如何根据iOS中的内容设置UILabel的框架？

Question

我正在创建一个应用程序，我想根据文本设置自定义UIView的框架，然后我在UIView上添加UILabel。但有时我使用下面的代码在运行时没有得到正确的框架：

strImageBottomText = @"The next-generation entertainment for first web view just bottom of slide show image.";

CGSize maximumSize = CGSizeMake(320, 9999);

CGFloat cellHeight = 0;

CGSize titleLabelHeightSize = CGSizeZero;


if ([strImageBottomText respondsToSelector: @selector(boundingRectWithSize:options:attributes:context:)] == YES) {
    titleLabelHeightSize = [strImageBottomText boundingRectWithSize: maximumSize options: NSStringDrawingUsesLineFragmentOrigin
                                                          attributes: @{ NSFontAttributeName: [UIFont fontWithName:@"Cabin-SemiBold" size:15.0f] } context: nil].size;
} else {
    titleLabelHeightSize = [strImageBottomText sizeWithFont: [UIFont fontWithName:@"Cabin-SemiBold" size:15.0f]
                                           constrainedToSize:maximumSize
                                               lineBreakMode:NSLineBreakByWordWrapping];
}

  cellHeight += titleLabelHeightSize.height > 24 ? titleLabelHeightSize.height : 24;

    CGRect frame = CGRectMake(0, slideshow.frame.size.height, 320, cellHeight + 30);
    UIView *customView = [[UIView alloc] initWithFrame:frame];
    customView.backgroundColor = [UIColor colorWithRed:0/255.0 green:151/255.0 blue:207/255.0 alpha:1.0];

    UILabel *sectionTitle = [[UILabel alloc] init];

    sectionTitle.frame = CGRectMake(0, 0, 280, cellHeight);
    sectionTitle.text = strImageBottomText;
    sectionTitle.lineBreakMode = NSLineBreakByWordWrapping;
    sectionTitle.textAlignment = NSTextAlignmentCenter;
    sectionTitle.numberOfLines = 0;
    [sectionTitle sizeToFit];

    sectionTitle.font = [UIFont fontWithName:@"Cabin-SemiBold" size:15.0f];
    sectionTitle.backgroundColor = [UIColor clearColor];
    sectionTitle.textColor = [UIColor whiteColor];

    [customView addSubview:sectionTitle];

    [self.view addSubview:customView]; 

我想要输出如下截图：

你可以帮助我，我的代码在哪里做错了吗？谢谢