UILabel sizeToFit 不适用于自动布局 ios6

Please note在大多数情况下，Matt's solution的效果与预期相符.但如果这对你不起作用，请进一步阅读.

要使标签自动调整高度，需要执行以下操作:

1. 设置标签的布局约束
2. 将高度约束设置为低优先级.它应该低于ContentCompressionResistancePriority
3. 设置行数=0
4. 将ContentHuggingPriority设置为高于标签的高度优先级
5. 为标签设置首选项MaxLayoutWidth.标签使用该值来计算其高度

例如:

self.descriptionLabel = [[UILabel alloc] init];
self.descriptionLabel.numberOfLines = 0;
self.descriptionLabel.lineBreakMode = NSLineBreakByWordWrapping;
self.descriptionLabel.preferredMaxLayoutWidth = 200;

[self.descriptionLabel setContentHuggingPriority:UILayoutPriorityRequired forAxis:UILayoutConstraintAxisVertical];
[self.descriptionLabel setContentCompressionResistancePriority:UILayoutPriorityRequired forAxis:UILayoutConstraintAxisVertical];
[self.descriptionLabel setTranslatesAutoresizingMaskIntoConstraints:NO];
[self addSubview:self.descriptionLabel];

NSArray* constrs = [NSLayoutConstraint constraintsWithVisualFormat:@"|-8-[descriptionLabel_]-8-|" options:0 metrics:nil views:NSDictionaryOfVariableBindings(descriptionLabel_)];
[self addConstraints:constrs];
[self addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:|-8-[descriptionLabel_]" options:0 metrics:nil views:NSDictionaryOfVariableBindings(descriptionLabel_)]];
[self.descriptionLabel addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:[descriptionLabel_(220@300)]" options:0 metrics:nil views:NSDictionaryOfVariableBindings(descriptionLabel_)]];

Using Interface Builder

1. 设置四个约束条件.高度约束是强制性的.

2. 然后转到标签的属性判断器并将行数设置为0.

3. Go to the label's size inspector and increase vertical ContentHuggingPriority and vertical ContentCompressionResistancePriority.
   

4. Select and edit height constraint.
   

5. And decrease height constraint priority.
   

Enjoy. :)个