Issue ResearchKit#118: Adjust fitness quantity pair layout

This fixes a regression in quantity pair layout. The left view of
the quantity pair, the distance view, formerly always contained
content, which fixed the vertical height of the view. At some point
that content was no longer set, handling the no-pedometer-distance
case. The primary fix here is to ensure that a title and zero
quantity are present in the distance view, even if distance is
not available (as in the simulator).

Secondary fixes fix constraints to make them static, since they
do not need to be dynamically updated. We also introduce new baseline
constraints to better enforce alignment between the left and right
views.

Tested distance-only, heart-rate-only, both, and neither visible on
iPhone 6 on iOS 8.3. Tested with and without a value for heart rate,
with both visible.

Author: jwe-apple

ResearchKit/ActiveTasks/ORKActiveStepQuantityView.m

@@ -50,6 +50,8 @@ @implementation ORKActiveStepQuantityView {
     ORKQuantityLabel *_valueLabel;
     ORKTintedImageView *_imageView;
     UIView *_valueHolder;
+    
+    NSLayoutConstraint *_zeroWidthConstraint;
 }
 
 - (instancetype)initWithFrame:(CGRect)frame {
@@ -82,6 +84,7 @@ - (instancetype)initWithFrame:(CGRect)frame {
             view.isAccessibilityElement = NO;
         }
 
+        [self setupConstraints];
         [self setNeedsUpdateConstraints];
     }
     return self;
@@ -108,19 +111,13 @@ - (void)setImage:(UIImage *)image {
     _imageView.image = image;
 }
 
-- (void)updateConstraints {
-    [self removeConstraints:[self constraints]];
+- (void)setupConstraints {
 
     const CGFloat TitleBaselineToValueBaseline = 40;
     const CGFloat ValueBaselineToBottom = 36;
 
-    if (! _enabled) {
-        NSLayoutConstraint *zeroWidthConstraint = [NSLayoutConstraint constraintWithItem:self attribute:NSLayoutAttributeWidth relatedBy:NSLayoutRelationEqual toItem:nil attribute:NSLayoutAttributeNotAnAttribute multiplier:1 constant:0];
-        zeroWidthConstraint.priority = UILayoutPriorityRequired-1;
-        [self addConstraint:zeroWidthConstraint];
-    }
-    NSDictionary *views = NSDictionaryOfVariableBindings(_titleLabel, _valueLabel, _imageView);
     NSMutableArray *additionalConstraints = [NSMutableArray array];
+    NSDictionary *views = NSDictionaryOfVariableBindings(_titleLabel, _valueLabel, _imageView);
     [additionalConstraints addObjectsFromArray:[NSLayoutConstraint constraintsWithVisualFormat:@"V:|[_titleLabel]"
                                                                                        options:0
                                                                                        metrics:nil
@@ -176,10 +173,20 @@ - (void)updateConstraints {
                                                                   attribute:NSLayoutAttributeRight
                                                                  multiplier:1 constant:0]];
     for (NSLayoutConstraint *constraint in additionalConstraints) {
-        constraint.priority = UILayoutPriorityDefaultHigh;
+        constraint.priority = UILayoutPriorityRequired-2;
     }
-    [self addConstraints:additionalConstraints];
 
+    [NSLayoutConstraint activateConstraints:additionalConstraints];
+    
+    
+    NSLayoutConstraint *zeroWidthConstraint = [NSLayoutConstraint constraintWithItem:self attribute:NSLayoutAttributeWidth relatedBy:NSLayoutRelationEqual toItem:nil attribute:NSLayoutAttributeNotAnAttribute multiplier:1 constant:0];
+    zeroWidthConstraint.priority = UILayoutPriorityRequired-1;
+    _zeroWidthConstraint = zeroWidthConstraint;
+    _zeroWidthConstraint.active = !_enabled;
+}
+
+- (void)updateConstraints {
+    _zeroWidthConstraint.active = !_enabled;
     [super updateConstraints];
 }
 
@@ -206,7 +213,6 @@ - (UIAccessibilityTraits)accessibilityTraits {
 
 @implementation ORKQuantityPairView {
     UIView *_metricKeyline;
-    NSArray *_constraints;
 }
 
 - (instancetype)initWithFrame:(CGRect)frame {
@@ -226,16 +232,13 @@ - (instancetype)initWithFrame:(CGRect)frame {
         [self addSubview:_leftView];
         [self addSubview:_rightView];
         [self addSubview:_metricKeyline];
-        [self setNeedsUpdateConstraints];
+        [self setupConstraints];
     }
     return self;
 }
 
-- (void)updateConstraints {
-    if (_constraints) {
-        [self removeConstraints:_constraints];
-        _constraints = nil;
-    }
+- (void)setupConstraints {
+    
     NSMutableArray *constraints = [NSMutableArray array];
     NSDictionary *views = NSDictionaryOfVariableBindings(_leftView, _rightView, _metricKeyline);
 
@@ -255,6 +258,20 @@ - (void)updateConstraints {
     }
     [constraints addObjectsFromArray:horizConstraints];
 
+    // Ensure baseline alignment of title and value
+    [constraints addObject:[NSLayoutConstraint constraintWithItem:_leftView.titleLabel
+                                                        attribute:NSLayoutAttributeFirstBaseline
+                                                        relatedBy:NSLayoutRelationEqual
+                                                           toItem:_rightView.titleLabel
+                                                        attribute:NSLayoutAttributeFirstBaseline
+                                                       multiplier:1 constant:0]];
+    [constraints addObject:[NSLayoutConstraint constraintWithItem:_leftView.valueLabel
+                                                        attribute:NSLayoutAttributeFirstBaseline
+                                                        relatedBy:NSLayoutRelationEqual
+                                                           toItem:_rightView.valueLabel
+                                                        attribute:NSLayoutAttributeFirstBaseline
+                                                       multiplier:1 constant:0]];
+    
     [constraints addObjectsFromArray:[NSLayoutConstraint constraintsWithVisualFormat:@"H:[_leftView][_metricKeyline(==s)]"
                                                                              options:NSLayoutFormatAlignAllTop|NSLayoutFormatDirectionLeftToRight
                                                                              metrics:@{@"s":@(1/scale)}
@@ -289,9 +306,7 @@ - (void)updateConstraints {
     equalWidthConstraint.priority = UILayoutPriorityDefaultLow;
     [constraints addObject:equalWidthConstraint];
 
-    [self addConstraints:constraints];
-    _constraints = constraints;
-    [super updateConstraints];
+    [NSLayoutConstraint activateConstraints:constraints];
 }
 
 - (void)setKeylineHidden:(BOOL)keylineHidden {

ResearchKit/ActiveTasks/ORKFitnessContentView.m

@@ -106,11 +106,14 @@ - (instancetype)initWithFrame:(CGRect)frame {
         self.backgroundColor = [[UIColor redColor] colorWithAlphaComponent:0.2];
         _quantityPairView.backgroundColor = [[UIColor orangeColor] colorWithAlphaComponent:0.2];
 #endif
-        
+      
+        [self setDistanceInMeters:0];
+        [self heartRateView].title = ORKLocalizedString(@"FITNESS_HEARTRATE_TITLE", nil);
+
         [self addSubview:_quantityPairView];
         [self addSubview:_imageView];
         [self addSubview:_timerLabel];
-        [self setNeedsUpdateConstraints];
+        [self setupConstraints];
 
         [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(localeDidChange:) name:NSCurrentLocaleDidChangeNotification object:nil];
 
@@ -147,11 +150,7 @@ - (void)updateConstraintConstants {
     _topConstraint.constant = (CaptionBaselineToTimerTop - CaptionBaselineToStepViewTop);
 }
 
-- (void)updateConstraints {
-    if (_constraints) {
-        [self removeConstraints:_constraints];
-        _constraints = nil;
-    }
+- (void)setupConstraints {
     NSMutableArray *constraints = [NSMutableArray array];
     NSDictionary *views = NSDictionaryOfVariableBindings(_timerLabel, _imageView, _quantityPairView, _imageSpacer1, _imageSpacer2);
     [constraints addObjectsFromArray:[NSLayoutConstraint constraintsWithVisualFormat:@"V:[_timerLabel][_imageSpacer1(>=0)][_imageView]"
@@ -239,8 +238,6 @@ - (void)updateConstraints {
     [constraints addObject:maxWidthConstraint];
 
     [self addConstraints:constraints];
-    _constraints = constraints;
-    [super updateConstraints];
 }
 
 - (void)setImage:(UIImage *)image {
@@ -277,7 +274,6 @@ - (void)setHasHeartRate:(BOOL)hasHeartRate {
 - (void)setHeartRate:(NSString *)heartRate {
     _heartRate = heartRate;
     [self heartRateView].value = heartRate;
-    [self heartRateView].title = ORKLocalizedString(@"FITNESS_HEARTRATE_TITLE", nil);
 }
 
 - (void)updateKeylineVisible {