ios - UILabel 在 iPhone 旋转时恢复为默认文本

Question

这是一个有点奇怪的问题，我不确定从哪里开始调试。我在标准 View 上有一个 UILabel，我根据特定条件更新文本。在 IB 中，我设置了默认文本“正在加载...”，然后 viewDidAppear 方法根据条件更新文本。这工作正常，但是，如果我随后旋转我的 iPhone(或模拟器)，它会将 UILabel 恢复为“正在加载...”的标准文本。

有趣的是，当我在 iPad 上查看它时，无论是模拟器还是实际设备，它都没有将文本更改回默认值，而是按照我的预期运行。

我已经尝试检测方向变化并重置文本，但这没有任何效果，这有点像标签已锁定为默认状态。

很乐意在必要时提供代码，但我真的不确定什么代码是相关的，因为它是一个直接的标签并更新了它的文本。

谢谢

import UIKit

class PredictionViewController: UIViewController {

    var predictionData: Predictions!
    var embeddedVC: PredictionsTableViewController?

    @IBOutlet weak var messageTextBox: UILabel!
    @IBOutlet weak var predictionSubmitButton: UIButton!
    @IBOutlet weak var predictionSubmitButtonHeight: NSLayoutConstraint!

    override func viewDidLoad() {
        super.viewDidLoad()

        // Do any additional setup after loading the view.

        //self.messageTextBox.isEditable = false
        NotificationCenter.default.addObserver(self, selector: #selector(settingChanged(notification:)), name: UserDefaults.didChangeNotification, object: nil)
    }

    override func viewDidAppear(_ animated: Bool) {
        let preferences = UserDefaults.standard
        if (preferences.object(forKey: "regID") == nil)
        {
            loadLoginScreen()
        }
        else {
            let sv = UIViewController.displaySpinner(onView: self.view)
            let predictionStatus = preferences.object(forKey: "predictionStatus") as! String

            switch (predictionStatus) {
                case "inplay":
                    setInplay(view: self)
                case "finished":
                    setFinished(view: self)
                case "predict":
                    setPredict(view: self)
                default:
                    self.messageTextBox.text = "Error!"
            }
            if (self.messageTextBox.isHidden) {
                self.messageTextBox.isHidden = false
            }
            UIViewController.removeSpinner(spinner: sv)
        }
    }

    override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
        if (segue.identifier == "predictionSegue") {
            if let vc = segue.destination as? PredictionsTableViewController {
                // get a reference to the embedded VC
                self.embeddedVC = vc
            }
        }
    }

    @objc func settingChanged(notification: NSNotification) {
        let preferences = UserDefaults.standard
        let predictionStatus = preferences.object(forKey: "predictionStatus") as! String

        switch (predictionStatus) {
            case "inplay":
                setInplay(view: self)
            case "finished":
                setFinished(view: self)
            case "predict":
                setPredict(view: self)
            default:
                messageTextBox.text = "Error!"
        }
    }

    func setInplay(view: PredictionViewController) {
        view.messageTextBox.text = "In Play!"
        view.predictionSubmitButtonHeight.constant = 0
    }

    func setFinished(view: PredictionViewController) {
        view.messageTextBox.text = "Finished!"
        view.predictionSubmitButtonHeight.constant = 0
    }

    func setPredict(view: PredictionViewController) {
        view.messageTextBox.text = "Predict Now!"
        view.predictionSubmitButton.isEnabled = true
        view.predictionSubmitButton.setTitle("Submit", for: .normal)
        view.predictionSubmitButtonHeight.constant = 58
    }

    @IBAction func predictionSubmitButtonAction(_ sender: UIButton) {
        let preferences = UserDefaults.standard
        let sv = UIViewController.displaySpinner(onView: self.view)
        CheckTime(finished: { isSuccess in

            switch (isSuccess) {
            case "inplay":
                preferences.set("inplay", forKey: "predictionStatus")
                //too late alert
            case "finished":
                preferences.set("finished", forKey: "predictionStatus")
                //too late alert
            case "predict":
                preferences.set("predict", forKey: "predictionStatus")

                if let predictionData = self.embeddedVC?.getPredictionData() {
                    //send back to website
                    let regID = preferences.object(forKey: "regID")
                    let url = URL(string: "[URL]")
                    let session = URLSession.shared

                    let request = NSMutableURLRequest(url: url!)
                    request.httpMethod = "POST"
                    let bodyData = "{}"

                    request.httpBody = bodyData.data(using: String.Encoding.utf8);
                    let task = session.dataTask(with: request as URLRequest, completionHandler: {
                        (data, response, error) in

                        guard let data = data, let _ = response, error == nil else
                        {
                            DispatchQueue.main.async(
                                execute: {
                                    UIViewController.removeSpinner(spinner: sv)
                                    self.displayAlertMessage(message: "response error: \(String(describing: error?.localizedDescription))", type: "error")
                            }
                            )
                            return
                        }

                        do {

                            let decoder = JSONDecoder()
                            let predictionResult = try decoder.decode(ReturnData.self, from: data)

                            DispatchQueue.main.async(
                                execute: {
                                    if (predictionResult.success) {
                                        self.displayAlertMessage(message: predictionResult.message, type: "message", title: "Predictions Received")
                                    }
                                    else {
                                        self.displayAlertMessage(message: "response error: \(String(describing: error?.localizedDescription))", type: "error")
                                    }
                                    UIViewController.removeSpinner(spinner: sv)
                                }
                            )
                        } catch {
                            DispatchQueue.main.async(
                                execute: {
                                    UIViewController.removeSpinner(spinner: sv)
                                    self.displayAlertMessage(message: "response error: \(error)", type: "error")
                            }
                            )
                            return
                        }
                    })

                    task.resume()
                }
            default:
                UIViewController.removeSpinner(spinner: sv)
                self.messageTextBox.text = "Error!"
                preferences.set("error", forKey: "predictionStatus")
            }
            preferences.synchronize()

            if (self.messageTextBox.isHidden) {
                self.messageTextBox.isHidden = false
            }

        })
    }

}

override func viewWillTransition(to size: CGSize, with coordinator: UIViewControllerTransitionCoordinator) {
        super.viewWillTransition(to: size, with: coordinator)
        if UIDevice.current.orientation.isLandscape {
            print("Landscape")
            //imageView.image = UIImage(named: const2)
        } else {
            print("Portrait")
            //imageView.image = UIImage(named: const)
        }
        self.messageTextBox.text = "Error!"
}

Answer 1

你能使用这个 Delegate 方法来实现屏幕方向吗？

override func viewWillTransition(to size: CGSize, with coordinator: UIViewControllerTransitionCoordinator) {
    coordinator.animate(alongsideTransition: { (UIViewControllerTransitionCoordinatorContext) -> Void in

    }, completion: { (UIViewControllerTransitionCoordinatorContext) -> Void in
        //refresh view once rotation is completed not in will transition as it returns incorrect frame size.Refresh here
        **//---> Set the text for label here.**

    })
    super.viewWillTransition(to: size, with: coordinator)
}