change thinking ‣ Autolayout works in a different way than what you were used to ‣ Don't go calculating frames anymore ‣ Define how an element should behave according to it's peers: ‣ parent ‣ siblings ‣ Don't think in absolute terms, but think in relational terms ‣ Think flexible: it's not because an element has a certain size at one point, it will have the same size at another point
superviews left edge" view.left = (superview.left + 20) y = m * x + c (y%=%attribute1%=%view.left)% (x%=%attribute2%=%superview.left)% (m%=%multiplier%=%1)% (c%=%constant%=%20)
leading ~ left or right depending on language settings ‣ trailing ~ right or left depending on language settings ‣ width ‣ height ‣ centerX ‣ centerY ‣ baseline
each other ‣ adding a second width constraint does not remove or override a previous one ‣ remove first one manually ‣ constraints can cross view hierarchy ‣ add constraint from view to superview of superview ‣ only if scope of view hierarchy uses autolayout! (no custom framesetting)
no subviews) ‣ view knows what size it wants to be (eg UIButton) ‣ autolayout will size view to its intristic content size if no constraints control the width/height :%(CGSize)intrinsicContentSize; Returns%the%natural%size%for%the%receiving%view,%considering% only%properties%of%the%view%itself.% ‣ You can override this method in a subclass to change the default behavior ‣ return UIViewNoIntrinsicMetric when there's no intristic size defined for an axis
this: % |[%%%%%%%Click%Me%%%%%%]|% and you've pinned the edges to a larger superview with priority 500. ! Then, if hugging priority > 500 it'll look like this: % |[Click%Me]%%%%%%%%%%%%%|% If hugging priority < 500 it'll look like this: % |[%%%%%%%Click%Me%%%%%%]|% ! If the superview now shrinks and if the compression resistance priority > 500, it'll look like this % |[Click%|Me]% else if compression resistance priority < 500, it could look like this: % |[Cli..]|
HEAD WILL EXPLODE ‣ Use visual format ‣ HEAD WILL EXPLODE MOAR ‣ Use UIView+AutoLayout Cocoapod ‣ Provides descriptive methods creating constraints ‣ Still verbose but quite readable ‣ Best of both worlds
code ‣ If you create a view manually, use: ! ! ‣ if you don’t, you’ll get a lot of constraint errors! view%=%[UIView%new];% view.translatesAutoresizingMaskIntoConstraints%=%NO;
on UIView. ‣ Easy creation of 1 or more NSLayoutConstraints. ‣ Some methods return 1 constraint, some an NSArray containing constraints ‣ Does not add constraints, just creates them ‣ you need to add them yourself :(void)addConstraint:(NSLayoutConstraint%*)constraint;% :(void)addConstraints:(NSArray%*)constraints;
view to the same edge of the superview with an inset. ! :%(NSLayoutConstraint%*)autoPinEdgeToSuperviewEdge:(ALEdge)edge%withInset: (CGFloat)inset%relation:(NSLayoutRelation)relation;% ‣ Pins the given edge of the view to the same edge of the superview with an inset as a maximum or minimum. ! :%(NSArray%*)autoPinEdgesToSuperviewEdgesWithInsets:(UIEdgeInsets)insets;% ‣ Pins the edges of the view to the edges of its superview with the given edge insets. Pin to superview edges
:%(NSLayoutConstraint%*)autoCenterInSuperviewAlongAxis:(ALAxis)axis;% ‣ Centers the view along the given axis (horizontal or vertical) within its superview. ! :%(NSLayoutConstraint%*)autoPinCenterAxis:(ALAxis)axis% %% % % % %%%toPositionInSuperview:(CGFloat)value;% ‣ Pins the given center axis of the view to a fixed position (X or Y value, depending on axis) in the superview. Centering in superview
to a given edge of another view. ! :%(NSLayoutConstraint%*)autoPinEdge:(ALEdge)edge%toEdge:(ALEdge)toEdge% ofView:(UIView%*)peerView%withOffset:(CGFloat)offset;% ‣ Pins an edge of the view to a given edge of another view with an offset. ! :%(NSLayoutConstraint%*)autoPinEdge:(ALEdge)edge%toEdge:(ALEdge)toEdge% ofView:(UIView%*)peerView%withOffset:(CGFloat)offset%relation: (NSLayoutRelation)relation;% ‣ Pins an edge of the view to a given edge of another view with an offset as a maximum or minimum. Pin to other views
to the same axis of another view. ! :%(NSLayoutConstraint%*)autoAlignAxis:(ALAxis)axis%% %%%%%%%%%%%%%%%%%%%%%toSameAxisOfView:(UIView%*)peerView%% %% % % % % %%%%%%withOffset:(CGFloat)offset;% ‣ Aligns an axis of the view to the same axis of another view with an offset. Aligning views
! :%(NSLayoutConstraint%*)autoSetDimension:(ALDimension)dimension%% % % % % % % % % %toSize:(CGFloat)size;% ‣ Sets the given dimension of the view to a specific size. ! :%(NSLayoutConstraint%*)autoSetDimension:(ALDimension)dimension%% %%% % % % % % % % %toSize:(CGFloat)size%% % % % % % % % %%%relation:(NSLayoutRelation)relation;% ‣ Sets the given dimension of the view to a specific size as a maximum or minimum. View dimensions
to a given dimension of another view. :%(NSLayoutConstraint%*)autoMatchDimension:(ALDimension)dimension%toDimension: (ALDimension)toDimension%ofView:(UIView%*)peerView%withOffset:(CGFloat)offset;% ‣ Matches a dimension of the view to a given dimension of another view with an offset. :%(NSLayoutConstraint%*)autoMatchDimension:(ALDimension)dimension%toDimension: (ALDimension)toDimension%ofView:(UIView%*)peerView%withOffset:(CGFloat)offset%relation: (NSLayoutRelation)relation;% ‣ Matches a dimension of the view to a given dimension of another view with an offset as a maximum or minimum. :%(NSLayoutConstraint%*)autoMatchDimension:(ALDimension)dimension%toDimension: (ALDimension)toDimension%ofView:(UIView%*)peerView%withMultiplier:(CGFloat)multiplier;% ‣ Matches a dimension of the view to a multiple of a given dimension of another view. :%(NSLayoutConstraint%*)autoMatchDimension:(ALDimension)dimension%toDimension: (ALDimension)toDimension%ofView:(UIView%*)peerView%withMultiplier:(CGFloat)multiplier% relation:(NSLayoutRelation)relation;% ‣ Matches a dimension of the view to a multiple of a given dimension of another view as a maximum or minimum. View dimension matching
given value for all constraints created using the UIView+AutoLayout category API within the given constraints block. ‣ NOTE: This method will have no effect (and will NOT set the priority) on constraints created or added using the SDK directly within the block! ‣ Use the auto… methods of UIView+AutoLayout Priorities
view. :%(void)autoRemoveConstraintsAffectingViewAndSubviews;% ‣ Recursively removes all explicit constraints that affect the view and its subviews. Additional%methods%if%you%do%want%to%remove%the% :%(void)autoRemoveConstraintsAffectingViewIncludingImplicitConstraints: (BOOL)shouldRemoveImplicitConstraints;% ‣ Removes all constraints that affect the view, optionally including implicit constraints. : (void)autoRemoveConstraintsAffectingViewAndSubviewsIncludingImplicitConstra ints:(BOOL)shouldRemoveImplicitConstraints;% ‣ Recursively removes all constraints from the view and its subviews, optionally including implicit constraints. Removal of constraints
warning when removing constraints: ‣ The constraint solving engine is not optimised for the removal of constraints ‣ Removing a lot of constraints can have serious impact on performance ‣ Use with care and in small quantities ‣ You can change the priority of a constraint to “disable” it (but you have to remember the original value to reenable it)
only apply to 1 view (eg setting dimensions) ‣ create on view ‣ add to view ‣ When constraints apply to more than 1 view eg pin one view to another ‣ create on target view ‣ add to common superview of both views (usually the same)
translatesAutoresizingMaskIntoConstraints ‣ Display the view hierarchy from the root to find where things go wrong ‣ errors don’t provide any context ! ‣ look for address of view giving errors, and then you’ll get an idea of what context the error is happing in po%[[[[UIApplication%sharedApplication]%windows]% objectAtIndex:0]%recursiveDescription]
‣ (unless you give it a size constraint) ‣ initWithFrame: not really useful anymore ‣ Don’t use frame/bounds calculations in constraints ‣ exception: in layoutSubViews ‣ Try to minimalise the number of constraints ‣ solving takes time ‣ more constraints, more complex
‣ call layoutIfNeeded in animation ‣ Make sure you do this on the correct “top level view” otherwise nothing will animate! self.offsetConstraint.constant%=%[self%calculateOffset];% [UIView%animationWithDuration:0.3%animations:^{% % [self.view%layoutIfNeeded];% }];
constraints ‣ call setNeedsUpdateConstraints ‣ let the system decide when to update ‣ or updateConstraintsIfNeeded ‣ immediate action ‣ only needed when your constraint change might affect other constraints ‣ don’t forget to relayout your views ‣ call setNeedsLayout ‣ or layoutIfNeeded