更改 navigationItem 的 barButtonItem

Question

我有一个 UIViewController。我使用 navigationItem 的 rightBarButtonItem 作为“重新加载按钮”。当按下重新加载按钮时，我使用 leftBarButtonItem 在应用程序正在处理要重新加载的数据时显示活动指示器。到这里为止一切都很好。
这是一些代码：

- (void)initSpinner {
    activityIndicator = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleWhite];
    activityButton = [[UIBarButtonItem alloc] initWithCustomView: activityIndicator];
    self.navigationItem.leftBarButtonItem = activityButton;
}

- (void)spinBegin {
    [activityIndicator startAnimating];
}

- (void)spinEnd {
    [activityIndicator stopAnimating];
}
- (void)viewDidLoad {
     [self initSpinner];
     [super viewDidLoad];
    //more stuff going on here....
}
-(void) loadView{
    self.navigationItem.rightBarButtonItem = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemRefresh target:self action:@selector(refreshFeeds:)];
}

现在我被要求稍微改变逻辑。
rightBarButtonItem 保持原样。 leftBarButtonItem 仍然在那里显示活动指示器，但是当没有处理时，它应该显示另一个按钮，按下时将显示一个新视图（用于某些信息）。
所以我做了这些改变：

- (void)initSpinner {
    activityIndicator = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleWhite];
    activityButton = [[UIBarButtonItem alloc] initWithCustomView: activityIndicator];
}

- (void)spinBegin {
    self.navigationItem.leftBarButtonItem = activityButton;
    [activityIndicator startAnimating];
}

- (void)spinEnd {
    [activityIndicator stopAnimating];
     self.navigationItem.leftBarButtonItem =infoBarButton; //= [[[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemRefresh target:self action:@selector(refreshFeeds:)] autorelease];
}
-(void) loadView{
    self.navigationItem.rightBarButtonItem = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemRefresh target:self action:@selector(refreshFeeds:)];

    if (infoBarButton == nil){
        UIImage *buttonImage = [UIImage imageNamed:@"info.png"];
        UIButton *aButton = [UIButton buttonWithType:UIButtonTypeCustom];
        [aButton setImage:buttonImage forState:UIControlStateNormal];
        aButton.frame = CGRectMake(0.0, 0.0, 25, 25);

        // Initialize the UIBarButtonItem
        infoBarButton = [[UIBarButtonItem alloc] initWithCustomView:aButton];

        // Set the Target and Action for aButton
        [aButton addTarget:self action:@selector(showInfo:) forControlEvents:UIControlEventTouchUpInside];


    }
    self.navigationItem.leftBarButtonItem = infoBarButton;
}

虽然它似乎正在工作（信息按钮在那里，当我按下“重新加载”时，activityIndi​​cator 将占据它的位置，直到处理完成），我在调试器控制台中得到以下信息：

__NSAutoreleaseNoPool(): Object 0x15ef30 of class UINavigationItem autoreleased with no pool in place - just leaking
 __NSAutoreleaseNoPool(): Object 0x1abd90 of class UIBarButtonItem autoreleased with no pool in place - just leaking
__NSAutoreleaseNoPool(): Object 0x1acb20 of class UIButton autoreleased with no pool in place - just leaking
__NSAutoreleaseNoPool(): Object 0x15ef30 of class UINavigationItem autoreleased with no pool in place - just leaking
__NSAutoreleaseNoPool(): Object 0x1ad030 of class UIActivityIndicatorView autoreleased with no pool in place - just leaking
__NSAutoreleaseNoPool(): Object 0x1ad030 of class UIActivityIndicatorView autoreleased with no pool in place - just leaking
__NSAutoreleaseNoPool(): Object 0x1a8c40 of class UINavigationButton autoreleased with no pool in place - just leaking
Object 0x941c of class NSCFString autoreleased with no pool in place - just leaking
//MORE similar messages following...

我做错了什么？我希望有人可以提供帮助...
提前致谢。

Answer 1

我的猜测是您正在后台线程中运行“重新加载”任务，当它完成时，您从后台线程调用 spinEnd。如果后台线程没有适当的自动释放池，您将看到这些警告。

由于您应该只从主线程调用UIKit 方法，因此您应该通过以下方式调用spinEnd：

[self performSelectorOnMainThread:@selector(spinEnd) withObject:nil waitUntilDone:NO];

Answer 2

您的属性是retained 吗？你正在做和alloc] init...，但在将它们分配给你的属性后没有释放它们。我建议查看Memory Management Guide