两个按钮与AutoLayout战斗

Question

我有一个看起来像这样的视图

 ----------------------------------
| [button 1]            [button 2] |
 ----------------------------------

但我遇到一个问题，其中一个或另一个将接管全宽。我似乎无法找到压缩阻力/内容拥抱的正确组合来获得我想要的东西。

我正在使用以下可视布局代码：

H:|-(leftPadding)-[button1]-(>=middlePadding)-[button2]-(rightPadding)-|
V:|-(topPadding)-[button1]-(bottomPadding)-|
V:|-(topPadding)-[button2]-(bottomPadding)-|

填充值当前都是8.此外，按钮不应重叠，因此第二个按钮的宽度应优先于第一个按钮。

在应用中，标签可能会发生变化，所以我想看起来像：

 ----------------------------------
| [button 1]   [some other button] |
 ----------------------------------

或：

 ----------------------------------
| [some other button]   [button 2] |
 ----------------------------------

当我更新按钮文本时，是否还需要执行其他操作？

Answer 1

对于左侧按钮（标题可能会压缩），请将压缩阻力和内容拥抱优先级保留为默认设置。换句话说，什么也不做。

对于右键（标题可能未压缩），请增加其抗压缩优先级。默认的抗压缩优先级为750.将此值增加到751就足够了。

[button2 setContentCompressionResistancePriority:751 forAxis:UILayoutConstraintAxisHorizontal];

如果你在IB中这样做：

左键（标题可以压缩）：

右键（标题无法压缩）：

更新： 用于定位按钮的约束：

Answer 2

[targetView setNeedsUpdateConstraints]礼貌地请求ui更新下次运行的约束，或[targetView layoutIfNeeded]立即强制执行约束计算。在此，更改标题后，目标视图是您的按钮。按钮上的内部UILabel如何配置为行为/调整大小将影响结果。

尝试以下内容。

#import "ADViewController.h"

@interface ADViewController ()
@property (nonatomic) UIButton *button1;
@property (nonatomic) UIButton *button2;
@end

@implementation ADViewController

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.

    self.button1 = [UIButton buttonWithType:UIButtonTypeSystem];
    [self.button1 setTranslatesAutoresizingMaskIntoConstraints:NO];
    [self.button1 setTitle:@"button1" forState:UIControlStateNormal];
    [self.button1.titleLabel setAdjustsFontSizeToFitWidth:YES];
    [self.button1 setTag:1];
    [self.button1 addTarget:self action:@selector(growTitle:) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:self.button1];

    self.button2 = [UIButton buttonWithType:UIButtonTypeSystem];
    [self.button2 setTranslatesAutoresizingMaskIntoConstraints:NO];
    [self.button2 setTitle:@"button2" forState:UIControlStateNormal];
    [self.button2.titleLabel setAdjustsFontSizeToFitWidth:YES];
    [self.button2 setTag:2];
    [self.button2 addTarget:self action:@selector(growTitle:) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:self.button2];
}

- (void)viewWillAppear:(BOOL)animated
{

    NSString *hString = @"H:|-[_button1(>=minButtonWidth)]-(>=minMiddle)-[_button2(>=minButtonWidth)]-|";
    NSString *vString1 = @"V:|-[_button1]-|";
    NSString *vString2 = @"V:|-[_button2]-|";

    NSDictionary *metrics = @{@"minMiddle": @40,
                              @"minButtonWidth": @100 };
    NSDictionary *views = NSDictionaryOfVariableBindings(_button1,_button2);
    NSMutableArray *cons = [NSMutableArray arrayWithArray:
                            [NSLayoutConstraint constraintsWithVisualFormat:hString
                                                                    options:0
                                                                    metrics:metrics
                                                                      views:views]];
    [cons addObjectsFromArray:[NSLayoutConstraint constraintsWithVisualFormat:vString1
                                                                      options:0
                                                                      metrics:metrics
                                                                        views:views]];
    [cons addObjectsFromArray:[NSLayoutConstraint constraintsWithVisualFormat:vString2
                                                                      options:0
                                                                      metrics:metrics
                                                                        views:views]];
    [self.view addConstraints:cons];
}

- (void)growTitle:(UIButton *)button
{
    [button setTitle:[NSString stringWithFormat:@"%@-%ld", button.titleLabel.text, button.tag]
            forState:UIControlStateNormal];
    [button setNeedsUpdateConstraints];
}

@end