Android Beta app crashes when opening from Playstore (but works otherwise)

Question

New developer here.

I just recently finished an app I'm working on, and published it as a beta version to the Play Store. Before sending this to my beta testers, I sent a link to myself just to see if it works. When I clicked the link and installed the app from the Play Store it appears to have loaded to my device just fine. But then when I open the app, it crashes before it even opens. I get an "Unfortunately, App Name has stopped" message.

Just to double check and make certain I didn't mess anything up last minute before publishing, I uninstalled and ran the app from my device using Android Studio and it runs just fine.

The only thing I can think may be causing this are a few things I did before building the APK.

First, in my build.gradle file I inserted "optimize" to this line of code:

buildTypes {
        release {
            runProguard true
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
        }
    }

Then in the proguard-rules.pro I added the following:

-assumenosideeffects class android.util.Log {
    public static boolean isLoggable(java.lang.String, int);
    public static int v(...);
    public static int i(...);
    public static int w(...);
    public static int d(...);
    public static int e(...);
}
-ignorewarnings

The "assumenosideeffects" line - as I understand it - is to weed out my Logs so they don't run in the Play Store version.

I added the "ignorewarnings" line because on building the APK, I got 78 (yellow) warnings, all of which had to do with Facebook. But I have no facebook integration and never even attempted to write any code to integrate facebook. So I assumed that adding the ignorewarnings line wouldn't impede the function of the app. Was I mistaken?

So that's my problem. Any ideas what the isue may be?

Thanks so much for your help. I have benefited a lot from this community, and I appreciate it so much :)

EDIT

Stack Trace is below:

java.lang.RuntimeException: Unable to create application com.offyear.www.offyear.Application: java.lang.IllegalArgumentException: Default constructor for class com.a.lb is not accessible.
at android.app.ActivityThread.handleBindApplication(ActivityThread.java:4447)
at android.app.ActivityThread.access$1300(ActivityThread.java:141)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1316)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:137)
at android.app.ActivityThread.main(ActivityThread.java:5103)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:525)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.IllegalArgumentException: Default constructor for class com.a.lb is not accessible.
at com.a.gy.c(Unknown Source)
at com.a.gy.C(Unknown Source)
at com.a.ed.a(Unknown Source)
at com.offyear.www.offyear.Application.onCreate(Unknown Source)
at android.app.Instrumentation.callApplicationOnCreate(Instrumentation.java:1007)
at android.app.ActivityThread.handleBindApplication(ActivityThread.java:4444)
... 10 more

Answer 1

OK, not really sure what the source of the problem was, but I did finally resolve the issue - figured I'd post it in case anyone else runs into similar trouble.

Apparently something in the proguard code was messing things up. So I just deleted all the proguard code, set runProguard to false in gradle and deleted "optimize."

App installed and ran from Google Play with no problem after that.