在那里创建子类UITableViewCell的自动布局的限制？ [英] where to create autolayout constraints for subclassed uitableviewcell?

问题描述

我想使用自动布局为一个UITableViewCell子类，我创造，我会AP preciate什么方法一些建议把布局约束创建code。我一直在寻找周围，所有的信息，我找到在viewDidLoad方法添加子视图后添加约束会谈。据我所知viewDidLoad中不是一个UITableViewCell子类的选项。

I am trying to use autolayout for a uitableviewcell subclass I am creating and I would appreciate some advice on what method to put the layout constraint creation code. I have been searching around and all the information I find talks about adding constraints after adding subviews in the viewDidLoad method. As far as I know viewDidLoad isn't an option for a uitableviewcell subclass.

我使用界面生成器来创建自定义单元格，并动态地在我的code分配。没有什么特别的存在......我子类的UITableViewCell这样我就可以添加自定义的UIView到单元格。同样，没有什么特别天崩地裂...我的困难在于当我试图来定位我的自定义的UIView相对于我加入细胞在Interface Builder的标签。

I am using interface builder to create a custom cell and dynamically allocating it in my code. Nothing special there... I subclass the uitableviewcell so I can add a custom uiview to the cell. Again, nothing particularly Earth shattering... My difficulty comes when I try to position my custom uiview with respect to a label I added to the cell in interface builder.

这是code创建自定义的UIView，并将其添加到单元格的内容视图：

This is the code to create the custom uiview and add it to the cell's content view:

- (id)initWithCoder:(NSCoder *)decoder
{
    if ((self = [super initWithCoder:decoder]))
    {
        [self initSelf];
    }
    return self;
}

- (id)initWithStyle:(UITableViewCellStyle)style reuseIdentifier:(NSString *)reuseIdentifier
{
    if ((self = [super initWithStyle:style reuseIdentifier:reuseIdentifier]))
    {
        [self initSelf];
    }
    return self;
}

- (void) initSelf
{
    // Initialization code
    _badgeLabel = @"";

    if (!_customBadge)
    {
        _customBadge = [CustomBadge customBadgeWithString:self.badgeLabel];
    }

    // hide the badge until needed
    self.customBadge.hidden = YES;

    // add badge to the cell view hierarchy
    [self.customBadge setTranslatesAutoresizingMaskIntoConstraints:NO];
    [self.customBadge setContentHuggingPriority:UILayoutPriorityDefaultHigh forAxis:UILayoutConstraintAxisHorizontal];
    [self.customBadge setContentHuggingPriority:UILayoutPriorityDefaultHigh forAxis:UILayoutConstraintAxisVertical];

    [self.contentView addSubview:self.customBadge];
}

如果我把约束code在initSelf没有结束时会发生。我_customBadge的位置停留在其默认值。当我把约束code在layoutSubviews定位应用;但我pretty确保它是放错了地方。这里的code：

If I put the constraint code at the end of initSelf nothing happens. The position of my _customBadge stays at its' default. When I put the constraint code in layoutSubviews the positioning is applied; but I am pretty sure it is the wrong place. Here's the code:

- (void) layoutSubviews
{
    [self.contentView addConstraint:[NSLayoutConstraint
                                     constraintWithItem:self.customBadge
                                     attribute:NSLayoutAttributeLeft
                                     relatedBy:NSLayoutRelationEqual
                                     toItem:self.competence
                                     attribute:NSLayoutAttributeRight
                                     multiplier:1.0
                                     constant:-14.0]];

    [self.contentView addConstraint:[NSLayoutConstraint
                                     constraintWithItem:self.customBadge
                                     attribute:NSLayoutAttributeTop
                                     relatedBy:NSLayoutRelationEqual
                                     toItem:self.competence
                                     attribute:NSLayoutAttributeTop
                                     multiplier:1.0
                                     constant:0.0]];

    [super layoutSubviews];
}

谁能告诉我在哪里，这code应该去？当然，我创建重复的约束每一个布局发生时。

Can anyone tell me where this code should go? Surely I am creating duplicate constraints every time a layout happens.

感谢

推荐答案

您将需要更新像约束：

-(void)updateConstraints{
 // add your constraints if not already there
 [super updateConstraints];
}

添加您的意见后，上海华你需要调用 [自setNeedsUpdateConstraints] 来开始使用它们。这样渲染运行时将调用 updateConstraints 在正确的时间。

After adding your views to superview you need to call [self setNeedsUpdateConstraints] to start using them. By doing so the rendering runtime will call updateConstraints at the right time.

这篇关于在那里创建子类UITableViewCell的自动布局的限制？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！