Kotlin协程抛出JobCancellationException和触发器观察者

Question

我在MVVM架构中实现kotlin coroutines，以取代我的RxJava依赖。

我的问题：在注销之后(这个细节很重要，因为在新启动时没有异常)，在启动viewModelScopeAND时抛出JobCancellationException协程异常。我所有的observers在LoginActivity被触发(wtf ?)，即使try/catch块没有执行(断点)，所以它完全打破了我的代码逻辑。

我的图层如下：Activity,setOnClickListener触发，调用viewModel函数->ViewModel，在viewModelScope中创建coroutine，调用suspend function->Repository,suspended function从viewModel调用，并调用ApiService中的suspend function->suspend function使Api调用

Usecase：我登录我的应用程序刚启动(LoginActivity)。我的堆栈被清除以启动MainActivity。我去SettingsActivity注销。我注销并再次清除堆栈以启动一个全新的LoginActivity。当我尝试再次登录时，我有exception抛出，我的observers被触发。

LoginActivty:

override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_login)
tvLogin.setSafeOnClickListener { login() }
}
private fun login() {
Firebase.analytics.logEvent("hit_login", null)
runOnUiThread {
pDialog = SweetAlertDialog(this, SweetAlertDialog.PROGRESS_TYPE)
pDialog!!.progressHelper.barColor = Color.parseColor("#2A6022")
pDialog!!.titleText =
"<font color='#2A6022'>" + resources.getString(R.string.signing) + "</font>"
pDialog!!.setCancelable(false)
}
var pwd = etPassword.text.toString()
if (passedBiometric) {
pwd = sessionManager.decrypt(sessionManager.loadUsername())
}
passedBiometric = false
viewModel.login(etUsername.text.toString(), pwd)
viewModel.error.observe(this, {
Toast.makeText(this, getString(it), Toast.LENGTH_SHORT).show()
})
viewModel.loadingState.observe(this, {
Timber.e("LoadingState Observer triggered")
when (it) {
LoadingState.LOADED -> {
pDialog!!.dismiss()
Timber.e("LOADED")
startMainActivity()
}
LoadingState.FAILED -> {
pDialog!!.dismiss()
Timber.e("FAILED")
viewModel.error.value?.let { errorRsc ->
Toast.makeText(this, getString(errorRsc), Toast.LENGTH_SHORT).show()
}
}
LoadingState.LOADING -> {
pDialog!!.show()
Timber.e("LOADING")
}
}
})
}
private fun startMainActivity() {
val intent = Intent(this, MainActivity::class.java)
intent.flags = Intent.FLAG_ACTIVITY_NEW_TASK or Intent.FLAG_ACTIVITY_CLEAR_TASK
intent.action = this.intent.action
intent.putExtra(ProfileFragment.USER, viewModel.user.value)
startActivity(intent)
finish()
}

LoginViewModel:

class LoginViewModel(private val repo: ApiRepository, private val sessionManager: SessionManager) :
ViewModel() {
private val _error = MutableLiveData<Int>()
val error: LiveData<Int>
get() = _error
private val _loadingState = MutableLiveData<LoadingState>()
val loadingState: LiveData<LoadingState>
get() = _loadingState
private val token = MutableLiveData<SessionToken>()
private val _user = MutableLiveData<User>()
val user: LiveData<User>
get() = _user
fun login(username: String, password: String) {
try {
Timber.e("enter try block outside viewModelScope.launch")
viewModelScope.launch {
try {
Timber.e("try block inside viewModelScope.launch")
_loadingState.value = LoadingState.LOADING
token.value = repo.login(username, password)
sessionManager.storeSessionToken(token.value!!.token)
sessionManager.storeUsername(username)
sessionManager.encrypt(username, password)
_user.value = repo.getUser()
_loadingState.value = LoadingState.LOADED
} catch (e: Exception) {
Timber.e("catch block inside viewModelScope.launch")
if (e is HttpException) {
when (e.code()) {
500, 503 -> {
_error.value = R.string.error_api_down
}
400 -> {
_error.value = R.string.error_bad_credentials
}
}
}
_loadingState.value = LoadingState.FAILED
}
}
}
catch (e: Exception){
Timber.e("Catch block outside viewmodelScope.launch")
when (e){
is CancellationException -> { Timber.e("CancellationException caught")}
else -> { Timber.e("Unknown caught")}
}
}
}
}

ApiRepository:

class ApiRepository(
private val apiService: ApiService,
private val sessionManager: SessionManager
) {
suspend fun login(username: String, password: String): SessionToken {
val map = mutableMapOf<String, String>()
map["username"] = username
map["password"] = password
return apiService.login(
JSONObject(map.toMap()).toString()
.toRequestBody("application/json".toMediaTypeOrNull())
)
}
suspend fun getUser(): User {
return apiService.getUser(sessionManager.loadSessionToken())
}
}

ApiService:

interface ApiService {
companion object {
private const val AUTH = "Authorization"
}
@POST(ApiRouting.URL_TOKEN)
suspend fun login(@Body requestBody: RequestBody): SessionToken
@GET(ApiRouting.URL_GET_USER)
suspend fun getUser(@Header(AUTH) token: String): User
}

SettingsActivity:

private fun initListeners() {
tvLogout.setSafeOnClickListener {
DashboardManager.clearValues()
sessionManager.clearSessionToken()
val intent = Intent(this, LoginActivity::class.java)
intent.flags = Intent.FLAG_ACTIVITY_NEW_TASK or Intent.FLAG_ACTIVITY_CLEAR_TASK
startActivity(intent)
finish()
}
}

TLDR:为什么抛出异常?为什么观察者会被触发?为什么这种情况只发生在注销后，而不是在新启动时?

我尝试在启动中添加coroutineScope，并使用withContext(Dispatchers.IO)在存储库中添加另一个作用域，但它没有改变任何东西

我是kotlin coroutines的初学者，所以如果你有任何建议，链接或任何可能有助于欢迎。或者，如果您需要任何其他代码块，请告诉我。

编辑：我添加了几个日志(LoginViewModel和MainActivity)来详细说明当我进入围绕viewModelScope.launch的try catch块以及当我的MainActivity启动时(observer在LoginAvtivity中触发后的下一个动作)。

让你更多地看到一个新的(和成功的)开始是什么样子的:

E/LoginViewModel: enter try block outside viewModelScope.launch
E/LoginViewModel$login: try block inside viewModelScope.launch
E/LoginActivity$login: LoadingState Observer triggered
V/ViewRootImpl: The specified message queue synchronization  barrier token has not been posted or has already been removed
E/LoginActivity$login: LOADING
LoadingState Observer triggered
LOADING
I/okhttp.OkHttpClient: --> POST http://45.153.184.141/api-token-auth/
Content-Type: application/json; charset=utf-8
Content-Length: 46
--> END POST (46-byte body)
E/LoginActivity$login: LoadingState Observer triggered
LOADING
D/DecorView: onWindowFocusChangedFromViewRoot hasFocus: true, DecorView@7175d32[LoginActivity]
W/Choreographer: Already have a pending vsync event.  There should only be one at a time.
V/ViewRootImpl: The specified message queue synchronization  barrier token has not been posted or has already been removed
W/Choreographer: Already have a pending vsync event.  There should only be one at a time.
I/okhttp.OkHttpClient: <-- 200 OK http://xx.xx.xx.xx/api-token-auth/ (237ms)
Date: Wed, 03 Mar 2021 21:31:39 GMT
Server: WSGIServer/0.2 CPython/3.8.2
Content-Type: application/json
Allow: POST, OPTIONS
X-Frame-Options: DENY
Content-Length: 52
Vary: Cookie
X-Content-Type-Options: nosniff
<-- END HTTP (52-byte body)
W/r.myweedmanage: Accessing hidden method Lsun/misc/Unsafe;->getObject(Ljava/lang/Object;J)Ljava/lang/Object; (greylist, linking, allowed)
Accessing hidden method Lsun/misc/Unsafe;->putObject(Ljava/lang/Object;JLjava/lang/Object;)V (greylist, linking, allowed)
W/r.myweedmanage: Accessing hidden method Lsun/misc/Unsafe;->getObject(Ljava/lang/Object;J)Ljava/lang/Object; (greylist, linking, allowed)
Accessing hidden method Lsun/misc/Unsafe;->putInt(Ljava/lang/Object;JI)V (greylist, linking, allowed)
W/r.myweedmanage: Accessing hidden method Lsun/misc/Unsafe;->getLong(Ljava/lang/Object;J)J (greylist,core-platform-api, linking, allowed)
Accessing hidden method Lsun/misc/Unsafe;->getLong(Ljava/lang/Object;J)J (greylist,core-platform-api, linking, allowed)
D/TransportRuntime.SQLiteEventStore: Storing event with priority=DEFAULT, name=FIREPERF for destination cct
D/TransportRuntime.JobInfoScheduler: Scheduling upload for context TransportContext(cct, DEFAULT, MSRodHRwczovL2ZpcmViYXNlbG9nZ2luZy1wYS5nb29nbGVhcGlzLmNvbS92MS9maXJlbG9nL2xlZ2FjeS9iYXRjaGxvZ1xBSXphU3lDY2traUg4aTJaQVJ3T3MxTEV6RktsZDE1YU9HOG96S28=) with jobId=877081683 in 30000ms(Backend next call timestamp 1614807010307). Attempt 1
I/okhttp.OkHttpClient: --> GET http://45.153.184.141/api/users/profile/
Authorization: Token token
--> END GET
D/OnePlusJankManager:  Chor uploadMDM JANK_TYPE_ONCE mViewTitle = com.weedmanager.myweedmanager/com.weedmanager.myweedmanager.authentication.LoginActivity--- jank level = 1
I/okhttp.OkHttpClient: <-- 200 OK http://45.153.184.141/api/users/profile/ (83ms)
Date: Wed, 03 Mar 2021 21:31:40 GMT
Server: WSGIServer/0.2 CPython/3.8.2
Content-Type: application/json
Vary: Accept
Allow: GET, HEAD, OPTIONS
X-Frame-Options: DENY
Content-Length: 103
X-Content-Type-Options: nosniff
<-- END HTTP (103-byte body)
W/r.myweedmanage: Accessing hidden method Lsun/misc/Unsafe;->putObject(Ljava/lang/Object;JLjava/lang/Object;)V (greylist, linking, allowed)
W/r.myweedmanage: Accessing hidden method Lsun/misc/Unsafe;->getInt(Ljava/lang/Object;J)I (greylist, linking, allowed)
Accessing hidden method Lsun/misc/Unsafe;->getObject(Ljava/lang/Object;J)Ljava/lang/Object; (greylist, linking, allowed)
E/LoginActivity$login: LoadingState Observer triggered
W/r.myweedmanage: Accessing hidden method Lsun/misc/Unsafe;->getLong(Ljava/lang/Object;J)J (greylist,core-platform-api, linking, allowed)
Accessing hidden method Lsun/misc/Unsafe;->getLong(Ljava/lang/Object;J)J (greylist,core-platform-api, linking, allowed)
E/LoginActivity$login: LOADED
D/TransportRuntime.SQLiteEventStore: Storing event with priority=DEFAULT, name=FIREPERF for destination cct
D/DecorView: onWindowFocusChangedFromViewRoot hasFocus: true, DecorView@4a8ec73[LoginActivity]
D/TransportRuntime.JobInfoScheduler: Upload for context TransportContext(cct, DEFAULT, MSRodHRwczovL2ZpcmViYXNlbG9nZ2luZy1wYS5nb29nbGVhcGlzLmNvbS92MS9maXJlbG9nL2xlZ2FjeS9iYXRjaGxvZ1xBSXphU3lDY2traUg4aTJaQVJ3T3MxTEV6RktsZDE1YU9HOG96S28=) is already scheduled. Returning...
E/LoginActivity$login: LoadingState Observer triggered
LOADED
E/LoginActivity$login: LoadingState Observer triggered
LOADED
D/OnePlusJankManager:  Chor uploadMDM JANK_TYPE_ONCE mViewTitle = com.weedmanager.myweedmanager/com.weedmanager.myweedmanager.authentication.LoginActivity--- jank level = 1
V/FA: Recording user engagement, ms: 1494
W/ActivityThread: handleWindowVisibility: no activity for token android.os.BinderProxy@c6ecc8e
V/FA: Activity paused, time: 1057027342
D/FA: Event not sent since app measurement is disabled
V/FA: onActivityCreated
E/MainActivity: MainActivity onCreate

现在在注销后发生魔术时:

E/LoginViewModel: enter try block outside viewModelScope.launch
D/FA: Event not sent since app measurement is disabled
E/LoginActivity$login: LoadingState Observer triggered
E/LoginActivity$login: LOADED
V/ViewRootImpl: The specified message queue synchronization  barrier token has not been posted or has already been removed
V/FA: Recording user engagement, ms: 8496
V/FA: Connecting to remote service
V/FA: Activity paused, time: 1057275561
W/Choreographer: Already have a pending vsync event.  There should only be one at a time.
D/FA: Event not sent since app measurement is disabled
W/ActivityThread: handleWindowVisibility: no activity for token android.os.BinderProxy@24faad3
E/MainActivity: MainActivity onCreate

所以我们可以清楚地看到，它没有进入viewModelScope.launch内部的try块，因为没有显示日志，也没有发出请求(profiler也是空的)，但是在viewModelScope.launch

周围的try/catch块中没有捕获Exception

。当我用breakpoint和step over调试我的代码时，我发现了JobCancellationException。

我试图通过从viewModelScope.launch更改为CoroutineScope(Dispatchers.IO).launch来改变我的范围(只是为了根据问题下面的评论测试这个范围)，它正在崩溃。

Answer 1

我终于解决了我的问题。事实上，我使用Koindependency injection。我只是替换了single:

val viewModelModule = module {
single { StatsViewModel(get()) }
single{ LoginViewModel(get(), get()) }
}

由viewModel:

val viewModelModule = module {
viewModel { StatsViewModel(get()) }
viewModel { LoginViewModel(get(), get()) }
}

的确，single会产生singleton，所以通过使用viewModel关键字，viewModel被绑定到Android组件的生命周期。

https://insert-koin.io/docs/reference/koin-android/viewmodel/

Answer 2

所以，在我的情况下，我使用liveData builder，在观察者端，在接收到单个值后，我移除观察者，所以当remove observer被调用时，livedata builder的协程被取消，JobCancellationException被抛出，所以解决方案很简单，当我得到新的实时数据时，我调用remove observer，所以对于之前的数据，我们可以使用remove oberserver。