用处： 菊花图
仅有两个方法：[aiv startAnimating]
[aiv stopAnimating]
-(void)viewDidLoad
{
[super viewDidLoad];
self.aiv = [[UIActivityIndicatorView alloc]initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleWhiteLarge];
self.aiv.frame = CGRectMake(20,20,100,100);
[self.view addSubView:self.aiv];
self.startBtn = [[UIButton alloc]buttonWithType:UIButtonTypeRoundedRect];
self.startBtn.frame = CGRectMake(20,100,100,50);
[self.startBtn setTitle:@"start" forState:UIControlStateNormal];
[self addTarget:self action:@selector(start:) forControlEvents:UIControlEventTouchUpInside];
[self.view addSubView:self.startBtn];
}
-(IBAction)start:(id)sender
{
//UIButton* btn = (UIButton*)sender;
[self.aiv startAnimation];
}