add a transparent view into a translucent view

Question

I want a view like the picture attached, the full view's background is translucent, and the view in green frame is transparent. I tried addSubview and set subview's alpha but it is not worked.

Answer 1

You can override your drawRect method. Fill it all with translucent, then fill in the transparent part with clear color:

- (void)drawRect:(CGRect)rect {
    // fill it all with translucent
    [yourTranslucentUIColor setFill];
    UIRectFill( rect );


    CGRect yourMiddleHoleRect = CGRectMake(* calculate your rect here);

    [[UIColor clearColor] setFill];
    UIRectFill( yourMiddleHoleRect );
}

I think this will give you a cleaner result than other options.

You could even draw in those green frame indicators here if you wanted.

Answer 2

我相信实现此目标的唯一方法是在透明视图周围添加4个半透明视图。

Answer 3

first you have to add the translucent view over the background view by CGContextDrawImage . Then use CGContextSetBlendMode to clear the portion.

Refer the below project to achieve this.

https://github.com/akopanev/iOS-Scratch-n-See