iOS controlling UIView alpha behaviour for subviews

ios uiview alpha
Louis Boux picture Louis Boux · Dec 20, 2011 · Viewed 10.1k times · Source

In my example, I have 3 views: one red view containing two white views. I change the red container view's alpha to 0.3 and this happens (look at the image, the current result).

By seeing this, I can only assume (tell me if I'm wrong) that setting a view's alpha will also set all of its subviews' alphas. My question is : is there a way to simply tell the red view to act as a whole so that setting its alpha would give something that looks like the wanted result (in the image)?

results

This is what it looks like without any alpha :

enter image description here

Answer

Torsten picture Torsten · Sep 12, 2012

To elaborate on Mark's answer: If you set UIViewGroupOpacity in the Info.plist, it will change the behavior for all views in your app, if you are interested in only fixing the rendering of this particular view, you could also use this snippet:

redContainerView.layer.shouldRasterize = YES;
// No setting rasterizationScale, will cause blurry images on retina.
redContainerView.layer.rasterizationScale = [[UIScreen mainScreen] scale];

Related questions

Swift UIView background color opacity

I have a UIView with a UILabel in it. I want the UIView to have white background color, but with an opacity of 50%. The problem whith setting view.alpha = 0.5 is that the label will have an opacity of 50% as well, …

Read More
what's the difference between view's hidden = yes and alpha = 0.0f

I have a question about UIView, what's the difference between views hidden, alpha and opaque? The effect of setting view: hidden = yes and view.alpha = 0.0f is the same.

Read More
UIView alpha vs. UIColor alpha

I would like to know the difference between: Assigning my UIView a color with <1 alpha vs Assigning it a non-transparent color but giving the UIView a <1 alpha value. On the screenshot I have made two UIViews with two …

Read More