当iphone在loading比较多数据时，怎么样让窗口显示等待图标

[[CCDirector sharedDirector]UIActivityIndicatorView *activityIndicator= [[UIActivityIndicatorView alloc] 
                            initWithFrame:CGRectMake(0.0f, 0.0f, 32.0f,32.0f)];
 
[activityIndicator setActivityIndicatorViewStyle:UIActivityIndicatorViewStyleGray]; 
[contentView addSubview:activityIndicator]; 

[activityIndicator startAnimating];

        //loading data.....

[activityIndicator stopAnimating];

[activityIndicator release];