StrictMode getSharedPreferences failure on API 27

[pyricau]

Steps to Reproduce

Just start the app on an API 27 device

Updating the config triggers a check for whether heap dumping is enabled in the UI, which in turns triggers a shared preferences load which apparently triggers a strict mode failure. This is likely a stupid AOSP bug (SharedPref loading used to be fully async when loading and block if necessary of first getter call)

D/LeakCanary: LeakCanary is running and ready to detect memory leaks.
D/StrictMode: StrictMode policy violation; ~duration=7 ms: android.os.StrictMode$StrictModeDiskReadViolation: policy=327743 violation=2
        at android.os.StrictMode$AndroidBlockGuardPolicy.onReadFromDisk(StrictMode.java:1440)
        at java.io.UnixFileSystem.checkAccess(UnixFileSystem.java:251)
        at java.io.File.exists(File.java:807)
        at android.app.ContextImpl.getDataDir(ContextImpl.java:2197)
        at android.app.ContextImpl.getPreferencesDir(ContextImpl.java:517)
        at android.app.ContextImpl.getSharedPreferencesPath(ContextImpl.java:714)
        at android.app.ContextImpl.getSharedPreferences(ContextImpl.java:368)
        at android.content.ContextWrapper.getSharedPreferences(ContextWrapper.java:167)
        at leakcanary.internal.activity.screen.AboutScreenKt.getDumpEnabledInAboutScreen(AboutScreen.kt:63)
        at leakcanary.internal.HeapDumpControl.iCanHasHeap(HeapDumpControl.kt:58)
        at leakcanary.internal.InternalLeakCanary$invoke$2.run(InternalLeakCanary.kt:140)
        at android.os.Handler.handleCallback(Handler.java:790)
        at android.os.Handler.dispatchMessage(Handler.java:99)
        at android.os.Looper.loop(Looper.java:164)
        at android.app.ActivityThread.main(ActivityThread.java:6494)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807)
D/AndroidRuntime: Shutting down VM
E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.example.leakcanary, PID: 29107
    android.os.StrictMode$StrictModeViolation: policy=327743 violation=2
        at android.os.StrictMode.executeDeathPenalty(StrictMode.java:1686)
        at android.os.StrictMode.-wrap3(Unknown Source:0)
        at android.os.StrictMode$AndroidBlockGuardPolicy.handleViolation(StrictMode.java:1679)
        at android.os.StrictMode$AndroidBlockGuardPolicy$1.run(StrictMode.java:1557)
        at android.os.Handler.handleCallback(Handler.java:790)
        at android.os.Handler.dispatchMessage(Handler.java:99)
        at android.os.Looper.loop(Looper.java:164)
        at android.app.ActivityThread.main(ActivityThread.java:6494)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807)

[pyricau]

Need to gather more context on why strict mode is failing on this, then figure out possible fixes.

[opatry]

AFAIK, the first time shared prefs are loaded, they are read from file system, so I/O access on UI Thread raises such StrictMode issue. Seems legit to me 🤔

[pyricau]

Looks like this is still happening on Android 10, slightly different stacktrace:

    Process: com.example.leakcanary, PID: 11907
    java.lang.RuntimeException: StrictMode ThreadPolicy violation
        at android.os.StrictMode$AndroidBlockGuardPolicy.onThreadPolicyViolation(StrictMode.java:1768)
        at android.os.StrictMode$AndroidBlockGuardPolicy.lambda$handleViolationWithTimingAttempt$0$StrictMode$AndroidBlockGuardPolicy(StrictMode.java:1687)
        at android.os.-$$Lambda$StrictMode$AndroidBlockGuardPolicy$9nBulCQKaMajrWr41SB7f7YRT1I.run(Unknown Source:6)
        at android.os.Handler.handleCallback(Handler.java:883)
        at android.os.Handler.dispatchMessage(Handler.java:100)
        at android.os.Looper.loop(Looper.java:214)
        at android.app.ActivityThread.main(ActivityThread.java:7356)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:930)
     Caused by: android.os.strictmode.DiskReadViolation
        at android.os.StrictMode$AndroidBlockGuardPolicy.onReadFromDisk(StrictMode.java:1556)
        at android.app.SharedPreferencesImpl.awaitLoadedLocked(SharedPreferencesImpl.java:261)
        at android.app.SharedPreferencesImpl.getBoolean(SharedPreferencesImpl.java:330)
        at leakcanary.internal.InternalLeakCanary.getDumpEnabledInAboutScreen$leakcanary_android_core_debug(InternalLeakCanary.kt:121)
        at leakcanary.internal.HeapDumpControl.iCanHasHeap(HeapDumpControl.kt:57)
        at leakcanary.internal.InternalLeakCanary$invoke$2.run(InternalLeakCanary.kt:161)
        at android.os.Handler.handleCallback(Handler.java:883) 
        at android.os.Handler.dispatchMessage(Handler.java:100) 
        at android.os.Looper.loop(Looper.java:214) 
        at android.app.ActivityThread.main(ActivityThread.java:7356)

Basically retrieving it works fine but then reading the values starts blocking and thrown. Grrr

[pyricau]

Fixed by #1995