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POAuto Layout Constraints Throwing Exception
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  1. POAuto Layout Constraints Throwing Exception
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    copied!<p>I am using auto layouts on fields I am loading into table view cells. For each cell I clear all subviews out of the contentView and load my own views based on the type of field I need. Most cells are fine, but when this one comes into view, I get an exception.</p> <p>Here is the code for the cell:</p> <pre><code>UILabel *questionText = [[UILabel alloc] init]; questionText.text = self.field.questionText; questionText.font = font; questionText.numberOfLines = 0; questionText.adjustsFontSizeToFitWidth = NO; questionText.lineBreakMode = NSLineBreakByWordWrapping; [questionText setTranslatesAutoresizingMaskIntoConstraints:NO]; [self.contentView addSubview:questionText]; UIView *listContainer = [[UIView alloc] init]; listContainer.backgroundColor = [UIColor whiteColor]; listContainer.layer.cornerRadius = 8; listContainer.layer.borderWidth = 1.0; [listContainer setTranslatesAutoresizingMaskIntoConstraints:NO]; [self.contentView addSubview:listContainer]; // Get the views dictionary NSDictionary *viewsDictionary = NSDictionaryOfVariableBindings(questionText, listContainer); //Create the constraints using the visual language format NSString *format = @"V:|-10-[questionText]-10-[listContainer]-10-|"; NSArray *constraintsArray = [NSLayoutConstraint constraintsWithVisualFormat:format options:NSLayoutFormatAlignAllLeft metrics:nil views:viewsDictionary]; [self.contentView addConstraints:constraintsArray]; format = @"|-10-[questionText]-10-|"; constraintsArray = [NSLayoutConstraint constraintsWithVisualFormat:format options:NSLayoutFormatAlignAllLeft metrics:nil views:viewsDictionary]; [self.contentView addConstraints:constraintsArray]; format = @"|-10-[listContainer]-10-|"; constraintsArray = [NSLayoutConstraint constraintsWithVisualFormat:format options:NSLayoutFormatAlignAllLeft metrics:nil views:viewsDictionary]; [self.contentView addConstraints:constraintsArray]; ToggleButton *prevCheckbox; ToggleButton *checkbox; for (AssessmentAnswer *answer in self.field.answers) { checkbox = [[ToggleButton alloc] initWithText:answer.text ofType:ToggleButtonTypeCheckbox]; [checkbox setTranslatesAutoresizingMaskIntoConstraints:NO]; [listContainer addSubview:checkbox]; viewsDictionary = NSDictionaryOfVariableBindings(checkbox); format = @"|-10-[checkbox]-10-|"; constraintsArray = [NSLayoutConstraint constraintsWithVisualFormat:format options:NSLayoutFormatAlignAllCenterY metrics:nil views:viewsDictionary]; [listContainer addConstraints:constraintsArray]; if (prevCheckbox) { // This is not the first item [listContainer addConstraint:[NSLayoutConstraint constraintWithItem:checkbox attribute:NSLayoutAttributeTop relatedBy:NSLayoutRelationEqual toItem:prevCheckbox attribute:NSLayoutAttributeBottom multiplier:1.0 constant:20.0]]; } else { // This is the first item [listContainer addConstraint:[NSLayoutConstraint constraintWithItem:checkbox attribute:NSLayoutAttributeTop relatedBy:NSLayoutRelationEqual toItem:listContainer attribute:NSLayoutAttributeTop multiplier:1.0 constant:10.0]]; } prevCheckbox = checkbox; } if (checkbox) { // This is the last checkbox [listContainer addConstraint:[NSLayoutConstraint constraintWithItem:listContainer attribute:NSLayoutAttributeBottom relatedBy:NSLayoutRelationEqual toItem:checkbox attribute:NSLayoutAttributeBottom multiplier:1.0 constant:10.0]]; } </code></pre> <p>In this case, there is only one item in <code>self.field.answers</code>. Font is the same value as what is used below.</p> <p>Here is the code for the cell height:</p> <pre><code>UIFont *font = [UIFont fontWithName:@"Helvetica" size:14.0]; //Find height of question text CGFloat questionTextHeight = [field.questionText sizeWithFont:font constrainedToSize:CGSizeMake(width - (2 * PAD_X), CGFLOAT_MAX) lineBreakMode:NSLineBreakByWordWrapping].height; //Find height of each row CGFloat listHeight = 0.0; for (AssessmentAnswer *answer in field.answers) { listHeight += MAX([answer.text sizeWithFont:font constrainedToSize:CGSizeMake(width - 43.0 - [ToggleButton getImageWidth], CGFLOAT_MAX) lineBreakMode:NSLineBreakByWordWrapping].height, [ToggleButton getImageHeight]) + 20.0; } // Question text height + list height + spacers return questionTextHeight + listHeight + 30.0; </code></pre> <p>Here is the code that creates the insides of a ToggleButton, which is a UIButton:</p> <pre><code>for (UIView *subview in self.subviews) { [subview removeFromSuperview]; } // Add the toggle button image self.toggleImgView = [[UIImageView alloc] init]; [self.toggleImgView setTranslatesAutoresizingMaskIntoConstraints:NO]; [self addSubview:self.toggleImgView]; // Add the label self.toggleLabel = [[UILabel alloc] init]; self.toggleLabel.font = [UIFont fontWithName:@"Helvetica" size:14.0f]; self.toggleLabel.numberOfLines = 0; self.toggleLabel.adjustsFontSizeToFitWidth = NO; self.toggleLabel.lineBreakMode = NSLineBreakByWordWrapping; self.toggleLabel.backgroundColor = [UIColor clearColor]; [self.toggleLabel setTranslatesAutoresizingMaskIntoConstraints:NO]; [self addSubview:self.toggleLabel]; // Get the views dictionary NSDictionary *viewsDictionary = NSDictionaryOfVariableBindings(_toggleImgView, _toggleLabel); //Create the constraints using the visual language format NSString *format = [NSString stringWithFormat:@"|-0-[_toggleImgView(%f)]-3-[_toggleLabel]-0-|", IMAGE_WIDTH]; NSArray *constraintsArray = [NSLayoutConstraint constraintsWithVisualFormat:format options:nil metrics:nil views:viewsDictionary]; [self addConstraints:constraintsArray]; viewsDictionary = NSDictionaryOfVariableBindings(_toggleLabel); format = [NSString stringWithFormat:@"V:|-0-[_toggleLabel(&gt;=%f)]-0-|", IMAGE_HEIGHT]; constraintsArray = [NSLayoutConstraint constraintsWithVisualFormat:format options:NSLayoutFormatAlignAllLeft metrics:nil views:viewsDictionary]; [self addConstraints:constraintsArray]; [self addConstraint:[NSLayoutConstraint constraintWithItem:self.toggleImgView attribute:NSLayoutAttributeHeight relatedBy:NSLayoutRelationEqual toItem:self.toggleImgView attribute:NSLayoutAttributeWidth multiplier:1.0 constant:0.0]]; [self addConstraint:[NSLayoutConstraint constraintWithItem:self.toggleImgView attribute:NSLayoutAttributeCenterY relatedBy:NSLayoutRelationEqual toItem:self.toggleLabel attribute:NSLayoutAttributeCenterY multiplier:1.0 constant:0.0]]; </code></pre> <p>Here is the exception readout I am getting:</p> <pre><code>Unable to simultaneously satisfy constraints. 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) ( "&lt;NSLayoutConstraint:0x1f28c4f0 V:[UILabel:0x1f288f10(&gt;=27)]&gt;", "&lt;NSLayoutConstraint:0x1f291460 V:[ToggleButton:0x1f068e50]-(10)-| (Names: '|':UIView:0x1f0182a0 )&gt;", "&lt;NSLayoutConstraint:0x1f293830 V:[UILabel:0x1f288f10]-(0)-| (Names: '|':ToggleButton:0x1f068e50 )&gt;", "&lt;NSLayoutConstraint:0x1f28b480 V:|-(10)-[UILabel:0x1f062890] (Names: '|':UITableViewCellContentView:0x1f1c23d0 )&gt;", "&lt;NSLayoutConstraint:0x1f29b070 V:|-(10)-[ToggleButton:0x1f068e50] (Names: '|':UIView:0x1f0182a0 )&gt;", "&lt;NSLayoutConstraint:0x1f289810 V:[UIView:0x1f0182a0]-(10)-| (Names: '|':UITableViewCellContentView:0x1f1c23d0 )&gt;", "&lt;NSLayoutConstraint:0x1f292eb0 V:|-(0)-[UILabel:0x1f288f10] (Names: '|':ToggleButton:0x1f068e50 )&gt;", "&lt;NSLayoutConstraint:0x1f28dc90 V:[UILabel:0x1f062890]-(10)-[UIView:0x1f0182a0]&gt;", "&lt;NSAutoresizingMaskLayoutConstraint:0x1f1e5ed0 h=--&amp; v=--&amp; V:[UITableViewCellContentView:0x1f1c23d0(60)]&gt;" ) Will attempt to recover by breaking constraint &lt;NSLayoutConstraint:0x1f293830 V:[UILabel:0x1f288f10]-(0)-| (Names: '|':ToggleButton:0x1f068e50 )&gt; Break on objc_exception_throw to catch this in the debugger. The methods in the UIConstraintBasedLayoutDebugging category on UIView listed in &lt;UIKit/UIView.h&gt; may also be helpful. </code></pre> <p>I don't get why I am getting the exception because all the heights add up. This scenario is happening with a few other cell types so any insight would be helpful.</p>
 

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