使用 UserDefaults 终止时保留应用程序

Question

我想使用 userdefaults 保存图像，我想要实现的是在图像被更改并且应用程序终止它之后。图像用户更改仍然存在。我如何使用 userdefaults 实现此目的。

这是我在用户选择图像并将其保存在 userdefaults 时的代码

var data: Data? //I make a reference data to save imageData in pickerController
@objc func handleImagePicker() {
    let imagePickerController = UIImagePickerController()
    imagePickerController.allowsEditing = true
    imagePickerController.sourceType = .photoLibrary
    imagePickerController.delegate = self

    present(imagePickerController, animated: true)
}

@objc func imagePickerController(_ picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [UIImagePickerController.InfoKey : Any]) {
    if let editedImage = info[.editedImage] as? UIImage {
        guard let imageData = editedImage.jpegData(compressionQuality: 0.5) else { return }
        self.data = NSKeyedArchiver.archivedData(withRootObject: imageData)
        UserDefaults.standard.set(data, forKey: "profileImageEditedKey")
        UserDefaults.standard.synchronize()
        profileImageView.image = editedImage.withRenderingMode(.alwaysOriginal)
    } else if let originalImage = info[.originalImage] as? UIImage {
        guard let imageData = originalImage.jpegData(compressionQuality: 1) else { return }
        self.data = NSKeyedArchiver.archivedData(withRootObject: imageData)
        UserDefaults.standard.set(data, forKey: "profileImageOriginalKey")
        UserDefaults.standard.synchronize()
        profileImageView.image = originalImage.withRenderingMode(.alwaysOriginal)
    }
    dismiss(animated: true)
}

这是我在应用程序终止后获取数据时放置在 viewWillAppear 中的代码

private func fetchData() {
    guard let data = data else { return }
    guard let image = NSKeyedUnarchiver.unarchiveObject(with: data) as? UIImage else { return }

    profileImageView.image = image.withRenderingMode(.alwaysOriginal)
    print("fetch...")
}

Answer 1

在userdefaults中保存大数据不是一个好主意，通常不推荐，因为这不是保存图像的最有效方式；一种更有效的方法是将图像保存在应用程序的文档目录中。你使用 Data write func 来做到这一点。还有其他第三个库。

如果你坚持使用UserDefaults

保存图片

guard let imageData = editedImage.jpegData(compressionQuality: 0.5) else { return }
UserDefaults.standard.set(imageData, forKey: "profileImageEditedKey")
UserDefaults.standard.synchronize()

从UserDefaults

获取图像

guard let data = UserDefaults.standard.object(forKey: "profileImageOriginalKey") as? Data else {
    return;
}
let image = UIImage.init(data: data);

使用 UserDefaults 终止时保留应用程序

Persist app when terminate using UserDefaults

ios

swift

persistence

nsuserdefaults