How to make a transparent cut on UIVisualEffectView? - ios

Question

In my app , I made a see through UIView by subclassing simple UIView's. However, If I try to do the same using UIVisualEffectView, I am not able to do it.
Here is what I am able to do using normal UIView:
When I use the UIVisualEffectView in place of green UIView,I cannot see the see through UIView , even though see through UIView is added to the UIVisualEffectView as subview.
Code:
- (void)drawRect:(CGRect)rect { //this is same for the UIVIew and for the UIVisualEffectView
[super drawRect:rect];
CGContextRef context = UIGraphicsGetCurrentContext();
// Clear any existing drawing on this view
// Remove this if the hole never changes on redraws of the UIView
CGContextClearRect(context, self.bounds);
// Create a path around the entire view
UIBezierPath *clipPath = [UIBezierPath bezierPathWithRect:self.bounds];
// Your transparent window. This is for reference, but set this either as a property of the class or some other way
CGRect transparentFrame;
// Add the transparent window
UIBezierPath *path = [UIBezierPath bezierPathWithRoundedRect:transparentFrame cornerRadius:5.0f];
[clipPath appendPath:path];
// NOTE: If you want to add more holes, simply create another UIBezierPath and call [clipPath appendPath:anotherPath];
// This sets the algorithm used to determine what gets filled and what doesn't
clipPath.usesEvenOddFillRule = YES;
// Add the clipping to the graphics context
[clipPath addClip];
// set your color
UIColor *tintColor = [UIColor greenColor];
// (optional) set transparency alpha
CGContextSetAlpha(context, 0.7f);
// tell the color to be a fill color
[tintColor setFill];
// fill the path
[clipPath fill];
}
Question: Why this didn't work with UIVisualEffectView ?

Answer 1

Add following global variables in your ViewController.h file-
CAShapeLayer *fillLayer;
UIVisualEffectView *overlayView;
Add following methods in your ViewController.m file-
-(void)addOverlay:(CGRect)rect{
float x = rect.origin.x;
float y = rect.origin.y;
UIBezierPath *path = [UIBezierPath bezierPathWithRoundedRect:CGRectMake(0, 0, self.view.bounds.size.width, self.view.bounds.size.height) cornerRadius:0];
UIBezierPath *circlePath = [UIBezierPath bezierPathWithRoundedRect:CGRectMake(x, y, rect.size.width, rect.size.height) cornerRadius:5];
[path appendPath:circlePath];
[path setUsesEvenOddFillRule:YES];
[self removeOverlay];
overlayView = [[UIVisualEffectView alloc] initWithFrame:CGRectMake(0, 0, self.view.bounds.size.width, self.view.bounds.size.height+64)];
overlayView.backgroundColor = [UIColor clearColor];
[self.view addSubview:overlayView];
fillLayer = [CAShapeLayer layer];
fillLayer.path = path.CGPath;
fillLayer.fillRule = kCAFillRuleEvenOdd;
fillLayer.fillColor = [UIColor colorWithRed:78/255.0 green:103/255.0 blue:135/255.0 alpha:1.0].CGColor;
fillLayer.opacity = 0.85;
[[UIApplication sharedApplication].keyWindow.layer addSublayer:fillLayer];
}
-(void)removeOverlay{
[overlayView removeFromSuperview];
[fillLayer removeFromSuperlayer];
}
and call it as -
[self addOverlay:rect];