ProGuard leads to NullPointerException

Question

When setting

minifyEnabled true

in my gradle I get a NullPointerException when starting my app:

java.lang.RuntimeException: Unable to start activity ComponentInfo{de.ae.formulaecalendar/de.ae.formulaecalendar.view.calendar.CalendarActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v7.widget.RecyclerView.setLayoutManager(android.support.v7.widget.RecyclerView$LayoutManager)' on a null object reference

   at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2444)

   at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2504)

   at android.app.ActivityThread.-wrap11(ActivityThread.java)

   at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1367)

   at android.os.Handler.dispatchMessage(Handler.java:102)

   at android.os.Looper.loop(Looper.java:148)

   at android.app.ActivityThread.main(ActivityThread.java:5461)

   at java.lang.reflect.Method.invoke(Native Method)

   at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)

   at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)

Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v7.widget.RecyclerView.setLayoutManager(android.support.v7.widget.RecyclerView$LayoutManager)' on a null object reference

   at de.ae.formulaecalendar.view.calendar.CalendarActivity.onCreate(Unknown Source)

   at android.app.Activity.performCreate(Activity.java:6251)

   at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1107)

   at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2397)

   at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2504) 

   at android.app.ActivityThread.-wrap11(ActivityThread.java) 

   at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1367) 

   at android.os.Handler.dispatchMessage(Handler.java:102) 

   at android.os.Looper.loop(Looper.java:148) 

   at android.app.ActivityThread.main(ActivityThread.java:5461) 

   at java.lang.reflect.Method.invoke(Native Method) 

   at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) 

   at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)

While reading through StackOverflow I found some settings for the proguard-rules.pro file:

######### KEEP ANDROID SUPPORT V7 AND DESIGN

-keep class android.support.v7.** { *; }

-keep interface android.support.v7.** { *; }

which didn't really solve this problem (but a previous NullPointerException).

Finally the important part of my gradle:

buildTypes {

    release {

        shrinkResources true

        minifyEnabled true

        proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'

        signingConfig signingConfigs.config

    }

}

When I disbale

minifyEnabled

everthing works fine.

Thanks for your help!

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Answer 1

I solved the problem:

After running Clean Project in Android Studio I got an error about a file called resource-release-stripped.ap_ that cannot be found. Some searching via Google showed up that I need to disable shrinkResources in the gradle file because it is not compatible with Jack.

ProGuard leads to NullPointerException

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