我正在为iPhone 4设置一些具体的限制，当应用程序在这个设备上运行时。在对齐和其他方面，一切看起来都很好。
但是，我得到了一个错误，我所有的约束，试图恢复他们通过打破约束。
这个方法在我的viewDidLoad中被调用当它检测到它是否是iPhone 4
- (void) addConstraints {
// removing automatic system constraints
[self.view removeConstraints:self.view.constraints];
[self.view setTranslatesAutoresizingMaskIntoConstraints:NO];
NSDictionary *views = NSDictionaryOfVariableBindings(appBackground, myCustomer, myItemDetails, myItemQuantity, myItemPrice, myNext, myBtn); // UIImageView, UITextField, UIButton
for (UIView *view in [views allValues]) {
view.translatesAutoresizingMaskIntoConstraints = NO;
}
NSDictionary *metrics = @{@"width": @210.0, @"height": @42.0, @"verticalSpacing": @34};
NSArray *constraints = [NSLayoutConstraint constraintsWithVisualFormat:@"V:|[appBackground]|"
options:0
metrics:nil
views:views];
constraints = [constraints arrayByAddingObjectsFromArray:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|[appBackground]|"
options:0
metrics:nil
views:views]];
constraints = [constraints arrayByAddingObjectsFromArray:[NSLayoutConstraint constraintsWithVisualFormat:@"V:|-(85)-[myCustomer(==height)]-(verticalSpacing)-[myItemDetails(==height)]-(verticalSpacing)-[myItemQuantity(==height)]-(verticalSpacing)-[myItemPrice(==height)]-(18)-[myNext(==35)]-(71.5)-[myBtn(==50)]-(7.5)-|"
options:0
metrics:metrics
views:views]];
constraints = [constraints arrayByAddingObjectsFromArray:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|-50-[myCustomer(==width)]-|"
options:0
metrics:metrics
views:views]];
constraints = [constraints arrayByAddingObjectsFromArray:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|-50-[myItemDetails(==width)]-|"
options:0
metrics:metrics
views:views]];
constraints = [constraints arrayByAddingObjectsFromArray:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|-50-[myItemQuantity(==width)]-|"
options:0
metrics:metrics
views:views]];
constraints = [constraints arrayByAddingObjectsFromArray:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|-50-[myItemPrice(==width)]-|"
options:0
metrics:metrics
views:views]];
constraints = [constraints arrayByAddingObjectsFromArray:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|-78-[myNext(==173)]-|"
options:0
metrics:metrics
views:views]];
constraints = [constraints arrayByAddingObjectsFromArray:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|-11.5-[myBtn(==54)]-|"
options:0
metrics:metrics
views:views]];
[self.view addConstraints:constraints];
}
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)
(
"<NSLayoutConstraint:0xb8282f0 H:|-(50)-[UITextField:0xb823fc0] (Names: '|':UIView:0xb82f360 )>",
"<NSLayoutConstraint:0xb828320 H:[UITextField:0xb823fc0(210)]>",
"<NSLayoutConstraint:0xb82be10 H:[UITextField:0xb823fc0]-(NSSpace(20))-| (Names: '|':UIView:0xb82f360 )>",
"<NSLayoutConstraint:0xb82d3d0 H:|-(78)-[UIButton:0xb82ad50] (Names: '|':UIView:0xb82f360 )>",
"<NSLayoutConstraint:0xb82d420 H:[UIButton:0xb82ad50(173)]>",
"<NSLayoutConstraint:0xb82d450 H:[UIButton:0xb82ad50]-(NSSpace(20))-| (Names: '|':UIView:0xb82f360 )>"
)
Will attempt to recover by breaking constraint
<NSLayoutConstraint:0xb82d450 H:[UIButton:0xb82ad50]-(NSSpace(20))-| (Names: '|':UIView:0xb82f360 )>
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.
2014-08-03 14:03:29.239 iReceipt[2886:607] 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:0xb8282f0 H:|-(50)-[UITextField:0xb823fc0] (Names: '|':UIView:0xb82f360 )>",
"<NSLayoutConstraint:0xb828320 H:[UITextField:0xb823fc0(210)]>",
"<NSLayoutConstraint:0xb82be10 H:[UITextField:0xb823fc0]-(NSSpace(20))-| (Names: '|':UIView:0xb82f360 )>",
"<NSLayoutConstraint:0xb82d480 H:|-(11.5)-[UIButton:0xb820120] (Names: '|':UIView:0xb82f360 )>",
"<NSLayoutConstraint:0xb82e390 H:[UIButton:0xb820120(54)]>",
"<NSLayoutConstraint:0xb82e3c0 H:[UIButton:0xb820120]-(NSSpace(20))-| (Names: '|':UIView:0xb82f360 )>"
)
Will attempt to recover by breaking constraint
<NSLayoutConstraint:0xb82e3c0 H:[UIButton:0xb820120]-(NSSpace(20))-| (Names: '|':UIView:0xb82f360 )>
这三个约束:
"<NSLayoutConstraint:0xb8282f0 H:|-(50)-[UITextField:0xb823fc0] (Names: '|':UIView:0xb82f360 )>",
"<NSLayoutConstraint:0xb828320 H:[UITextField:0xb823fc0(210)]>",
"<NSLayoutConstraint:0xb82be10 H:[UITextField:0xb823fc0]-(NSSpace(20))-| (Names: '|':UIView:0xb82f360 )>",
规定父视图宽度为50 + 210 + 20 == 280点。
这三个约束:
"<NSLayoutConstraint:0xb82d3d0 H:|-(78)-[UIButton:0xb82ad50] (Names: '|':UIView:0xb82f360 )>",
"<NSLayoutConstraint:0xb82d420 H:[UIButton:0xb82ad50(173)]>",
"<NSLayoutConstraint:0xb82d450 H:[UIButton:0xb82ad50]-(NSSpace(20))-| (Names: '|':UIView:0xb82f360 )>"
规定同一个父视图的宽度为78 + 173 + 20 == 271点。
显然，这些不可能同时为真。你得决定你到底想在这里发生什么。我们不能读懂你的想法，UIKit也不能。
通常，你不会在按钮上设置宽度限制;您让它使用其固有大小，并为内容拥抱和抗压缩提供适当的优先级。此外，您可能不希望在按钮的任何一侧设置硬间距。要么让这个间距不受约束地变化，这样按钮就可以保持其固有大小，降低该约束的优先级，这样它是可选的，要么设置一个不等式，这样你就有了最小间距，而不是精确间距。
你限制你的观点太多了。例如，你必须留下左边距、宽度和右边距灵活的一个，并让自动布局引擎拉伸它。
一个不带数字的破折号表示默认距离，为20像素。因此，如果你去掉
上的尾随约束@"H:|-78-[myNext(==173)]-|"
@"H:|-11.5-[myBtn(==54)]-|"
@"H:|-78-[myNext(==173)]"
@"H:|-11.5-[myBtn(==54)]"
布局引擎会拉伸按钮的右距，使其适合包含视图。当然，还有其他方法可以放松这些限制，这取决于您的设计目标。
就我个人而言，我不再使用自动布局的标准API了。我使用库purellayout，它将自动布局抽象得非常好!