Masonry is a light-weight layout framework which wraps AutoLayout with a nicer syntax. Masonry has its own layout DSL which provides a chainable way of describing your NSLayoutConstraints which results in layout code that is more concise and readable. Masonry supports iOS and Mac OS X.
For examples take a look at the Masonry iOS Examples project in the Masonry workspace. You will need to run <code>pod install</code> after downloading.
Under the hood Auto Layout is a powerful and flexible way of organising and laying out your views. However creating constraints from code is verbose and not very descriptive. Imagine a simple example in which you want to have a view fill its superview but inset by 10 pixels on every side
Even with such a simple example the code needed is quite verbose and quickly becomes unreadable when you have more than 2 or 3 views. Another option is to use Visual Format Language (VFL), which is a bit less long winded. However the ASCII type syntax has its own pitfalls and its also a bit harder to animate as <code>NSLayoutConstraint constraintsWithVisualFormat:</code> returns an array.
Heres the same constraints created using MASConstraintMaker
Or even shorter
Also note in the first example we had to add the constraints to the superview <code>[superview addConstraints:...</code>. Masonry however will automagically add constraints to the appropriate view.
Masonry will also call <code>view1.translatesAutoresizingMaskIntoConstraints = NO;</code> for you.
<code>.equalTo</code> equivalent to NSLayoutRelationEqual <code>.lessThanOrEqualTo</code> equivalent to NSLayoutRelationLessThanOrEqual <code>.greaterThanOrEqualTo</code> equivalent to NSLayoutRelationGreaterThanOrEqual
These three equality constraints accept one argument which can be any of the following:
MASViewAttribute
NSLayoutAttribute
view.mas_left
NSLayoutAttributeLeft
view.mas_right
NSLayoutAttributeRight
view.mas_top
NSLayoutAttributeTop
view.mas_bottom
NSLayoutAttributeBottom
view.mas_leading
NSLayoutAttributeLeading
view.mas_trailing
NSLayoutAttributeTrailing
view.mas_width
NSLayoutAttributeWidth
view.mas_height
NSLayoutAttributeHeight
view.mas_centerX
NSLayoutAttributeCenterX
view.mas_centerY
NSLayoutAttributeCenterY
view.mas_baseline
NSLayoutAttributeBaseline
if you want view.left to be greater than or equal to label.left :
Auto Layout allows width and height to be set to constant values. if you want to set view to have a minimum and maximum width you could pass a number to the equality blocks:
However Auto Layout does not allow alignment attributes such as left, right, centerY etc to be set to constant values. So if you pass a NSNumber for these attributes Masonry will turn these into constraints relative to the view’s superview ie:
Instead of using NSNumber, you can use primitives and structs to build your constraints, like so:
An array of a mixture of any of the previous types
<code>.priority</code> allows you to specify an exact priority <code>.priorityHigh</code> equivalent to UILayoutPriorityDefaultHigh <code>.priorityMedium</code> is half way between high and low <code>.priorityLow</code> equivalent to UILayoutPriorityDefaultLow
Priorities are can be tacked on to the end of a constraint chain like so:
Masonry also gives you a few convenience methods which create multiple constraints at the same time. These are called MASCompositeConstraints
You can chain view attributes for increased readability:
Sometimes you need modify existing constraints in order to animate or remove/replace constraints. In Masonry there are a few different approaches to updating constraints.
You can hold on to a reference of a particular constraint by assigning the result of a constraint make expression to a local variable or a class property. You could also reference multiple constraints by storing them away in an array.
Alternatively if you are only updating the constant value of the constraint you can use the convience method <code>mas_updateConstraints</code> instead of <code>mas_makeConstraints</code>
<code>mas_updateConstraints</code> is useful for updating a set of constraints, but doing anything beyond updating constant values can get exhausting. That's where <code>mas_remakeConstraints</code> comes in.
<code>mas_remakeConstraints</code> is similar to <code>mas_updateConstraints</code>, but instead of updating constant values, it will remove all of its contraints before installing them again. This lets you provide different constraints without having to keep around references to ones which you want to remove.
You can find more detailed examples of all three approaches in the Masonry iOS Examples project.
Laying out your views doesn't always goto plan. So when things literally go pear shaped, you don't want to be looking at console output like this:
Masonry adds a category to NSLayoutConstraint which overrides the default implementation of <code>- (NSString *)description</code>. Now you can give meaningful names to views and constraints, and also easily pick out the constraints created by Masonry.
which means your console output can now look like this:
For an example of how to set this up take a look at the Masonry iOS Examples project in the Masonry workspace.
In your Podfile
<code>pod 'Masonry'</code>
If you want to use masonry without all those pesky 'mas_' prefixes. Add #define MAS_SHORTHAND to your prefix.pch before importing Masonry
<code>#define MAS_SHORTHAND</code>
Get busy Masoning
<code>#import "Masonry.h"</code>
Copy the included code snippets to <code>~/Library/Developer/Xcode/UserData/CodeSnippets</code> to write your masonry blocks at lightning speed!
<code>mas_make</code> -> <code>[<view> mas_makeConstraints:^(MASConstraintMaker *make){<code>}];</code>
<code>mas_update</code> -> <code>[<view> mas_updateConstraints:^(MASConstraintMaker *make){<code>}];</code>
<code>mas_remake</code> -> <code>[<view> mas_remakeConstraints:^(MASConstraintMaker *make){<code>}];</code>
Not limited to subset of Auto Layout. Anything NSLayoutConstraint can do, Masonry can do too!
Great debug support, give your views and constraints meaningful names.
Constraints read like sentences.
No crazy macro magic. Masonry won't pollute the global namespace with macros.
Not string or dictionary based and hence you get compile time checking.
Eye candy
Mac example project
More tests and examples
程式猿神奇的手，每時每刻，這雙手都在改變着世界的互動方式！
本文轉自當天真遇到現實部落格園部落格，原文連結：http://www.cnblogs.com/XYQ-208910/p/5011166.html，如需轉載請自行聯系原作者
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