CAAffineTransformationMakeRotation problem - iphone

Question

I have a problem with CAAffineTransformationMakeRotation. M trying to rotate a UIView with 22.5 degrees in ViewDidLoad, and after a delay of 1 sec,the View flyin to the screen.
the code is:
-(void)ViewDidiLoad{
imgView1 = [[UIView alloc] initWithFrame:CGRectMake(20,150,.1,400)];
[imgView1 setBackgroundColor:[UIColor blackColor]];
[self.view addSubview:imgView1];
CGAffineTransform trans = CGAffineTransformMakeRotation(3.14159/8);
imgView1.transform = trans;
[self performSelector:#selector(img1_enter) withObject:nil afterDelay:1];
}
-(void)img1_enter{
CGRect frame = [imgView1 frame];
[UIView beginAnimations:nil context:nil];
[UIView setAnimationDuration:2.99];
frame.origin.x = 550;
[UIView commitAnimations];
[UIView beginAnimations:nil context:nil];
[UIView setAnimationDuration:2.99];
[imgView1 setFrame :frame];
[UIView commitAnimations];
}
The problem is that when this view fly's in..its width and height changes. I've tried without rotating the View(i.e without AffineTransformation), it works properly.
Is there any other method to rotate the View??

Answer 1

You could incorporate the already existing transform to preserve the current size respectively aspect ratio:
imgView1.transform = CGAffineTransformConcat(trans, imgView1.transform);
Also the documentation of the UIView class says that the frame property is undefined if the transform is not the identity transform, so you must not use it after you applied a rotation.

Answer 2

The frame-rectangle represents the position and size of the view within the coordinate-system of its superview. The bounds-rectangle represents the inner coordinate-system of the view, so the bounds-rectangle is sort of responsible for the actual pixel-amount (respectively the amount of columns and rows) of the view.
If the contentMode is set to UIViewContentModeRedraw and you alter the frame-rectangle, then the size of the bounds-rectangle automatically gets adjusted that it fits the size of the frame-rectangle and vice-versa, else the bounds-rectangle stays untouched. For rendering the difference between the frame-rectangle and the bounds-rectangle is compensated by an automatically created transform-matrix.
The last two sentences are only true, iff the transform-property of the view is the identity matrix. If it isn't, the frame-property is invalid and you alone are responsible to provide a proper transform from the coordinate-system of the view to the coordinate-system of its super-view. So if you want to apply a rotation, you also have apply a proper translation and scaling to get the view where you want it to be relative to the coordinates of its super-view.
So in your case, you could set the bounds-rectangle to CGRectMake(-width/2, -height/2, width, height) and set its transform to
CGAffineTransformConcat(
CGAffineTransformMakeRotation(angle),
CGAffineTransformMakeTranslation(x, y)
)
, where x and y are the center-coordinates of the view within the coordinate-system of its super-view.