目标 C：以编程方式添加带有约束的 UI 按钮

Question

我想创建固定尺寸的按钮，无论屏幕大小和方向如何，都设置为从右上角固定距离，但无法实现。

我尝试了以下代码，该代码仅在框架位置固定后才能在纵向模式下正确显示。

self.closeBtn = [UIButton buttonWithType:UIButtonTypeCustom];
self.closeBtn.frame = CGRectMake(260, 30, 50, 28);
self.closeBtn.layer.cornerRadius = 4;
self.closeBtn.layer.borderWidth = 1;
self.closeBtn.layer.borderColor = [UIColor colorWithRed:179.0/255.0 green:179.0/255.0 blue:179.0/255.0 alpha:1.0].CGColor;
[self.closeBtn setTitleColor:[UIColor colorWithRed:230.0/255.0 green:230.0/255.0 blue:230.0/255.0 alpha:1.0] forState:UIControlStateNormal];
self.closeBtn.backgroundColor = [UIColor colorWithRed:0.0 green:0.0 blue:0.0 alpha:0.75];
[self.closeBtn setTitle:@"Done" forState:UIControlStateNormal];
[self.closeBtn.titleLabel setFont:[UIFont fontWithName:@"HelveticaNeue-Medium" size:12.0]];
[self.closeBtn addTarget:self action:@selector(closeBtnClicked:) forControlEvents:UIControlEventTouchUpInside];

//NSLayoutConstraint* doneconstraint = [NSLayoutConstraint constraintWithItem:self.closeBtn attribute:NSLayoutAttributeTrailing relatedBy:NSLayoutRelationEqual toItem:self.view attribute:NSLayoutAttributeTrailing multiplier:1.0 constant:5.0];
//[self addConstraint:doneconstraint];
[self.view addSubview:self.closeBtn];

我也尝试添加约束 [取消注释 2 行]，但它给出了以下错误

无法同时满足约束。 以下列表中的至少一个约束可能是您不想要的。试试这个：（1）查看每个约束并尝试找出您不期望的； (2) 找到添加了一个或多个不需要的约束的代码并修复它。 （注意：如果您看到不理解的 NSAutoresizingMaskLayoutConstraints，请参阅 UIView 属性 translatesAutoresizingMaskIntoConstraints 的文档）

我对错误的猜测是框架和约束指定了按钮的不同位置，但我是新手，所以我不确定发生了什么以及如何修复。

一种解决方案是在旋转时更改框架，但我认为使用约束会更简洁。

Answer 1

试试这个代码，把 60 换成你想要的

 self.closeBtn = [UIButton buttonWithType:UIButtonTypeCustom];
self.closeBtn.frame = CGRectMake(260, 30, 50, 28);
self.closeBtn.layer.cornerRadius = 4;
self.closeBtn.layer.borderWidth = 1;
self.closeBtn.layer.borderColor = [UIColor colorWithRed:179.0/255.0 green:179.0/255.0 blue:179.0/255.0 alpha:1.0].CGColor;
[self.closeBtn setTitleColor:[UIColor colorWithRed:230.0/255.0 green:230.0/255.0 blue:230.0/255.0 alpha:1.0] forState:UIControlStateNormal];
self.closeBtn.backgroundColor = [UIColor colorWithRed:0.0 green:0.0 blue:0.0 alpha:0.75];
[self.closeBtn setTitle:@"Done" forState:UIControlStateNormal];
[self.closeBtn.titleLabel setFont:[UIFont fontWithName:@"HelveticaNeue-Medium" size:12.0]];
[self.view addSubview:self.closeBtn];
[self.closeBtn addTarget:self action:@selector(closeBtnClicked:) forControlEvents:UIControlEventTouchUpInside];
self.closeBtn.translatesAutoresizingMaskIntoConstraints = NO;
NSLayoutConstraint * c_1 =[NSLayoutConstraint constraintWithItem:self.view
                                                       attribute:NSLayoutAttributeRight
                                                       relatedBy:NSLayoutRelationEqual
                                                          toItem:self.closeBtn
                                                       attribute:NSLayoutAttributeRight
                                                      multiplier:1.0 constant:60];
NSLayoutConstraint * c_2 =[NSLayoutConstraint constraintWithItem:self.view
                                                       attribute:NSLayoutAttributeTop
                                                       relatedBy:NSLayoutRelationEqual
                                                          toItem:self.closeBtn
                                                       attribute:NSLayoutAttributeTop
                                                      multiplier:1.0 constant:-1*60];
NSLayoutConstraint * equal_w = [NSLayoutConstraint constraintWithItem:self.closeBtn
                                                            attribute:NSLayoutAttributeWidth
                                                            relatedBy:NSLayoutRelationEqual
                                                               toItem:nil
                                                            attribute:0
                                                           multiplier:1.0
                                                             constant:70];
NSLayoutConstraint * equal_h = [NSLayoutConstraint constraintWithItem:self.closeBtn
                                                            attribute:NSLayoutAttributeHeight
                                                            relatedBy:NSLayoutRelationEqual
                                                               toItem:nil
                                                            attribute:0
                                                           multiplier:1.0
                                                             constant:28];
[self.view addConstraints:@[c_1,c_2]];
[self.closeBtn addConstraints:@[equal_w,equal_h]];

截图是