ios - UITableViewCell 未显示警报 View

Question

在 OrderFormViewController 中，我有一个 tableView ，在 tableViewCell 中，我有一个 cameraButton，点击时会显示警报。

现在，当出现 OrderFormViewController 时(未推送)，它会加载 tableView 及其单元格(行数为 1 硬编码) 。

我在 cameraButton 的 IBAction 下有以下代码:

@IBAction func cameraButtonPressed(_ sender: Any) {
        //DispatchQueue.main.async {
            let alert = UIAlertController(title: "Choose Image From", message: nil, preferredStyle: .alert)
            alert.addAction(UIAlertAction(title: "Camera", style: .default, handler: { _ in
                if(UIImagePickerController .isSourceTypeAvailable(UIImagePickerControllerSourceType.camera))
                {
                    self.imagePicker.sourceType = UIImagePickerControllerSourceType.camera
                    self.imagePicker.allowsEditing = true
                    UIApplication.shared.keyWindow?.rootViewController?.present(self.imagePicker, animated: true, completion: nil)
                }
                else
                {
                    let alert  = UIAlertController(title: "Warning", message: "You don't have camera", preferredStyle: .alert)
                    alert.addAction(UIAlertAction(title: "OK", style: .default, handler: nil))
                    UIApplication.shared.keyWindow?.rootViewController?.present(alert, animated: true, completion: nil)
                }
            }))

            alert.addAction(UIAlertAction(title: "Gallery", style: .default, handler: { _ in
                self.imagePicker.sourceType = UIImagePickerControllerSourceType.photoLibrary
                self.imagePicker.allowsEditing = false
                UIApplication.shared.keyWindow?.rootViewController?.present(self.imagePicker, animated: true, completion: nil)
            }))

            //alert.addAction(UIAlertAction(title: "Cancel", style: .cancel, handler: nil))

            alert.addAction(UIAlertAction.init(title: "Cancel", style: .cancel, handler: nil))

            UIApplication.shared.keyWindow?.rootViewController?.present(alert, animated: true, completion: nil)
        //}
    }

我已经搜索过这个，所以这就是为什么我尝试 UIApplication.shared.keyWindow?.rootViewController 并尝试从 DispatchQueue.main.async 运行它，但是一些UIApplication.shared.keyWindow?.rootViewController?.present(alert,animated:true,completion:nil)不起作用。

更新 如果我按下 View Controller ，它就会工作。但我需要一个针对呈现 View Controller 的解决方案。

Answer 1

我强烈建议重构整个解决方案以使用委托(delegate) - 将显示警报的操作从 UITableViewCell 委托(delegate)给 OrderFormViewController，然后只需使用

self.present(alert, animated: true, completion: nil)

因为使用 UIApplication.shared.keyWindow?.rootViewController 非常脆弱。

所以只是为您勾画一下，我相信最好的方法是:

class OrderFormViewController: UITableViewController {

    override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCell(withIdentifier: "customCell", for: indexPath) as! CustomCell
        // set the delegate
        cell.delegate = self
        return cell
    }
}

extension OrderFormViewController: CustomCellDelegate {
    func customCellDelegateButtonPressed(_ customCell: CustomCell) {

        let alert = UIAlertController(title: "Choose Image From", message: nil, preferredStyle: .alert)
        // configure the alert

        // now the presentation of the alert is delegated here to OrderFormViewController, so it can simply use self to present
        self.present(alert, animated: true, completion: nil)
    }
}

protocol CustomCellDelegate: class {
    func customCellDelegateButtonPressed(_ customCell: CustomCell /*, potentially more parameters if needed */)
}

class CustomCell: UITableViewCell {
    // rest omitted for brevity

    weak var delegate: CustomCellDelegate?

    @IBAction func cameraButtonPressed(_ sender: Any) {
        delegate?.customCellDelegateButtonPressed(self)
    }
}