Beat'em Up game

Hi I'm from Brazil and I'm developing a Beat'em Up game for my conclusion work in universisty. I'm using a game api in this site trunk - sporksoft - Project Hosting on Google Code

This game api is exactly the same as the jme.

I'm having a problem, each time I use a game api method I have an null error and my app stop.

Code (Text):

1.  //Method that adjusts Axel's sprite
2.         public void adjustAxel( Sprite s, double mx, double my ){
3.             try{
4.                 mPositionX = (int) mX;
5.                 mPositionY = (int) mY;
6.  
7.                 mManager.append( mAxelSprite );
8.                 mAxelSprite.defineReferencePixel( mAxelWidth / 2, 0 );
9.                 mAxelSprite.setRefPixelPosition ( mPositionX, mPositionY);
10.                 mAxelSprite.setFrameSequence( mFrameSequence );
11.               }catch( Exception e ){
12.                         Log.e( CATEGORIA, "Error 2: " + e.getMessage() );
13.                    }
14.         }

I don't have an idea how to fix it, and in my country are very few people that develop in android platform so here I'm to search for help.

Greetings
John Peter