旋转进度--UiActivityIndicatorView

#pragma mark - 加载视图- (void)viewDidLoad {    [super viewDidLoad];    //    self.view.backgroundColor = [UIColor redColor];    self.activityIndicatorView = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleGray];    //指定frame属性    self.activityIndicatorView.frame = CGRectMake(20, 20, 100, 100);    [self.view addSubview:self.activityIndicatorView];        //初始化两个按钮    self.btnStart = [UIButton buttonWithType:UIButtonTypeRoundedRect];    self.btnStart.frame = CGRectMake(20, 100, 100, 50);    //设置标题    [self.btnStart setTitle:@"start" forState:UIControlStateNormal];    //添加开启事件方法    [self.btnStart addTarget:self action:@selector(start:) forControlEvents:UIControlEventTouchUpInside];    [self.view addSubview:self.btnStart];        //初始化两个按钮    self.btnFinish = [UIButton buttonWithType:UIButtonTypeRoundedRect];    self.btnFinish.frame = CGRectMake(20, 180, 100, 50);    //设置标题    [self.btnFinish setTitle:@"Finish" forState:UIControlStateNormal];    //添加开启事件方法    [self.btnFinish addTarget:self action:@selector(finish:) forControlEvents:UIControlEventTouchUpInside];    [self.view addSubview:self.btnFinish];     }#pragma mark - 开启动画-(IBAction)start:(id)sender{    [self.activityIndicatorView startAnimating];}#pragma mark - 关闭动画-(IBAction)finish:(id)sender{    [self.activityIndicatorView stopAnimating];}