UIActivityIndicatorView *indicator = nil;    indicator = (UIActivityIndicatorView *)[self.view viewWithTag:103];        if (indicator == nil) {                //初始化:        UIActivityIndicatorView *indicator = [[UIActivityIndicatorView alloc] initWithFrame:CGRectMake(0, 0, 80, 80)];                indicator.tag = 103;                //设置显示样式,见UIActivityIndicatorViewStyle的定义        indicator.activityIndicatorViewStyle = UIActivityIndicatorViewStyleWhiteLarge;                        //设置背景色        indicator.backgroundColor = [UIColor blackColor];                //设置背景透明        indicator.alpha = 0.5;                //设置背景为圆角矩形        indicator.layer.cornerRadius = 6;        indicator.layer.masksToBounds = YES;        //设置显示位置        [indicator setCenter:CGPointMake(self.view.frame.size.width / 2.0, self.view.frame.size.height / 2.0)];                //开始显示Loading动画        [indicator startAnimating];                [self.view addSubview:indicator];                [indicator release];    }    //开始显示Loading动画    [indicator startAnimating];

// 停止动画

    UIActivityIndicatorView *indicator = (UIActivityIndicatorView *)[self.view viewWithTag:103];

    //停止显示Loading动画

    [indicator stopAnimating];