Question

In my app, I allow the user to annotate a photo by adding arrows (custom ArrowView). There can be many arrows added, with various zoom & rotation.

I am trying implement selecting of arrow by touch. Currently, I am iterating & using

CGRectContainsPoint(arrowView.frame, touchPoint)

to decide which arrow to select based on a touch gesture.

But, this does not work well when some of the arrows are big & rotated to 45 degrees (since the frame becomes big).

Question:
I would like to use bounds of the arrow translated to parent co-ordinates instead of frame. How can I get this when scaling & rotation is applied?

Alternatively, is there a better method to solve this selection problem?

Answer 1

This code find the arrow under touchPoint:

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
    UITouch *touch = [touches anyObject];
    CGPoint touchPoint = [touch locationInView:self.view];
    UIView *arrow = [self.view hitTest:touchPoint withEvent:event];
}