参考：http://stackoverflow.com/questions/18729220/uialertview-addsubview-in-ios7

1、SignInViewController.h

#import <UIKit/UIKit.h>

@interface SignInViewController : UIViewController<UIAlertViewDelegate>{
    UIAlertView *remoteAlertView;
}
@end

2、SignInViewController.m

#import "SignInViewController.h"

@interface SignIniewController ()

@end

@implementation SignInViewController


-(void)dealloc{
    if (remoteAlertView) {
        [remoteAlertView release];
    }
    [super dealloc];
}


// 方法内：
    // 远程webservice方法
    RemoteLogic *remoteLogic = [[RemoteLogic alloc] init];
    // 启动动画
    [self remoteAnimation:@"正在获取服务器时间, 请稍候..."];
    // 异步加载数据
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
        // 获取webservice数据
        delegate.serverTime = remoteLogic.getServerTime;
        dispatch_async(dispatch_get_main_queue(), ^{
            // 关闭动画
            [remoteAlertView dismissWithClickedButtonIndex:0 animated:YES];
            // 获取webservice数据后操作 do something
        });
    });



#pragma mark - Animation
-(void)remoteAnimation:(NSString *)message{

    if (remoteAlertView) {
        [remoteAlertView release];
    }
    remoteAlertView =  [[UIAlertView alloc] initWithTitle:@"提示" message:message delegate:self cancelButtonTitle:nil otherButtonTitles:nil, nil ];
    UIActivityIndicatorView *aiView = [[UIActivityIndicatorView alloc] initWithFrame:CGRectMake(125.0, 80.0, 30.0, 30.0)];
    aiView.activityIndicatorViewStyle = UIActivityIndicatorViewStyleWhiteLarge;
    //check if os version is 7 or above. ios7.0及以上UIAlertView弃用了addSubview方法
    if ([[[UIDevice currentDevice] systemVersion] compare:@"7.0"] != NSOrderedAscending) {
        [remoteAlertView setValue:aiView forKey:@"accessoryView"];
    }else{
        [remoteAlertView addSubview:aiView];
    }
    [remoteAlertView show];
    [aiView startAnimating];
    [aiView release];
}