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Introduction

SkinKit is an iOS-Framework that allows you to easily customize the appearance of your app. It provides a simple API for loading skins and helps you to quickly build custom app designs by making useful defaults.

Features

• Simple interface for loading skins.
• Skins encapsulate the appearance modifications that make your app look special.
• Useful defaults: When using SKDefaultSkin or a subclass, you don't need to specify every single property. Instead the skin makes useful assumptions by calculating colors based on properties you provide. For example, when the baseTintColor is specified the backgroundColor is automagically set to a lighter version of that color while the tabBarTintColor gets a darker one. To learn more about that magic, read the Building skins section.
• The framework allows customization of UI elements that don't support the UIAppearance proxy, such as setting the background color (or a pattern image) on a regular UIView.
• Use bundles for your skins.

Installation

It's recommended to use a workspace where you put both your project and the SkinKit framework as siblings. It may also work if you put SkinKit as a subproject of your app, but I haven"t tested it yet.

Requirements

• iOS 6.0 or newer
• Xcode 4.5 or newer

Note: The framework uses ARC. However, since it builds as a seperate target, you're not forced to use ARC in your main project.

Using a workspace

1. Create a workspace in Xcode.
2. Copy your main project to the workspace or create a new one.
3. Add the SkinKit project (not the demo!) as a sibling to the workspace.
4. Drag the libSkinKit.a to your project's "Link Binary with Library" build phase.
5. Set header search path to: "$(BUILT_PRODUCTS_DIR)", check "recursive".
6. Add "Other linker flags": "-ObjC".

Usage

Once you've successfully installed the framework, it can now be used in your project. It is useful to load the skin when the app has just started. To do so, import the framework to your AppDelegate class:

import <SkinKit/SkinKit.h>

Loading skins

A good place to load the skin for your app is in the application:didFinishLaunchingWithOptions: method of your AppDelegate:

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    // 1. get an instance of the shared skin manager
    SKSkinManager *skinManager = [SKSkinManager sharedSkinManager];
    
    // 2. set your custom skin subclass
    skinManager.skin = [[MyFancySkin alloc] init];
     
    // 3. finally apply customizations
    [skinManager applySkin];
    
    // Do your regular initialization here
     
    return YES;
}

This piece of code first retrieves an instance of the SKSkinManager class which is responsible for applying custom appearance modifications to your UI elements. It mainly relies on the UIAppearance proxy that was introduced in iOS 5.0 and further enhanced in iOS 6.0.
The next step is to set a skin that should be used to modify the app's appearance. A skin functions as a data source (much like a UITableViewDataSource). The skin manager may ask the skin for colors to tint UI elements or for custom images to be used for the navigation bar or bar button items etc.. Learn more about skins and how to build them in the Building skins section.
Finally call applySkin for the modifications to take effect.

Customize views

Some UI elements (like a regular UIView, UIScrollView or UITableView) don't have a UIAppearance proxy. However SkinKit provides a way to do custom appearance modifications on these elements as well. One way to do this is to manually apply the skin to individual views:

// skin a UIView
[[[SKSkinManager] sharedSkinManager] applySkinToView:theView];

// skin a UIScrollView
[[[SKSkinManager] sharedSkinManager] applySkinToScrollView:theScrollView];

// skin a UITableView
[[[SKSkinManager] sharedSkinManager] applySkinToTableView:theTableView];

This gives you fine granular control of the views you want to customize, but requires a lot of code.
If, for example, you wish to set the background color of all "top-level" views, i.e. the views that are directly associated to a UIViewController, there's also a handy way to do this:

[SKSkinManager sharedSkinManager].automaticallyApplySkinForViews = YES;

This works by having a category on UIViewController automatically call the methods shown above (applySkinTo*View) on the view controller's root view.

Building skins

This is actually the fun part!
A skin could be created in three ways:

1. Create a class that implements the SKSkinDataSource protocol.
2. Create a bundle and provide your customizations in the bundle's Info.plist file.
3. Mix the above two approaches!

SKSkinDataSource

You can build a new skin by creating a class that conforms to the SKSkinDataSource protocol. The protocol defines a list of methods that you need to implement in order that the skin manager (SKSkinManager) knows how to customize your UI. You can use an arbitrary class (such as your app delegate) that implements the protocol, but it's strongly recommended to use a separate class for this purpose that could also be reused in a future project.

For convenience, SkinKit provides two classes that already implement the SKSkinDataSource protocol:

1. SKSkin loads values from the skin's bundle Info.plist file if available, otherwise returns nil for all attributes.
2. SKDefaultSkin is a subclass of SKSkin that makes useful assumptions, such as calculating the background color from the base tint color.

You should prefer using one of these two classes over creating a new that implements the protocol and only override the methods you need.

Using bundles

A bundle is a special kind of folder that has the extension .bundle. If you plan to use images for your skin, a bundle is required. The bundle must have the following structure:

MyFancySkin.bundle/Contents
MyFancySkin.bundle/Contents/Info.plist (optional)
MyFancySkin.bundle/Contents/Resources (place your image files here, optional)

Note: If your skin class is named MyFancySkin the bundle name must be MyFancySkin.bundle. However, you don't even need a separate class for your skin, if you instantiate it like this: id<SKSkinDataSource> skin = [[SKSkin alloc] initWithBundleName:@"MyFanceBundleOnlySkin"] or id<SKSkinDataSource> skin = [[SKDefaultSkin alloc] initWithBundleName:@"MyFanceBundleOnlySkin"].

The Info.plist file can be used to specify custom appearance attributes (currently only color values are supported) by providing a dictionary named SKSkinDataSource:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
	<key>CFBundleIdentifier</key>
	<string>SkinKit.Skin.MyFancySkin</string>
	<key>CFBundleName</key>
	<string>MyFancySkin</string>
	<key>SKSkinDataSource</key>
	<dict>
		<key>controlBaseTintColor</key>
		<dict>
			<key>name</key>
			<string>orange</string>
		</dict>
		<key>backgroundColor</key>
		<dict>
			<key>hsb</key>
			<dict>
				<key>h</key>
				<string>0.7</string>
				<key>s</key>
				<string>0.2</string>
				<key>b</key>
				<string>0.7</string>
				<key>a</key>
				<string>1.0</string>
			</dict>
		</dict>
		<key>accentTintColor</key>
		<dict>
			<key>hex</key>
			<string>#df4</string>
		</dict>
		<key>baseTintColor</key>
		<dict>
			<key>rgb</key>
			<string>1.0 0.3 0.5</string>
		</dict>
	</dict>
</dict>
</plist>

See further sections for a complete list of available style attributes.
As shown in the example above, color values can be specified in several ways:

• RGB string: "red green blue" or "red green blue alpha"
• RGB dictionary with keys "r", "g", "b", "a" (optional)
• HSB string: "hue saturation brightness" or "hue saturation brightness alpha"
• HSB dictionary with keys "h", "s", "b", "a" (optional)
• Hex string: "rrggbb", "rrggbbaa", "rgb", "rgba". Optionally with leading "#" or "0x".
• Name: e.g. "red" or "darkGray". See here for a list of color names (just omit the "Color" suffix).

All color components must be float values between 0.0f and 1.0f. The alpha component is optional and defaults to 1.0f.

Skinnable UI elements

General attributes

UITabBar

UINavigationBar

UIToolbar

UISearchBar

UIBarButtonItem

UITableView

UIScrollView

Controls

Skinnable controls: UISwitch, UIStepper, UISegmentedControl, UISlider, UIProgressView

Planned features and improvements

• Shared skins.
• Custom layout.
• UICollectionView customization (appearance and layout).
• Skin generator companion app for Mac or iOS.
• CSS files.

Motivation

The SkinKit framework is the result of a seminar (iOS Advanced Topics) at the Technical University Munich in summer 2012. The challenge was to create an open-source-licensed iOS framework that builds as a static library.
// TODO: more information

License

SkinKit is released under the MIT license:

Copyright (c) <2012> <Dominique d'Argent>

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.