ios - 将缩略图附加到通知时，文件去了哪里？

Question

我正在向富通知添加缩略图。我生成用作附件的图像，如下所示:

let url = URL(fileURLWithPath: NSTemporaryDirectory(), isDirectory: true)
let fileURL = url.appendingPathComponent("someImageName", isDirectory: false).appendingPathExtension("png")
do{
    try UIImagePNGRepresentation(image)?.write(to: fileURL)
}catch{
    print("Could not write: ", error)
}

这是成功的。如果我现在运行这段代码:

let content = try? FileManager.default.contentsOfDirectory(atPath: NSTemporaryDirectory())
print(content ?? "error")

它打印出这个:["someImageName.png"]。

然后我创建附件，如下所示:

let attachment = try? UNNotificationAttachment(identifier: "image", url: url, options: nil)
let content = UNMutableNotificationContent()
content.title = "Test"
content.attachments = [attachment!]
let request = UNNotificationRequest(identifier: "someID", content:content, trigger: /*someTrigger*/)
UNUserNotificationCenter.current().add(request, withCompletionHandler:...)

一切正常。通知已发送，并附上附件。但是如果我现在打印出临时文件夹的内容，它是空的!我之前保存的图像已从此文件夹中删除。

经过反复试验，我发现在我添加通知的同时删除了图像。为什么我的通知会删除我的图片？我找不到这方面的任何文档!

如果我执行以上所有操作，但注释掉这一行://content.attachments = [attachment!]，这意味着我存储的图像将不会作为附件添加到我的通知中，然后我的图片没有从临时文件夹中删除!

这些文件在使用后是否被清理？或者我是否必须在通知消失后查看不同的文件夹并手动清理它们？我不希望我的应用程序创建数百张永远不会再使用的图像，而且无法删除它们。

Answer 1

这些天我遇到了同样的问题，答案在文档中，乍一看不是很容易看到，但它就在那里:

关于UNNotificationAttachment:

...Once validated, attached files are moved into the attachment data store so that they can be accessed by all of the appropriate processes.

关于初始化方法:

When you schedule a notification request containing the attachment, the attachment's file is moved to a new location to facilitate access by the appropriate processes. After the move, the only way to access the file is using the methods of the UNUserNotificationCenter object.

注意:

Attachments located inside an app's bundle are copied instead of moved.

所以我决定:

像你一样写文件并在 NSTemporaryDirectory() 中写一个副本我用这个例子轻松创建和删除 TempDirectory (Swift 4.0)(感谢 Ole Begemman ):

import Foundation

/// A wrapper around a temporary file in a temporary directory. The directory
/// has been especially created for the file, so it's safe to delete when you're
/// done working with the file.
///
/// Call `deleteDirectory` when you no longer need the file.
struct TemporaryFile {
    let directoryURL: URL
    let fileURL: URL
    /// Deletes the temporary directory and all files in it.
    let deleteDirectory: () throws -> Void
    
    /// Creates a temporary directory with a unique name and initializes the
    /// receiver with a `fileURL` representing a file named `filename` in that
    /// directory.
    ///
    /// - Note: This doesn't create the file!
    init(creatingTempDirectoryForFilename filename: String) throws {
        let (directory, deleteDirectory) = try FileManager.default
            .urlForUniqueTemporaryDirectory()
        self.directoryURL = directory
        self.fileURL = directory.appendingPathComponent(filename)
        self.deleteDirectory = deleteDirectory
    }
}

extension FileManager {
    /// Creates a temporary directory with a unique name and returns its URL.
    ///
    /// - Returns: A tuple of the directory's URL and a delete function.
    ///   Call the function to delete the directory after you're done with it.
    ///
    /// - Note: You should not rely on the existence of the temporary directory
    ///   after the app is exited.
    func urlForUniqueTemporaryDirectory(preferredName: String? = nil) throws
        -> (url: URL, deleteDirectory: () throws -> Void)
    {
        let basename = preferredName ?? UUID().uuidString
        
        var counter = 0
        var createdSubdirectory: URL? = nil
        repeat {
            do {
                let subdirName = counter == 0 ? basename : "\(basename)-\(counter)"
                let subdirectory = temporaryDirectory
                    .appendingPathComponent(subdirName, isDirectory: true)
                try createDirectory(at: subdirectory, withIntermediateDirectories: false)
                createdSubdirectory = subdirectory
            } catch CocoaError.fileWriteFileExists {
                // Catch file exists error and try again with another name.
                // Other errors propagate to the caller.
                counter += 1
            }
        } while createdSubdirectory == nil
        
        let directory = createdSubdirectory!
        let deleteDirectory: () throws -> Void = {
            try self.removeItem(at: directory)
        }
        return (directory, deleteDirectory)
    }
}

使用 TempURL 附加文件后，文件被移动，您可以删除 TempDirectory。

后来进行了一些测试，可以肯定的是，我终于发现我的文件(在我的案例中是一张图片)存储在这里:

URL: file:///var/mobile/Library/SpringBoard/PushStore/Attachments/com.YourApp.Name/8e52c6673f6e735f83535486bf750ba1118a3ade.png

提示或清理通知中心后，文件被删除是。

为什么会这样？ -> 沙盒!当我将我的文件附加到触发器(此处为 UNCalendarNotificationTrigger)时，我将负责我的文件的日历命名为在我的通知中显示它，但要处理它，它必须将文件放在 HIS 目录中。

希望对您有所帮助，我花了一段时间才找到所有的谜团!