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Question

My Use case is to achieve screencast using MediaProjection API over socket connection (between two wired device):

I have added below permissions for USB access:

<uses-feature android:name="android.hardware.usb.host" />
<uses-permission android:name="android.permission.MANAGE_USB" />
<uses-permission android:name="android.permission.USB_PERMISSION" />
<uses-permission android:name="android.permission.QUERY_ALL_PACKAGES"/>
<uses-permission android:name="android.permission.USB_PERMISSION" />

I have added below intent filters for activity in which I have implemented usb connection:

<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" />

device_filter.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <usb-device vendor-id="1234" product-id="5678" />
</resources>

Here’s code snippets for USB connection:

Method 1:

class UsbReceiver extends BroadcastReceiver {

    private String TAG = UsbReceiver.class.getSimpleName();

    @Override
    public void onReceive(Context context, Intent intent) {
        String action = 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) {
                        // call method to set up device communication
                    }
                } else {
                    Log.i(TAG, "Permission denied");
                }
            }

        }
    }
}

ServerActivity.java

private UsbManager usbManager;
private UsbDevice usbDevice;
private UsbDeviceConnection usbConnection;
private UsbInterface usbInterface;
private UsbEndpoint endpointIn, endpointOut;
private AppLauncherActivity appLauncherActivity;
private UsbDeviceReceiver usbDeviceReceiver;
private UsbReceiver usbReceiver;

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
          usbManager = (UsbManager) getSystemService(context.USB_SERVICE);
          if (usbManager == null) {
            Log.e(TAG, "UsbManager is null after initialization.");
          } else {
            Log.d(TAG, "UsbManager initialized successfully.");
          }
      
    }
    
    usbReceiver = new UsbReceiver();
    PendingIntent mPermissionIntent = PendingIntent.getBroadcast(this, 0, new Intent(
                ACTION_USB_PERMISSION), 0);
    IntentFilter filter = new IntentFilter(ACTION_USB_PERMISSION);

    registerReceiver(usbReceiver, filter);
    
    for (Map.Entry<String, UsbDevice> dev : usbManager.getDeviceList().entrySet()) {
            if (dev.getValue().getVendorId() == 1234) {
                usbDevice = dev.getValue();
            }
    }

    if (usbDevice != null) {
            if (!usbManager.hasPermission(usbDevice)) {
                usbManager.requestPermission(usbDevice, mPermissionIntent);
            } else {
                Log.d(TAG, "Permission already granted.");
                // Set up USB connection here if permission is already granted
                setupUsbConnection();
            }
    }


    private void setupUsbConnection() {
        if (usbDevice != null) {
            usbConnection = usbManager.openDevice(usbDevice);
            if (usbConnection != null) {
                // Proceed with USB communication setup
                Log.d(TAG, "USB connection established.");
                // Additional code to handle USB data transfer...
            } else {
                Log.e(TAG, "Failed to open USB connection.");
            }
        }
    }

public void startUsbServer() {

//        UsbManager - to access the state of the USB and to communicate with connected hardware peripherals
//        UsbDevice - to communicate with the hardware peripheral if the Android-powered device is acting as the USB host
//        UsbAccessory - if the peripheral is acting as the USB host

        // Discover and set up USB device for communication
        if (usbManager == null) {
//            /questions/28137280/how-to-grant-permission-to-open-usb-device-with-usb-manager-opendevice-always
            Log.e(TAG, "UsbManager is null");
            return;
        } else {
            // or register receiver here
        }

        // Get the list of connected USB devices
        HashMap<String, UsbDevice> deviceList = usbManager.getDeviceList();

        if (deviceList == null || deviceList.isEmpty()) {
            Log.d(TAG, "No USB devices connected");
            return;
        }

        // Iterate through connected devices
        for (UsbDevice device : deviceList.values()) {
            if (device != null) {
                // Get Vendor ID and Product ID
                int vendorId = device.getVendorId();
                int productId = device.getProductId();

                Log.d(TAG, "Vendor ID: " + vendorId);
                Log.d(TAG, "Product ID: " + productId);

                // You can also display this info in your UI or use it as needed

            } else {
                Log.e(TAG, "UsbDevice is null");
            }
        }

    @Override
    public void usbDeviceDetached() {
        Log.d(TAG, "USB Device Detached");
    }

    @Override
    public void usbDeviceAttached(UsbDevice usbDevice) {
        Log.d(TAG, "USB Device Attached: " + usbDevice.getDeviceName());
    }

Method 2:

In Method 2 I’m just creating broadcast receiver differently, and calling this in oncreate():

public class UsbDeviceReceiver extends BroadcastReceiver {

    private String TAG = UsbDeviceReceiver.class.getSimpleName();
    private UsbListener usbListener;

    public void UsbDevicesReceiver(UsbListener usbListener) {
        this.usbListener = usbListener;
    }

    @Override
    public void onReceive(Context context, Intent intent) {
        String action = intent.getAction();

        if (UsbManager.ACTION_USB_DEVICE_DETACHED.equals(action)) {
            usbListener.usbDeviceDetached();
        } else if (UsbManager.ACTION_USB_DEVICE_ATTACHED.equals(action)) {
            UsbDevice usbDevice = intent.getParcelableExtra(UsbManager.EXTRA_DEVICE);
            usbListener.usbDeviceAttached(usbDevice);
        }
    }

    public interface UsbListener {
        void usbDeviceDetached();
        void usbDeviceAttached(UsbDevice usbDevice);
    }
}

Above mentioned is the setup I tried for usb connection but it shows null instance log:

2024-09-12 12:28:31.515  9076-9076  ServerActivity  com.r.screenmediaprojection   E  UsbManager is null

Also, As I’m not able to get usbmanager instance I’m not able to retrieve ccorrect vendor id of my device. I’m connecting two device using C to C cable while building socket connnection.

Please checkout given snippets and share insights to fix this issue…

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Danh mục

Getting USBmanager null instance