我之前尝试过在IB中使用自动布局约束，并且理解了它们的工作原理以及需要避免歧义等问题。
但是当你有多个视图时，情况会变得有些复杂，往往会出现问题。
所以，我刚刚读到一个关于一个人遇到同样问题并使用ASCII代码创建约束的博客。
我有一个UITableView，其中包含一个根据内容量动态调整大小的自定义UITableViewCell。这是自动布局的完美对象。
因此，我尝试了几种方法，现在我缩小了内容，只在单元格中放置了一个标签。
我想让标签填充整个单元格，并围绕其添加边框。
也就是说，标准大小点从每个单元格的边缘内部计算。
我是这样做的...
- (id)initWithStyle:(UITableViewCellStyle)style reuseIdentifier:(NSString *)reuseIdentifier
{
self = [super initWithStyle:style reuseIdentifier:reuseIdentifier];
if (self) {
_label = [[UILabel alloc] initWithFrame:CGRectMake(0, 0, 10, 10)];
_label.textColor = [UIColor colorWithWhite:0.53 alpha:1.0];
_label.backgroundColor = [UIColor yellowColor];
[self addSubview:_label];
NSDictionary *views = NSDictionaryOfVariableBindings(_label);
[self addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:|-[_label]-|"
options:0
metrics:nil
views:views]];
[self addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"|-[_label]-|"
options:0
metrics:nil
views:views]];
self.backgroundView = [[UIView alloc] initWithFrame:CGRectZero];
self.backgroundColor = [UIColor clearColor];
}
return self;
}
但是当单元格被显示时，标签位于左上角，与我用来初始化它的CGRect完全相同，并且会出现关于约束的许多错误...
Unable to simultaneously satisfy constraints.
Probably at least one of the constraints in the following list is one you don't want. Try this: (1) look at each constraint and try to figure out which you don't expect; (2) find the code that added the unwanted constraint or constraints and fix it. (Note: If you're seeing NSAutoresizingMaskLayoutConstraints that you don't understand, refer to the documentation for the UIView property translatesAutoresizingMaskIntoConstraints)
(
"<NSAutoresizingMaskLayoutConstraint:0x1f859e40 h=--& v=--& UILabel:0x1f864a00.midX == + 5>",
"<NSLayoutConstraint:0x1f86a4f0 H:|-(NSSpace(20))-[UILabel:0x1f864a00] (Names: '|':MyCell:0x1f857740 )>"
)
Will attempt to recover by breaking constraint
<NSLayoutConstraint:0x1f86a4f0 H:|-(NSSpace(20))-[UILabel:0x1f864a00] (Names: '|':MyCell:0x1f857740 )>
Break on objc_exception_throw to catch this in the debugger.
The methods in the UIConstraintBasedLayoutDebugging category on UIView listed in <UIKit/UIView.h> may also be helpful.
2013-03-07 11:56:14.841 unasys[13082:907] Unable to simultaneously satisfy constraints.
Probably at least one of the constraints in the following list is one you don't want. Try this: (1) look at each constraint and try to figure out which you don't expect; (2) find the code that added the unwanted constraint or constraints and fix it. (Note: If you're seeing NSAutoresizingMaskLayoutConstraints that you don't understand, refer to the documentation for the UIView property translatesAutoresizingMaskIntoConstraints)
(
"<NSLayoutConstraint:0x1f85f7b0 V:|-(NSSpace(20))-[UILabel:0x1f864a00] (Names: '|':MyCell:0x1f857740 )>",
"<NSAutoresizingMaskLayoutConstraint:0x1f859ec0 h=--& v=--& UILabel:0x1f864a00.midY == + 5>"
)
Will attempt to recover by breaking constraint
<NSLayoutConstraint:0x1f85f7b0 V:|-(NSSpace(20))-[UILabel:0x1f864a00] (Names: '|':MyCell:0x1f857740 )>
Break on objc_exception_throw to catch this in the debugger.
The methods in the UIConstraintBasedLayoutDebugging category on UIView listed in <UIKit/UIView.h> may also be helpful.
2013-03-07 11:56:14.854 unasys[13082:907] Unable to simultaneously satisfy constraints.
Probably at least one of the constraints in the following list is one you don't want. Try this: (1) look at each constraint and try to figure out which you don't expect; (2) find the code that added the unwanted constraint or constraints and fix it. (Note: If you're seeing NSAutoresizingMaskLayoutConstraints that you don't understand, refer to the documentation for the UIView property translatesAutoresizingMaskIntoConstraints)
(
"<NSLayoutConstraint:0x1f86a540 H:[UILabel:0x1f864a00]-(NSSpace(20))-| (Names: '|':MyCell:0x1f857740 )>",
"<NSAutoresizingMaskLayoutConstraint:0x1f859e40 h=--& v=--& UILabel:0x1f864a00.midX == + 5>",
"<NSAutoresizingMaskLayoutConstraint:0x1f859e80 h=--& v=--& H:[UILabel:0x1f864a00(10)]>",
"<NSAutoresizingMaskLayoutConstraint:0x1ed8e150 h=--& v=--& H:[MyCell:0x1f857740(320)]>"
)
Will attempt to recover by breaking constraint
<NSLayoutConstraint:0x1f86a540 H:[UILabel:0x1f864a00]-(NSSpace(20))-| (Names: '|':MyCell:0x1f857740 )>
Break on objc_exception_throw to catch this in the debugger.
The methods in the UIConstraintBasedLayoutDebugging category on UIView listed in <UIKit/UIView.h> may also be helpful.
2013-03-07 11:56:14.858 unasys[13082:907] Unable to simultaneously satisfy constraints.
Probably at least one of the constraints in the following list is one you don't want. Try this: (1) look at each constraint and try to figure out which you don't expect; (2) find the code that added the unwanted constraint or constraints and fix it. (Note: If you're seeing NSAutoresizingMaskLayoutConstraints that you don't understand, refer to the documentation for the UIView property translatesAutoresizingMaskIntoConstraints)
(
"<NSAutoresizingMaskLayoutConstraint:0x1eda7260 h=--& v=--& V:[MyCell:0x1f857740(143)]>",
"<NSAutoresizingMaskLayoutConstraint:0x1f859f00 h=--& v=--& V:[UILabel:0x1f864a00(10)]>",
"<NSLayoutConstraint:0x1f85f870 V:[UILabel:0x1f864a00]-(NSSpace(20))-| (Names: '|':MyCell:0x1f857740 )>",
"<NSAutoresizingMaskLayoutConstraint:0x1f859ec0 h=--& v=--& UILabel:0x1f864a00.midY == + 5>"
)
Will attempt to recover by breaking constraint
<NSLayoutConstraint:0x1f85f870 V:[UILabel:0x1f864a00]-(NSSpace(20))-| (Names: '|':MyCell:0x1f857740 )>
我不知道从哪里开始调试它。虽然约束条件非常简单，但却完全失败了。
有人能告诉我如何让这个约束条件生效吗？
NSAutoresizingMaskLayoutConstraint，并且不知道它为什么存在，那么您可能忘记了在某个地方关闭translatesAutoresizingMaskIntoConstraints。 - iain