iOS 以编程方式生成的 View 具有导致与自动布局冲突的隐藏约束

Question

这是一个链接到 View Controller 的非常基本的 View 。该 View 有一个带有编码约束的 UILabel。代码实际上运行正确，但控制台正在注册约束冲突，我无法弄清楚是代码的哪一部分造成了冲突。

LocationView.m文件

#import "LocationView.h"

@implementation LocationView

@synthesize locationTitle;    

- (id)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:frame];
    if (self) {
        // Initialization code
        [self setBackgroundColor: [UIColor blueColor]];
        locationTitle = [[UILabel alloc]init];
        [locationTitle setTranslatesAutoresizingMaskIntoConstraints:NO];
        locationTitle.backgroundColor = [UIColor whiteColor];
        [self addSubview:locationTitle];

        NSDictionary *viewLocationTitle = NSDictionaryOfVariableBindings(locationTitle);

        [self addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|[locationTitle]|"
                                                                     options:0
                                                                     metrics:0
                                                                       views:viewLocationTitle]];

        [self addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:|-[locationTitle(50)]|"
                                                                     options:0
                                                                     metrics:0
                                                                       views:viewLocationTitle]];

- (void)updateConstraints {
    [super updateConstraints]; 
}
@end

控制台错误

Unable to simultaneously satisfy constraints. 
(
    "<NSLayoutConstraint:0x109510990 V:|-(NSSpace(20))-[UILabel:0x10950b660]   (Names: '|':LocationView:0x10950acc0 )>",
    "<NSLayoutConstraint:0x109510c10 V:[UILabel:0x10950b660(50)]>",
    "<NSLayoutConstraint:0x109510c60 V:[UILabel:0x10950b660]-(0)-|   (Names: '|':LocationView:0x10950acc0 )>",
    "<NSAutoresizingMaskLayoutConstraint:0x108f3ae00 h=--& v=--& V:[LocationView:0x10950acc0(568)]>"
)

Answer 1

我想您是说您希望它的高度为 50 点并固定到 super View 的顶部和底部(您在标签前后添加了 |)。

尝试将垂直约束更改为

@"V:|-[locationTitle(50)]"

或者您可以为其中一个约束添加较低的优先级，但我猜这就是您的意思。