how to understand this error
<p>I have published on google play my app.
Google is telling me that my app, when was being used by users, crashed 2 times.
I tested my app a lot of times, but i never get that error, and i don't know how to simulate that error.</p>

<pre><code>java.lang.RuntimeException: Unable to resume activity {com.mdp.slotmachine/com.mdp.slotmachine.CoverActivity}: java.lang.NullPointerException
at android.app.ActivityThread.performResumeActivity(ActivityThread.java:2444)
at android.app.ActivityThread.handleResumeActivity(ActivityThread.java:2472)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1986)
at android.app.ActivityThread.access$600(ActivityThread.java:123)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1147)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:137)
at android.app.ActivityThread.main(ActivityThread.java:4429)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:795)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:562)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.NullPointerException
at android.app.ContextImpl.startService(ContextImpl.java:1088)
at android.content.ContextWrapper.startService(ContextWrapper.java:359)
at com.mdp.slotmachine.CoverActivity.onResume(Unknown Source)
at android.app.Instrumentation.callActivityOnResume(Instrumentation.java:1154)
at android.app.Activity.performResume(Activity.java:4539)
at android.app.ActivityThread.performResumeActivity(ActivityThread.java:2434)
... 12 more
</code></pre>

<p>The error seems to be in CoverActivity class, inside onResume method. As you can see i don't do anything in onResume method.</p>

<pre><code>  @Override
  protected void onResume() {
  super.onPause();

  //check if i'm publishing the app on samsung store
        if(MainActivity.samsung){   

          // here i check if my app was properly downloaded from samsung store by using Zirconia.
         // BUT I NEVER GET HERE; BECAUSE THE PREVIUOS VARIABLE (MainActivity.samsung) IS ALWAYS FALSE.
            if(!MainActivity.licensaSamsung){
                    finish();
            }
        }
  }
</code></pre>
