UIActivityIndicatorView的使用

用法一：只显示不停旋转的进度滚轮指示器。
//显示进度滚轮指示器
-(void)showWaiting {

progressInd=[[UIActivityIndicatorView alloc]initWithActivityIndicatorStyle:
UIActivityIndicatorViewStyleWhiteLarge];
progressInd.center=CGPointMake(self.view.center.x,240);
[self.navigationController.view addSubview:progressInd];
[progressInd startAnimating];
}
//消除滚动轮指示器
-(void)hideWaiting
{
[progressInd stopAnimating];
}

用法二：带有半透明背景的进度轮指示器。

//显示进度滚轮指示器
-(void)showWaiting:(UIView *)parent {

int width = 32, height = 32;

CGRect frame = CGRectMake(100, 200, 110, 70) ;//[parent frame]; //[[UIScreen mainScreen] applicationFrame];
int x = frame.size.width;
int y = frame.size.height;

frame = CGRectMake((x - width) / 2, (y - height) / 2, width, height);
UIActivityIndicatorView* progressInd = [[UIActivityIndicatorView alloc]initWithFrame:frame];
[progressInd startAnimating];
progressInd.activityIndicatorViewStyle = UIActivityIndicatorViewStyleWhiteLarge;

frame = CGRectMake((x - 70)/2, (y - height) / 2 + height, 80, 20);
UILabel *waitingLable = [[UILabel alloc] initWithFrame:frame];
waitingLable.text = @"Loading...";
waitingLable.textColor = [UIColor whiteColor];
waitingLable.font = [UIFont systemFontOfSize:15];
waitingLable.backgroundColor = [UIColor clearColor];

frame =  CGRectMake(100, 200, 110, 70) ;//[parent frame];
UIView *theView = [[UIView alloc] initWithFrame:frame];
theView.backgroundColor = [UIColor blackColor];
theView.alpha = 0.7;

[theView addSubview:progressInd];

[theView addSubview:waitingLable];

[progressInd release];

[waitingLable release];

[theView setTag:9999];
[parent addSubview:theView];
[theView release];

}

//消除滚动轮指示器
-(void)hideWaiting
{
[[self.view viewWithTag:9999] removeFromSuperview];
}

另一种实现
UIActivityIndicatorView *activityView = [[[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleWhiteLarge] autorelease];
activityView.frame = CGRectMake(139.0f-18.0f, 50.0f, 37.0f, 37.0f);
[self.loadingView addSubview:activityView];
[activityView startAnimating];
activityView.center = self.loadingView.center;

[activityView stopAnimating];