ios - 我可以在 ViewDidLoad 中加载 UICollectionView 的数据吗？

问题描述

我的应用程序的启动屏幕是一个集合视图。如果用户选择，他/她可以在应用启动时使用 Face ID/Touch ID “锁定”应用。我通过展示一个视图控制器来做到这一点，该控制器UIVisualEffectView在我的集合视图控制器之上包含一个。我在中截取我的集合视图控制器viewDidLoad，然后将截屏UIImageView放在UIVisualEffectView.

问题是，在截取屏幕截图并UIVisualEffectView出现控制器时未加载集合视图。屏幕截图包含导航栏，但视图的内容只是黑色的。我调用该函数在集合视图的viewDidLoad函数中显示视觉效果视图控制器。

有没有办法在我截屏之前加载集合视图的数据viewDidLoad？数据存储在核心数据中。我已经尝试将 Core Data 函数从移动viewWillAppear到viewDidLoad，但这也没有用。

编辑：我能够解决我的问题，但不能通过UICollectionView在 ViewDidLoad 中加载我的数据，因为这似乎是不可能的。我UIVisualEffectView直接在我的UICollectionView. 我还将它添加为子视图，UIApplication.shared.keyWindow以便它出现在导航栏上方。编辑后的代码在下面。

这是我的代码：

对于集合视图控制器：

import UIKit
import CoreData
import LocalAuthentication

var ssImage: UIImage?

class AlbumViewController: UIViewController {

// MARK: - Properties
@IBOutlet weak var albumCollectionView: UICollectionView!

var albums: [NSManagedObject] = []

// MARK: - Actions

func getScreenShot()-> UIImage? {

    var screenshotImage :UIImage?
    let layer = UIApplication.shared.keyWindow!.layer
    let scale = UIScreen.main.scale
    UIGraphicsBeginImageContextWithOptions(layer.frame.size, false, scale);
    guard let context = UIGraphicsGetCurrentContext() else {return nil}
    layer.render(in:context)
    screenshotImage = UIGraphicsGetImageFromCurrentImageContext()
    UIGraphicsEndImageContext()
    ssImage = screenshotImage
    print("Got screenshot.")
    return screenshotImage
}

// ViewDidLoad and ViewWillAppear
override func viewWillAppear(_ animated: Bool) {
    super.viewWillAppear(animated)

    //Core Date functions
    guard let appDelegate =
        UIApplication.shared.delegate as? AppDelegate else {
            return
    }
    let managedContext =
        appDelegate.persistentContainer.viewContext
    let fetchRequest =
        NSFetchRequest<NSManagedObject>(entityName: "Album")
    let sortDescriptor = NSSortDescriptor(key: "albumName", ascending: true, selector: #selector(NSString.localizedCaseInsensitiveCompare(_:)))
    fetchRequest.sortDescriptors = [sortDescriptor]
    do {
        albums = try managedContext.fetch(fetchRequest)
    } catch let error as NSError {
        print("Could not fetch. \(error), \(error.userInfo)")
    }

    //Setup
    self.albumCollectionView.reloadData()

}

override func viewDidLoad() {
    super.viewDidLoad()

    if AppSettings.requiresLogin == true {

        getScreenShot()
        let storyboard = UIStoryboard(name: "Main", bundle: nil)
        let rootController = storyboard.instantiateViewController(withIdentifier: "authenticateVC") as! LockedLaunchVC
        self.present(rootController, animated: false, completion: nil)
    }
}

//Core Data functions
func save(name: String) {
    guard let appDelegate =
        UIApplication.shared.delegate as? AppDelegate else {
            return
    }
    let managedContext =
        appDelegate.persistentContainer.viewContext
    let entity =
        NSEntityDescription.entity(forEntityName: "Album",
                                   in: managedContext)!
    let albumName = NSManagedObject(entity: entity,
                                    insertInto: managedContext)
    albumName.setValue(name, forKeyPath: "albumName")
    do {
        try managedContext.save()
        albums.append(albumName)
    } catch let error as NSError {
        print("Could not save. \(error), \(error.userInfo)")
    }
}
}

//Collection View functions
extension AlbumViewController: UICollectionViewDataSource, UICollectionViewDelegate {

func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
    return albums.count
}

func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
    let reuseIdentifier = "AlbumCell"
    // get a reference to our storyboard cell
    let cell = collectionView.dequeueReusableCell(withReuseIdentifier: reuseIdentifier, for: indexPath as IndexPath) as! AlbumsViewCell
    //Core Data methods
    let albumName = albums[indexPath.row]
    cell.albumNameLabel?.text = albumName.value(forKeyPath: "albumName") as? String
    //Return the finished cell
    return cell
}
}

对于 UIVisualEffectView 控制器：

import UIKit
import LocalAuthentication

class LockedLaunchVC: UIViewController {

    let bioIDAuth = BiometricIDAuth()

    @IBOutlet weak var screenshotImageView: UIImageView!
    @IBAction func unlockButtonTapped(_ sender: UIButton) {
        authAndDismiss()
    }

    func authAndDismiss(){
        bioIDAuth.authenticateUser() {
            self.dismiss(animated: true, completion: nil)
            print("Locked VC dismissed.")
        }
    }

    override func viewDidLoad() {
        super.viewDidLoad()
        self.modalTransitionStyle = .crossDissolve
    }

    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)
        screenshotImageView.image = ssImage
    }
}

编辑：我的集合视图控制器的修订代码：

import UIKit
import CoreData

class AlbumViewController: UIViewController {

// MARK: - Properties
@IBOutlet weak var albumCollectionView: UICollectionView!
@IBOutlet weak var lockedBlurView: UIVisualEffectView!
@IBOutlet weak var lockedLabelView: UIView!
@IBOutlet weak var lockedLabel: UILabel!

var albums: [NSManagedObject] = []

let bioIDAuth = BiometricIDAuth()

// MARK: - Actions

@IBAction func unwindToAlbumsScreen(sender: UIStoryboardSegue) {
}

@IBAction func unlockButtonTapped(_ sender: UIButton) {
    bioIDAuth.authenticateUser() {
        UIView.animate(withDuration: 0.25, animations: {self.lockedBlurView.alpha = 0})
    }

}

// ViewDidLoad and ViewWillAppear
override func viewWillAppear(_ animated: Bool) {
    super.viewWillAppear(animated)

    //Core Date functions
    guard let appDelegate =
        UIApplication.shared.delegate as? AppDelegate else {
            return
    }
    let managedContext =
        appDelegate.persistentContainer.viewContext
    let fetchRequest =
        NSFetchRequest<NSManagedObject>(entityName: "Album")
    let sortDescriptor = NSSortDescriptor(key: "albumName", ascending: true, selector: #selector(NSString.localizedCaseInsensitiveCompare(_:)))
    fetchRequest.sortDescriptors = [sortDescriptor]
    do {
        albums = try managedContext.fetch(fetchRequest)
    } catch let error as NSError {
        print("Could not fetch. \(error), \(error.userInfo)")
    }

    //Setup to do when the view will appear
    self.albumCollectionView.reloadData()

}

override func viewDidLoad() {
    super.viewDidLoad()
    lockedLabelView.layer.cornerRadius = 12
    switch bioIDAuth.biometricType() {
    case .faceID:
        lockedLabel.text = "Albums are locked.  Tap anywhere to use Face ID to unlock."
    case .touchID:
        lockedLabel.text = "Albums are locked.  Tap anywhere to use Touch ID to unlock."
    default:
        lockedLabel.text = "Albums are locked.  Tap anywhere to use your passcode to unlock."
    }

    if AppSettings.requiresLogin == false {
        lockedBlurView.alpha = 0
    }
}

override func viewDidAppear(_ animated: Bool) {
    super.viewDidAppear(animated)

    if AppSettings.requiresLogin == true {
        let curWin = UIApplication.shared.keyWindow
        curWin?.addSubview(lockedBlurView)
    }
}

//Core Data functions
func save(name: String) {
    guard let appDelegate =
        UIApplication.shared.delegate as? AppDelegate else {
            return
    }
    let managedContext =
        appDelegate.persistentContainer.viewContext
    let entity =
        NSEntityDescription.entity(forEntityName: "Album",
                                   in: managedContext)!
    let albumName = NSManagedObject(entity: entity,
                                    insertInto: managedContext)
    albumName.setValue(name, forKeyPath: "albumName")
    do {
        try managedContext.save()
        albums.append(albumName)
    } catch let error as NSError {
        print("Could not save. \(error), \(error.userInfo)")
    }
}
}

//Collection View functions
extension AlbumViewController: UICollectionViewDataSource, UICollectionViewDelegate {

func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
    return albums.count
}

// make a cell for each cell index path
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
    let reuseIdentifier = "AlbumCell"
    // get a reference to our storyboard cell
    let cell = collectionView.dequeueReusableCell(withReuseIdentifier: reuseIdentifier, for: indexPath as IndexPath) as! AlbumsViewCell
    //Core Data methods
    let albumName = albums[indexPath.row]
    cell.albumNameLabel?.text = albumName.value(forKeyPath: "albumName") as? String
    //Return the finished cell
    return cell
}

func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
    let albumNameFromCell = albums[indexPath.row]
    albumNameTapped = albumNameFromCell.value(forKeyPath: "albumName") as! String
    self.performSegue(withIdentifier: "albumCellTappedSegue", sender: self)
}
}

标签： iosswiftcore-datauicollectionviewviewdidload

ios - 我可以在 ViewDidLoad 中加载 UICollectionView 的数据吗？

问题描述

解决方案

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