UILabel没有在iOS8中显示子视图

Question

目前，我为背景制作了一个标签，并在UILabel上添加了UIButton。它在iOS 7中显示，但在iOS 8中它没有显示。如果我用UIView替换UILabel那么它工作正常。

如果我使用此代码在iOS 8中使用UILabel用于显示UILabel和子视图UIButton

 UILabel *downLabel = [[UILabel alloc]init];
downLabel.frame    = CGRectMake(0, SCREEN_HEIGHT*0.92, SCREEN_WIDTH,SCREEN_HEIGHT*0.08 );  
[downLabel setBackgroundColor:[UIColor colorWithRed:(66/255.f) green:(67/255.f) blue:(63/255.f)  alpha:1]];
downLabel.userInteractionEnabled = YES;
[self.view addSubview:downLabel];

UIButton *downbtnobj  = [[UIButton alloc]initWithFrame:CGRectMake(SCREEN_WIDTH*0.68,downLabel.frame.size.height/10,SCREEN_WIDTH*0.30,downLabel.frame.size.height/1.25)];

UIImage *btndownImage = [UIImage imageNamed:@"img 3.png"];
[downbtnobj setImage:btndownImage forState:UIControlStateNormal];
[downbtnobj addTarget:self action:@selector(bulletInButtonClicked) forControlEvents:UIControlEventTouchUpInside];
[downLabel addSubview:downbtnobj];

现在您只能看到UILabel正在显示，但UILabel上没有显示按钮。

另一个如果我用UIView替换UILabel然后它显示完美。

    UIView *downLabel = [[UIView alloc]init];
downLabel.frame    = CGRectMake(0, SCREEN_HEIGHT*0.92, SCREEN_WIDTH,SCREEN_HEIGHT*0.08 );
[downLabel setBackgroundColor:[UIColor colorWithRed:(66/255.f) green:(67/255.f) blue:(63/255.f)  alpha:1]];
downLabel.userInteractionEnabled = YES;
[self.view addSubview:downLabel];

 UIButton *downbtnobj  = [[UIButton alloc]initWithFrame:CGRectMake(SCREEN_WIDTH*0.68,downLabel.frame.size.height/10,SCREEN_WIDTH*0.30,downLabel.frame.size.height/1.25)];
  UIImage *btndownImage = [UIImage imageNamed:@"img 3.png"];
[downbtnobj setImage:btndownImage forState:UIControlStateNormal];
[downbtnobj addTarget:self action:@selector(bulletInButtonClicked) forControlEvents:UIControlEventTouchUpInside];
[downLabel addSubview:downbtnobj];

在这段代码中你可以看到我只用UIView替换UILabel。现在按钮显示。

可以帮助解决为什么子视图无法在iOS8中的UILabel上显示

Answer 1

目前还不清楚iOS 8中的标签有什么不同，但如果你在标签上调用layoutIfNeeded，则可以解决问题（需要在设置框架后），

UILabel *downLabel = [[UILabel alloc]init];
downLabel.frame    = CGRectMake(0, SCREEN_HEIGHT*0.92, SCREEN_WIDTH,SCREEN_HEIGHT*0.08 );  
[downLabel layoutIfNeeded];
[downLabel setBackgroundColor:[UIColor colorWithRed:(66/255.f) green:(67/255.f) blue:(63/255.f)  alpha:1]];
downLabel.userInteractionEnabled = YES;
[self.view addSubview:downLabel];

编辑后：

我还发现如果您设置文本（在创建标签后的任何时间），则会出现按钮。

Answer 2

非常简单的方法，你需要在UILabel上设置clipsToBounds

downLabel.clipsToBounds = YES;