如何从 Popover 调用主视图控制器的方法?
How to call from a Popover a method of the main view controller?
在一个 iOS 项目中,我有一个主要的 ViewController 和第二个 ViewController,第二个 ViewController 显示为带有按钮转场的弹出窗口在导航栏中。在那个弹出窗口中有一个带有此代码的按钮:
class Pop: UIViewController {
@IBAction func colorOnePressed(_ sender: Any) {
let vc = ViewController()
vc. zoomIn()
}
}
这是第一个视图控制器的方法:
class ViewController: UIViewController {
@IBOutlet weak var mainTextField: UITextView!
...
func zoomIn() {
mainTextField.font = UIFont(name: "Helvetica Neue", size: CGFloat(18.00))
}
}
不幸的是(显然对你们中的许多人来说)我得到了一个致命错误:"unexpectedly found nil while unwrapping an Optional value"。
您正在尝试从 ViewController 的新实例调用该方法。相反,您需要声明一个 delegate property in the Popover VC and pass the original parent VC within prepareForSegue:sender:
方法作为 Popover VC 的委托。
根据 and this answer by 对另一个问题的回答,我使用委托设计模式实现了这一点。如果它对某人有用,我 post 下面的代码。
注意:我通常看到您使用 UIPopoverPresentationControllerDelegate 协议,但我创建了一个自定义协议 (ZoomProtocol),因此我可以包含我的方法 (zoomOut())。
在主视图控制器中:
import UIKit
// declare a protocol, that lists variables and methods
// the delegate is expected to respond to
protocol ZoomProtocol {
func zoomOut()
}
// set this view controller as the delegate
class ViewController: UIViewController, ZoomProtocol {
...
// make your presenting view controller conform to the protocol
zoomOut() {
// do something
}
// pass the this view controller as a delegate for the Popover view controller
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if let pop = segue.destination as? PopViewController {
pop.delegate = self
}
}
}
在弹出视图控制器中:
import UIKit
class PopViewController: UIViewController {
var delegate : ZoomProtocol?
...
// when you want to, call the method on the presenting view controller
@IBAction func zoomOutButtonPressed(_ sender: Any) {
delegate?.zoomOut()
}
}
在父视图控制器中,覆盖准备设置弹出窗口:
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if segue.identifier == "yourPopoverIdentifier" {
let popoverVC = segue.destination
popoverVC.modalPresentationStyle = UIModalPresentationStyle.popover
popoverVC.popoverPresentationController!.delegate = self
}
}
然后在子视图控制器中,您只需调用 presentingViewController 即可访问父视图的功能。在这种情况下,父级是默认的视图控制器,ViewController.
@IBAction func buttonClick(_ sender: Any) {
let parentVC = self.presentingViewController as! ViewController
parentVC.functionOnParent()
}
在一个 iOS 项目中,我有一个主要的 ViewController 和第二个 ViewController,第二个 ViewController 显示为带有按钮转场的弹出窗口在导航栏中。在那个弹出窗口中有一个带有此代码的按钮:
class Pop: UIViewController {
@IBAction func colorOnePressed(_ sender: Any) {
let vc = ViewController()
vc. zoomIn()
}
}
这是第一个视图控制器的方法:
class ViewController: UIViewController {
@IBOutlet weak var mainTextField: UITextView!
...
func zoomIn() {
mainTextField.font = UIFont(name: "Helvetica Neue", size: CGFloat(18.00))
}
}
不幸的是(显然对你们中的许多人来说)我得到了一个致命错误:"unexpectedly found nil while unwrapping an Optional value"。
您正在尝试从 ViewController 的新实例调用该方法。相反,您需要声明一个 delegate property in the Popover VC and pass the original parent VC within prepareForSegue:sender:
方法作为 Popover VC 的委托。
根据
注意:我通常看到您使用 UIPopoverPresentationControllerDelegate 协议,但我创建了一个自定义协议 (ZoomProtocol),因此我可以包含我的方法 (zoomOut())。
在主视图控制器中:
import UIKit
// declare a protocol, that lists variables and methods
// the delegate is expected to respond to
protocol ZoomProtocol {
func zoomOut()
}
// set this view controller as the delegate
class ViewController: UIViewController, ZoomProtocol {
...
// make your presenting view controller conform to the protocol
zoomOut() {
// do something
}
// pass the this view controller as a delegate for the Popover view controller
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if let pop = segue.destination as? PopViewController {
pop.delegate = self
}
}
}
在弹出视图控制器中:
import UIKit
class PopViewController: UIViewController {
var delegate : ZoomProtocol?
...
// when you want to, call the method on the presenting view controller
@IBAction func zoomOutButtonPressed(_ sender: Any) {
delegate?.zoomOut()
}
}
在父视图控制器中,覆盖准备设置弹出窗口:
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if segue.identifier == "yourPopoverIdentifier" {
let popoverVC = segue.destination
popoverVC.modalPresentationStyle = UIModalPresentationStyle.popover
popoverVC.popoverPresentationController!.delegate = self
}
}
然后在子视图控制器中,您只需调用 presentingViewController 即可访问父视图的功能。在这种情况下,父级是默认的视图控制器,ViewController.
@IBAction func buttonClick(_ sender: Any) {
let parentVC = self.presentingViewController as! ViewController
parentVC.functionOnParent()
}