java - UsbDevice requestPermission 被拒绝，且未显示请求对话框提示

Question

我正在尝试使用连接到我的 Android 设备的 USB 摄像头设备。所以最初我通过 UsbManager.getDeviceList() 方法获得了连接的 USB 设备的详细信息。然后我遍历每个设备并请求许可(如果尚未授予许可)。

在请求权限之前，我已经注册了一个全局BroadCastReceiver来监听所请求权限的响应。

这是 MainActivity.java:

public class MainActivity extends AppCompatActivity {

    private UsbManager usbManager_;
    private static final String ACTION_USB_PERMISSION = "com.android.example.USB_PERMISSION";
    public PendingIntent permissionIntent;
    private static String TAG = "testing";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

//        SurroundView surroundView = new SurroundView(this);
//        setContentView(surroundView);

        usbManager_ = (UsbManager) getSystemService(USB_SERVICE);
        permissionIntent = PendingIntent.getBroadcast(this, 0, new Intent(ACTION_USB_PERMISSION), 0);

        requestUsbPermissions();
    }

    private final BroadcastReceiver usbReceiver = new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent intent) {
            String action = intent.getAction();
            Log.i(TAG, "received intent by broadcast " + intent.getAction());
            if (ACTION_USB_PERMISSION.equals(action)) {
                synchronized (this) {
                    UsbDevice device = (UsbDevice) intent.getParcelableExtra(UsbManager.EXTRA_DEVICE);
                    if (intent.getBooleanExtra(UsbManager.EXTRA_PERMISSION_GRANTED, false)) {
                        if (device != null) {
                            Log.i(TAG, "got the permission");
                        }
                    } else {
                        Log.d(TAG, "permission denied for device " + device);
                    }
                }
            }
        }
    };

    public void requestUsbPermissions(){
        HashMap<String, UsbDevice> deviceList = usbManager_.getDeviceList();
        IntentFilter filter = new IntentFilter(ACTION_USB_PERMISSION);
        this.registerReceiver(usbReceiver, filter);
        Log.i(TAG, "registered broadcast receiver!");
        Iterator<UsbDevice> deviceIterator = deviceList.values().iterator();
        while (deviceIterator.hasNext()) {
            UsbDevice device = deviceIterator.next();
            Log.i(TAG,
                    "Camera: device Id " + device.getDeviceId() + " device mName : " + device.getDeviceName());
            if (!usbManager_.hasPermission(device)) {
                Log.i(TAG, "requesting permission");
                usbManager_.requestPermission(device, permissionIntent);
            }
        }
    }
}

因此，当我运行该应用程序时，它会检测到已连接的一个 USB 设备并请求该设备的权限。但要求用户输入的对话框永远不会出现。相反，当 BroadCastReceiver 接收到 Intent 时，intent.getBooleanExtra(UsbManager.EXTRA_PERMISSION_GRANTED, false) 的值将始终为 false，这意味着权限已被拒绝。谁能向我解释一下为什么对话框一开始就没有出现以及为什么权限被自动拒绝。

这是我的 AndroidManifest.xml

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

    <uses-feature android:name="android.hardware.usb.host" android:required="true"/>
    <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION"/>
    <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>
    <uses-permission android:name="android.permission.INTERNET" />
    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />

    <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/AppTheme">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

下面是输出日志:

2020-05-01 17:56:05.282 30769-30769/com.example.vision_sdk_testing I/testing: registered broadcast receiver!
2020-05-01 17:56:05.283 30769-30769/com.example.vision_sdk_testing I/testing: Camera: device Id 1003 device mName : /dev/bus/usb/001/003
2020-05-01 17:56:05.283 30769-30769/com.example.vision_sdk_testing I/testing: requesting permission
2020-05-01 17:56:05.301 30769-30769/com.example.vision_sdk_testing I/testing: received intent by broadcast com.android.example.USB_PERMISSION
2020-05-01 17:56:05.302 30769-30769/com.example.vision_sdk_testing D/testing: permission denied for device UsbDevice[mName=/dev/bus/usb/001/003,mVendorId=1443,mProductId=38192,mClass=239,mSubclass=2,mProtocol=1,mManufacturerName=Sonix Technology Co., Ltd.,mProductName=USB 2.0 Camera,mVersion=1.00,mSerialNumberReader=android.hardware.usb.IUsbSerialReader$Stub$Proxy@d41ebfa,mConfigurations=[
    UsbConfiguration[mId=1,mName=null,mAttributes=128,mMaxPower=128,mInterfaces=[
    UsbInterface[mId=0,mAlternateSetting=0,mName=HD USB Camera,mClass=14,mSubclass=1,mProtocol=0,mEndpoints=[]]
    UsbConfiguration[mId=3,mName=null,mAttributes=3,mMaxPower=88,mInterfaces=[]]

感谢任何帮助。谢谢!

Answer 1

对我来说，我必须在设置菜单中进入应用程序的权限，并授予我的应用程序相机权限。我猜这是因为我的 USB 设备是相机？一旦我授予此权限，该应用程序就按照文档 https://developer.android.com/guide/topics/connectivity/usb/host 中所述工作。