I am truly stumped with a problem I am having with rotating a view. I am trying to make several views rotate around an arbitrary point (like a touch).
First of all, without fully explaining (just take my word for it) I would just like to say that due to the complexity of my view layout and what I need to accomplish, the "cheat" method, as it is sometimes called, where you add all the views that need to rotate to a bigger view and rotate that view, won't work for me.
I am changing the anchor point of the layer so that my view(s) will rotate around the point of a double tap. However, something that I can't quite figure out keeps throwing me for a loop. When I rotate it once (say 90º), and rotate it 90º again, instead of ending up at 180º (what you would expect), I am ending up at 270º (or some other weird number).
I will try and post enough code so that you can see what I am saying (and hopefully help me).
I have one instance variable declared in the .h
UIView *theView;
Here is the .m (you will need to import the QuartzCore framework)
- (void)viewDidLoad {
[super viewDidLoad];
theView = [[UIView alloc]initWithFrame:CGRectMake(140, 40, 40, 40)];
theView.backgroundColor = [UIColor blueColor];
[self.view addSubview:theView];
}
#define DegreesToRadians(x) ((x) * M_PI / 180.0)
-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event{
UITouch *touch = [touches anyObject];
CGPoint touchLocation = [touch locationInView:self.view];
if ([touch tapCount]==2) {
CGFloat xValue = ((touchLocation.x - theView.frame.origin.x)/theView.frame.size.width);
CGFloat yValue = ((touchLocation.y - theView.frame.origin.y)/theView.frame.size.height);
CGRect priorRect = theView.frame;
theView.layer.anchorPoint = CGPointMake(xValue, yValue);
theView.frame = priorRect;
static float rotationValue = 0.0f;
rotationValue += 90.0f;
[UIView beginAnimations:nil context:NULL];
[UIView setAnimationDuration:1.0f];
[UIView setAnimationCurve:UIViewAnimationCurveEaseInOut];
theView.transform = CGAffineTransformRotate(theView.transform, DegreesToRadians(rotationValue));
[UIView commitAnimations];
}
}
I have tried this with every different configuration I could possibly think of, so this example is just what I threw together because it seemed to be pretty concise. Anyway, PLEASE HELP ME!!!
The anchor point needs to be set appropriately.
Setting anchor point for UIView layer
If you only want to rotate at 90 degrees a tap, then don't aggregate the rotation, it rotationValue should always be 90 degrees.
If you want it to rotate a greater amount each time, then you'll have jumping issues, so you should see the following link for how to do that properly.