Building Your Game: Understanding Gestures and Movements - Beginning iOS6 Games Development - page 197

In Listing 8-18, we see the task doSetup for the class PanGestureController . The first thing we
do after specifying the size of the game area is specify the minYValue and the maxYValue for the
asteroids, so they cannot move within 72 points of the top or bottom of the screen. Next, we create
our three Asteroid objects, add them to the scene, and add them to the NSMutableArray asteroids .
Each Asteroid starts at the top of the screen.
The last thing we do in doSetup is create a UIPanGestureRecognizer , configure it to call panGesture :,
and add it to actorsView . The next section explains how we respond to these gestures to create the
desired behavior.
Responding to Pan Gestures
We have reviewed how to set up the class UIPanGestureController . Now we will explore how to
respond to this gesture in the task panGesture :, as shown in Listing 8-19.
Listing 8-19. PanGestureController.m (panGesture:)
-(void)panGesture:(UIPanGestureRecognizer*)panRecognizer{
if ([panRecognizer state] == UIGestureRecognizerStateBegan){
CGSize gameAreaSize=[self gameAreaSize];
CGPoint locationInView = [panRecognizer locationInView:actorsView];
if (locationInView.x<gameAreaSize.width/3.0){
asteroidIndex=0;
} else if (locationInView.x>gameAreaSize.width/3.0*2){
asteroidIndex=2;
} else {
asteroidIndex=1;
}
Asteroid* asteroid=[asteroids objectAtIndex:asteroidIndex];
startCenter=[asteroid center];
[asteroid setAnimationPaused:YES];
} else if ([panRecognizer state] == UIGestureRecognizerStateChanged){
Asteroid* asteroid=[asteroids objectAtIndex:asteroidIndex];
CGPoint locationInView = [panRecognizer locationInView:actorsView];
CGPoint center=[asteroid center];
center.y=locationInView.y;
if (center.y<[self minYValue]){
center.y=[self minYValue];
}
if (center.y>[self maxYValue]){
center.y=[self maxYValue];
}
[asteroid setCenter:center];
} else if ([panRecognizer state] == UIGestureRecognizerStateEnded){