如何通过 Swift (Xcode) 上的代码显示屏幕？

Question

我是 Xcode 的新手，我正在尝试为 iOS 构建一个应用程序。该应用程序必须有多个屏幕（视图控制器），但是当我尝试从第一个屏幕显示第二个屏幕时遇到了问题。

我想在单击特定按钮时显示第二个屏幕（这是典型的登录屏幕），因此当用户成功登录时，必须显示第二个屏幕。该按钮在“ViewController.swift”中有此代码

let username: String = txtUser.text!
let password: String = txtPassword.text!
var message: String
if(username=="" || password=="") {
  message = "You haven't introduced your username/password"
} else {
  message = "Welcome, \(username)"
}
let alert = UIAlertController(title:"Login", message:message, preferredStyle: UIAlertControllerStyle.alert)
alert.addAction(UIAlertAction(title:"ok", style: UIAlertActionStyle.default, handler:nil)

我试图通过右键单击按钮并拖动到第二个屏幕中来在“Main.storyboard”中添加“显示操作”，但是当我运行应用程序时，当我单击按钮：

2018-08-21 12:54:57.886357+0200 App[1370:33542] [MC] Lazy loading NSBundle MobileCoreServices.framework
2018-08-21 12:54:57.888305+0200 App[1370:33542] [MC] Loaded MobileCoreServices.framework
2018-08-21 12:55:00.959900+0200 App[1370:33542] [MC] System group container for systemgroup.com.apple.configurationprofiles path is /Users/erd/Library/Developer/CoreSimulator/Devices/CD00D9C1-1400-4E0E-8CA9-4D46B6EF352E/data/Containers/Shared/SystemGroup/systemgroup.com.apple.configurationprofiles
2018-08-21 12:55:00.961220+0200 App[1370:33542] [MC] Reading from private effective user settings.
2018-08-21 12:55:05.137241+0200 App[1370:33542] <UIView: 0x7fbc4dd14060; frame = (0 0; 414 736); autoresize = W+H; layer = <CALayer: 0x6040002322e0>>'s window is not equal to <UIAlertController: 0x7fbc4e070c00>'s view's window!
2018-08-21 12:55:27.262709+0200 App[1370:33542] <UIView: 0x7fbc4dd14060; frame = (0 0; 414 736); autoresize = W+H; layer = <CALayer: 0x6040002322e0>>'s window is not equal to <UIAlertController: 0x7fbc4e938a00>'s view's window!
2018-08-21 12:55:41.425141+0200 App[1370:33542] <UIView: 0x7fbc4dd14060; frame = (0 0; 414 736); autoresize = W+H; layer = <CALayer: 0x6040002322e0>>'s window is not equal to <UIAlertController: 0x7fbc4e017000>'s view's window!

但是，我尝试通过一个新按钮来完成它并且效果很好（没有上面的错误）

有没有办法通过代码显示第二个屏幕？如果是，那对我来说会更容易，因为我只需要在用户输入正确的用户名+密码时显示该屏幕。

提前谢谢你！

Answer 1

您可以使用以下定义的几种方式中的任何一种：

1. 您可以通过 Segue 进行此操作。请参阅此为segue： http://www.codingexplorer.com/segue-swift-view-controllers/

2. 使用 Push 到第二个 ViewController

let storyboard = UIStoryboard(name: "Main", bundle: nil)
let vc = storyboard.instantiateViewControllerWithIdentifier("NewsDetailsVCID") as SecondViewController 
navigationController?.pushViewController(vc, animated: true)

1. 使用 Present 到第二个 ViewController

let secondView = self.storyboard?.instantiateViewControllerWithIdentifier("secondViewPageID") as! SecondViewController
self.presentViewController(secondView, animated: true, completion: nil)

Answer 2

Swift 3 和 4

首先将导航控制器添加到初始视图控制器。然后在任何按钮操作中添加这些行。

    let mainStoryboard: UIStoryboard = UIStoryboard(name: "Main", bundle: nil)
    //Make sure You set Your ViewController Identifier
    let objectVC = mainStoryboard.instantiateViewController(withIdentifier: "SubcategoryListVC") as! SubcategoryListVC
    self.navigationController?.pushViewController(objectVC, animated: true)