按需重新加载 UITabBarController

Question

我有以下带有 2 个项目的 TabBarController。它显示正确。

当something 更改其值时，我正在从另一个控制器调用setupItems() 函数。

函数调用正确，问题是navFirstController.tabBarItem.image没有更新。

class TabBarController: UITabBarController {

  override func viewDidLoad() {
    super.viewDidLoad()
    setupItems()
  }

  func setupItems() {
    let scale: CGFloat = 0.35
    let navFirstController = UINavigationController(rootViewController: FirstController())

    let navSecondController = UINavigationController(rootViewController: SecondController())
    navSecondController.tabBarItem.image = UIImage.scale(image: UIImage(named: "image2")!, by: scale)
    navSecondController.tabBarItem.imageInsets = UIEdgeInsets(top: 8, left: 0, bottom: -8, right: 0)

    if something == true {
      navFirstController.tabBarItem.image = UIImage.scale(image: UIImage(named: "image1")!, by: scale)
    } else {
      navFirstController.tabBarItem.image = UIImage.scale(image: UIImage(named: "image3")!, by: scale)
    }

    navFirstController.tabBarItem.imageInsets = UIEdgeInsets(top: 8, left: 0, bottom: -8, right: 0)

    viewControllers = [navSecondController, navFirstController]
  }

}

我试过了：

1) viewControllers?.remove(at: 1) 以setupItems() 开头

2) navFirstController.removeFromParent() 以setupItems()开头

3) self.viewWillLayoutSubviews() 在setupItems() 的末尾

4) self.view.setNeedsLayout(), self.view.setNeedsDisplay() 结尾处setupItems()

Answer 1

我觉得我们不需要再次创建 viewControllers 对象来更改标签栏图像。 只是我们需要从 viewControllers 数组中获取 viewController 对象并更改图像。

class ViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view.
    }
}

class SecondViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()
    }

    @IBAction func btnClicked(_ sender: Any) {
        //change image of tab bar item on button clicked
        if let tabVC = self.tabBarController as? TabBarController {
            tabVC.changeImage()
        }
    }

}


class TabBarController: UITabBarController {

    override func viewDidLoad() {
        super.viewDidLoad()
        setupItems()
    }

    func setupItems() {
        let storyboard = UIStoryboard(name: "Main", bundle: Bundle.main)
        let firstVC = storyboard.instantiateViewController(withIdentifier: "First")
        let navFirstController = UINavigationController(rootViewController: firstVC)
        navFirstController.tabBarItem.image = UIImage(named: "Image1")

        let secondVC = storyboard.instantiateViewController(withIdentifier: "Second")
        let navSecondController = UINavigationController(rootViewController: secondVC)
        navSecondController.tabBarItem.image = UIImage(named: "Image2")

        viewControllers = [navSecondController, navFirstController]
    }

    func changeImage() {
        if let second = viewControllers?[1] as? UINavigationController {
            second.tabBarItem.selectedImage = UIImage(named: "Image3")
            second.tabBarItem.image = UIImage(named: "Image3")
        }
    }

}

注意如果要更改选定的标签栏项目图像，则更改“selectedImage”值，否则更改“image”值。

Answer 2

您可能需要将图像的渲染模式设置为UIImageRenderingModeAlwaysOriginal。

尝试改变这个：

  navFirstController.tabBarItem.image = UIImage.scale(image: UIImage(named: "image1")!, by: scale)

有了这个：

  navFirstController.tabBarItem.image = UIImage.scale(image: UIImage(named: "image1")!, by: scale).withRenderingMode(.alwaysOriginal)

编辑 - 示例代码

考虑这个设置：

• 初始视图控制器是一个自定义类 TabBarViewController
• 红色背景视图控制器是一个 UIViewController，故事板 ID 为“First”
• 橙色背景视图控制器是一个自定义类 SecondViewController，具有 IBAction 和情节提要 ID“Second”

Assets.xcassets 文件包含三张图片（40x40 png）：

TabBarViewController

import UIKit

class TabBarViewController: UITabBarController {

    var something: Bool = false

    override func viewDidLoad() {
        super.viewDidLoad()
        setupItems()
    }

    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)
    }

    func setupItems() {

        let storyboard = UIStoryboard(name: "Main", bundle: Bundle.main)

        let firstVC = storyboard.instantiateViewController(withIdentifier: "First")
        let navFirstController = UINavigationController(rootViewController: firstVC)
        navFirstController.tabBarItem.image = UIImage(named: "image1")!.withRenderingMode(.alwaysOriginal)

        let secondVC = storyboard.instantiateViewController(withIdentifier: "Second")
        let navSecondController = UINavigationController(rootViewController: secondVC)

        navSecondController.tabBarItem.image = UIImage(named: "image2")!.withRenderingMode(.alwaysOriginal)
        navSecondController.tabBarItem.imageInsets = UIEdgeInsets(top: 8, left: 0, bottom: -8, right: 0)

        if something == true {
            navFirstController.tabBarItem.image = UIImage(named: "image3")!.withRenderingMode(.alwaysOriginal)
        } else {
            navFirstController.tabBarItem.image = UIImage(named: "image1")!.withRenderingMode(.alwaysOriginal)
        }

        navFirstController.tabBarItem.imageInsets = UIEdgeInsets(top: 8, left: 0, bottom: -8, right: 0)

        viewControllers = [navSecondController, navFirstController]
    }

}

SecondViewController

import Foundation
import UIKit

class SecondViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()
    }

    @IBAction func btnClicked(_ sender: Any) {
        //change image of tab bar item on button clicked
        if let tabVC = self.tabBarController as? TabBarViewController {
            tabVC.something = !tabVC.something
            tabVC.setupItems()
        }
    }

}

输出