set UILabel's backgroundColor to nil is incorrect

Question

ouyang2013 OP

Created Mar ’21

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I create a UILabel object in viewDidLoad of UIViewController like below:

Code Block language-(void) viewDidLoad {
           [super viewDidLoad];
     
      UILabel *tt = [UILabel new];
       tt.text = @"abcd";
       tt.frame = CGRectMake(100, 100, 100, 50);
       tt.backgroundColor = nil;
       [self.view addSubview:tt];
}

I set the tt.backgroundColor is nil。 but when UILabel appeared, the backgroundColor is black ! and I adjust tt.text=@"abcd中"。 the backgroundColor is working and the color is clear。

PS:
Xcode version :11.3 (11C29)
iPhone11 simulator。

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Answer 1

Claude31 OP

Mar ’21

set the tt.backgroundColor is nil

This should results in a transparent background color.
Why nil and not .clear ?

I adjust tt.text=@"abcd中"

I tried (in Swift, no change). Still black if color is nil.
Where do you change the value ? In viewDidLoad ?

Reason may be that chinese characters are handled specially when drawing ?
See this: https://stackoverflow.com/questions/48056901/setting-nil-background-for-uilabel-for-iphone-application

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