iphone - 在 UINavigationBar 中居中 UILabel

Question

我有一个 UINavigationBar 并设置了 leftBarButtonItem 和 rightBarButtonItem。左栏设置为:

UIButton *backButton = [UIButton buttonWithType:UIButtonTypeCustom];
        [backButton setImage:[UIImage imageNamed:@"back.png"] forState:UIControlStateNormal];
        UIBarButtonItem *myButton = [[[UIBarButtonItem alloc] initWithCustomView:backButton] autorelease];
        self.navigationItem.leftBarButtonItem = myButton;

右栏按钮设置为:

UIButton *doneBtn = [UIButton buttonWithType:UIButtonTypeCustom];
 UIImage *doneButtonImage = nil;
        doneButtonImage = [UIImage imageNamed:@"done.png"];
        [doneBtn setImage:doneButtonImage forState:UIControlStateNormal];
  doneBarButtonItem = [[UIBarButtonItem alloc] initWithCustomView:doneBtn];
    self.navigationItem.rightBarButtonItem = doneBarButtonItem;

back 的宽度是 23px，done 是 72px，所以它们不相等。现在的问题是我有一个标签，我想一直在中心..如果标签中的文本太长以至于它干扰了右栏按钮，我想剪辑文本。这是我的设置方式:

titleLabel = [[UILabel alloc] initWithFrame:CGRectZero];
    titleLabel.text = self.pageTitle; // Can't change
    titleLabel.adjustsFontSizeToFitWidth = YES;
    titleLabel.clipsToBounds = YES;
    titleLabel.numberOfLines = 1;
    titleLabel.font = [UIFont fontWithName:@"PTSans-Narrow" size:30.0]; 
    titleLabel.textColor = [UIColor colorWithWhite:0.6 alpha:1.0];
    titleLabel.backgroundColor = [UIColor yellowColor];
    titleLabel.autoresizingMask = UIViewAutoresizingFlexibleHeight;
    titleLabel.textAlignment = UITextAlignmentCenter;
    [titleLabel sizeToFit];
    titleLabel.frameHeight = self.navigationController.navigationBar.frameHeight;


 self.navigationItem.titleView = titleLabel;

但是这并没有使标题居中。我该怎么做呢？

Answer 1

我建议先算一下self.pageTitle的宽度然后相应地设置 titleLabel 的位置。我更喜欢这个:-

titleLabel = [[UILabel alloc] init];
titleLabel.text = self.pageTitle; // Can't change

**CGSize maximumTitleLabelSize = CGSizeMake(200,40);//Set maximum width that an self.pageTitle can have.
CGSize expectedLabelSize = [titleLabel.text titleLabel.font 
                                            constrainedToSize:maximumTitleLabelSize
                                                lineBreakMode:UILineBreakModeWordWrap];
//adjust the label the the new width.
CGRect newFrame = titleLabel.frame;
newFrame.size.width = expectedLabelSize.width;
titleLabel.size.width = newFrame.size.width;**    
if(titleLabel.size.width==100)
{
titleLabel.frame = cgRectMake(85,5,titleLabel.size.width,30);
}
else if(titleLabel.size.width==200)
{
titleLabel.frame = cgRectMake(36,5,titleLabel.size.width,30);
}

titleLabel.adjustsFontSizeToFitWidth = YES;
titleLabel.clipsToBounds = YES;
titleLabel.numberOfLines = 1;
titleLabel.font = [UIFont fontWithName:@"PTSans-Narrow" size:30.0]; 
titleLabel.textColor = [UIColor colorWithWhite:0.6 alpha:1.0];
titleLabel.backgroundColor = [UIColor yellowColor];
titleLabel.autoresizingMask = UIViewAutoresizingFlexibleHeight;
titleLabel.textAlignment = UITextAlignmentCenter;
[titleLabel sizeToFit];
titleLabel.frameHeight = self.navigationController.navigationBar.frameHeight;

self.navigationItem.titleView = titleLabel;

试试这个。它会对你有帮助。谢谢 :)