为什么alpha不变？我想backgroundView是可见的，而负载网络负载

Question

1. 列表项

UIView *backgroundViewLoad = [[UIView alloc] initWithFrame:self.view.frame]; 
[self.view addSubview:backgroundLoad]; 

UIActivityIndicate *activity = [[UIActivityIndicate alloc] init]; 
activity.center = backgroundViewLoad.center; 
[backgroundViewLoad addSubview:activity]; 

[backgroundViewLoad setAlpha:1]; 

//load Network Data 

[UIView setAlpha:0]; 

Answer 1

你还没有添加子视图backgroundViewLoad，只是改变这一点：

[self.view addSubview:backgroundLoad]; 

这样：

[self.view addSubview: backgroundViewLoad];