restrict UIPanGestureRecognizer in UIView Mask - ios

Question

I am masking UIView(240 * 240) in tringular shape using UIBezierPath as follows:
path = [UIBezierPath new];
[path moveToPoint:(CGPoint){0, 240}];
[path addLineToPoint:(CGPoint){120,0}];
[path addLineToPoint:(CGPoint){240,240}];
[path addLineToPoint:(CGPoint){0,240}];
[path closePath];
CAShapeLayer *mask = [CAShapeLayer new];
mask.frame = self.viewShape.bounds;
mask.path = path.CGPath;
self.viewShape.layer.mask = mask;
In above Image triangular area is mask. Now I have image of "Coca-Cola" which is to be moved only in triangular mask. So, for that I have apply UIPanGestureRecognizer to UIIMageView and restrict its frame in following way.
- (void)handlePanGesture:(UIPanGestureRecognizer *)gestureRecognizer
{
CGPoint touchLocation = [gestureRecognizer locationInView:self.viewShape];
CGRect boundsRect;
BOOL isInside = [path containsPoint:CGPointMake(self.innerView.center.x, self.innerView.center.y)];
NSLog(#"value:%d",isInside);
if (isInside) {
NSLog(#"inside");
self.innerView.center = touchLocation;
}else{
NSLog(#"outside");
}
}
My above if condition executes successfully but when control goes into else condition I am not able to drag back my ImageView inside mask frame.
So, My question is when else block(outside) called I should be able to drag imageView again inside the Mask's frame.
How can I achieve this?

Answer 1

saving reference to last center of imageview is a way to achieve this.
in your customView;
CGPoint lastValidCenter; //initially it is the center of imageview;
and in the code
NSLog(#"value:%d",isInside);
if (isInside) {
NSLog(#"inside");
self.innerView.center = touchLocation;
lastValidCenter = self.innerView.center;
}else{
NSLog(#"outside");
self.innerView.center = lastValidCenter;
}

Answer 2

There is a problem in your calculation. What you need to do is to check the top-left and top-right corner of the UIImageView for contains point with UIBezirePath instance.
It is so because when the image will move both of these corners are the ones which will try to go out first. So just put a check and you'll get your desired output.
BOOL isInside = [path containsPoint:CGPointMake(CGRectGetMinX(self.innerView.bounds), CGRectGetMinY(self.innerView.bounds))];
isInside = isInside || [path containsPoint:CGPointMake(CGRectGetMaxX(self.innerView.bounds), CGRectGetMinY(self.innerView.bounds))];
if (isInside) {
//Move your UIImageView
}
else {
//Don't move
}

Answer 3

I modified some portion of Meth's code. The code is as follows:
self.innerView.center = touchLocation;
BOOL isInside = [path containsPoint:CGPointMake(self.innerView.center.x, self.innerView.center.y)];
if (isInside) {
NSLog(#"inside");
self.innerView.center = touchLocation;
lastValidCenter = self.innerView.center;
}else{
NSLog(#"outside");
self.innerView.center = lastValidCenter;
}