Swift 上的 USB 连接代理

Question

Swift 中是否有一个代表可以让我的 class 知道何时通过计算机的 USB 插入新设备？我想知道我的程序何时可以使用新设备。

Answer 1

这个答案对我有用但它需要一些调整，比如创建一个桥接头文件来导入一些特定的 IOKit 部分。

首先，将 IOKit.framework 添加到您的项目中（单击 "Linked Frameworks and Libraries" 中的“+”）。

然后创建一个新的空“.m”文件，不管它的名字是什么。 Xcode 然后会询问它是否应该制作一个 "bridging header"。说是。

忽略“.m”文件。在 Xcode 刚刚创建的新 "YOURAPPNAME-Bridging-Header.h" 文件中，添加以下行：

#include <IOKit/IOKitLib.h>
#include <IOKit/usb/IOUSBLib.h>
#include <IOKit/hid/IOHIDKeys.h>

现在您可以使用链接答案中的代码了。这是一个简化版本：

class USBDetector {
    class func monitorUSBEvent() {
        var portIterator: io_iterator_t = 0
        let matchingDict = IOServiceMatching(kIOUSBDeviceClassName)
        let gNotifyPort: IONotificationPortRef = IONotificationPortCreate(kIOMasterPortDefault)
        let runLoopSource: Unmanaged<CFRunLoopSource>! = IONotificationPortGetRunLoopSource(gNotifyPort)
        let gRunLoop: CFRunLoop! = CFRunLoopGetCurrent()
        CFRunLoopAddSource(gRunLoop, runLoopSource.takeRetainedValue(), kCFRunLoopDefaultMode)
        let observer = UnsafeMutablePointer<Void>(unsafeAddressOf(self))
        _ = IOServiceAddMatchingNotification(gNotifyPort,
                                              kIOMatchedNotification,
                                              matchingDict,
                                              deviceAdded,
                                              observer,
                                              &portIterator)
        deviceAdded(nil, iterator: portIterator)
        _ = IOServiceAddMatchingNotification(gNotifyPort,
                                              kIOTerminatedNotification,
                                              matchingDict,
                                              deviceRemoved,
                                              observer,
                                              &portIterator)
        deviceRemoved(nil, iterator: portIterator)
    }
}

func deviceAdded(refCon: UnsafeMutablePointer<Void>, iterator: io_iterator_t) {
    var kr: kern_return_t = KERN_FAILURE
    while case let usbDevice = IOIteratorNext(iterator) where usbDevice != 0 {
        let deviceNameAsCFString = UnsafeMutablePointer<io_name_t>.alloc(1)
        defer {deviceNameAsCFString.dealloc(1)}
        kr = IORegistryEntryGetName(usbDevice, UnsafeMutablePointer(deviceNameAsCFString))
        if kr != KERN_SUCCESS {
            deviceNameAsCFString.memory.0 = 0
        }
        let deviceName = String.fromCString(UnsafePointer(deviceNameAsCFString))
        print("Active device: \(deviceName!)")
        IOObjectRelease(usbDevice)
    }
}

func deviceRemoved(refCon: UnsafeMutablePointer<Void>, iterator: io_iterator_t) {
    // ...
}

注意：deviceAdded 和 deviceRemoved 需要是函数（不是方法）。

要使用此代码，只需启动观察器：

USBDetector.monitorUSBEvent()

这将列出当前插入的设备，并且在每个新的 USB 设备 plug/unplug 事件中它将打印设备名称。

Answer 2

Eric Aya 的回答已经很好了，但这里有一个 Swift 3 改编。我将大部分丑陋的东西包裹在 USBWatcher class 中；将自己设置为该对象的委托来接收通知。

您可以 copy/paste 将以下内容放入 playground 中以查看它的工作情况 — 该示例只是在设备 connected/disconnected.

时向控制台记录一条消息

不幸的是，IOKit APIs 没有得到与其他一些 C APIs 相同的 Swift-化处理（例如 CoreGraphics）。 io_name_t 是一个笨重的元组，而不是一个适当的结构，C 结构通常导入到 Swift 的方式； io_object_t 不是真正的引用类型，因此它不能利用 ARC。也许在未来这会改变——如果你想看到更好的 Swift API，你应该 file an enhancement request.

import Foundation
import IOKit
import IOKit.usb

public protocol USBWatcherDelegate: class {
    /// Called on the main thread when a device is connected.
    func deviceAdded(_ device: io_object_t)

    /// Called on the main thread when a device is disconnected.
    func deviceRemoved(_ device: io_object_t)
}

/// An object which observes USB devices added and removed from the system.
/// Abstracts away most of the ugliness of IOKit APIs.
public class USBWatcher {
    private weak var delegate: USBWatcherDelegate?
    private let notificationPort = IONotificationPortCreate(kIOMasterPortDefault)
    private var addedIterator: io_iterator_t = 0
    private var removedIterator: io_iterator_t = 0

    public init(delegate: USBWatcherDelegate) {
        self.delegate = delegate

        func handleNotification(instance: UnsafeMutableRawPointer?, _ iterator: io_iterator_t) {
            let watcher = Unmanaged<USBWatcher>.fromOpaque(instance!).takeUnretainedValue()
            let handler: ((io_iterator_t) -> Void)?
            switch iterator {
            case watcher.addedIterator: handler = watcher.delegate?.deviceAdded
            case watcher.removedIterator: handler = watcher.delegate?.deviceRemoved
            default: assertionFailure("received unexpected IOIterator"); return
            }
            while case let device = IOIteratorNext(iterator), device != IO_OBJECT_NULL {
                handler?(device)
                IOObjectRelease(device)
            }
        }

        let query = IOServiceMatching(kIOUSBDeviceClassName)
        let opaqueSelf = Unmanaged.passUnretained(self).toOpaque()

        // Watch for connected devices.
        IOServiceAddMatchingNotification(
            notificationPort, kIOMatchedNotification, query,
            handleNotification, opaqueSelf, &addedIterator)

        handleNotification(instance: opaqueSelf, addedIterator)

        // Watch for disconnected devices.
        IOServiceAddMatchingNotification(
            notificationPort, kIOTerminatedNotification, query,
            handleNotification, opaqueSelf, &removedIterator)

        handleNotification(instance: opaqueSelf, removedIterator)

        // Add the notification to the main run loop to receive future updates.
        CFRunLoopAddSource(
            CFRunLoopGetMain(),
            IONotificationPortGetRunLoopSource(notificationPort).takeUnretainedValue(),
            .commonModes)
    }

    deinit {
        IOObjectRelease(addedIterator)
        IOObjectRelease(removedIterator)
        IONotificationPortDestroy(notificationPort)
    }
}

extension io_object_t {
    /// - Returns: The device's name.
    func name() -> String? {
        let buf = UnsafeMutablePointer<io_name_t>.allocate(capacity: 1)
        defer { buf.deallocate(capacity: 1) }
        return buf.withMemoryRebound(to: CChar.self, capacity: MemoryLayout<io_name_t>.size) {
            if IORegistryEntryGetName(self, [=10=]) == KERN_SUCCESS {
                return String(cString: [=10=])
            }
            return nil
        }
    }
}


import PlaygroundSupport
PlaygroundPage.current.needsIndefiniteExecution = true

class Example: USBWatcherDelegate {
    private var usbWatcher: USBWatcher!
    init() {
        usbWatcher = USBWatcher(delegate: self)
    }

    func deviceAdded(_ device: io_object_t) {
        print("device added: \(device.name() ?? "<unknown>")")
    }

    func deviceRemoved(_ device: io_object_t) {
        print("device removed: \(device.name() ?? "<unknown>")")
    }
}

let example = Example()

Swift 上的 USB 连接代理

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