Kotlin and Android Development featuring Jetpack: End Ch. 11 app runs but consistently crashes

dachristenson · 6 December 2023 22:03

I’ve got to the end of Ch. 11, and the app runs, with all tabs displaying what they should – at first. After switching around between Standings, Players, Leaders, etc., the app always eventually has problems reloading, for instance, Standings. Then, I’ll try to load Leaders, and it crashes with this error (as far as I can tell, it’s always mentioning the LeadersListFragment). Is this due to the “experimental” status of some of the packages imported, or is it something else? It happens on both my Samsung tablet and on the virtual Pixel 3a.

FATAL EXCEPTION: main
                                                                                                    Process: com.example.abl, PID: 13592
                                                                                                    androidx.fragment.app.Fragment$InstantiationException: Unable to instantiate fragment com.example.abl.leaders.LeadersListFragment: could not find Fragment constructor
                                                                                                    	at androidx.fragment.app.Fragment.instantiate(Fragment.java:687)
                                                                                                    	at androidx.fragment.app.FragmentContainer.instantiate(FragmentContainer.java:57)
                                                                                                    	at androidx.fragment.app.FragmentManager$3.instantiate(FragmentManager.java:525)
                                                                                                    	at androidx.fragment.app.FragmentState.instantiate(FragmentState.java:84)
                                                                                                    	at androidx.fragment.app.FragmentStateManager.<init>(FragmentStateManager.java:91)
                                                                                                    	at androidx.fragment.app.FragmentManager.restoreSaveStateInternal(FragmentManager.java:2562)
                                                                                                    	at androidx.fragment.app.Fragment.restoreChildFragmentState(Fragment.java:1988)
                                                                                                    	at androidx.fragment.app.Fragment.onCreate(Fragment.java:1967)
                                                                                                    	at androidx.fragment.app.Fragment.performCreate(Fragment.java:3094)
                                                                                                    	at androidx.fragment.app.FragmentStateManager.create(FragmentStateManager.java:504)
                                                                                                    	at androidx.fragment.app.FragmentStateManager.moveToExpectedState(FragmentStateManager.java:268)
                                                                                                    	at androidx.fragment.app.FragmentManager.executeOpsTogether(FragmentManager.java:1943)
                                                                                                    	at androidx.fragment.app.FragmentManager.removeRedundantOperationsAndExecute(FragmentManager.java:1845)
                                                                                                    	at androidx.fragment.app.FragmentManager.execPendingActions(FragmentManager.java:1782)
                                                                                                    	at androidx.fragment.app.FragmentManager$5.run(FragmentManager.java:565)
                                                                                                    	at android.os.Handler.handleCallback(Handler.java:938)
                                                                                                    	at android.os.Handler.dispatchMessage(Handler.java:99)
                                                                                                    	at android.os.Looper.loop(Looper.java:246)
                                                                                                    	at android.app.ActivityThread.main(ActivityThread.java:8653)
                                                                                                    	at java.lang.reflect.Method.invoke(Native Method)
                                                                                                    	at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:602)
                                                                                                    	at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1130)
                                                                                                    Caused by: java.lang.NoSuchMethodException: com.example.abl.leaders.LeadersListFragment.<init> []
                                                                                                    	at java.lang.Class.getConstructor0(Class.java:2332)
                                                                                                    	at java.lang.Class.getConstructor(Class.java:1728)
                                                                                                    	at androidx.fragment.app.Fragment.instantiate(Fragment.java:672)
                                                                                                    	at androidx.fragment.app.FragmentContainer.instantiate(FragmentContainer.java:57) 
                                                                                                    	at androidx.fragment.app.FragmentManager$3.instantiate(FragmentManager.java:525) 
                                                                                                    	at androidx.fragment.app.FragmentState.instantiate(FragmentState.java:84) 
                                                                                                    	at androidx.fragment.app.FragmentStateManager.<init>(FragmentStateManager.java:91) 
                                                                                                    	at androidx.fragment.app.FragmentManager.restoreSaveStateInternal(FragmentManager.java:2562) 
                                                                                                    	at androidx.fragment.app.Fragment.restoreChildFragmentState(Fragment.java:1988) 
                                                                                                    	at androidx.fragment.app.Fragment.onCreate(Fragment.java:1967) 
                                                                                                    	at androidx.fragment.app.Fragment.performCreate(Fragment.java:3094) 
                                                                                                    	at androidx.fragment.app.FragmentStateManager.create(FragmentStateManager.java:504) 
                                                                                                    	at androidx.fragment.app.FragmentStateManager.moveToExpectedState(FragmentStateManager.java:268) 
                                                                                                    	at androidx.fragment.app.FragmentManager.executeOpsTogether(FragmentManager.java:1943) 
                                                                                                    	at androidx.fragment.app.FragmentManager.removeRedundantOperationsAndExecute(FragmentManager.java:1845) 
                                                                                                    	at androidx.fragment.app.FragmentManager.execPendingActions(FragmentManager.java:1782) 
                                                                                                    	at androidx.fragment.app.FragmentManager$5.run(FragmentManager.java:565) 
                                                                                                    	at android.os.Handler.handleCallback(Handler.java:938) 
                                                                                                    	at android.os.Handler.dispatchMessage(Handler.java:99) 
                                                                                                    	at android.os.Looper.loop(Looper.java:246) 
                                                                                                    	at android.app.ActivityThread.main(ActivityThread.java:8653) 
                                                                                                    	at java.lang.reflect.Method.invoke(Native Method) 
                                                                                                    	at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:602) 
                                                                                                    	at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1130) 
2023-12-06 14:58:29.915 13592-13592 Process                 com.example.abl                      I  Sending signal. PID: 13592 SIG: 9

mfazio23 · 7 December 2023 04:23

Directly related to the exception: it’s throwing an exception because LeadersListFragment does not have an empty constructor (since we send in a leader type value), but something is trying to create an instance automatically.

That being said, I pulled down your latest code and it’s loading just fine for me. Is everything checked in and up to date on GitHub?

dachristenson · 8 December 2023 11:28

@mfazio23

Well, I actually pushed some changes that make the latest commit not build for me (a rookie mistake, I’m sure) just as a backup of my progress. The latest commit that I can build and install is commit b4bf069 “To mid p284; works, then crashes.” I went and took a short video of a typical test session on my Samsung tablet, and I’ve posted it as an unlisted video on YouTube. As you can see (hopefully), the crash doesn’t happen right away, but after switching views a few times. This happens on both my real Samsung Galaxy Tab A and the emulated phone in Android Studio.

GitHub repo: GitHub - dachristenson/Android_Baseball_League: Working through Part II of "Kotlin and Android Development Featuring Jetpack" by Michael Fazio.

mfazio23 · 17 December 2023 16:09

Alright, this took me a bit since my original app still works as written, so I’m thinking this is due to a change in one of the navigation library. It’s seems like it’s trying to be helpful and re-create your Fragment automatically, but since it doesn’t know the leaderType it can’t.

I’d say the proper approach here is to send the leaderType as an argument to the LeadersListFragment rather than as a constructor parameter:

val leaderType = if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.TIRAMISU) {
    arguments?.getSerializable(LEADER_TYPE_KEY, LeaderType::class.java)
} else {
    arguments?.getSerializable(LEADER_TYPE_KEY) as? LeaderType
} ?: LeaderType.Batting

You can then remove leaderType from the constructor. Note that the extra version check logic is due to arguments?.getSerializable(LEADER_TYPE_KEY) being deprecated for API level 33, but our app supports lower versions.

You can also do this the easy way and make the constructor parameter nullable:

class LeadersListFragment(private val leaderType: LeaderType? = LeaderType.Batting)

Sorry this took a bit for me to get back to you!

dachristenson · 19 December 2023 04:34

I went with the second option, making leaderType nullable in the constructor, and that seems to stop the crashing; thanks!

I also tried the first, longer option, but I guess I wasn’t right about where that code was supposed to go, as Android Studio didn’t like it anywhere I tried putting it. Where should the code below go? I admit that I was a bit confused by the wording that I should “send the leaderType as an argument to the LeadersListFragment rather than as a constructor parameter”. These sound like the same thing to me.

mfazio23:

val leaderType = if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.TIRAMISU) {
    arguments?.getSerializable(LEADER_TYPE_KEY, LeaderType::class.java)
} else {
    arguments?.getSerializable(LEADER_TYPE_KEY) as? LeaderType
} ?: LeaderType.Batting

mfazio23 · 31 December 2023 20:21

Apologies for the delays on my end, holidays got in the way!

That snippet I posted should live inside the onCreateView(...) function of LeadersListFragment. You also need to add the leader type as an argument when creating the fragment in the first place. When you create the LeadersListFragment, you need to include a Bundle:

LeadersListFragment().apply {
    arguments = Bundle().apply {
        putSerializable(LEADER_TYPE_KEY, leaderType)
    }
}

LEADER_TYPE_KEY is a const val defined in the companion object of LeadersFragment. You can then re-use that key when getting the value out in the LeadersListFragment.

Hopefully this helps!

dachristenson · 3 January 2024 05:27

Oh, so for defining the LEADER_TYPE_KEY, just add this to LeadersFragment, right?

companion object {
        const val LEADER_TYPE_KEY = "leaderType"
    }

mfazio23 · 5 January 2024 05:33

Yup! You can access it in both fragments and it ensures that the key is the same on both ends.

dachristenson · 5 January 2024 05:43

Great! Thanks!