委托無法在第二視圖控制器中調用

Question

我想在第一個視圖控制器中單擊按鈕時將圖像傳遞給第二個控制器。 我無法理解，即使我已經將我的第一個視圖控制器的引用提供給第二個控制器，然后也沒有調用該委托

1，這里是我的第一個視圖控制器的代碼

protocol ViewControllerDelegate: class{
func Imagine(get: UIImage?)
}
class ViewController: UIViewController  {
let button = UIButton()
weak var delegate:ViewControllerDelegate?
var image = UIImage(named:"face1.png")
override func viewDidLoad() {
    super.viewDidLoad()
    addButton()
    addConstraints()

    // Do any additional setup after loading the view, typically from a nib.
}


func addButton() -> Void {
     button.setImage(UIImage(named:"face1.png"), for: .normal)
     button.layer.borderColor = UIColor.white.cgColor
     button.clipsToBounds = true
     button.showsTouchWhenHighlighted = true
     button.addTarget(self, action: #selector(buttonPressed), for: .touchUpInside)
     view.addSubview(button)
}
func buttonPressed() -> Void {
    pressed()
    let alert = UIAlertController(title: "Alert", message: "Image 🤓 sent to Tab 3", preferredStyle: UIAlertControllerStyle.alert)
    let ok = UIAlertAction(title: "OK", style: UIAlertActionStyle.cancel, handler: nil)
    alert.addAction(ok)
    self.present(alert, animated: true, completion:nil)

}

func addConstraints() -> Void {
    button.snp.makeConstraints { (make) in
        make.width.height.equalTo(150)
        make.center.equalToSuperview()
       }

}

func pressed(){
    delegate?.Imagine(get: UIImage(named:"face1.png"))
}


}

2.這是第二視圖控制器的代碼

class ViewController3: UIViewController, ViewControllerDelegate{
var imageView=UIImageView()
var obj:ViewController?
override func viewDidLoad() {
    super.viewDidLoad()
     view.backgroundColor = UIColor.white
    // getImage = UIImage(named: "face3.png")
     addView()
     addConstraints()
    **obj.delegate = self**
}


func addView() -> Void{

    view.addSubview(imageView)
}


func addConstraints() -> Void {
    imageView.snp.makeConstraints { (make) in
        make.width.height.equalTo(150)
        make.center.equalToSuperview()
                                  }
    }
//NOT Called
    func Imagine(get: UIImage?) {
    imageView.image = get
}
}

3.這是我的標簽欄控制器

class ViewController4: UITabBarController ,UITabBarControllerDelegate {
var v:ViewController?
override func viewDidLoad() {
    super.viewDidLoad()
    view.backgroundColor = UIColor.white
    self.delegate = self
}

override func viewWillAppear(_ animated: Bool) {
    super.viewWillAppear(true)

    let tab1 = ViewController()
    let tab1BarItem = UITabBarItem(title: "Tab1", image:UIImage(named:"bell-off-7.png"), selectedImage:UIImage(named:"bell-7.png") )
    tab1.tabBarItem = tab1BarItem


    let tab2 = ViewController2()
    let tab2BarItem = UITabBarItem(title: "Tab2", image: UIImage(named:"bell-off-7.png"), selectedImage: UIImage(named:"bell-7.png"))
    tab2.tabBarItem = tab2BarItem


    let tab3 = ViewController3()

    let tab3BarItem = UITabBarItem(title: "Tab3", image:     UIImage(named:"bell-off-7.png"), selectedImage: UIImage(named:"bell-7.png"))
    tab3.tabBarItem = tab3BarItem
    self.viewControllers = [tab1,tab2,tab3]
}

}

Answer 1

切換選項卡時必須設置圖像。 當前，您正在做的是更改尚未顯示的viewController的圖像。

您可以將標簽添加到每個項目，並使用didSelectViewController委托函數

在tabBar的ViewController中添加變量tappedImage，例如

var tappedImage:UIImage?
override func viewWillAppear(_ animated: Bool) {
    super.viewWillAppear(true)

    let tab1 = ViewController()
    let tab1BarItem = UITabBarItem(title: "Tab1", image:UIImage(named:"bell-off-7.png"), selectedImage:UIImage(named:"bell-7.png") )
    tab1BarItem.tag = 0
    tab1.tabBarItem = tab1BarItem


    let tab2 = ViewController2()
    let tab2BarItem = UITabBarItem(title: "Tab2", image: UIImage(named:"bell-off-7.png"), selectedImage: UIImage(named:"bell-7.png"))
    tab2BarItem.tag = 1
    tab2.tabBarItem = tab2BarItem


    let tab3 = ViewController3()

    let tab3BarItem = UITabBarItem(title: "Tab3", image:     UIImage(named:"bell-off-7.png"), selectedImage: UIImage(named:"bell-7.png"))
    tab3BarItem.tag = 2
    tab3.tabBarItem = tab3BarItem
    self.viewControllers = [tab1,tab2,tab3]
}

    func Imagine(get: UIImage?) {
        tappedImage = get
    }

        func tabBarController(tabBarController: UITabBarController, didSelectViewController viewController: UIViewController) {
            if let secondVC = viewController as? ViewController2 {
              secondVC.selectedImage = tappedImage
           }
        }

在ViewController2的viewWillAppear設置tappedImage為imageView “形象