iOS UIView 的alpha属性

当透明度的值设置为0的时候，相当于hidden

 

 

alpha
 Property
The view’s alpha value.

Declaration
SWIFT
var alpha: CGFloat
OBJECTIVE-C
@property(nonatomic) CGFloat alpha
Discussion
The value of this property is a floating-point number in the range 0.0 to 1.0, where 0.0 represents totally transparent and 1.0 represents totally opaque. This value affects only the current view and does not affect any of its embedded subviews.

Changes to this property can be animated.

Availability
Available in iOS 2.0 and later.