#import <UIKit/UIKit.h>

//加入头文件

#import "MBProgressHUD.h"

@interface RootViewController : UIViewController

<MBProgressHUDDelegate> {

    MBProgressHUD *HUD;

}

@end

#import "RootViewController.h"

//加入头文件

#import <unistd.h>

@interface RootViewController ()

@end

@implementation RootViewController

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil

{

    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];

    if (self) {

        // Custom initialization

    }

    return self;

}

- (void)viewDidLoad

{

    [super viewDidLoad];

    // Do any additional setup after loading the view.

    //转动3s后停止

    HUD = [[MBProgressHUD alloc] initWithView:self.navigationController.view];

    HUD.delegate = self;

    [HUD showWhileExecuting:@selector(myTask) onTarget:self withObject:nil animated:YES];

    [self.navigationController.view addSubview:HUD];

}

//等待3s

- (void)myTask {

    sleep(3);

}