PAINTROID-815 Crash at App Start

[harissabil]

Summary

Release builds crash on launch / app start after process death. Reproduce with Developer Options > "Don't keep activities", open the app, press Home, reopen.

androidx.fragment.app.g: Unable to instantiate fragment a.e: could not find Fragment constructor
Caused by: java.lang.NoSuchMethodException: a.e.<init> []

FragmentManager restores fragments reflectively through their no-arg constructor. R8 cannot see that call, so it removes the constructor. Confirmed with apkanalyzer that the constructor is missing from the release build.

R8 full mode became the default with the AGP 8 upgrade. release-2.13.0 built with AGP 7.2.1, does not crash.

a.e has not been retraced against the release mapping, so the exact fragment is not confirmed. PaintroidApplicationFragment is the most likely. The fix is a keep rule in app/proguard-rules.pro, using -keepclassmembers rather than -keep so class names stay obfuscated.

Tested with a minified release build; the rule no longer crashes with "Don't keep activities" option enabled.

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