通過USB電纜使用AOA協議在兩個android設備之間建立通信

Question

我正在嘗試通過USB OTG電纜將兩個Android設備與API 14+連接起來，

但是當我訪問以下兩個API時，我得到的是null值

mUsbManager.getDeviceList();

mUsbManager.getAccessoryList();

請幫助我分享您的想法或示例應用程序的任何示例（如果有）。

Answer 1

您是否出於意圖要求許可，以查看附件內容？

您是在定義自己的自定義類型和通信層，還是嘗試通過adb ....來實現？ 這里的更多信息可能很好。 但就目前而言，您需要知道是否可以看到該設備。

這個問題在AOA v2頁面中有所定義： https : //source.android.com/devices/accessories/aoa2.html

文本復制自： http : //mobilemerit.com/android-app-for-usb-host-with-source-code/

private void checkInfo() {
        manager = (UsbManager) getSystemService(Context.USB_SERVICE);
        /*
         * this block required if you need to communicate to USB devices it's
         * take permission to device
         * if you want than you can set this to which device you want to communicate   
         */
        // ------------------------------------------------------------------
        mPermissionIntent = PendingIntent.getBroadcast(this, 0, new Intent(
                ACTION_USB_PERMISSION), 0);
        IntentFilter filter = new IntentFilter(ACTION_USB_PERMISSION);
        registerReceiver(mUsbReceiver, filter);
        // -------------------------------------------------------------------
        HashMap<string , UsbDevice> deviceList = manager.getDeviceList();
        Iterator<usbdevice> deviceIterator = deviceList.values().iterator();
        String i = "";
        while (deviceIterator.hasNext()) {
            device = deviceIterator.next();
            manager.requestPermission(device, mPermissionIntent);
            i += "\n" + "DeviceID: " + device.getDeviceId() + "\n"
                    + "DeviceName: " + device.getDeviceName() + "\n"
                    + "DeviceClass: " + device.getDeviceClass() + " - "
                    + "DeviceSubClass: " + device.getDeviceSubclass() + "\n"
                    + "VendorID: " + device.getVendorId() + "\n"
                    + "ProductID: " + device.getProductId() + "\n";
        }

        textInfo.setText(i);
    }

    private final BroadcastReceiver mUsbReceiver = new BroadcastReceiver() {

        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.d("ERROR", "permission denied for device " + device);
                    }
                }
            }
        }
};