Java.lang.nullpointerexception And Unknown Source

I'm having a hard time fixing some issues with my code. I tested it on my phone and it works good. But if I test it on a Galaxy Tab 4, it gives me java.lang.NullPointerException an

Solution 1:

Try to change the package name, it happens that some package names are not accepted by android. I don't know why but it even doesn't accept com.android.wifi

Faced same problem few days back and successfully solved by using a different package name

and make sure you use 'lower cases' and add com in the starting.

Solution 2:

Thanks for help, now if the problem appears again I will know what to try. I've found it. My main.xml layout large resource was not containing one of the buttons declared above. I might look like a fool now, but it happens. Thanks again for answers and comments.