以编程方式添加的笔尖文件自定义视图是半透明的

Question

I have a storyboard. I loaded a custom UIView from nib file to one of my UIViewController programatically.

Opaque and alpha values are checked and 1 respectively.

Even though the UIView is semi-transparent.

What would be the problem here?

Answer 1

A subview's maximum alpha value is the alpha value of its parent view.

The alpha of the child view is effectively the product of the two alpha values. A child with alpha of 1 on a parent with alpha of 0.5 will effectively have a 0.5 alpha.

If you need to put an opaque subview on a translucent or transparent parent view, there are two approaches.

The first approach is to move the would-be parent view to a subview as well so that both views are subviews of the same parent view. That parent view is just a clear-background view that acts as a container but has an alpha of 1.

The second approach is to make the parent view transparent or translucent while leaving its alpha at 1. This is done by setting its colors to have non-1 alpha values. For example:

[UIColor colorWithRed:1 green:0 blue:0 alpha: 0.3];

Rather than just:

someView.alpha = 0.3;