类UITabBarController是一个特殊的UIViewController,它可以包含多个UIViewController,并且在页面底部显示一个Tabbar作为UIViewController的切换显示开关。
如下案例,展示了包含两个UIViewController的UITabBarController,可以通过底部的Tabbar来切换显示:
import UIKit
class Page1: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
let cc = UILabel(frame: CGRect(x: 10,y: 50,width: 200,height: 50))
cc.text = "Page #1"
cc.textColor = UIColor.black
self.view.addSubview(cc)
}
}
class Page2: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
let cc = UILabel(frame: CGRect(x: 10,y: 50,width: 200,height: 50))
cc.text = "Page #2"
cc.textColor = UIColor.black
self.view.addSubview(cc)
}
}
class Tabbar: UITabBarController, UITabBarControllerDelegate {
override func viewDidLoad() {
super.viewDidLoad()
delegate = self
}
override func viewWillAppear(_ animated: Bool) {
viewControllers = [Page1(),Page2()]
let r = UIImage.imageWithColor(UIColor.black)
viewControllers![0].tabBarItem = UITabBarItem(title: "Page 1",
image:r,
tag:0)
viewControllers![1].tabBarItem = UITabBarItem(title: "Page 2",
image: r,
tag:1)
}
//Delegate methods
func tabBarController(_ tabBarController: UITabBarController, didSelect viewController: UIViewController) {
print("did select viewController: \(viewController.tabBarItem.tag)")
}
}
@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {
var window: UIWindow?
func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
self.window = UIWindow(frame: UIScreen.main.bounds)
self.window!.rootViewController = Tabbar()
self.window!.rootViewController!.view.backgroundColor = UIColor.white
self.window?.makeKeyAndVisible()
return true
}
}
// same code
extension UIImage {
class func imageWithColor(_ color: UIColor) -> UIImage {
let rect = CGRect(x: 0.0, y: 0.0, width: 10.0,height: 10.0 )
UIGraphicsBeginImageContext(rect.size)
let context = UIGraphicsGetCurrentContext()
context?.setFillColor(color.cgColor)
context?.fill(rect)
let image = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()
return image!
}
}
//let r = UIImage.imageWithColor(UIColor.redColor()).imageWithRenderingMode(.AlwaysOriginal)
//let b = UIImage.imageWithColor(UIColor.blueColor()).imageWithRenderingMode(.AlwaysOriginal)
可以点击屏幕显示的下方按钮切换视图控制器。
本案例中,共有三个需要关注的类:
Page1,Page2。都是UIViewController的子类,内含一个UILabel区别显示为Page #1,Page #2
-
Tabbar 是UITabBarController的子类,实现协议UITabBarControllerDelegate,并在viewDidLoad时设置委托到自身;属性viewControllers是一个数组,用于装入多个UIViewController的实例,当执行:
func viewWillAppear(_ animated: Bool)
初始化此数组,创建需要选择的UIViewController实例进来。
Tabbar就是一个UIViewController的子类,因此可以把它设置到self.window!.rootViewController上,从而成为window的rootViewController。
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