UsbDevice requestPermission is denied without showing the request dialog prompt

Question

I'm trying to use usb camera devices connected to my android device. So initially i have got the details of the usb devices connected through UsbManager.getDeviceList() method. Then i iterated through every device and requested for permission if permission was already not granted.

Prior to requesting the permission i have registered a global BroadCastReceiver to listen to the response of the requested permission.

Here is the 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);
            }
        }
    }
}

So when i run the app it detects one usb device connected and requests permission for the same. But the dialog box which asks for user input never comes. Instead when the intent is received by the BroadCastReceiver the value of intent.getBooleanExtra(UsbManager.EXTRA_PERMISSION_GRANTED, false) will always be false which means the permission is already denied. Can anyone explain to me why the dialog box is not coming in the first place and why the permission is denied automatically.

Here is my 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>

And below is the output log:

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=[]]

Any help is appreciated. Thanks!

Answer 1

For me, I had to go into the app's permissions in the settings menu and give my app the Camera permission. I'm guessing it's because my USB device is a camera? Once I granted this permission, the app worked just as described in the docs https://developer.android.com/guide/topics/connectivity/usb/host