CGFloat const gestureMinimumTranslation = 20.0;
typedef enum :NSInteger {
kCameraMoveDirectionNone,
kCameraMoveDirectionUp,
kCameraMoveDirectionDown,
kCameraMoveDirectionRight,
kCameraMoveDirectionLeft
} CameraMoveDirection;
@interfaceViewController ()
{
CameraMoveDirection direction;
}
@end
@implementation ViewController
- (void)viewDidLoad
{
[super viewDidLoad];
UIPanGestureRecognizer *recognizer = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(handleSwipe:)];
[self.viewWithGestureRecognizer addGestureRecognizer:recognizer];
}
// This is my gesture recognizer handler, which detects movement in a particular
// direction, conceptually tells a camera to start moving in that direction
// and when the user lifts their finger off the screen, tells the camera to stop.
- (void)handleSwipe:(UIPanGestureRecognizer *)gesture
{
CGPoint translation = [gesture translationInView:self.view];
if (gesture.state ==UIGestureRecognizerStateBegan)
{
direction = kCameraMoveDirectionNone;
}
else if (gesture.state == UIGestureRecognizerStateChanged && direction == kCameraMoveDirectionNone)
{
direction = [self determineCameraDirectionIfNeeded:translation];
// ok, now initiate movement in the direction indicated by the user's gesture
switch (direction) {
case kCameraMoveDirectionDown:
NSLog(@"Start moving down");
break;
case kCameraMoveDirectionUp:
NSLog(@"Start moving up");
break;
case kCameraMoveDirectionRight:
NSLog(@"Start moving right");
break;
case kCameraMoveDirectionLeft:
NSLog(@"Start moving left");
break;
default:
break;
}
}
elseif (gesture.state == UIGestureRecognizerStateEnded)
{
// now tell the camera to stop
NSLog(@"Stop");
}
}
// This method will determine whether the direction of the user's swipe
- (CameraMoveDirection)determineCameraDirectionIfNeeded:(CGPoint)translation
{
if (direction != kCameraMoveDirectionNone)
return direction;
// determine if horizontal swipe only if you meet some minimum velocity
if (fabs(translation.x) > gestureMinimumTranslation)
{
BOOL gestureHorizontal = NO;
if (translation.y ==0.0)
gestureHorizontal = YES;
else
gestureHorizontal = (fabs(translation.x / translation.y) >5.0);
if (gestureHorizontal)
{
if (translation.x >0.0)
return kCameraMoveDirectionRight;
else
return kCameraMoveDirectionLeft;
}
}
// determine if vertical swipe only if you meet some minimum velocity
else if (fabs(translation.y) > gestureMinimumTranslation)
{
BOOL gestureVertical = NO;
if (translation.x ==0.0)
gestureVertical = YES;
else
gestureVertical = (fabs(translation.y / translation.x) >5.0);
if (gestureVertical)
{
if (translation.y >0.0)
return kCameraMoveDirectionDown;
else
return kCameraMoveDirectionUp;
}
}
return direction;
}
@end