應用NSLayoutConstraints到UIView子類

Question

我已經使用自動版式約束IB之前試過，我瞭解他們的工作，他們必須明確等等

但是當你有超過一對夫婦的意見更它變得有點複雜並且往往會破裂。

所以，我剛剛讀了一篇關於一個有相同問題的人的博客，並使用ASCII代碼來創建約束。

我有一個UITableView與自定義的UITableViewCell具有基於內容量的動態大小。自動佈局的完美人選。

所以，我嘗試了幾種方法來做到這一點，現在我已經減少了內容，以便在單元格中只有一個標籤。

我想如果標籤填充單元格周圍有一個邊框。

即標準尺寸從單元的每個邊緣進入。

我已經做了這樣的...

- (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; 
} 

但在顯示單元當標籤是在左上角酷似的CGRect我用來初始化它，我得到這個負載的約束錯誤...

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)> 

我不知道從哪裏開始調試這個。約束是絕對最小的，但仍然完全失敗。

有人能指出我如何得到這個約束的正確方向嗎？

Answer 1

行後

_label = [[UILabel alloc] initWithFrame:CGRectMake(0, 0, 10, 10)]; 

添加

[_label setTranslatesAutoresizingMaskIntoConstraints:NO]; 

默認情況下，autoresizingmask也變成了限制，這與您所設定的限制衝突，使得它ambigious

的docs are here：setTranslatesAutoresizingMaskIntoConstraints