[Bug] AppStartTrace.onActivityResumed : java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.ViewTreeObserver android.view.View.getViewTreeObserver()' on a null object reference

[aboulianne-ludia]

Description

In our live app, our top crash used to happen when our UnityPlayerActivity would receive onResume. (call stack will be shown below).
Looking at the code of AppStartTrace.java at line 355 (at revision a350561 on April 25th, 2024 ), the line is:

353    if (isExperimentTTIDEnabled) {
354      View rootView = activity.findViewById(android.R.id.content);
355      rootView.getViewTreeObserver().addOnDrawListener(onDrawCounterListener);  // crash happens here

It is unclear why, in certain cases, line 354 would return null.
The crash disappeared when we disabled ExperimentTTID by adding
<meta-data android:name="experiment_app_start_ttid" android:value="false" />
to our AndroidManifest.xml

We have never reproduced the issue internally, or never noticed that it happened.
It seems to happen on Android 12 and above.

Would a null check against rootView resolve the issue? Or is there a deeper reason and that value should never be null?
Since our app is large, maybe the view hasn't finished initialization at that point? (Google Play vitals has flagged our Warm app start metric as problematic, if that helps.)

Reproducing the issue

No known reproduction steps.

Firebase Unity SDK Version

11.7.0

Unity editor version

2022.3.27f1

Installation Method

Unity Package Manager

Problematic Firebase Component(s)

Performance

Other Firebase Component(s) in use

Analytics, Crashlytics, DynamicLinks, Messaging

Additional SDKs you are using

• Google Play (Play Games, App Update, App Bundle)
• Tapjoy
• Unity Ads
• Facebook
• Adjust
• Airship
• Helpshift
• Ironsource
• Applovin

Targeted Platform(s)

Android

Unity editor platform

Mac, Windows

Scripting Runtime

IL2CPP

Release Distribution Type

Pre-built SDK from https://firebase.google.com/download/unity

Relevant Log Output

truncated call stack of crash:
Caused by java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.ViewTreeObserver android.view.View.getViewTreeObserver()' on a null object reference
       at com.google.firebase.perf.metrics.AppStartTrace.onActivityResumed(AppStartTrace.java:355)
       at android.app.Application.dispatchActivityResumed(Application.java:436)
       at android.app.Activity.dispatchActivityResumed(Activity.java:1489)
       at android.app.Activity.onResume(Activity.java:2081)
       at com.unity3d.player.UnityPlayerActivity.onResume(UnityPlayerActivity.java:97)

If using CocoaPods for Apple platforms, the project's Podfile.lock

Expand Podfile.lock snippet

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[google-oss-bot]

I couldn't figure out how to label this issue, so I've labeled it for a human to triage. Hang tight.

[argzdev]

Hey @aboulianne-ludia, thanks for reaching out. For context, the Firebase Unity SDK acts as a wrapper for the native SDKs. In this case, since the error seems native, most likely the fix should be applied on the Firebase Android SDK repository. Could you reach out to them and file an issue there?

That said, there's not much we can do about this on the Firebase Unity SDK side. I'll go ahead and close this thread for now. Feel free to come back here if you think this change should be done on the Unity SDK side.