我之前尝试过在 IB 中使用 AutoLayout 约束，我了解它们是如何工作的，并且它们需要明确等...
但是，当您有多个视图时，它会变得有点复杂并且容易中断。
所以，我刚刚阅读了一篇关于一个人有同样问题并使用 ASCII 代码来创建约束的博客。
我有一个带有自定义 UITableViewCell 的 UITableView，它具有基于内容量的动态大小。自动布局的完美候选者。
所以，我尝试了几种方法，现在我已经减少了内容，以便单元格中只有一个标签。
如果标签用边框填充单元格，我想要什么。
即标准尺寸从单元格的每个边缘指向。
我已经这样做了......
- (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;
}
但是当显示单元格时，标签位于左上角，就像我用来初始化它的 CGRect 一样，我得到了关于约束的大量错误......
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 )>
而且我不知道从哪里开始调试它。约束绝对是最小的，但仍然完全失败。
有人能指出我如何让这个约束发挥作用的正确方向吗？