatolii, Aug 04 '18 at 16:24
@saiedmomen I only run into the problem if app is recreated after being killed by the system. And, no, there is no db operations in onNext — Tuesday Four AM, Aug 04 '18 at 20:06
What happens if you remove `subscribeOn(Schedulers.io())`and `observeOn(AndroidSchedulers.mainThread())`from `viewModel.students`? — Anatolii, Aug 04 '18 at 21:01
I suspect it is this line `val students: Flowable> = studioRepository.students` - as per stacktrace you are getting the students and this is evaluated immediately on the calling thread that instantiates the class. — Mark, Aug 05 '18 at 12:43
@MarkKeen I call val students: Flowable> = studioRepository.students with subscribeOn(Schedulers.io()) from the View — Tuesday Four AM, Aug 05 '18 at 21:47
Yes, but it is evaluated immediately .. it is not deffered until subscription. Try `val students: Flowable> = Flowable.defer { studioRepository.students }` — Mark, Aug 05 '18 at 22:10

rxJava and app lifecycle error

0 Answers0