tableHeaderView位于第一个单元格的顶部

Question

我正在尝试以编程方式创建一个tableview,在tableHeaderView中有一个搜索栏.由于某种原因,搜索栏出现在第一个单元格的顶部.

我正在使用Masonry来构建约束.

有人能指出我做错了什么.

- (void)setupViews {

...
    self.tableView = [[UITableView alloc] initWithFrame:CGRectZero];
    [self.view addSubview:self.tableView];

    self.searchBar = [[UISearchBar alloc] initWithFrame:CGRectZero];
    self.tableView.tableHeaderView = self.searchBar;
...
}

- (void)updateViewConstraints {

    [self.searchBar mas_updateConstraints:^(MASConstraintMaker *make) {
        make.width.equalTo(self.view);
        make.height.equalTo(@(44));
    }];

    [self.tableView mas_updateConstraints:^(MASConstraintMaker *make) {
        make.self.top.equalTo(self.view);
        make.self.bottom.equalTo(self.toolbar.mas_top);
        make.width.equalTo(self.view);
    }];
...
}

您可以在此处看到标题与单元格处于同一级别.

Answer 1

感谢您的帮助,我在GitHub上找到了一个要点,其中谈到了使用AutoLayout更改tableViewHeader的大小:

https://gist.github.com/andreacremaschi/833829c80367d751cb83

- (void) sizeHeaderToFit {
    UIView *headerView = self.tableHeaderView;

    [headerView setNeedsLayout];
    [headerView layoutIfNeeded];
    CGFloat height = [headerView systemLayoutSizeFittingSize:UILayoutFittingCompressedSize].height;

    headerView.frame = ({
        CGRect headerFrame = headerView.frame;
        headerFrame.size.height = height;
        headerFrame;
    });

    self.tableHeaderView = headerView;
}

如果我在updateViewConstraints期间调用此方法,那么它可以工作.

但是,我并不完全理解它.

Answer 2

在Swift 3.0中使用Extension

extension UITableView {

    func setTableHeaderView(headerView: UIView?) {
        // set the headerView
        tableHeaderView = headerView

        // check if the passed view is nil
        guard let headerView = headerView else { return }

        // check if the tableHeaderView superview view is nil just to avoid
        // to use the force unwrapping later. In case it fail something really
        // wrong happened
        guard let tableHeaderViewSuperview = tableHeaderView?.superview else {
            assertionFailure("This should not be reached!")
            return
        }

        // force updated layout
        headerView.setNeedsLayout()
        headerView.layoutIfNeeded()

        // set tableHeaderView width
        tableHeaderViewSuperview.addConstraint(headerView.widthAnchor.constraint(equalTo: tableHeaderViewSuperview.widthAnchor, multiplier: 1.0))

        // set tableHeaderView height
        let height = headerView.systemLayoutSizeFitting(UILayoutFittingCompressedSize).height
        tableHeaderViewSuperview.addConstraint(headerView.heightAnchor.constraint(equalToConstant: height))
    }

    func setTableFooterView(footerView: UIView?) {
        // set the footerView
        tableFooterView = footerView

        // check if the passed view is nil
        guard let footerView = footerView else { return }

        // check if the tableFooterView superview view is nil just to avoid
        // to use the force unwrapping later. In case it fail something really
        // wrong happened
        guard let tableFooterViewSuperview = tableFooterView?.superview else {
            assertionFailure("This should not be reached!")
            return
        }

        // force updated layout
        footerView.setNeedsLayout()
        footerView.layoutIfNeeded()

        // set tableFooterView width
        tableFooterViewSuperview.addConstraint(footerView.widthAnchor.constraint(equalTo: tableFooterViewSuperview.widthAnchor, multiplier: 1.0))

        // set tableFooterView height
        let height = footerView.systemLayoutSizeFitting(UILayoutFittingCompressedSize).height
        tableFooterViewSuperview.addConstraint(footerView.heightAnchor.constraint(equalToConstant: height))
    }
}