无法获取请求 UVC 设备权限的对话框

Question

我正在尝试开发一个应用程序来连接 phone 与特定的 UVC 相机。当我用 USB 数据线插入设备并能够枚举不同的接口时，我成功检测到该设备。我的问题是，当我尝试请求访问此设备的权限以打开相机界面时，没有对话框出现在用户面前，我的接收器的 onReceive 回调被立即调用。

这是我添加 USB 和相机权限的清单：

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.experiment"
    android:versionCode="1"
    android:versionName="alpha">

    <uses-permission android:name="android.permission.CAMERA" />
    <uses-permission android:name="android.permission.USB_PERMISSION" />
    <uses-permission android:name="android.permission.FOREGROUND_SERVICE" />

    <uses-feature android:name="android.hardware.usb.host" />
    <uses-feature android:name="android.hardware.camera" android:required="false" />

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/Theme.Experiment">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
            <intent-filter>
                <action android:name="android.hardware.usb.action.USB_DEVICE_ATTACHED" />
            </intent-filter>
            <meta-data android:name="android.hardware.usb.action.USB_DEVICE_ATTACHED"
                android:resource="@xml/device_filter" />
        </activity>
    </application>
</manifest>

这是我的 MainActivity.kt :

package com.example.experiment

import android.app.PendingIntent
import android.content.BroadcastReceiver
import android.content.Context
import android.content.Intent
import android.content.IntentFilter
import android.hardware.usb.*
import android.os.Bundle
import android.util.Log
import android.widget.Button
import android.widget.TextView
import androidx.appcompat.app.AppCompatActivity

private const val ACTION_USB_PERMISSION = "com.android.example.USB_PERMISSION"
private const val USB_SUBCLASS_CONTROL = 1
private const val USB_SUBCLASS_STREAMING = 2
private const val TAG = "EXPERIMENT"

class MainActivity : AppCompatActivity() {
    private lateinit var usbManager: UsbManager
    private lateinit var textLabel: TextView
    private lateinit var permissionIntent: PendingIntent
    private lateinit var device: UsbDevice
    private lateinit var devIf: UsbInterface
    private lateinit var conn: UsbDeviceConnection
    private lateinit var bytes: ByteArray
    private var open = false

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        Log.d(TAG, "**************************************************************")
        usbManager = getSystemService(Context.USB_SERVICE) as UsbManager

        permissionIntent = PendingIntent.getBroadcast(this, 0, Intent(ACTION_USB_PERMISSION), 0)
        val filter = IntentFilter(ACTION_USB_PERMISSION)
        registerReceiver(usbReceiver, filter)

        setContentView(R.layout.activity_main)
        textLabel = findViewById<TextView>(R.id.textlabel)
        val myButton: Button = findViewById(R.id.button_to_press)
        myButton.setOnClickListener {
            detectUSB()
        }
    }

    private val usbReceiver = object : BroadcastReceiver() {
        override fun onReceive(context: Context, intent: Intent) {
            Log.d(TAG,"onReceive called")
            if (ACTION_USB_PERMISSION == intent.action) {
                Log.d(TAG, "USB permission action")
                synchronized(this) {
                    device = intent.getParcelableExtra(UsbManager.EXTRA_DEVICE)
                    Log.d(TAG, "got device")
                    if (intent.getBooleanExtra(UsbManager.EXTRA_PERMISSION_GRANTED, false)) {
                        device.apply {
                            //call method to set up device communication
                            Log.d(TAG, "trying to open device")
                            conn = usbManager.openDevice(device)
                            open = true
                        }
                    } else {
                        Log.d(TAG, "permission denied for device $device")
                    }
                }
            }
        }
    }

    private fun detectUSB() {
        val deviceList: HashMap<String, UsbDevice> = usbManager.deviceList
        val deviceIterator: Iterator<UsbDevice> = deviceList.values.iterator()
        var i = ""
        while (deviceIterator.hasNext()) {
            val device = deviceIterator.next()
            if (device.vendorId == 0xABCD && device.productId == 0x0123) {
                if (!usbManager.hasPermission(device)) {
                    Log.d(TAG, "request sent")
                    usbManager.requestPermission(device, permissionIntent)
                } else {
                    Log.d(TAG, "got permission to use device")
                    open = true
                }
                if (!open) {
                    i += "waiting for device permission"
                } else {
                    if (!conn.releaseInterface(devIf))
                    {
                        i += """releaseInterface failed""".trimIndent()
                    }
                    conn.close()
                    i += """
device closed""".trimIndent()
                    open = false
                }
            }
            i += """
            DeviceID: ${device.deviceId}
            DeviceName: ${device.deviceName}
            DeviceClass: ${device.deviceClass} - ${translateDeviceClass(device.deviceClass)}
            DeviceSubClass: ${device.deviceSubclass}
            VendorID: ${device.vendorId}
            ProductID: ${device.productId}
            InterfaceCount: ${device.interfaceCount}
            """
        }
        textLabel.text = i
    }

    private fun translateDeviceClass(deviceClass: Int): String {
        return when (deviceClass) {
            UsbConstants.USB_CLASS_APP_SPEC -> "Application specific USB class"
            UsbConstants.USB_CLASS_AUDIO -> "USB class for audio devices"
            UsbConstants.USB_CLASS_CDC_DATA -> "USB class for CDC devices (communications device class)"
            UsbConstants.USB_CLASS_COMM -> "USB class for communication devices"
            UsbConstants.USB_CLASS_CONTENT_SEC -> "USB class for content security devices"
            UsbConstants.USB_CLASS_CSCID -> "USB class for content smart card devices"
            UsbConstants.USB_CLASS_HID -> "USB class for human interface devices (for example, mice and keyboards)"
            UsbConstants.USB_CLASS_HUB -> "USB class for USB hubs"
            UsbConstants.USB_CLASS_MASS_STORAGE -> "USB class for mass storage devices"
            UsbConstants.USB_CLASS_MISC -> "USB class for wireless miscellaneous devices"
            UsbConstants.USB_CLASS_PER_INTERFACE -> "USB class indicating that the class is determined on a per-interface basis"
            UsbConstants.USB_CLASS_PHYSICA -> "USB class for physical devices"
            UsbConstants.USB_CLASS_PRINTER -> "USB class for printers"
            UsbConstants.USB_CLASS_STILL_IMAGE -> "USB class for still image devices (digital cameras)"
            UsbConstants.USB_CLASS_VENDOR_SPEC -> "Vendor specific USB class"
            UsbConstants.USB_CLASS_VIDEO -> "USB class for video devices"
            UsbConstants.USB_CLASS_WIRELESS_CONTROLLER -> "USB class for wireless controller devices"
            else -> "Unknown USB class!"
        }
    }
}

我在 https://developer.android.com/reference/android/hardware/usb/UsbManager#requestPermission(android.hardware.usb.UsbDevice,%20android.app.PendingIntent) 上读到，对于 UVC 设备，我需要获得我添加的摄像头许可，但我仍然没有获得许可对话框并且无法打开我的设备。我在这里错过了什么？我怎样才能获得访问我的设备的权限？如果我对任何其他未标记为 UVC 的 USB 设备使用相同的代码，我每次都会收到对话框。

感谢您的帮助！

Answer 1

我找到了问题的原因：如here、Android 10 在开发过程中破坏了 UVC 支持，无法访问此类设备。这已在 Pixels phone 上修复，但在大多数设备上未修复，例如我的设备（华为 P20 pro）。

要解决此问题，需要将目标 sdk 版本更改为版本 27。在 Android Studio 中，这可以通过打开项目的模块设置并更改默认配置选项卡中的 目标 SDK 版本 来完成。您不需要更改 编译 Sdk 版本。请注意，选择此类 SDK 版本将阻止您将应用发布到 android 商店。

无法获取请求 UVC 设备权限的对话框

Fail to get dialog box to request permission for UVC device

permissions

android

kotlin

uvc