ios - 如何使用自动布局为 UIViews 设置相等的宽度 "Constraint with item format"

Question

在我的应用程序中，我在 View Controller 上插入了 UIViews。我的主要要求是我想使用自动布局“项目格式约束”为两个 UIView 设置相等的宽度。

为此，我编写了一些代码，但没有得到相等的宽度。我在这里做错了什么？

我想得到如下图所示的结果(即需要为两个 UIView 设置相等的宽度)。

我的代码:

#import "ViewController8.h"

@interface ViewController8 ()
{
    UIView * myView1;
    UIView * myView2;
}
@end

@implementation ViewController8

- (void)viewDidLoad {
    [super viewDidLoad];

    myView1 = [[UIView alloc] init];
    myView1.backgroundColor = [UIColor lightGrayColor];
    myView1.translatesAutoresizingMaskIntoConstraints = NO;
    [self.view addSubview:myView1];

    myView2 = [[UIView alloc] init];
    myView2.backgroundColor = [UIColor redColor];
    myView2.translatesAutoresizingMaskIntoConstraints = NO;
    [self.view addSubview:myView2];

    [self operation2];
}

-(void)operation2
{
    //Applying autolayouts for myview2

    [self.view addConstraint:[NSLayoutConstraint constraintWithItem:myView2
                                                          attribute:NSLayoutAttributeHeight
                                                          relatedBy:NSLayoutRelationEqual
                                                             toItem:nil
                                                          attribute:0
                                                         multiplier:1.0
                                                           constant:50]];

    [self.view addConstraint:[NSLayoutConstraint constraintWithItem:myView2
                                                          attribute:NSLayoutAttributeTrailing
                                                          relatedBy:NSLayoutRelationEqual
                                                             toItem:self.view
                                                          attribute:NSLayoutAttributeTrailing
                                                         multiplier:1.0
                                                           constant:-10]];

    [self.view addConstraint:[NSLayoutConstraint constraintWithItem:myView2
                                                          attribute:NSLayoutAttributeBottom
                                                          relatedBy:NSLayoutRelationEqual
                                                             toItem:self.view
                                                          attribute:NSLayoutAttributeBottom
                                                         multiplier:1.0
                                                           constant:-30]];

    //Applying autolayouts for myview1

    [self.view addConstraint:[NSLayoutConstraint constraintWithItem:myView1
                                                          attribute:NSLayoutAttributeLeading
                                                          relatedBy:NSLayoutRelationEqual
                                                             toItem:self.view
                                                          attribute:NSLayoutAttributeLeading
                                                         multiplier:1.0
                                                           constant:10]];

    [self.view addConstraint:[NSLayoutConstraint constraintWithItem:myView1
                                                          attribute:NSLayoutAttributeHeight
                                                          relatedBy:NSLayoutRelationEqual
                                                             toItem:nil
                                                          attribute:0
                                                         multiplier:1.0
                                                           constant:50]];

    [self.view addConstraint:[NSLayoutConstraint constraintWithItem:myView1
                                                          attribute:NSLayoutAttributeTrailing
                                                          relatedBy:NSLayoutRelationEqual
                                                             toItem:myView2
                                                          attribute:NSLayoutAttributeLeading
                                                         multiplier:1.0
                                                           constant:-30]];

    [self.view addConstraint:[NSLayoutConstraint constraintWithItem:myView1
                                                          attribute:NSLayoutAttributeBottom
                                                          relatedBy:NSLayoutRelationEqual
                                                             toItem:self.view
                                                          attribute:NSLayoutAttributeBottom
                                                         multiplier:1.0
                                                           constant:-30]];
}

Answer 1

您发布的代码中不存在等宽约束。尝试添加这个

[self.view addConstraint:[NSLayoutConstraint constraintWithItem:myView1
  attribute:NSLayoutAttributeWidth 
  relatedBy:NSLayoutRelationEqual 
  toItem:nil 
  attribute:NSLayoutAttributeNotAnAttribute 
  multiplier:1.0 
  constant:200]];


[self.view addConstraint:[NSLayoutConstraint constraintWithItem:myView2
  attribute:NSLayoutAttributeWidth 
  relatedBy:NSLayoutRelationEqual 
  toItem:myView1
  attribute:NSLayoutAttributeWidth 
  multiplier:1.0 
  constant:0]];