Autolayout约束冲突

试图创建一个视图UITextField,并UILabel超越它.以下代码有什么问题？

- (UIView *)tableHeaderView{
    NSArray *constraints;
    UIView *view = [[UIView alloc]initWithFrame:(CGRect){0,0,self.view.frame.size.width, 88}];

    UITextField *tf = [[UITextField alloc]init];
    tf.borderStyle = UITextBorderStyleRoundedRect;
    tf.text = _filter.name;
    [view addSubview:tf];

    UILabel *titleLabel = [[UILabel alloc] init];
    titleLabel.textAlignment = NSTextAlignmentCenter;
    titleLabel.translatesAutoresizingMaskIntoConstraints = NO;
    titleLabel.text = [NSString stringWithFormat:NSLocalizedString(@"Found results: %d", nil), _filter.resultsCount];
    [view addSubview:titleLabel];

    constraints = [NSLayoutConstraint constraintsWithVisualFormat:@"|-[titleLabel]-|" options:0 metrics:nil views:NSDictionaryOfVariableBindings(titleLabel)];
    [view addConstraints:constraints];

    constraints = [NSLayoutConstraint constraintsWithVisualFormat:@"|-[tf]-|" options:0 metrics:nil views:NSDictionaryOfVariableBindings(tf)];
    [view addConstraints:constraints];

    constraints = [NSLayoutConstraint constraintsWithVisualFormat:@"V:|[titleLabel]-8-[tf]|" options:0 metrics:nil views:NSDictionaryOfVariableBindings(titleLabel, tf)];
    [view addConstraints:constraints];
}

错误信息:

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) 
(
    "",
    "",
    ""
)

Will attempt to recover by breaking constraint 


Break on objc_exception_throw to catch this in the debugger.
The methods in the UIConstraintBasedLayoutDebugging category on UIView listed in  may also be helpful.
2014-07-14 14:01:30.216 DossierPolice[4724:60b] 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) 
(
    "",
    "",
    "",
    ""
)

Will attempt to recover by breaking constraint 


Break on objc_exception_throw to catch this in the debugger.
The methods in the UIConstraintBasedLayoutDebugging category on UIView listed in  may also be helpful.
2014-07-14 14:01:30.217 DossierPolice[4724:60b] 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) 
(
    "",
    "",
    "",
    ""
)

Will attempt to recover by breaking constraint 


Break on objc_exception_throw to catch this in the debugger.
The methods in the UIConstraintBasedLayoutDebugging category on UIView listed in  may also be helpful.

Jernej Stras.. 11

你忘了把它设置translatesAutoresizingMaskIntoConstraints为NO开启tf.此属性可防止布局引擎自动将旧样式自动调整掩码转换为约束,这就是错误的原因.