androidkotlinandroid-widgetkotlin-lateinit

Why am i getting kotlin.UninitializedPropertyAccessException even if lateinit property is initialized (probably)


Ok so I declared a lateinit var job in a widget as below.

class TempHumidDisplayWidget : AppWidgetProvider(), CoroutineScope {
    private lateinit var job: Job
    override val coroutineContext: CoroutineContext
        get() = Dispatchers.Main + job
    ...

In the onEnabled function, i initialized it:

override fun onEnabled(context: Context) {
    job = Job()
    Log.i("com.github.animeshz", "On enabled")
    ...

And inside the onUpdate function I am going to use launch which calls the get function of coroutineContext for dispatching a coroutine, which uses the job variable.

override fun onUpdate(
    context: Context,
    appWidgetManager: AppWidgetManager,
    appWidgetIds: IntArray
) {
    // There may be multiple widgets active, so update all of them
    for (appWidgetId in appWidgetIds) {
        launch { updateAppWidget(context, appWidgetManager, appWidgetId) }
    }
}

And inside the logcat, I am getting the following error:

4425-4425/? I/com.github.animeshz: On enabled
...
2020-05-01 11:06:06.639 4425-4425/? E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.github.animeshz.shivamwidget, PID: 4425
    java.lang.RuntimeException: Unable to start receiver com.github.animeshz.shivamwidget.TempHumidDisplayWidget: kotlin.UninitializedPropertyAccessException: lateinit property job has not been initialized
        at android.app.ActivityThread.handleReceiver(ActivityThread.java:3183)
        at android.app.ActivityThread.-wrap18(ActivityThread.java)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1636)
        at android.os.Handler.dispatchMessage(Handler.java:102)
        at android.os.Looper.loop(Looper.java:154)
        at android.app.ActivityThread.main(ActivityThread.java:6334)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)
     Caused by: kotlin.UninitializedPropertyAccessException: lateinit property job has not been initialized
        at com.github.animeshz.shivamwidget.TempHumidDisplayWidget.getCoroutineContext(TempHumidDisplayWidget.kt:26)
        at kotlinx.coroutines.CoroutineContextKt.newCoroutineContext(CoroutineContext.kt:33)
        at kotlinx.coroutines.BuildersKt__Builders_commonKt.launch(Builders.common.kt:50)
        at kotlinx.coroutines.BuildersKt.launch(Unknown Source)
        at kotlinx.coroutines.BuildersKt__Builders_commonKt.launch$default(Builders.common.kt:47)
        at kotlinx.coroutines.BuildersKt.launch$default(Unknown Source)
        at com.github.animeshz.shivamwidget.TempHumidDisplayWidget.onUpdate(TempHumidDisplayWidget.kt:38)
        at android.appwidget.AppWidgetProvider.onReceive(AppWidgetProvider.java:66)
        at android.app.ActivityThread.handleReceiver(ActivityThread.java:3171)
        at android.app.ActivityThread.-wrap18(ActivityThread.java) 
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1636) 
        at android.os.Handler.dispatchMessage(Handler.java:102) 
        at android.os.Looper.loop(Looper.java:154) 
        at android.app.ActivityThread.main(ActivityThread.java:6334) 
        at java.lang.reflect.Method.invoke(Native Method) 
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886) 
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776) 

It is clear that onEnabled is called before the onUpdate method but the job variable is not initialized somehow, I don't know how to fix or debug it further

How is this possible that the job variable initialized in the onEnabled is actually not initialized in the onUpdate function? Is this a bug or something?

Any help would be appreciated, thanks in advance!


Solution

  • This is just spitballing, since I don't know details of widgets in Android, but something like this could work:

    class TempHumidDisplayWidget : AppWidgetProvider() {
        companion object {
            val jobs = mutableMapOf<Context, Job>()
    
            fun getScope(context: Context): CoroutineScope {
                val job = jobs[context] ?: throw IllegalStateException("Context $context not enabled currently")
                return object : CoroutineScope { 
                    override val coroutineContext: CoroutineContext = Dispatchers.Main + job
                    ...
                }
            }
        }
    
        override fun onEnabled(context: Context) {
            jobs[context] = Job()
            ...
        }
    
        override fun onDisabled(context: Context) {
            jobs.remove(context)?.cancel()
            ...
        }
    
        override fun onUpdate(
            context: Context,
            appWidgetManager: AppWidgetManager,
            appWidgetIds: IntArray
        ) {
            val scope = getScope(context)
            for (appWidgetId in appWidgetIds) {
                scope.launch { updateAppWidget(context, appWidgetManager, appWidgetId) }
            }
        }
    }
    

    It's generally a bad idea to keep references to Contexts "statically", but this could be all right because they are removed in onDisabled. Or maybe use WeakHashMap instead.