Question

当我遇到这个问题时，我一直在阅读Big Nerd Ranch的iOS编程并完成第15章关于相机的工作。只有按住相机按钮，相机才会弹出。我在我的takePicture函数中添加了一个断点，并注意到点击甚至没有调用函数，而是持有。两个代表都包含在我的控制器中，所以这不应该是一个问题。按钮是一个UIBarButtonItem，连接到我的控制器上的takePicture函数。

import UIKit

class DetailViewController: UIViewController, UITextFieldDelegate, UINavigationControllerDelegate, UIImagePickerControllerDelegate {

    @IBOutlet var nameField: CustomTextField!
    @IBOutlet var serialNumberField: CustomTextField!
    @IBOutlet var valueField: CustomTextField!
    @IBOutlet var dateLabel: UILabel!
    @IBOutlet var imageView: UIImageView!
    @IBAction func backgroundTapped(_ sender: UITapGestureRecognizer) {
        view.endEditing(true)
    }

    @IBAction func takePicture(_ sender: UIBarButtonItem) {

        let imagePicker = UIImagePickerController()
        // If the device has a camera, take a picture; otherwise, just pic from photo library
        if UIImagePickerController.isSourceTypeAvailable(.camera) {
            imagePicker.sourceType = .camera
        } else {
            imagePicker.sourceType = .photoLibrary
        }
        imagePicker.delegate = self
        // Place image picker on the screen

        present(imagePicker, animated: true, completion: nil)

    }
    override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
        switch segue.identifier {
        case "changeDate"?:
            let dateCreatedViewController = segue.destination as! DateCreatedViewController
            dateCreatedViewController.item = item
        default:
            preconditionFailure("Unexpected segue identifier.")
        }
    }
    var item: Item! {
        didSet {
            navigationItem.title = item.name
        }
    }
    let numberFormatter: NumberFormatter = {
        let formatter = NumberFormatter()
        formatter.numberStyle = .decimal
        formatter.minimumFractionDigits = 2
        formatter.maximumFractionDigits = 2
        return formatter
    }()

    let dateFormatter: DateFormatter = {
        let formatter = DateFormatter()
        formatter.dateStyle = .medium
        formatter.timeStyle = .none
        return formatter
    }()
    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)

        nameField.text = item.name
        serialNumberField.text = item.serialNumber
        valueField.text = numberFormatter.string(from: NSNumber(value: item.valueInDollars))
        dateLabel.text = dateFormatter.string(from: item.dateCreated)
    }
    override func viewWillDisappear(_ animated: Bool) {
        super.viewWillDisappear(animated)

        // Clear first responder
        view.endEditing(true)

        // "Save" changes to item
        item.name = nameField.text ?? ""
        item.serialNumber = serialNumberField.text

        if let valueText = valueField.text, let value = numberFormatter.number(from: valueText) {
            item.valueInDollars = value.intValue
        } else {
            item.valueInDollars = 0
        }
    }
    func textFieldShouldReturn(_ textField: UITextField) -> Bool {
        textField.resignFirstResponder()
        return true
    }

}

还添加了访问相机和库的权限。加载相机需要一段时间吗？怎么回事？

Answer 1

问题是您的识别器手势事件正在影响您的按钮。首先要点击按钮。首先删除viewcontroller中的识别器手势。

并考虑使用viewcontrollers的扩展名，如下所示：

extension UIViewController {
    func hideKeyboardWhenTappedAround() {
        let tap: UITapGestureRecognizer = UITapGestureRecognizer(target: self, action: #selector(UIViewController.dismissKeyboard))
        tap.cancelsTouchesInView = false

        view.addGestureRecognizer(tap)
    }

    func dismissKeyboard() {
        view.endEditing(true)
    }
}


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

Answer 2

看起来连接到调试器UIImagePickerController需要更长时间来初始化，断开设备与调试器的连接，它应该打开得更快。您也可以尝试将开放代码放入：

DispatchQueue.main.async {

}

Swift：UIBarButtonItem只通过按住按钮调用动作来显示UIImagePickerController的界面

2 个答案: