在工具栏中添加自定义标签不起作用

我正在尝试在 UINavigationController 的工具栏中添加自定义标签。我遵循了这个问题的最佳答案question但它似乎对我不起作用，我不知道为什么。自定义文本不会出现，但按钮会出现。当我按下它时它会突出显示，但没有文字。

这是我的代码：

- (void) editToolbar{
    NSArray *toolbarItemsCopy = [self.toolbarItems copy];

    //set up the label
    self.notificationsLabel = [[UILabel alloc] initWithFrame:CGRectMake(0.0 , 11.0f, self.view.frame.size.width/0.25, 21.0f)];
    self.notificationsLabel.font = [UIFont fontWithName:@"Helvetica" size:20];
    self.notificationsLabel.backgroundColor = [UIColor clearColor];
    //self.notificationsLabel.textColor = [UIColor colorWithRed:157.0/255.0 green:157.0/255.0 blue:157.0/255.0 alpha:1.0];
    self.notificationsLabel.textColor = [UIColor blueColor];
    self.notificationsLabel.text = @"Checking server";
    self.notificationsLabel.textAlignment = UITextAlignmentCenter;

    //init a button with custom view using the label
    UIBarButtonItem *notif = [[UIBarButtonItem alloc] initWithCustomView:self.notificationsLabel];

    //add to the toolbarItems
    NSMutableArray *toolbarItemsMutableArray = [[NSMutableArray alloc]init];

    NSLog(@"toolbar %i", self.toolbarItems.count);

    //have to add the custom bar button item in a certain place in the toolbar, it should be the 3rd item
    for (int i = 0; i < toolbarItemsCopy.count; i++) {
        if (i == 2){                
            [toolbarItemsMutableArray addObject:notif];
        }
        NSLog(@"toolbar item %i %@", i,[toolbarItemsCopy objectAtIndex:i]);
        [toolbarItemsMutableArray addObject:[toolbarItemsCopy objectAtIndex:i]];
    }
    if (toolbarItemsCopy.count == 4){
    }else{
        //remove the previous custom label
        [toolbarItemsMutableArray removeObjectAtIndex:3];
    }
    self.toolbarItems = toolbarItemsMutableArray;
    //[self.navigationController.toolbar setItems: toolbarItemsMutableArray animated:YES];

    NSLog(@"toolbar %i", self.toolbarItems.count);
}https://stackoverflow.com/questions/ask

这是 NSLog 打印的内容：

Catalogue[361:10403] toolbar 4
Catalogue[361:10403] toolbar item 0 <UIBarButtonItem: 0x8a24650>
Catalogue[361:10403] toolbar item 1 <UIBarButtonItem: 0x8a36cd0>
Catalogue[361:10403] toolbar item 2 <UIBarButtonItem: 0x8a36d30>
Catalogue[361:10403] toolbar item 3 <UIBarButtonItem: 0x8a382f0>
Catalogue[361:10403] toolbar 5

这就是我解决它的方法：

我必须在函数内分配并初始化 UILabel，而不是使用 ivar。

UILabel *notificationsLabel = [[UILabel alloc] initWithFrame:CGRectMake(0.0 , 11.0f, self.view.frame.size.width, 21.0f)];
    notificationsLabel.font = [UIFont fontWithName:@"Helvetica" size:16];
    notificationsLabel.backgroundColor = [UIColor clearColor];
    //self.notificationsLabel.textColor = [UIColor colorWithRed:157.0/255.0 green:157.0/255.0 blue:157.0/255.0 alpha:1.0];
    notificationsLabel.textColor = [UIColor whiteColor];
    notificationsLabel.text = @"Checking server";
    notificationsLabel.textAlignment = UITextAlignmentCenter;

我确信这段代码会对您有所帮助。在牢记此代码的同时更改您的代码。我已经研究过这个并且效果很好，

UIToolbar *toolBar=[[UIToolbar alloc]initWithFrame:CGRectMake(0, 0, 320, 44)];
[self.view addSubview:toolBar];

UILabel *titleLbl = [[UILabel alloc] initWithFrame:CGRectMake(0.0 , 11.0f,     self.view.frame.size.width, 21.0f)];
[titleLbl setFont:[UIFont fontWithName:@"Helvetica-Bold" size:18]];
[titleLbl setBackgroundColor:[UIColor clearColor]];
[titleLbl setTextColor=[UIColor blueColor];
[titleLbl setText:@"Title"];
[titleLbl setTextAlignment:UITextAlignmentCenter];

UIBarButtonItem *button = [[UIBarButtonItem alloc] initWithCustomView:titleLbl];
NSArray *toolbarItemArr = [NSArray arrayWithObjects:button, nil];
[toolBar setItems:toolbarItemArr animated:YES];

为了更好地理解，您可以点击以下链接：UIToolBar类参考 and UIBarButtonItem 类参考