正确的子类和UITableViewHeaderFooterView的自动布局 [英] Correct subclassing and autolayout of UITableViewHeaderFooterView
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问题描述
下面是我如何在我UITableViewHeaderFooterView视图设置东西了。
- （ID）initWithFrame：方法（的CGRect）帧
{
自= [超级initWithFrame：方法框架]
如果（个体经营）{
[self.contentView addSubview：self.createHeader];
}
返回自我;
} - （UIView的*）createHeader
{
UIView的* headerContainer = [[UIView的页头]初始化];
headerContainer.backgroundColor =的UIColor blackColor]
*的UILabel标签= [[的UILabel页头] initWithFrame：方法CGRectZero];
label.translatesAutoresizingMaskIntoConstraints = NO;
label.text = @TITLENAME [headerContainer addSubview：标号]; NSLayoutConstraint *约束= [NSLayoutConstraint constraintWithItem：标签
属性：NSLayoutAttributeLeading
relatedBy：NSLayoutRelationEqual
toItem：headerContainer
属性：NSLayoutAttributeLeft
事半功倍：1.F常数：16.f];
[headerContainer addConstraint：约束];约束= [NSLayoutConstraint constraintWithItem：标签
属性：NSLayoutAttributeTrailing
relatedBy：NSLayoutRelationEqual
toItem：headerContainer
属性：NSLayoutAttributeRight
事半功倍：1.F常数：-16.f];
[headerContainer addConstraint：约束];约束= [NSLayoutConstraint constraintWithItem：标签
属性：NSLayoutAttributeTop
relatedBy：NSLayoutRelationEqual
toItem：headerContainer
属性：NSLayoutAttributeTop
事半功倍：1.F常数：0.f];
[headerContainer addConstraint：约束];约束= [NSLayoutConstraint constraintWithItem：标签
属性：NSLayoutAttributeBottom
relatedBy：NSLayoutRelationEqual
toItem：headerContainer
属性：NSLayoutAttributeBottom
事半功倍：1.F常数：0.f];
[headerContainer addConstraint：约束];返回headerContainer;
}
我得到这个自动布局错误：
大概在以下列表中的约束条件中的至少一个是一个你不想要的。
试试这个：（1）看一下每个约束和揣摩，你不要指望;
（2）找到code，它增加了不必要的约束或限制并修复它。
（注：如果你看到你不明白NSAutoresizingMaskLayoutConstraints，
参考文档UIView的财产translatesAutoresizingMaskIntoConstraints）（
＆所述; NSLayoutConstraint：0xd4bd7e0的UILabel：0x17254980.leading ==的UIView：0x172547d0.left + 16＆gt;中，
＆LT; NSLayoutConstraint：0xd4bd810的UILabel：0x17254980.trailing ==的UIView：0x172547d0.right - 16取代;，
＆所述; NSAutoresizingMaskLayoutConstraint：0xd402510 H = - ＆放大器; V = - ＆放大器; H：[UIView的：0x172547d0（0）]＆gt;中
）将试图打破约束恢复
＆LT; NSLayoutConstraint：0xd4bd810的UILabel：0x17254980.trailing ==的UIView：0x172547d0.right - 16取代;
解决方案
线索是正确的，在错误： translatesAutoresizingMaskIntoConstraints
我会说，你需要下面的行添加到您的 createHeader 方法：
headerContainer.translatesAutoresizingMaskIntoConstraints = NO;
下面是第二个想法。它看起来像要居中内headerContainer您的标签，对不对？相反的：
NSLayoutConstraint *约束= [NSLayoutConstraint constraintWithItem：标签
属性：NSLayoutAttributeLeading
relatedBy：NSLayoutRelationEqual
toItem：headerContainer
属性：NSLayoutAttributeLeft
事半功倍：1.F常数：16.f];
[headerContainer addConstraint：约束];约束= [NSLayoutConstraint constraintWithItem：标签
属性：NSLayoutAttributeTrailing
relatedBy：NSLayoutRelationLessThanOrEqual
toItem：headerContainer
属性：NSLayoutAttributeRight
事半功倍：1.F常数：-16.f];
[headerContainer addConstraint：约束];
尝试：
NSLayoutConstraint *约束= [NSLayoutConstraint constraintWithItem：标签
属性：NSLayoutAttributeLeading
relatedBy：NSLayoutRelationEqual
toItem：headerContainer
属性：NSLayoutAttributeLeft
事半功倍：1.F常数：16.f];
[headerContainer addConstraint：约束];约束= [NSLayoutConstraint constraintWithItem：标签
属性：NSLayoutAttributeTrailing
relatedBy：NSLayoutRelationEqual
toItem：标签
属性：NSLayoutAttributeLeading
事半功倍：1.F常数：0];
[headerContainer addConstraint：约束];
Here's how I set stuff up in my UITableViewHeaderFooterView view.
- (id)initWithFrame:(CGRect)frame
{
self = [super initWithFrame:frame];
if (self) {
[self.contentView addSubview:self.createHeader];
}
return self;
}
- (UIView *)createHeader
{
UIView *headerContainer = [[UIView alloc] init];
headerContainer.backgroundColor = [UIColor blackColor];
UILabel *label = [[UILabel alloc] initWithFrame:CGRectZero];
label.translatesAutoresizingMaskIntoConstraints = NO;
label.text = @"titlename";
[headerContainer addSubview:label];
NSLayoutConstraint *constraint = [NSLayoutConstraint constraintWithItem:label
attribute:NSLayoutAttributeLeading
relatedBy:NSLayoutRelationEqual
toItem:headerContainer
attribute:NSLayoutAttributeLeft
multiplier:1.f constant:16.f];
[headerContainer addConstraint:constraint];
constraint = [NSLayoutConstraint constraintWithItem:label
attribute:NSLayoutAttributeTrailing
relatedBy:NSLayoutRelationEqual
toItem:headerContainer
attribute:NSLayoutAttributeRight
multiplier:1.f constant:-16.f];
[headerContainer addConstraint:constraint];
constraint = [NSLayoutConstraint constraintWithItem:label
attribute:NSLayoutAttributeTop
relatedBy:NSLayoutRelationEqual
toItem:headerContainer
attribute:NSLayoutAttributeTop
multiplier:1.f constant:0.f];
[headerContainer addConstraint:constraint];
constraint = [NSLayoutConstraint constraintWithItem:label
attribute:NSLayoutAttributeBottom
relatedBy:NSLayoutRelationEqual
toItem:headerContainer
attribute:NSLayoutAttributeBottom
multiplier:1.f constant:0.f];
[headerContainer addConstraint:constraint];
return headerContainer;
}
I get this autolayout error:
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:0xd4bd7e0 UILabel:0x17254980.leading == UIView:0x172547d0.left + 16>",
"<NSLayoutConstraint:0xd4bd810 UILabel:0x17254980.trailing == UIView:0x172547d0.right - 16>",
"<NSAutoresizingMaskLayoutConstraint:0xd402510 h=--& v=--& H:[UIView:0x172547d0(0)]>"
)
Will attempt to recover by breaking constraint
<NSLayoutConstraint:0xd4bd810 UILabel:0x17254980.trailing == UIView:0x172547d0.right - 16>
解决方案
The clue is right there in the error: translatesAutoresizingMaskIntoConstraints.
I would say you need to add the following line to your createHeader method:
headerContainer.translatesAutoresizingMaskIntoConstraints = NO;
Here's a second idea. It looks like you want to center your label inside headerContainer, right? Instead of:
NSLayoutConstraint *constraint = [NSLayoutConstraint constraintWithItem:label
attribute:NSLayoutAttributeLeading
relatedBy:NSLayoutRelationEqual
toItem:headerContainer
attribute:NSLayoutAttributeLeft
multiplier:1.f constant:16.f];
[headerContainer addConstraint:constraint];
constraint = [NSLayoutConstraint constraintWithItem:label
attribute:NSLayoutAttributeTrailing
relatedBy: NSLayoutRelationLessThanOrEqual
toItem:headerContainer
attribute:NSLayoutAttributeRight
multiplier:1.f constant:-16.f];
[headerContainer addConstraint:constraint];
Try:
NSLayoutConstraint *constraint = [NSLayoutConstraint constraintWithItem:label
attribute:NSLayoutAttributeLeading
relatedBy:NSLayoutRelationEqual
toItem:headerContainer
attribute:NSLayoutAttributeLeft
multiplier:1.f constant:16.f];
[headerContainer addConstraint:constraint];
constraint = [NSLayoutConstraint constraintWithItem:label
attribute:NSLayoutAttributeTrailing
relatedBy:NSLayoutRelationEqual
toItem:label
attribute:NSLayoutAttributeLeading
multiplier:1.f constant:0];
[headerContainer addConstraint:constraint];
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