You'll need to learn to debug your application. Then you can do the things that cause the bug, and see the values of your variables at that time. Another usefull thing is the logging system. You can find more information here if you're using Eclipse: How to Debug Android application line by line using Eclipse?
Your switch definitely needs break-statements if you are going to implement code for each case in the future:
switch(eventCode){
case MotionEvent.ACTION_DOWN:
return true;
break;
case MotionEvent.ACTION_MOVE:
return true;
break;
case MotionEvent.ACTION_UP:
return true;
break;
default:
return true;
}