@interface UIProgressHUD : NSObject

- (void) show: (BOOL) yesOrNo;

- (UIProgressHUD *) initWithWindow: (UIView *) window;

@end

@interface HelloController : UIViewController

@end

@implementation HelloController

- (void) killHUD: (id) aHUD

{

[aHUD show:NO];

[aHUD release];

}

- (void) presentSheet

{

id HUD = [[UIProgressHUD alloc] initWithWindow:self.view];

    [HUD setText:@"Downloading File. Please wait."];

    [HUD show:YES];

    [self performSelector:@selector(killHUD:) withObject:HUD afterDelay:5.0];

}

调用 presentSheet