在状态菜单打开时更改状态菜单项的标题会导致我的 Cocoa 应用程序崩溃

Question

好的，这个问题变得越来越复杂，所以我将完全从头开始，然后重新开始。我设法创建了一个非常基本的 Cocoa 应用程序来演示我的问题。

那么问题来了：

在线程内部，我在应用程序的状态栏菜单中设置菜单项的标题。 当应用程序尝试更改菜单项的标题并且我打开了菜单时，大多数情况下它可以正常工作，但有时它会使应用程序崩溃。

这里是示例应用的完整代码：

MenubarFailAppDelegate.h

#import <Cocoa/Cocoa.h>

@interface MenubarFailAppDelegate : NSObject <NSApplicationDelegate> {  
    IBOutlet NSMenu *statusMenu;
    NSStatusItem *statusItem;
    IBOutlet NSMenuItem *menuItem;

    int currentDelay;
}

@end

MenubarFailAppDelegate.m

#import "MenubarFailAppDelegate.h"

@implementation MenubarFailAppDelegate

- (id)init {

    self = [super init];

    if (self != nil)
    {
        currentDelay = 0;
    }

    return self;    

}

- (void)awakeFromNib {

    // Create status menu item
    statusItem = [[[NSStatusBar systemStatusBar] statusItemWithLength:NSVariableStatusItemLength] retain];
    [statusItem setMenu:statusMenu];
    [statusItem setTitle:@"Fail"];
    [statusItem setHighlightMode:YES];

    currentDelay = 3;
    [NSThread detachNewThreadSelector:@selector(changeStatusItemTitleLoopThread)
                             toTarget:self
                           withObject:nil]; 

}

- (void)changeStatusItemTitleLoopThread {

    NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];

    while (currentDelay > 0) {
        // Sleep for one second
        NSDate *future = [NSDate dateWithTimeIntervalSinceNow:1];
        [NSThread sleepUntilDate:future];

        // Decrement current delay
        currentDelay--;
    }

    NSLog(@"Setting menu item title");
    [menuItem setTitle:@"lol cat"];

    [pool release];

}

@end

这是在记录“设置菜单项标题”后程序崩溃时出现的崩溃报告：

#0  0x7fff870f74c0 in HIStandardMenuView::FetchItemCache
#1  0x7fff870f6345 in HIStandardMenuView::GetOptimalSizeSelf
#2  0x7fff870f612b in HIView::GetOptimalSizeWithLimitsSelf
#3  0x7fff870f5fb5 in HIView::SendGetOptimalBounds
#4  0x7fff870f5edb in HIView::GetOptimalSize
#5  0x7fff870f5dc1 in HandleCalculateMenuSize
#6  0x7fff8709b600 in MenuData::EventHandler
#7  0x7fff87093997 in DispatchEventToHandlers
#8  0x7fff87092ee6 in SendEventToEventTargetInternal
#9  0x7fff87092d57 in SendEventToEventTargetWithOptions
#10 0x7fff870f5b7a in _CalcMenuSizeOnDevice
#11 0x7fff8710811c in RecalcAndResizeMenu
#12 0x7fff8720efa6 in ResizeMenuArray
#13 0x7fff8720eff6 in ResizeOpenMenus
#14 0x7fff87093997 in DispatchEventToHandlers
#15 0x7fff87092ee6 in SendEventToEventTargetInternal
#16 0x7fff87092d57 in SendEventToEventTargetWithOptions
#17 0x7fff870c012a in ToolboxEventDispatcherHandler
#18 0x7fff87093d91 in DispatchEventToHandlers
#19 0x7fff87092ee6 in SendEventToEventTargetInternal
#20 0x7fff870b0ba9 in SendEventToEventTarget
#21 0x7fff870bdeed in AcquireEventFromQueue
#22 0x7fff870ba737 in ReceiveNextEventCommon
#23 0x7fff87104db8 in IsUserStillTracking
#24 0x7fff870f1a48 in TrackMenuCommon
#25 0x7fff87215ac9 in PopUpMenuSelectCore
#26 0x7fff87215dce in _HandlePopUpMenuSelection7
#27 0x7fff864d71c9 in _NSSLMPopUpCarbonMenu3
#28 0x7fff86706e71 in -[NSStatusBarButtonCell trackMouse:inRect:ofView:untilMouseUp:]
#29 0x7fff8640a4b5 in -[NSControl mouseDown:]
#30 0x7fff86324763 in -[NSWindow sendEvent:]
#31 0x7fff86707c10 in -[NSStatusBarWindow sendEvent:]
#32 0x7fff86259ee2 in -[NSApplication sendEvent:]
#33 0x7fff861f0922 in -[NSApplication run]
#34 0x7fff861e95f8 in NSApplicationMain
#35 0x100001499 in main at main.m:13

Answer 1

通常不建议在线程代码中更改 UI。您需要更改线程中的菜单标题是否有令人信服的理由？我建议将实际更改分派回主线程。您可以在后台线程中进行所需的任何计算，并使用 performSelectorOnMainThread 对标题进行实际更改。