ios - subview 宽度不适合自动布局的 super View

Question

我正在向 UICollectionViewCell 添加一个 subview 。我以编程方式添加约束以使其填充单元格，但宽度未填充单元格。

当我在 View 调试器中查看它时，它说位置不明确。这怎么可能，因为我指定所有 4 个边都固定到 super View ？

这是调试器中的 View 。内部的白色 View 应适合父级宽度(蓝色边框):

检查父 View 上的约束会显示“位置不明确”警告:

我使用的代码如下:

[self.contentView addSubview:calloutView];
calloutView.translatesAutoresizingMaskIntoConstraints = NO;
self.contentView.translatesAutoresizingMaskIntoConstraints = NO;

[self.contentView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|-0-[calloutView]-0-|" options:NSLayoutFormatDirectionLeadingToTrailing metrics:nil views:NSDictionaryOfVariableBindings(calloutView) ]];
[self.contentView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:|-0-[calloutView]-0-|" options:NSLayoutFormatDirectionLeadingToTrailing metrics:nil views:NSDictionaryOfVariableBindings(calloutView) ]];

Answer 1

问题好像和contentView的使用有关，你必须使用cell本身来实现你想要的，这是代码和工作，查看下图

#import "CollectionViewCell.h"

@interface CollectionViewCell()
@property UIView * testView;
@end


@implementation CollectionViewCell

@synthesize testView;

-(void)awakeFromNib
{
    [super awakeFromNib];

    testView = [[UIView alloc]initWithFrame:CGRectZero];
    testView.translatesAutoresizingMaskIntoConstraints = NO;

    [self addSubview:testView];

    [self addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"H:|-2-[testView]-2-|" options:NSLayoutFormatDirectionLeadingToTrailing metrics:nil views:NSDictionaryOfVariableBindings(testView) ]];
    [self addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:|-2-[testView]-2-|" options:NSLayoutFormatDirectionLeadingToTrailing metrics:nil views:NSDictionaryOfVariableBindings(testView) ]];

    self.testView.layer.borderWidth = 2;
    self.testView.layer.borderColor = [UIColor blueColor].CGColor;
}

@end

希望对你有帮助，祝好