Rotate view using CGAfffineTransformRotate - objective-c

Question

I have a circular image which I am trying to rotate, so that the yellow and black striped circle stays under the user's finger and rotates in both directions. I have this so far:
- (void)handleJogShuttle:(UIPanGestureRecognizer *)recognizer {
UIView *shuttle = [recognizer view];
if ([recognizer state] == UIGestureRecognizerStateBegan ||
[recognizer state] == UIGestureRecognizerStateChanged) {
[recognizer view].transform = CGAffineTransformRotate([[recognizer view] transform],M_PI / 20.0f);
[recognizer setTranslation:CGPointZero inView:[shuttle superview]];
}
}
Also, currently, the slightest movement can cause the view to rotate in a full circle, which is obviously not desired.

Answer 1

#import "RotationTestViewController.h"
#interface RotationTestViewController()
-(void)transformSpinnerwithTouches:(UITouch *)touchLocation;
-(CGPoint)vectorFromPoint:(CGPoint)firstPoint toPoint:(CGPoint)secondPoint;
-(void)animateView:(UIView *)theView toPosition:(CGAffineTransform) newTransform;
#end
#implementation RotationTestViewController
- (void)viewDidLoad {
[super viewDidLoad];}
-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
for (UITouch *touch in touches)
{
// Send to the dispatch method, which will make sure the appropriate subview is acted upon
// currentTouch=touch;
}
}
-(void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
{
for (UITouch *touch in touches){
// Sends to the dispatch method, which will make sure the appropriate subview is acted upon
}
}
-(void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
UITouch *touch=[[event allTouches]anyObject];
if (touch.view==Spinner)
{
[self transformSpinnerwithTouches:touch];
}
}
-(void)transformSpinnerwithTouches:(UITouch *)touchLocation
{
CGPoint touchLocationpoint = [touchLocation locationInView:self.view];
CGPoint PrevioustouchLocationpoint = [touchLocation previousLocationInView:self.view];
//origin is the respective piont from that i gonna measure the angle of the current position with respective to previous position ....
CGPoint origin;
origin.x=Spinner.center.x;
origin.y=Spinner.center.y;
CGPoint previousDifference = [self vectorFromPoint:origin toPoint:PrevioustouchLocationpoint];
CGAffineTransform newTransform =CGAffineTransformScale(Spinner.transform, 1, 1);
CGFloat previousRotation = atan2(previousDifference.y, previousDifference.x);
CGPoint currentDifference = [self vectorFromPoint:origin toPoint:touchLocationpoint];
CGFloat currentRotation = atan2(currentDifference.y, currentDifference.x);
CGFloat newAngle = currentRotation- previousRotation;
temp1=temp1+newAngle;
NSLog(#"Angle:%F\n",(temp1*180)/M_PI);
newTransform = CGAffineTransformRotate(newTransform, newAngle);
[self animateView:Spinner toPosition:newTransform];
}
-(void)animateView:(UIView *)theView toPosition:(CGAffineTransform) newTransform
{
[UIView setAnimationsEnabled:YES];
[UIView beginAnimations:nil context:NULL];
[UIView setAnimationCurve:UIViewAnimationCurveLinear];
[UIView setAnimationBeginsFromCurrentState:YES];
[UIView setAnimationDuration:0.0750];
Spinner.transform = newTransform;
[UIView commitAnimations];
}
//-(CGFloat)distanceFromPoint:(CGPoint)fromPoint toPoint:(CGPoint)toPoint
//
//{
//float x = toPoint.x - fromPoint.x;
//float y = toPoint.y - fromPoint.y;
//return hypot(x, y);
//}
-(CGPoint)vectorFromPoint:(CGPoint)firstPoint toPoint:(CGPoint)secondPoint
{
CGFloat x = secondPoint.x - firstPoint.x;
CGFloat y = secondPoint.y - firstPoint.y;
CGPoint result = CGPointMake(x, y);
//NSLog(#"%f %f",x,y);
return result;
}
-(void) dealloc
{
[Spinner release];
[super dealloc];
}

Answer 2

I suspect this method gets called A LOT. Try using NSLog and check how many time it does.
Anyway, you are not calculating the angle properly, you could try using
-(CGPoint)translationInView:(UIView *)view
from the recognizer to calculate the correct angle to rotate.