UIActivityIndicatorView的两种形式

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;
    CGRectframe =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 = [[UILabelalloc] initWithFrame:frame];
    waitingLable.text = @"Loading...";
    waitingLable.textColor = [UIColorwhiteColor];
    waitingLable.font = [UIFontsystemFontOfSize:15];
    waitingLable.backgroundColor = [UIColor clearColor];
 
    frame =  CGRectMake(100, 200, 110, 70) ;//[parent frame];
    UIView *theView = [[UIViewalloc] 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];
}