Android 上的最小蓝牙键盘

Question

I am trying to write a minimal implementation of a Bluetooth Keyboard for Android using GATT. They are plenty of examples out there, but something is still missing. The device connects to my Windows Machine. Then the GATT database is read:

onCharacteristicReadRequest: 00002a50-0000-1000-8000-00805f9b34fb, id: 7, offset: 0, data: 02 00 00 00 00 00 00 
onCharacteristicReadRequest: 00002a4a-0000-1000-8000-00805f9b34fb, id: 8, offset: 0, data: 01 11 00 02 
onCharacteristicReadRequest: 00002a4d-0000-1000-8000-00805f9b34fb, id: 9, offset: 0, data: 00 00
onDescriptorReadRequest: 00002908-0000-1000-8000-00805f9b34fb, id: 10, offset: 0, data: 00 01 
onDescriptorReadRequest: 00002902-0000-1000-8000-00805f9b34fb, id: 11, offset: 0, data: 00 00
onCharacteristicReadRequest: 00002a4b-0000-1000-8000-00805f9b34fb, id: 12, offset: 0, data: 05 0c 09 01 a1 01 05 07 15 00 25 01 75 01 95 08 09 e0 09 e1 09 e2 09 e3 09 e4 09 e5 09 e6 09 e7 81 02 05 07 95 01 75 08 15 04 25 df 19 04 29 df 81 00 c0 
onDescriptorReadRequest: 00002907-0000-1000-8000-00805f9b34fb, id: 13, offset: 0, data: 2a 4d
onDescriptorWriteRequest: 00002902-0000-1000-8000-00805f9b34fb, id: 18, offset: 0, data: 01 00

After that I try to send a key stroke of key H as follows:

public void sendTestNotification(BluetoothDevice device) {
        BluetoothGattCharacteristic report = gattServer.getService(UUID.fromString(HID_SERVICE)).getCharacteristic(
                UUID.fromString(BtConstants.REPORT_CHARACTERISTIC));
        byte[] data = {0x0, 0xB};
        report.setValue(data);
        // (permission check - omitted)
        gattServer.notifyCharacteristicChanged(device, report, true);
    }

But nothing happens.

Is something apparently wrong with the GATT configuration?

Answer 1

The approach I used here was contstructing a GATT database from scratch and adding different characteristics manually. I still cannot say, that is wrong here, however the better approach is to use HID profile. You will still have to deal with the Report Map Characteristic, but it's the only hurdle in this case.