UITableViewCell子类的奇怪布局约束

Question

我刚遇到一个关于奇怪的UITableViewCell子类布局的奇怪问题。 我已经在代码中配置了所有这些东西的UITableViewCell子类。

• iPhone 5S和下部WORK PERFECT

• iPhone 6或加上WRONG :(

我确定这是子类问题。

(lldb) po _tableView 
<UITableView: 0x7fa5db054c00; frame = (0 0; 375 618); clipsToBounds = YES; gestureRecognizers = <NSArray: 0x7fa5d96649e0>; layer = <CALayer: 0x7fa5d96632a0>; contentOffset: {0, 0}; contentSize: {375, 15552}> 

代码：

@interface ColorCell : UITableViewCell 

@end 

@implementation ColorCell 

- (instancetype)initWithStyle:(UITableViewCellStyle)style reuseIdentifier:(NSString *)reuseIdentifier 
{ 
    self = [super initWithStyle:style reuseIdentifier:reuseIdentifier]; 
    if (self) { 
    self.background = [UIView new]; 
    self.top   = [UIView new]; 
    self.bottom  = [UIView new]; 

    self.contentView.translatesAutoresizingMaskIntoConstraints = NO; 
    self.background.translatesAutoresizingMaskIntoConstraints = NO; 
    self.top.  translatesAutoresizingMaskIntoConstraints = NO; 
    self.bottom. translatesAutoresizingMaskIntoConstraints = NO; 

    [self.contentView addSubview:self.background]; 
    [self.background addSubview:self.top]; 
    [self.background addSubview:self.bottom]; 

    self.top.backgroundColor  = [UIColor purpleColor]; 
    self.bottom.backgroundColor  = [UIColor blackColor]; 

    } 
    return self; 
} 

- (void)updateConstraints 
{ 
    [super updateConstraints]; 
    if (!self.didSetupConstraints) { 

    NSDictionary *viewsDictionary = NSDictionaryOfVariableBindings(_firstColor,_secondColor,_thirdColor,_fourthColor,_fifthColor,_background,_top,_bottom,_title,_stars,_favourites); 

    NSString *format; 
    NSArray *constraintsArray; 
    NSDictionary *metrics = @{@"topHeight":@100.0, @"bottomHeight":@50}; 

    format = @"V:|[_background]|"; 
    constraintsArray = [NSLayoutConstraint constraintsWithVisualFormat:format options:NSLayoutFormatAlignAllCenterX metrics:nil views:viewsDictionary]; 
    [self.contentView addConstraints:constraintsArray]; 

    format = @"H:|[_background]|"; 
    constraintsArray = [NSLayoutConstraint constraintsWithVisualFormat:format options:NSLayoutFormatAlignAllCenterX metrics:nil views:viewsDictionary]; 
    [self.contentView addConstraints:constraintsArray]; 

    format = @"V:|[_top(topHeight)][_bottom(bottomHeight)]|"; 
    constraintsArray = [NSLayoutConstraint constraintsWithVisualFormat:format options:0 metrics:metrics views:viewsDictionary]; 
    [_background addConstraints:constraintsArray]; 

    format = @"H:|[_bottom]|"; 
    constraintsArray = [NSLayoutConstraint constraintsWithVisualFormat:format options:0 metrics:nil views:viewsDictionary]; 
    [_background addConstraints:constraintsArray]; 

    format = @"H:|[_top]|"; 
    constraintsArray = [NSLayoutConstraint constraintsWithVisualFormat:format options:0 metrics:nil views:viewsDictionary]; 
    [_background addConstraints:constraintsArray]; 

    self.didSetupConstraints = YES; 
    } 
} 

感谢。

编辑：

(lldb) po [[UIWindow keyWindow] recursiveDescription] 
<UIWindow: 0x7fa91341ce00; frame = (0 0; 375 667); gestureRecognizers = <NSArray: 0x7fa91341b290>; layer = <UIWindowLayer: 0x7fa91341c610>> 
| <UILayoutContainerView: 0x7fa913703e70; frame = (0 0; 375 667); autoresize = W+H; gestureRecognizers = <NSArray: 0x7fa91343f400>; layer = <CALayer: 0x7fa913702480>> 
| | <UINavigationTransitionView: 0x7fa913621e80; frame = (0 0; 375 667); clipsToBounds = YES; autoresize = W+H; layer = <CALayer: 0x7fa91361d7e0>> 
| | | <UIViewControllerWrapperView: 0x7fa9159678d0; frame = (0 0; 375 667); autoresize = W+H; layer = <CALayer: 0x7fa91343f150>> 
| | | | <UIView: 0x7fa913441190; frame = (0 0; 375 667); autoresize = W+H; layer = <CALayer: 0x7fa913443820>> 
| | | | | <UITableView: 0x7fa913841400; frame = (0 0; 375 618); clipsToBounds = YES; gestureRecognizers = <NSArray: 0x7fa91342f520>; layer = <CALayer: 0x7fa913435060>; contentOffset: {0, 0}; contentSize: {375, 15582}> 
| | | | | | <UITableViewWrapperView: 0x7fa913445200; frame = (0 0; 375 618); gestureRecognizers = <NSArray: 0x7fa913440320>; layer = <CALayer: 0x7fa9134319d0>; contentOffset: {0, 0}; contentSize: {375, 618}> 
| | | | | | | <ColorCell: 0x7fa913637230; baseClass = UITableViewCell; frame = (0 600; 375 150); autoresize = W; layer = <CALayer: 0x7fa9136375b0>> 
| | | | | | | | <UITableViewCellContentView: 0x7fa913637630; frame = (0 0; 375 150); gestureRecognizers = <NSArray: 0x7fa913637960>; layer = <CALayer: 0x7fa913637700>> 
| | | | | | | | | <UIView: 0x7fa9136379c0; frame = (0 0; 324 150); layer = <CALayer: 0x7fa913637a90>> 
| | | | | | | | | | <UIView: 0x7fa913638730; frame = (0 0; 324 100); layer = <CALayer: 0x7fa913638800>> 
| | | | | | | | | | | <UIView: 0x7fa913637ab0; frame = (0 0; 0 0); layer = <CALayer: 0x7fa913637b80>> 
| | | | | | | | | | | <UIView: 0x7fa913637ba0; frame = (0 0; 0 0); layer = <CALayer: 0x7fa913637c70>> 
| | | | | | | | | | | <UIView: 0x7fa913637c90; frame = (0 0; 0 0); layer = <CALayer: 0x7fa913637d60>> 
| | | | | | | | | | | <UIView: 0x7fa913637d80; frame = (0 0; 0 0); layer = <CALayer: 0x7fa913637e50>> 
| | | | | | | | | | | <UIView: 0x7fa913637e70; frame = (0 0; 0 0); layer = <CALayer: 0x7fa913637f40>> 
| | | | | | | | | | <UIView: 0x7fa913638820; frame = (0 100; 324 50); layer = <CALayer: 0x7fa9136388f0>> 
| | | | | | | | | | | <UILabel: 0x7fa913637f60; frame = (8 8; 240 34); userInteractionEnabled = NO; layer = <_UILabelLayer: 0x7fa913636920>> 
| | | | | | | | | | | | <_UILabelContentLayer: 0x7fa9135b5ba0> (layer) 
| | | | | | | | | | | <UIImageView: 0x7fa913638290; frame = (256 25; 17 0); userInteractionEnabled = NO; layer = <CALayer: 0x7fa913638390>> 
| | | | | | | | | | | <UILabel: 0x7fa9136383b0; frame = (281 -100; 35 0); clipsToBounds = YES; userInteractionEnabled = NO; layer = <_UILabelLayer: 0x7fa913638510>> 

奇点： 如果我删除self.contentView.translatesAutoresizingMaskIntoConstraints = NO和它的作品完美。但奇怪的问题是提出了限制的警告。

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:0x7fad5b9764e0 'UIView-Encapsulated-Layout-Height' V:[UITableViewCellContentView:0x7fad5b971a20(44)]>", 
    "<NSLayoutConstraint:0x7fad5b976fb0 V:|-(0)-[UIView:0x7fad5b971db0] (Names: '|':UITableViewCellContentView:0x7fad5b971a20)>", 
    "<NSLayoutConstraint:0x7fad5b976db0 V:[UIView:0x7fad5b971db0]-(0)-| (Names: '|':UITableViewCellContentView:0x7fad5b971a20)>", 
    "<NSLayoutConstraint:0x7fad5b9763c0 V:|-(0)-[UIView:0x7fad5b972b70] (Names: '|':UIView:0x7fad5b971db0)>", 
    "<NSLayoutConstraint:0x7fad5b977730 V:[UIView:0x7fad5b972b70(100)]>", 
    "<NSLayoutConstraint:0x7fad5b976410 V:[UIView:0x7fad5b972b70]-(0)-[UIView:0x7fad5b972c60]>", 
    "<NSLayoutConstraint:0x7fad5b9777b0 V:[UIView:0x7fad5b972c60(50)]>", 
    "<NSLayoutConstraint:0x7fad5b977800 V:[UIView:0x7fad5b972c60]-(0)-| (Names: '|':UIView:0x7fad5b971db0)>" 
) 

Will attempt to recover by breaking constraint 
<NSLayoutConstraint:0x7fad5b976410 V:[UIView:0x7fad5b972b70]-(0)-[UIView:0x7fad5b972c60]> 

Make a symbolic breakpoint at UIViewAlertForUnsatisfiableConstraints to catch this in the debugger. 
The methods in the UIConstraintBasedLayoutDebugging category on UIView listed in <UIKit/UIView.h> may also be helpful. 

Answer 1

因为这不是编程方式创建你应该不需要self.contentView.translatesAutoresizingMaskIntoConstraints = NO;。此外，您需要在覆盖的结尾处拨打[super updateConstraints]，而不是开头。编辑包括错误（来自下面的评论）：这里发生的是UIView-Encapsulated-Layout-Height是为自定义单元格创建的iOS 8约束。单元格被创建后，如果约束被修改，您将会得到这个错误。有几种方法来管理它;在这种情况下，我还是要提一下，因为你只需要添加约束一次，请尝试添加不在updateConstraints中的约束，而是在initWithStyle：reuseIdentifier中添加约束。

这个问题更加微妙，而iOS8的一个新问题是：在某些时候，你的tableView认为行高是44，所以它创建了一个约束设置单元格高度为44的值。然后添加这些约束条件，但tableView不重新计算高度，所以你会得到错误。如果像@Rob在上面注意到的那样，那么你将高度设置为44就可以了。它不会解决你的问题是一些约束是告诉tableView高度应该是44，但无论你可以应该设置estimatedRowHeight为150，因为这看起来像一个安全的估计，或者如果他们都肯定会是150刚刚设置rowHeight对此。

Answer 2

我终于找出了约束警告的原因。

我删除- (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath委托方法和警告消失。

因此，答案是明确的：我不应该做的事约束更新在heightForRowAtIndexPath。相反，我只是返回rowHeight，然后修复问题。