代表无法调用第二个视图控制器

Question

我想通过单击第一个视图控制器中的按钮将图像传递给第二个控制器。我无法理解，即使我已经将我的 1 个视图控制器的引用提供给我的第二个控制器，那么委托也没有被调用

1.这是我的第一个视图控制器的代码

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.这是第二个视图控制器的代码

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.这是我的标签栏控制器

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

您必须在切换标签时设置图像。 目前，您正在做的是更改尚未显示的 viewController 的图像。

您可以为每个项目添加标签并使用didSelectViewController委托功能

在 tabBar ViewController 中添加一个变量 tappedImage 像

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 中将 tappedImage 设置为 imageView 的图像