Chapter 13 Gestures

thepianoguy · September 20th, 2010, 11:30 AM

This chapter presented the information clearly, but I disliked how the implementations of the various gestures ignored changes made by other gestures. i.e. a "zoom" followed by a rotation would no longer be "zoomed", a rotation followed by a zoom wouldn't be rotated. The following changes allow you to make the changes cumulative.

Code:

@synthesize imageView;


CGAffineTransform currentState;
BOOL senderState = YES;

-(IBAction)handlePinchGesture:(UIGestureRecognizer *)sender
{
	if (senderState) {
		currentState = sender.view.transform;
		senderState = NO;
	}
	
	CGFloat factor = [(UIPinchGestureRecognizer *)sender scale];

	sender.view.transform = CGAffineTransformScale(currentState, factor, factor);

	
	if(sender.state == UIGestureRecognizerStateEnded)
	{
		senderState = YES;
	}
}

-(IBAction)handleRotationGesture:(UIGestureRecognizer *)sender
{
	if (senderState) {
		currentState = sender.view.transform;
		senderState = NO;
	}
	CGFloat rotation = [(UIRotationGestureRecognizer *)sender rotation];
	
	sender.view.transform = CGAffineTransformRotate(currentState, rotation);
	
	if (sender.state == UIGestureRecognizerStateEnded) {
		senderState = YES;
	}
}

-(IBAction)handlePanGesture:(UIGestureRecognizer *)sender
{
	if (senderState) {
		currentState = sender.view.transform;
		senderState = NO;
	}
	CGPoint translation = [(UIPanGestureRecognizer *)sender translationInView:imageView];
	
	sender.view.transform = CGAffineTransformTranslate(currentState, translation.x, translation.y);
	
	if (sender.state == UIGestureRecognizerStateEnded) {
		senderState = YES;
	}
}

The variables
CGPoint netTranslation;
CGFloat lastScaleFactor=1;
CGFloat netRotation;
are no longer needed since you get the information about the current state from the view.