UINavigationBar中的活动指标

Question

我已经阅读了关于这个特定主题的一些答案，但由于某种原因，我的代码似乎不起作用。它位于UISearchBarDelegate委托方法-(void)searchBarSearchButtonClicked:(UISearchBar *)searchBar

中

UIActivityIndicatorView *activityIndicator = [[UIActivityIndicatorView alloc] initWithFrame:CGRectMake(0, 0, 20, 20)];
UIBarButtonItem *activity = [[UIBarButtonItem alloc] initWithCustomView:activityIndicator];
[[self navigationItem] setRightBarButtonItem:activity];
[activity release];
[activityIndicator startAnimating];

非常感谢任何帮助或建议！

Answer 1

我认为UIActivityIndicatorView的指定初始值设定项为initWithActivityIndicatorStyle:。尝试像这样创建activityIndicator。

UIActivityIndicatorView *activityIndicator = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleWhite];

Answer 2

试试这个

UIView *view_actviti = [[UIView alloc] initWithFrame:CGRectMake(6,310,59,32)];
    UIActivityIndicatorView *act =[[UIActivityIndicatorView alloc] init];
    act.frame=CGRectMake(0, 0, 30, 30);
    UIBarButtonItem *actItem = [[[UIBarButtonItem alloc] initWithCustomView:view_actviti] autorelease];
    [view_actviti addSubview:act];
    self.navigationItem.rightBarButtonItem = actItem;
    [act startAnimating];

Answer 3

试试这个：

UIActivityIndicatorView *activityIndicator = 
    [[UIActivityIndicatorView alloc] initWithFrame:CGRectMake(0, 0, 20, 20)];
UIBarButtonItem * barButton = 
    [[UIBarButtonItem alloc] initWithCustomView:activityIndicator];

[[self navigationItem] setRightBarButtonItem:barButton];

[barButton release];
[activityIndicator startAnimating];

还可以使用它来停止和删除activityIndi​​cator：

[[self navigationItem] setLRightBarButtonItem:nil];
[activityIndicator stopAnimating];
[activityIndicator release];