我们有选择性地使用自动布局约束,主要是为了将标签相对于可编辑字段元素(通常是UITextView、UITextField)进行定位。但是,自从为这些字段实现自动布局以来,每当我们卸载视图、释放内存等操作时,就会出现一个令人讨厌的异常和崩溃。异常发生在尝试在卸载视图之前从视图中删除约束时。
我们的视图/控制器层次结构如下:
UITableViewController (plain style, but with cell appearance to mimic grouped style)
--> UITableViewCell
----> UIViewController (container for editable form)
------> UICollectionViewController (editable form)
--------> UICollectionViewCell
-----------> UIViewController (editable field)
--------------> UILabel (field label) **HAS CONSTRAINTS**
--------------> UITextView / UITextField (field value) **HAS CONSTRAINTS**
经常在释放/替换/重新加载上层表格单元时,我们会遇到一个巨大的异常并崩溃,因为它试图在内部释放/卸载视图层次结构。
我已经试图通过捕获异常(没有帮助)和在释放/卸载之前强制删除所有受影响视图及其子视图上的约束(在viewWillDisappear:
中),但似乎都没有帮助。我甚至尝试一步步删除这些约束,看看是否有特定的约束导致问题,但当我们准备消失时,在容器上调用removeConstraint:
或removeConstraints:
时所有约束都会崩溃。
我很困惑!这里是我们异常的一部分--大约剪掉了3000行,如果你需要更多,请问。
Exception while deallocating view: { Rows:
0x18911270.posErrorMarker == 4 + 1*0x18911270.negError + 1*0x189112f0.marker + -1*0x189113f0.negError + 1*0x189113f0.posErrorMarker + 1*0x18911a60.marker + -0.5*0x1892dae0.negError + 0.5*0x1892dae0.posErrorMarker + 1*0x18951520.negError + -1*0x18951520.posErrorMarker + -0.5*0x18958090.negError + 0.5*0x18958090.posErrorMarker
0x189112b0.negError == 12 + 1*0x189112b0.posErrorMarker + -1*0x189112f0.marker + 1*0x189113f0.negError + -1*0x189113f0.posErrorMarker + -1*0x18911a60.marker + 1*0x18925530.marker + 0.5*0x1892dae0.negError + -0.5*0x1892dae0.posErrorMarker + 1*0x1893e080.marker + 0.5*0x18958090.negError + -0.5*0x18958090.posErrorMarker + 1*0x18963640.marker
0x18911370.negError == 9 + -1*0x189112f0.marker + 1*0x18911370.posErrorMarker + 1*0x18925530.marker + 1*0x1892dae0.negError + -1*0x1892dae0.posErrorMarker + 1*0x1893e080.marker + 1*0x18963640.marker
0x189113b0.slackMarker == 2 + -1*0x189107d0.marker + 1*0x18910b90.negError + -1*0x18910b90.posErrorMarker +
........ EXPLETIVES DELETED .........
UITableView:0xca2b000.contentHeight == 36 + 1*0xc221c00.marker
UITableView:0xca2b000.contentWidth == 704 + 1*0xc239470.marker
UITableView:0xca2b000.minX == 0 + 1*0xc2a23f0.marker + -0.5*0xc2a2590.marker
UITableView:0xca2b000.minY == 0 + 1*0xc2a25d0.marker + -0.5*0xc2a2630.marker
UITableViewCellContentView:0x18ab13d0.Height == 174 + 1*0x18abd4f0.marker
UITableViewCellContentView:0x18ab13d0.Width == 704 + 1*0x18abd470.marker
........ EXPLETIVES DELETED .........
<NSAutoresizingMaskLayoutConstraint:0x18988bc0 h=-&- v=-&- UIView:0x18911e50.midY == UIView:0x1892d0c0.midY> Marker:0x18988bc0.marker
<NSAutoresizingMaskLayoutConstraint:0x18994b40 h=-&- v=-&- UIView:0xc4a6fb0.midX == UIView:0xc4b4990.midX> Marker:0x18994b40.marker
<NSAutoresizingMaskLayoutConstraint:0x18998480 h=-&- v=-&- UIView:0x18915180.width == UIView:0xc4c5970.width> Marker:0x18998480.marker
<NSAutoresizingMaskLayoutConstraint:0x18aae320 h=--& v=--& TapSectionalTableViewCell:0x18a3d270.midX == + 352> Marker:0x18aae320.marker
<NSAutoresizingMaskLayoutConstraint:0x18aae410 h=--& v=--& H:[TapSectionalTableViewCell:0x18a3d270(704)]> Marker:0x18aae410.marker
<NSAutoresizingMaskLayoutConstraint:0x18aae450 h=--& v=--& TapSectionalTableViewCell:0x18a3d270.midY == + 144> Marker:0x18aae450.marker
........ EXPLETIVES DELETED .........
<NSAutoresizingMaskLayoutConstraint:0xc2de2f0 h=--& v=--& TapGenericCollectionCell:0xc2ac500.midX == + 499> Marker:0xc2de2f0.marker
<NSAutoresizingMaskLayoutConstraint:0xc2de3b0 h=--& v=--& V:[TapGenericCollectionCell:0xc2ac500(34)]> Marker:0xc2de3b0.marker
<NSAutoresizingMaskLayoutConstraint:0xc2de430 h=-&- v=-&- UIView:0x18953f80.height == UIView:0xc2acb20.height> Marker:0xc2de430.marker
<NSAutoresizingMaskLayoutConstraint:0xc2de520 h=-&- v=-&- UIView:0x18923af0.height == UIView:0xc2ae570.height> Marker:0xc2de520.marker
<NSAutoresizingMaskLayoutConstraint:0xc2de560 h=--& v=--& H:[TapGenericCollectionCell:0xc2ac500(280)]> Marker:0xc2de560.marker
........ EXPLETIVES DELETED .........
<NSContentSizeLayoutConstraint:0xc2f5730 H:[_UIBaselineLayoutStrut:0x18994a30(0)] Hug:250 CompressionResistance:750> Marker:0xc2f5730.posErrorMarker
<NSContentSizeLayoutConstraint:0xc2f5730 H:[_UIBaselineLayoutStrut:0x18994a30(0)] Hug:250 CompressionResistance:750> Marker:0xc2f5730.posErrorMarker
<NSContentSizeLayoutConstraint:0xc2f5770 V:[_UIBaselineLayoutStrut:0x18994a30(18)] Hug:250 CompressionResistance:750> Marker:0xc2f5770.posErrorMarker
internal error. Cannot find an outgoing row head for incoming head UIView:0x189712b0.Width, which should never happen.'
/**** BEGIN Individual Field Controller - This code is from the base individual field controller used in our editable form collection *****/
- (void)viewDidLoad {
[super viewDidLoad];
self.view.clipsToBounds = YES;
self.view.opaque = YES;
CGRect viewFrame = self.view.frame;
viewFrame.size = [self defaultFieldSize];
self.view.frame = viewFrame;
if (self.backgroundColor) {
self.view.backgroundColor = self.backgroundColor;
}
else {
self.view.backgroundColor = [UIColor whiteColor];
}
[self createLabelAndField];
[self setLabelAndFieldContraints];
[self.view addConstraints:self.labelValueConstraints];
[self.view setNeedsUpdateConstraints];
}
- (void)createLabelAndField {
[self removeLabelAndField];
UILabel *label = [[UILabel alloc] init];
label.font = self.labelFont;
label.textColor = self.labelColor;
label.lineBreakMode = NSLineBreakByWordWrapping;
label.textAlignment = NSTextAlignmentLeft;
label.adjustsFontSizeToFitWidth = NO;
label.numberOfLines = 0;
if (self.backgroundColor) {
label.backgroundColor = self.backgroundColor;
}
else {
label.backgroundColor = [UIColor whiteColor];
}
[self.view addSubview:label];
self.label = label;
/// EXAMPLE valueView initialization from a subclass that handles long text
TapEditableTextView *textView = [[TapEditableTextView alloc] init];
if (self.hasLabelOverValue) {
textView.shouldMimicTextField = NO;
}
else {
textView.shouldMimicTextField = YES;
}
textView.delegate = self;
textView.keyboardType = UIKeyboardTypeDefault;
textView.font = self.valueFont;
textView.textColor = self.valueColor;
textView.textAlignment = NSTextAlignmentLeft;
textView.normalBackgroundColor = self.backgroundColor;
textView.editable = NO;
textView.textLines = self.textLines;
self.valueTextView = textView;
self.valueView = textView;
[self.view addSubview:textView];
}
- (void)removeLabelAndField {
[self clearConstraints];
if (self.label) {
[self.label removeFromSuperview];
self.label = nil;
}
if (self.valueView) {
[self.valueView removeFromSuperview];
self.valueView = nil;
}
}
- (void)clearConstraints {
if (self.isViewLoaded && self.labelValueConstraints) {
[self.view removeConstraints:self.labelValueConstraints];
}
self.labelValueConstraints = nil;
self.labelToValueHorizConstraint = nil;
self.valueWidthConstraint = nil;
}
// This is called in our field's viewDidLoad, after we've created our label and valueView (UITextField, UITextView, etc)
- (void)setLabelAndFieldContraints {
[self clearConstraints];
self.labelValueConstraints = [NSMutableArray array];
self.label.translatesAutoresizingMaskIntoConstraints = NO;
self.valueView.translatesAutoresizingMaskIntoConstraints = NO;
NSLayoutConstraint *constraint = nil;
constraint = [NSLayoutConstraint
constraintWithItem:self.label attribute:NSLayoutAttributeLeft
relatedBy:NSLayoutRelationEqual
toItem:self.view attribute:NSLayoutAttributeLeft
multiplier:1.0f constant:self.labelValueGap];
constraint.priority = UILayoutPriorityRequired;
[self.labelValueConstraints addObject:constraint];
constraint = [NSLayoutConstraint
constraintWithItem:self.label attribute:NSLayoutAttributeTop
relatedBy:NSLayoutRelationEqual
toItem:self.view attribute:NSLayoutAttributeTop
multiplier:1.0f constant:0];
constraint.priority = 550;
[self.labelValueConstraints addObject:constraint];
constraint = [NSLayoutConstraint
constraintWithItem:self.label attribute:NSLayoutAttributeBottom
relatedBy:NSLayoutRelationEqual
toItem:self.view attribute:NSLayoutAttributeBottom
multiplier:1.0f constant:0];
constraint.priority = 400;
[self.labelValueConstraints addObject:constraint];
constraint = [NSLayoutConstraint
constraintWithItem:self.valueView attribute:NSLayoutAttributeTop
relatedBy:NSLayoutRelationEqual
toItem:self.view attribute:NSLayoutAttributeTop
multiplier:1.0f constant:0];
constraint.priority = UILayoutPriorityRequired;
[self.labelValueConstraints addObject:constraint];
constraint = [NSLayoutConstraint
constraintWithItem:self.valueView attribute:NSLayoutAttributeBottom
relatedBy:NSLayoutRelationEqual
toItem:self.view attribute:NSLayoutAttributeBottom
multiplier:1.0f constant:0];
constraint.priority = 499;
[self.labelValueConstraints addObject:constraint];
constraint = [NSLayoutConstraint
constraintWithItem:self.valueView attribute:NSLayoutAttributeRight
relatedBy:NSLayoutRelationEqual
toItem:self.view attribute:NSLayoutAttributeRight
multiplier:1.0f constant: -(kDisclosureWidth + self.labelValueGap) ];
constraint.priority = 901;
[self.labelValueConstraints addObject:constraint];
constraint = [NSLayoutConstraint
constraintWithItem:self.valueView attribute:NSLayoutAttributeLeading
relatedBy:NSLayoutRelationGreaterThanOrEqual
toItem:self.label attribute:NSLayoutAttributeTrailing
multiplier:1.0f constant:self.labelValueGap];
constraint.priority = UILayoutPriorityDefaultHigh + 1;
[self.labelValueConstraints addObject:constraint];
self.labelToValueHorizConstraint = constraint;
constraint = [NSLayoutConstraint
constraintWithItem:self.label attribute:NSLayoutAttributeBaseline
relatedBy:NSLayoutRelationEqual
toItem:self.valueView attribute:NSLayoutAttributeBaseline
multiplier:1.0f constant:0.f];
constraint.priority = 600;
[self.labelValueConstraints addObject:constraint];
constraint = [NSLayoutConstraint
constraintWithItem:self.valueView attribute:NSLayoutAttributeWidth
relatedBy:NSLayoutRelationEqual
toItem:self.view attribute:NSLayoutAttributeWidth
multiplier:(1.f - self.labelWidthPercentage) constant:0];
constraint.priority = 305;
[self.labelValueConstraints addObject:constraint];
self.valueWidthConstraint = constraint;
[self setCompressionAndHuggingForLabelView:self.label];
[self setCompressionAndHuggingForValueView:self.valueView];
}
- (void)setCompressionAndHuggingForLabelView:(UILabel *)labelView {
if (!labelView) {
return;
}
[labelView setContentCompressionResistancePriority:510 forAxis:UILayoutConstraintAxisHorizontal];
[labelView setContentCompressionResistancePriority:UILayoutPriorityDefaultHigh forAxis:UILayoutConstraintAxisVertical];
[labelView setContentHuggingPriority:450 forAxis:UILayoutConstraintAxisHorizontal];
[labelView setContentHuggingPriority:UILayoutPriorityDefaultHigh forAxis:UILayoutConstraintAxisVertical];
}
- (void)setCompressionAndHuggingForValueView:(UIView *)valueView {
if (!valueView) {
return;
}
[valueView setContentCompressionResistancePriority:509 forAxis:UILayoutConstraintAxisHorizontal];
[valueView setContentCompressionResistancePriority:UILayoutPriorityDefaultHigh forAxis:UILayoutConstraintAxisVertical];
[valueView setContentHuggingPriority:300 forAxis:UILayoutConstraintAxisHorizontal];
[valueView setContentHuggingPriority:650 forAxis:UILayoutConstraintAxisVertical];
}
/****** END Individual Field Controller ******/
setNeedsUpdateConstraints
而是应该调用setNeedsLayout
。根据关于updateConstraints
的文档,“自定义视图应通过重写此方法来设置它们自己的约束条件。”虽然我怀疑这不是问题所在,但总体上代码看起来还不错。需要更多关于你的应用程序的信息:你是否使用 CoreData?什么是“可编辑表单集合”?这里的结构是什么? :) - Matt Mc