Objective-C to Java conversion for porting iPhone apps to Android?

Question

can anybody help me to convert this objective-c code to android java.

- (void)ccTouchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
    if (_mouseJoint != NULL) return;

    UITouch *myTouch = [touches anyObject];

    CGPoint location = [myTouch locationInView:[myTouch view]];

    location = [[CCDirector sharedDirector] convertToGL:location];

    b2Vec2 locationWorld = b2Vec2(location.x/PTM_RATIO, location.y/PTM_RATIO);

    if (_paddleFixture->TestPoint(locationWorld)) {

        b2MouseJointDef md;
        md.bodyA = _groundBody;
        md.bodyB = _paddleBody;
        md.target = locationWorld;
        md.collideConnected = true;
        md.maxForce = 1000.0f * _paddleBody->GetMass();

        _mouseJoint = (b2MouseJoint *)_world->CreateJoint(&md);
        _paddleBody->SetAwake(true);
    }

}

I tried below is my code but getting exception. java.lang.nullpointer . Is anything wrong ?

public boolean ccTouchesBegan(MotionEvent event) {

         if (_mouseJoint != null){ 
             return true;

        }
         else{


         CGPoint convertedLocation = CCDirector.sharedDirector().convertToGL(CGPoint.make(event.getX(), event.getY()));
         Vector2 locationWorld = new Vector2(convertedLocation.x/PTM_RATIO, convertedLocation.y/PTM_RATIO);

         // return CCTouchDispatcher.kEventHandled;
           //_mouseJoint.setTarget(locationWorld);

        if(_paddleFixture.testPoint(locationWorld)){

             MouseJointDef md = new MouseJointDef();
             md.bodyA = _body;
             md.bodyB = _paddleBody;
             md.target.set(locationWorld);
             md.collideConnected = true;
             md.maxForce = (float)(1000.0f * _paddleBody.getMass());
             _mouseJoint =  (MouseJoint) _world.createJoint(md);
             _paddleBody.setAwake(true);
         }
        }
     //return CCTouchDispatcher.kEventHandled;

        return true;
    }

Answer 1

The key difference between obj-c and pretty much any other language is that you don't have to check for null (or nil in obj-c). Basically you need to see what line your exception is occurring on, and wrap that with a null check.