Swift theme color top solution

1. Conventional theme color usage points

Before an application is released, the theme color will be set to unify the style of the application (there may be multiple themes). There are several aspects in setting the theme color, as follows:

1. In the TabBar section, set the image highlight and text height color

2. NavigationBar part, set the navigation bar color and font color

3. Apply labels, etc., set the font color

4. Apply image theme color

The setting points of theme color are generally based on the above four aspects. The theme color of the picture can be processed by changing the picture. There are different processing methods for 1-3 items processed by code. The general processing methods are as follows:

Step 1: Separation of changes

1. Use Swift extension syntax to extend UIColor and unify the application theme color in the extension (suitable for a single theme color)

2. Write the theme color configuration into a file and parse it with the corresponding logic. This method encapsulates the theme color logic into a theme color management class (suitable for multiple themes)

Step 2: Discretely use the class encapsulated in the previous step

1. Use the UIColor method in the extension to set any theme color, including background color, text color, etc.

Here is the extension of UIColor

 extension UIColor { 
  
 //Theme color  
 class func applicationMainColor() -> UIColor {
 return UIColor(red: 238 / 255 , green: 64 / 255 , blue: 86 / 255 , alpha: 1 )
 } 
  
 //Second theme color  
 class func applicationSecondColor() -> UIColor {
 return UIColor.lightGrayColor()
 } 
  
 //Warning color  
 class func applicationWarningColor() -> UIColor {
 return UIColor(red: 0.1 , green: 1 , blue: 0 , alpha: 1 )
 } 
  
 //Link color  
 class func applicationLinkColor() -> UIColor {
 return UIColor(red: 59 / 255 , green: 89 / 255 , blue: 152 / 255 , alpha: 1 )
 } 
  
 }

2. TabBar theme color setting

Many applications use the TabBar control by default, but the settings of the TabBar theme color and other settings vary depending on the usage. Code creation is more flexible and it is easier to change the theme color. There is also a way to do unified processing when using Xib/Storyboard, as follows, iteratively change the default font color of the TabBar

 func configTabBar() {
       let items = self.tabBar.items
 for item in items as [UITabBarItem] {
           let dic = NSDictionary(object: UIColor.applicationMainColor(),
            forKey: NSForegroundColorAttributeName)
           item.setTitleTextAttributes(dic,
            forState: UIControlState.Selected)
 }
 }

Set the default selected color of TabBar images and text

self.tabBar.selectedImageTintColor = UIColor.applicationMainColor()

Tips注意事项

Changing this property's value provides visual feedback in the user interface, including the running of any associated animations. The selected item displays the tab bar item's selectedImage image, using the tab bar's selectedImageTintColor value. To prevent system coloring of an item, provide images using the UIImageRenderingModeAlwaysOriginal rendering mode.

在一些情况，正常状态为白色图片时，真机测试时，白色图片会出现偏色（显示结果为灰色），这是因为系统默认着色导致的，在创建UITabBarItem时，可通过使用UIImageRenderingModeAlwaysOriginal避免。示例代码如下：

 let imageNormal = UIImage(contentsOfFile: "imageNormal" )?.
 imageWithRenderingMode(UIImageRenderingMode.AlwaysOriginal)
 let imageSelected = UIImage(contentsOfFile: "imageSelected" )
 let tabBarItem = UITabBarItem(title: "title" ,
 image: imageNormal,
         selectedImage: imageSelected

3. Once and for all, use the Hook principle to set the NavigationBar color

NavigationBar is very commonly used in iOS applications. Its use mainly includes the following two scenarios

1. Code build directly

2. Xib/Storyboard construction

If it is built with pure code, it is relatively simple. You can directly use the extension of UIColor to set the color. In actual projects, some interfaces are created through Xib/Storyboard, and some are written in code, but this is not difficult for everyone. Use inheritance. Create a subclass that inherits from UINavigationController, and use this subclass to uniformly set the theme color. Then tell everyone in the project to force the use of UINavigationController subclasses, including Xib/Storyboard, etc. The question is what to do with old projects. This mandatory requirement can work. Is there a better way to let everyone use UINavigationController normally, and set all NavigationBars without anyone knowing? Post the code first, then explain

1. Create an extension of UIViewController

 extension UIViewController {
    func viewDidLoadForChangeTitleColor() {
        self.viewDidLoadForChangeTitleColor()
 if self.isKindOfClass(UINavigationController.classForCoder()) {
           self.changeNavigationBarTextColor(self as UINavigationController)
 }
 } 
  
    func changeNavigationBarTextColor(navController: UINavigationController) {
        let nav = navController as UINavigationController
        let dic = NSDictionary(object: UIColor.applicationMainColor(),
         forKey:NSForegroundColorAttributeName)
        nav.navigationBar.titleTextAttributes = dic
        nav.navigationBar.barTintColor = UIColor.applicationSecondColor()
        nav.navigationBar.tintColor = UIColor.applicationMainColor() 
  
 } 
  
 }

2. Write a tool class for Hook

 func swizzlingMethod(clzz: AnyClass, #oldSelector: Selector, #newSelector: Selector) {
    let oldMethod = class_getInstanceMethod(clzz, oldSelector)
    let newMethod = class_getInstanceMethod(clzz, newSelector)
    method_exchangeImplementations(oldMethod, newMethod)
 }

3. Call in AppDelegate

 func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: NSDictionary?) -> Bool {
        swizzlingMethod(UIViewController.self,
        oldSelector: "viewDidLoad" ,
        newSelector: "viewDidLoadForChangeTitleColor" )
 //do others  
 return   true  
 }

4. Principle

At the program entry, through the runtime mechanism, dynamically replace the UIViewController's periodic method viewDidLoad with the method viewDidLoadForChangeTitleColor that we specify. In viewDidLoadChangeTitleColor, two things need to be done:

Call the original viewDidLoad method

· Execute code related to modifying theme color

How to call the original viewDidLoad method:

In AppDelegate, we replace the viewDidLoad and viewDidLoadForChangeTitleColor method bodies by calling the swizzlingMethod method. The principle is as follows:

As can be seen from the figure above, when executed in viewDidLoadForChangeTitleColor:

 self.viewDidLoadForChangeTitleColor()

It will not cause a circular call, but instead call the viewDidLoad method body that we expect to execute.

3. Xib/Storyboard processing

How to deal with some theme colors set in Xib/Storyboard, such as text color, button highlight color, etc. Take UILabel as an example and create an extension

 extension UILabel {
 var colorString: String {
 set(newValue) {
 switch newValue {
 case   "main" :
                self.textColor = UIColor.applicationMainColor()
 case   "second" :
                self.textColor = UIColor.applicationSecondColor()
 case   "warning" :
                self.textColor = UIColor.applicationWarningColor()
 default :
                self.textColor = UIColor.applicationSecondColor()
 }
 }
 get {
 return self.colorString
 }
 }
 }

Edit in the Xib/Storyboard inspector, as shown below:

IV. Conclusion

1. When there is only one theme, the above method can be copied and used directly. When changing the theme, you only need to change the corresponding picture and modify the extension class of UIColor.

2. When there are multiple themes and users can switch themes freely, they can hijack viewWillAppear according to the Hook mechanism in the article, and they can also easily change the theme.

Link to this article: http://www.cocoachina.com/swift/20141127/10336.html