我正在尝试将 UIActivityIndicatorView 放在黑色背景上,但是我看不到它在旋转。为什么是这样?这是我所拥有的:
UIActivityIndicatorView *indicator = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleGray];
[indicator setCenter:CGPointMake(0, 15)];
[indicator setBackgroundColor:[UIColor blackColor]];
[indicator startAnimating];
[indicator hidesWhenStopped];