发现BLE服务后找不到通用属性服务

Question

我发现通用属性服务时遇到问题。
连接后，我要等待1600毫秒才能发现服务。
但是，在onServicesDiscovered回调中，我发现可用服务的列表不完整，其中缺少通用属性服务。

如有必要，我使用一种名为ensureServiceChangedEnabled的方法来启用通用属性服务的ServiceChanged特性的指示。但是，调用gatt.getService(GENERIC_ATTRIBUTE_SERVICE)（或gatt.getServices()）无法找到GATT服务。

这是我的代码：

在BluetoothGattCallback中

@Override
        public void onConnectionStateChange(final BluetoothGatt gatt, int status, int newState) {
            Log.d(TAG, "onConnectionStateChange; status : " + status + ", newState : " + newState);

            if (status == BluetoothGatt.GATT_SUCCESS) {
                if (newState == BluetoothProfile.STATE_CONNECTED) {
                    Log.d(TAG, "Connected to BLE device");

                    final int delay = 1600;
                    Handler handler = new Handler(mContext.getMainLooper());
                    handler.postDelayed(new Runnable() {
                        @Override
                        public void run() {
                            // Some proximity tags (e.g. nRF PROXIMITY) initialize bonding automatically when connected.
                            if (gatt.getDevice().getBondState() != BluetoothDevice.BOND_BONDING) {
                                gatt.discoverServices();
                            }
                        }
                    }, delay);
                } else if (newState == BluetoothProfile.STATE_DISCONNECTED) {
                    Log.d(TAG, "Disconnected from BLE device");

                    /* Have to force closing bluetoothGatt. Otherwise, onConnectionStateChange
                     * could be called multiple times
                     */
                    mBluetoothGatt.close();
                }
            } else {
                Log.d(TAG, "Unexpectedly disconnected from BLE device (" + status + ")");

                /* Have to force closing bluetoothGatt. Otherwise, onConnectionStateChange
                 * could be called multiple times
                 */
                mBluetoothGatt.close();
            }
        }

        // Service discovery completed
        @Override
        public void onServicesDiscovered(BluetoothGatt gatt, int status) {
            if (status == BluetoothGatt.GATT_SUCCESS) {
                Log.d(TAG, "onServicesDiscovered");

                // Get the list of all services discovered
                mAllServices = gatt.getServices();
                if (mAllServices == null) {
                    Log.w(TAG, "No BLE services found");
                    return;
                }

                if(mAllServices.size() == 0) {
                    Log.e(TAG, "No service found on this device");
                    return;
                }

                // On devices running Android 4.3-6.0 the Service Changed characteristic needs to be
                // enabled by the app (for bonded devices)
                if (Build.VERSION.SDK_INT < Build.VERSION_CODES.N) {
                    ensureServiceChangedEnabled();
                }

                // Synchronize mAllServicesUUID with mAllServices
                if(mAllServicesUUID != null) {
                    mAllServicesUUID.clear();
                } else {
                    mAllServicesUUID = new ArrayList<>();
                }
                for(int i = 0; i < mAllServices.size(); i++) {
                    mAllServicesUUID.add(i, mAllServices.get(i).getUuid());
                }

                mEventHandler.onServicesDiscovered(mAllServices);
            } else {
                Log.w(TAG, "Failed service discovery with status: " + status);
            }
        }

ensureServiceChangedEnabled方法

/**
     * When the device is bonded and has the Generic Attribute service and the Service Changed characteristic this method enables indications on this characteristic.
     * In case one of the requirements is not fulfilled this method returns <code>false</code>.
     *
     * @return <code>true</code> when the request has been sent, <code>false</code> when the device is not bonded, does not have the Generic Attribute service, the GA service does not have
     * the Service Changed characteristic or this characteristic does not have the CCCD.
     */
    private boolean ensureServiceChangedEnabled() {
        final BluetoothGatt gatt = mBluetoothGatt;
        if (gatt == null)
            return false;

        // The Service Changed indications have sense only on bonded devices
        final BluetoothDevice device = gatt.getDevice();
        if (device.getBondState() != BluetoothDevice.BOND_BONDED)
            return false;

        final BluetoothGattService gaService = gatt.getService(GENERIC_ATTRIBUTE_SERVICE);
        if (gaService == null)
            return false;

        final BluetoothGattCharacteristic scCharacteristic = gaService.getCharacteristic(SERVICE_CHANGED_CHARACTERISTIC);
        if (scCharacteristic == null)
            return false;

        return internalEnableIndications(scCharacteristic);
    }

结果：gaService是null