在Swift中以编程方式更改导航栏项

So I'm trying to change the left nav bar button item in viewWillAppear (the item needs to be changed back and forth, so viewDidLoad won't work). I have the following code in viewWillAppear:

所以我正在尝试更改viewWillAppear中的左侧导航栏按钮项（该项需要来回更改，因此viewDidLoad将无法工作）。我在viewWillAppear中有以下代码：

        // There is a diff 'left bar button item' defined in storyboard. I'm trying to replace it with this new one
        var refreshButton = UIBarButtonItem(barButtonSystemItem: UIBarButtonSystemItem.Refresh, target: self, action: {})
        self.navigationController.navigationItem.leftBarButtonItem = refreshButton
        // title and color of nav bar can be successfully changed
        self.navigationController.navigationBar.barTintColor = UIColor.greenColor()
        self.title = "Search result"

I used debugger to make sure every line is executed. But the 'leftBarButtonItem' wasn't updated. nav bar stuff however got updated successfully. I'm out of moves now. Ideas? Thanks!

我使用调试器来确保每一行都被执行。但是'leftBarButtonItem'没有更新。导航栏的东西，但成功更新。我现在没动了。想法？谢谢！

1 个解决方案

#1

The following code should work:

以下代码应该工作：

import UIKit

class ViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()

        let refreshButton = UIBarButtonItem(barButtonSystemItem: UIBarButtonSystemItem.Refresh, target: self, action: "buttonMethod")
        navigationItem.leftBarButtonItem = refreshButton

        navigationController?.navigationBar.barTintColor = UIColor.greenColor()
        title = "Search result"
    }

    func buttonMethod() {
        print("Perform action")
    }

}

If you really need to perform it in viewWillAppear:, here is the code:

如果你真的需要在viewWillAppear：中执行它，这里是代码：

import UIKit

class ViewController: UIViewController {

    var isLoaded = false

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

        if !isLoaded {
            let refreshButton = UIBarButtonItem(barButtonSystemItem: UIBarButtonSystemItem.Refresh, target: self, action: "buttonMethod")
            navigationItem.leftBarButtonItem = refreshButton
            isLoaded = true

            navigationController?.navigationBar.barTintColor = UIColor.greenColor()
            title = "Search result"
        }
    }

    func buttonMethod() {
        print("Perform action")
    }

}

You can learn more about the navigationItem properties with this previous question.

您可以使用上一个问题了解有关navigationItem属性的更多信息。

#1