到目前为止,我自己的最佳答案是设置tableHeaderView
一次并强制布局通过。这允许测量所需的尺寸,然后我用它来设置标题的框架。并且,正如常见的那样tableHeaderView
s,我必须再次设置它才能应用更改。
- (void)viewDidLoad
{
[super viewDidLoad];
self.header = [[SCAMessageView alloc] init];
self.header.titleLabel.text = @"Warning";
self.header.subtitleLabel.text = @"This is a message with enough text to span multiple lines. This text is set at runtime and might be short or long.";
//set the tableHeaderView so that the required height can be determined
self.tableView.tableHeaderView = self.header;
[self.header setNeedsLayout];
[self.header layoutIfNeeded];
CGFloat height = [self.header systemLayoutSizeFittingSize:UILayoutFittingCompressedSize].height;
//update the header's frame and set it again
CGRect headerFrame = self.header.frame;
headerFrame.size.height = height;
self.header.frame = headerFrame;
self.tableView.tableHeaderView = self.header;
}
对于多行标签,这还依赖于自定义视图(本例中的消息视图)设置preferredMaxLayoutWidth
每个:
- (void)layoutSubviews
{
[super layoutSubviews];
self.titleLabel.preferredMaxLayoutWidth = CGRectGetWidth(self.titleLabel.frame);
self.subtitleLabel.preferredMaxLayoutWidth = CGRectGetWidth(self.subtitleLabel.frame);
}
2015 年 1 月更新
不幸的是,这似乎仍然是必要的。这是布局过程的快速版本:
tableView.tableHeaderView = header
header.setNeedsLayout()
header.layoutIfNeeded()
let height = header.systemLayoutSizeFittingSize(UILayoutFittingCompressedSize).height
var frame = header.frame
frame.size.height = height
header.frame = frame
tableView.tableHeaderView = header
我发现将其移至 UITableView 的扩展中很有用:
extension UITableView {
//set the tableHeaderView so that the required height can be determined, update the header's frame and set it again
func setAndLayoutTableHeaderView(header: UIView) {
self.tableHeaderView = header
header.setNeedsLayout()
header.layoutIfNeeded()
let height = header.systemLayoutSizeFittingSize(UILayoutFittingCompressedSize).height
var frame = header.frame
frame.size.height = height
header.frame = frame
self.tableHeaderView = header
}
}
Usage:
let header = SCAMessageView()
header.titleLabel.text = "Warning"
header.subtitleLabel.text = "Warning message here."
tableView.setAndLayoutTableHeaderView(header)