爲什麼alpha不變？我想backgroundView是可見的，而負載網絡負載

Question

1. 列表項

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

你還沒有添加子視圖backgroundViewLoad，只是改變這一點：

[self.view addSubview:backgroundLoad]; 

這樣：

[self.view addSubview: backgroundViewLoad];