Android Ble doesn't find characteristic in GATT service on BLE devices

Question

I am having trouble developing android software for my BLE device. My software can find my devices and GATT service, but couldn't find any characteristic in my services.

I checked android-sdk-4.4.2 source,and found some code. https://android.googlesource.com/platform/external/bluetooth/bluedroid/+/android-sdk-4.4.2_r1 https://android.googlesource.com/platform/packages/apps/Bluetooth/+/android-sdk-4.4.2_r1

static char BASE_UUID[16] = {
    0xfb, 0x34, 0x9b, 0x5f, 0x80, 0x00, 0x00, 0x80,
    0x00, 0x10, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
};

int uuidType(unsigned char* p_uuid)
{
    int i = 0;
    int match = 0;
    int all_zero = 1;

    for(i = 0; i != 16; ++i)
    {
        if (i == 12 || i == 13)
            continue;

        if (p_uuid[i] == BASE_UUID[i])
            ++match;

        if (p_uuid[i] != 0)
            all_zero = 0;
    }
    if (all_zero)
        return 0;
    if (match == 12)
        return LEN_UUID_32;
    if (match == 14)
        return LEN_UUID_16;
    return LEN_UUID_128;
}

My BLE device UUID is 0000XXXX-AABB-1000-8000-00805F9B34FB. Does this code cause this trouble? Or does my BLE devices UUID have some problem?

Answer 1

This is what you are looking for. It is a callback for gatt.discoverServices(); and returns the UUID for each service and for each service it returns the characteristic UUID.

@Override
    // New services discovered
    public void onServicesDiscovered(BluetoothGatt gatt, int status) {
        if (status == BluetoothGatt.GATT_SUCCESS) {
            for (BluetoothGattService gattService : gatt.getServices()) {
                for (BluetoothGattCharacteristic mCharacteristic : gattService.getCharacteristics()) {
                    Log.i(TAG, "Found Characteristic: " + mCharacteristic.getUuid().toString());
                }
                Log.i(TAG, "onServicesDiscovered UUID: " + gattService.getUuid().toString());
            }
        } else {
            Log.w(TAG, "onServicesDiscovered received: " + status);
        }