如何调整超级视图的大小以适应所有具有自动布局的子视图?

The correct API to use is UIView systemLayoutSizeFittingSize:, passing either UILayoutFittingCompressedSize or UILayoutFittingExpandedSize.

对于使用自动布局的普通 UIView，只要您的约束是正确的，这应该可以工作.如果您想在 UITableViewCell 上使用它(例如确定行高)，那么您应该针对您的单元格 contentView 调用它并获取高度.

For a normal UIView using autolayout this should just work as long as your constraints are correct. If you want to use it on a UITableViewCell (to determine row height for example) then you should call it against your cell contentView and grab the height.

如果您的视图中有一个或多个 UILabel 是多行的，则需要进一步考虑.对于这些，必须正确设置 preferredMaxLayoutWidth 属性，以便标签提供正确的 intrinsicContentSize，这将用于 systemLayoutSizeFittingSize 的 计算.

Further considerations exist if you have one or more UILabel's in your view that are multiline. For these it is imperitive that the preferredMaxLayoutWidth property be set correctly such that the label provides a correct intrinsicContentSize, which will be used in systemLayoutSizeFittingSize's calculation.

根据要求，为表格视图单元格添加高度计算示例

使用自动布局计算表格单元格的高度不是很高效，但确实很方便，尤其是在您的单元格布局复杂的情况下.

Using autolayout for table-cell height calculation isn't super efficient but it sure is convenient, especially if you have a cell that has a complex layout.

如上所述，如果您使用多行 UILabel，则必须将 preferredMaxLayoutWidth 同步到标签宽度.我使用自定义 UILabel 子类来执行此操作:

As I said above, if you're using a multiline UILabel it's imperative to sync the preferredMaxLayoutWidth to the label width. I use a custom UILabel subclass to do this:

@implementation TSLabel

- (void) layoutSubviews
{
    [super layoutSubviews];

    if ( self.numberOfLines == 0 )
    {
        if ( self.preferredMaxLayoutWidth != self.frame.size.width )
        {
            self.preferredMaxLayoutWidth = self.frame.size.width;
            [self setNeedsUpdateConstraints];
        }
    }
}

- (CGSize) intrinsicContentSize
{
    CGSize s = [super intrinsicContentSize];

    if ( self.numberOfLines == 0 )
    {
        // found out that sometimes intrinsicContentSize is 1pt too short!
        s.height += 1;
    }

    return s;
}

@end

这是一个人为的 UITableViewController 子类，展示了 heightForRowAtIndexPath:

Here's a contrived UITableViewController subclass demonstrating heightForRowAtIndexPath:

#import "TSTableViewController.h"
#import "TSTableViewCell.h"

@implementation TSTableViewController

- (NSString*) cellText
{
    return @"Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.";
}

#pragma mark - Table view data source

- (NSInteger) numberOfSectionsInTableView: (UITableView *) tableView
{
    return 1;
}

- (NSInteger) tableView: (UITableView *)tableView numberOfRowsInSection: (NSInteger) section
{
    return 1;
}

- (CGFloat) tableView: (UITableView *) tableView heightForRowAtIndexPath: (NSIndexPath *) indexPath
{
    static TSTableViewCell *sizingCell;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{

        sizingCell = (TSTableViewCell*)[tableView dequeueReusableCellWithIdentifier: @"TSTableViewCell"];
    });

    // configure the cell
    sizingCell.text = self.cellText;

    // force layout
    [sizingCell setNeedsLayout];
    [sizingCell layoutIfNeeded];

    // get the fitting size
    CGSize s = [sizingCell.contentView systemLayoutSizeFittingSize: UILayoutFittingCompressedSize];
    NSLog( @"fittingSize: %@", NSStringFromCGSize( s ));

    return s.height;
}

- (UITableViewCell *) tableView: (UITableView *) tableView cellForRowAtIndexPath: (NSIndexPath *) indexPath
{
    TSTableViewCell *cell = (TSTableViewCell*)[tableView dequeueReusableCellWithIdentifier: @"TSTableViewCell" ];

    cell.text = self.cellText;

    return cell;
}

@end

一个简单的自定义单元格:

A simple custom cell:

#import "TSTableViewCell.h"
#import "TSLabel.h"

@implementation TSTableViewCell
{
    IBOutlet TSLabel* _label;
}

- (void) setText: (NSString *) text
{
    _label.text = text;
}

@end

还有，这是故事板中定义的约束的图片.请注意，标签上没有高度/宽度限制 - 这些是从标签的 intrinsicContentSize 推断出来的:

And, here's a picture of the constraints defined in the Storyboard. Note that there are no height/width constraints on the label - those are inferred from the label's intrinsicContentSize:

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