Using variables in one class in another class NullpointerException - RunTimeException

Question

I tried to do something extremely simple or I thought it was.

In my BluetoothChat, I set

public static boolean potato = false;

In the onCreateBundle of my MainActivity, I have

if(BluetoothChat.potato == false)
{
  tv.setText("it did not crash");
}

My application crashes immediately upon me switching windows from bluetoothchat to mainactivity. I receive java.lang.RuntimeException and java.lang.NullPointerException. However, the application does not crash and switches perfectly if I have the if statement commented out.

The reason for this is that while the program control enters into onCreate() method, still your BluetoothChat class is Null. Hence it gives NPE. — Lucifer
– Lucifer, Commented Apr 7, 2014 at 3:41
May be by calling a public constructor before your if condition. — Lucifer
– Lucifer, Commented Apr 7, 2014 at 3:44

Quasitonality · Accepted Answer · 2014-04-07 03:43:18Z

1

It looks like the error is coming from tv, not BlueToothChat.potato. Have you initialized the "tv" variable at that point in the code?

answered Apr 7, 2014 at 3:43

Quasitonality

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2 Comments

SeniorDesignStudy Over a year ago

I feel really stupid right now. That worked. Thank you.

Quasitonality Over a year ago

We all make this mistake once in a while! Whenever you get a NullPointerException, check for uninitialized variables; that's more often than not the problem.

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