I figured it out what was my problem...
I was trying to do:
mv = (MjpegView) findViewById(R.id.mv);
setContentView(R.layout.activity_test);
And was getting a NullPointerException.. I changed to:
setContentView(R.layout.activity_test);
mv = (MjpegView) findViewById(R.id.mv);
And now everything is working like is supposed to be :)