UIActivityView.m

#define activityViewTag                0x98751234

@interface UIView (UIViewUtils) 

- (void)showActivityViewAtCenter;
- (void)hideActivityViewAtCenter;
- (UIActivityIndicatorView*)createActivityViewAtCenter:(UIActivityIndicatorViewStyle)style;
- (UIActivityIndicatorView*)getActivityViewAtCenter;

@end

#import "UIViewUtils.h"


@implementation UIView (UIViewUtils)

- (UIActivityIndicatorView*)createActivityViewAtCenter:(UIActivityIndicatorViewStyle)style
{
    static int size = 30;
    
    UIActivityIndicatorView* activityView = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:style];
    activityView.frame = CGRectMake([UIScreen mainScreen].bounds.size.width/2 - size/2, [UIScreen mainScreen].bounds.size.height/2 - size*2, size, size);
    activityView.tag = activityViewTag;
    [self addSubview:activityView];
    [activityView release];
    
    return activityView;
}

- (UIActivityIndicatorView*)getActivityViewAtCenter
{
    UIView* view = [self viewWithTag:activityViewTag];
    if (view != nil && [view isKindOfClass:[UIActivityIndicatorView class]]){
        return (UIActivityIndicatorView*)view;
    }
    else {
        return nil;
    }
}

- (void)showActivityViewAtCenter
{
    UIActivityIndicatorView* activityView = [self getActivityViewAtCenter];
    if (activityView == nil){
        activityView = [self createActivityViewAtCenter:UIActivityIndicatorViewStyleWhite];
    }

    [activityView startAnimating];
}

- (void)hideActivityViewAtCenter
{
    UIActivityIndicatorView* activityView = [self getActivityViewAtCenter];
    if (activityView != nil){
        [activityView stopAnimating];
    }        
}


@end