Android send data to Bluetooth LE device, using HM-10 BLE Module

The previous post show how to "Modified BluetoothLeGatt sample for HM-10 (Bluetooth LE Module)", to receive data. In the original example code haven't handle send data from Android to Bluetooth LE device. It's modified to echo the received data back HM-10, to sender.


Modify BluetoothLeService.java to add method writeCharacteristic(BluetoothGattCharacteristic characteristic) to write data.

/*
 * Copyright (C) 2013 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.example.android.bluetoothlegatt;

import android.app.Service;
import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothDevice;
import android.bluetooth.BluetoothGatt;
import android.bluetooth.BluetoothGattCallback;
import android.bluetooth.BluetoothGattCharacteristic;
import android.bluetooth.BluetoothGattDescriptor;
import android.bluetooth.BluetoothGattService;
import android.bluetooth.BluetoothManager;
import android.bluetooth.BluetoothProfile;
import android.content.Context;
import android.content.Intent;
import android.os.Binder;
import android.os.IBinder;
import android.util.Log;

import java.util.List;
import java.util.UUID;

/**
 * Service for managing connection and data communication with a GATT server hosted on a
 * given Bluetooth LE device.
 */
public class BluetoothLeService extends Service {
    private final static String TAG = BluetoothLeService.class.getSimpleName();

    private BluetoothManager mBluetoothManager;
    private BluetoothAdapter mBluetoothAdapter;
    private String mBluetoothDeviceAddress;
    private BluetoothGatt mBluetoothGatt;
    private int mConnectionState = STATE_DISCONNECTED;

    private static final int STATE_DISCONNECTED = 0;
    private static final int STATE_CONNECTING = 1;
    private static final int STATE_CONNECTED = 2;

    public final static String ACTION_GATT_CONNECTED =
            "com.example.bluetooth.le.ACTION_GATT_CONNECTED";
    public final static String ACTION_GATT_DISCONNECTED =
            "com.example.bluetooth.le.ACTION_GATT_DISCONNECTED";
    public final static String ACTION_GATT_SERVICES_DISCOVERED =
            "com.example.bluetooth.le.ACTION_GATT_SERVICES_DISCOVERED";
    public final static String ACTION_DATA_AVAILABLE =
            "com.example.bluetooth.le.ACTION_DATA_AVAILABLE";
    public final static String EXTRA_DATA =
            "com.example.bluetooth.le.EXTRA_DATA";

    public final static UUID UUID_HEART_RATE_MEASUREMENT =
            UUID.fromString(SampleGattAttributes.HM_10);

    // Implements callback methods for GATT events that the app cares about.  For example,
    // connection change and services discovered.
    private final BluetoothGattCallback mGattCallback = new BluetoothGattCallback() {
        @Override
        public void onConnectionStateChange(BluetoothGatt gatt, int status, int newState) {
            String intentAction;
            if (newState == BluetoothProfile.STATE_CONNECTED) {
                intentAction = ACTION_GATT_CONNECTED;
                mConnectionState = STATE_CONNECTED;
                broadcastUpdate(intentAction);
                Log.i(TAG, "Connected to GATT server.");
                // Attempts to discover services after successful connection.
                Log.i(TAG, "Attempting to start service discovery:" +
                        mBluetoothGatt.discoverServices());

            } else if (newState == BluetoothProfile.STATE_DISCONNECTED) {
                intentAction = ACTION_GATT_DISCONNECTED;
                mConnectionState = STATE_DISCONNECTED;
                Log.i(TAG, "Disconnected from GATT server.");
                broadcastUpdate(intentAction);
            }
        }

        @Override
        public void onServicesDiscovered(BluetoothGatt gatt, int status) {
            if (status == BluetoothGatt.GATT_SUCCESS) {
                broadcastUpdate(ACTION_GATT_SERVICES_DISCOVERED);
            } else {
                Log.w(TAG, "onServicesDiscovered received: " + status);
            }
        }

        @Override
        public void onCharacteristicRead(BluetoothGatt gatt,
                                         BluetoothGattCharacteristic characteristic,
                                         int status) {
            if (status == BluetoothGatt.GATT_SUCCESS) {
                broadcastUpdate(ACTION_DATA_AVAILABLE, characteristic);
            }
        }

        @Override
        public void onCharacteristicChanged(BluetoothGatt gatt,
                                            BluetoothGattCharacteristic characteristic) {
            broadcastUpdate(ACTION_DATA_AVAILABLE, characteristic);
        }
    };

    private void broadcastUpdate(final String action) {
        final Intent intent = new Intent(action);
        sendBroadcast(intent);
    }

    private void broadcastUpdate(final String action,
                                 final BluetoothGattCharacteristic characteristic) {
        final Intent intent = new Intent(action);

        /*
        // This is special handling for the Heart Rate Measurement profile.  Data parsing is
        // carried out as per profile specifications:
        // http://developer.bluetooth.org/gatt/characteristics/Pages/CharacteristicViewer.aspx?u=org.bluetooth.characteristic.heart_rate_measurement.xml
        if (UUID_HEART_RATE_MEASUREMENT.equals(characteristic.getUuid())) {
            int flag = characteristic.getProperties();
            int format = -1;
            if ((flag & 0x01) != 0) {
                format = BluetoothGattCharacteristic.FORMAT_UINT16;
                Log.d(TAG, "Heart rate format UINT16.");
            } else {
                format = BluetoothGattCharacteristic.FORMAT_UINT8;
                Log.d(TAG, "Heart rate format UINT8.");
            }
            final int heartRate = characteristic.getIntValue(format, 1);
            Log.d(TAG, String.format("Received heart rate: %d", heartRate));
            intent.putExtra(EXTRA_DATA, String.valueOf(heartRate));
        } else {
            // For all other profiles, writes the data formatted in HEX.
            final byte[] data = characteristic.getValue();
            if (data != null && data.length > 0) {
                final StringBuilder stringBuilder = new StringBuilder(data.length);
                for(byte byteChar : data)
                    stringBuilder.append(String.format("%02X ", byteChar));
                intent.putExtra(EXTRA_DATA, new String(data) + "\n" + stringBuilder.toString());
            }
        }
        */

        Log.w(TAG, "broadcastUpdate()");

        final byte[] data = characteristic.getValue();

        Log.v(TAG, "data.length: " + data.length);

        if (data != null && data.length > 0) {
            final StringBuilder stringBuilder = new StringBuilder(data.length);
            for(byte byteChar : data) {
                stringBuilder.append(String.format("%02X ", byteChar));

                Log.v(TAG, String.format("%02X ", byteChar));
            }
            intent.putExtra(EXTRA_DATA, new String(data) + "\n" + stringBuilder.toString());
        }

        sendBroadcast(intent);
    }

    public class LocalBinder extends Binder {
        BluetoothLeService getService() {
            return BluetoothLeService.this;
        }
    }

    @Override
    public IBinder onBind(Intent intent) {
        return mBinder;
    }

    @Override
    public boolean onUnbind(Intent intent) {
        // After using a given device, you should make sure that BluetoothGatt.close() is called
        // such that resources are cleaned up properly.  In this particular example, close() is
        // invoked when the UI is disconnected from the Service.
        close();
        return super.onUnbind(intent);
    }

    private final IBinder mBinder = new LocalBinder();

    /**
     * Initializes a reference to the local Bluetooth adapter.
     *
     * @return Return true if the initialization is successful.
     */
    public boolean initialize() {
        // For API level 18 and above, get a reference to BluetoothAdapter through
        // BluetoothManager.
        if (mBluetoothManager == null) {
            mBluetoothManager = (BluetoothManager) getSystemService(Context.BLUETOOTH_SERVICE);
            if (mBluetoothManager == null) {
                Log.e(TAG, "Unable to initialize BluetoothManager.");
                return false;
            }
        }

        mBluetoothAdapter = mBluetoothManager.getAdapter();
        if (mBluetoothAdapter == null) {
            Log.e(TAG, "Unable to obtain a BluetoothAdapter.");
            return false;
        }

        return true;
    }

    /**
     * Connects to the GATT server hosted on the Bluetooth LE device.
     *
     * @param address The device address of the destination device.
     *
     * @return Return true if the connection is initiated successfully. The connection result
     *         is reported asynchronously through the
     *         {@code BluetoothGattCallback#onConnectionStateChange(android.bluetooth.BluetoothGatt, int, int)}
     *         callback.
     */
    public boolean connect(final String address) {
        if (mBluetoothAdapter == null || address == null) {
            Log.w(TAG, "BluetoothAdapter not initialized or unspecified address.");
            return false;
        }

        // Previously connected device.  Try to reconnect.
        if (mBluetoothDeviceAddress != null && address.equals(mBluetoothDeviceAddress)
                && mBluetoothGatt != null) {
            Log.d(TAG, "Trying to use an existing mBluetoothGatt for connection.");
            if (mBluetoothGatt.connect()) {
                mConnectionState = STATE_CONNECTING;
                return true;
            } else {
                return false;
            }
        }

        final BluetoothDevice device = mBluetoothAdapter.getRemoteDevice(address);
        if (device == null) {
            Log.w(TAG, "Device not found.  Unable to connect.");
            return false;
        }
        // We want to directly connect to the device, so we are setting the autoConnect
        // parameter to false.
        mBluetoothGatt = device.connectGatt(this, false, mGattCallback);
        Log.d(TAG, "Trying to create a new connection.");
        mBluetoothDeviceAddress = address;
        mConnectionState = STATE_CONNECTING;
        return true;
    }

    /**
     * Disconnects an existing connection or cancel a pending connection. The disconnection result
     * is reported asynchronously through the
     * {@code BluetoothGattCallback#onConnectionStateChange(android.bluetooth.BluetoothGatt, int, int)}
     * callback.
     */
    public void disconnect() {
        if (mBluetoothAdapter == null || mBluetoothGatt == null) {
            Log.w(TAG, "BluetoothAdapter not initialized");
            return;
        }
        mBluetoothGatt.disconnect();
    }

    /**
     * After using a given BLE device, the app must call this method to ensure resources are
     * released properly.
     */
    public void close() {
        if (mBluetoothGatt == null) {
            return;
        }
        mBluetoothGatt.close();
        mBluetoothGatt = null;
    }

    /**
     * Request a read on a given {@code BluetoothGattCharacteristic}. The read result is reported
     * asynchronously through the {@code BluetoothGattCallback#onCharacteristicRead(android.bluetooth.BluetoothGatt, android.bluetooth.BluetoothGattCharacteristic, int)}
     * callback.
     *
     * @param characteristic The characteristic to read from.
     */
    public void readCharacteristic(BluetoothGattCharacteristic characteristic) {
        if (mBluetoothAdapter == null || mBluetoothGatt == null) {
            Log.w(TAG, "BluetoothAdapter not initialized");
            return;
        }
        mBluetoothGatt.readCharacteristic(characteristic);
    }

    /**
     * Enables or disables notification on a give characteristic.
     *
     * @param characteristic Characteristic to act on.
     * @param enabled If true, enable notification.  False otherwise.
     */
    public void setCharacteristicNotification(BluetoothGattCharacteristic characteristic,
                                              boolean enabled) {
        if (mBluetoothAdapter == null || mBluetoothGatt == null) {
            Log.w(TAG, "BluetoothAdapter not initialized");
            return;
        }
        mBluetoothGatt.setCharacteristicNotification(characteristic, enabled);

        // This is specific to Heart Rate Measurement.
        if (UUID_HEART_RATE_MEASUREMENT.equals(characteristic.getUuid())) {
            BluetoothGattDescriptor descriptor = characteristic.getDescriptor(
                    UUID.fromString(SampleGattAttributes.CLIENT_CHARACTERISTIC_CONFIG));
            descriptor.setValue(BluetoothGattDescriptor.ENABLE_NOTIFICATION_VALUE);
            mBluetoothGatt.writeDescriptor(descriptor);
        }
    }

    /**
     * Retrieves a list of supported GATT services on the connected device. This should be
     * invoked only after {@code BluetoothGatt#discoverServices()} completes successfully.
     *
     * @return A {@code List} of supported services.
     */
    public List<BluetoothGattService> getSupportedGattServices() {
        if (mBluetoothGatt == null) return null;

        return mBluetoothGatt.getServices();
    }

    public void writeCharacteristic(BluetoothGattCharacteristic characteristic) {
        mBluetoothGatt.writeCharacteristic(characteristic);
    }
}

DeviceControlActivity.java
- Add bluetoothGattCharacteristicHM_10 to keep track of BluetoothGattCharacteristic object of HM-10.
- Echo back data to bluetoothGattCharacteristicHM_10 in BroadcastReceiver.

/*
 * Copyright (C) 2013 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.example.android.bluetoothlegatt;

import android.app.Activity;
import android.bluetooth.BluetoothGattCharacteristic;
import android.bluetooth.BluetoothGattService;
import android.content.BroadcastReceiver;
import android.content.ComponentName;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.content.ServiceConnection;
import android.os.Bundle;
import android.os.IBinder;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.ExpandableListView;
import android.widget.SimpleExpandableListAdapter;
import android.widget.TextView;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.UUID;

/**
 * For a given BLE device, this Activity provides the user interface to connect, display data,
 * and display GATT services and characteristics supported by the device.  The Activity
 * communicates with {@code BluetoothLeService}, which in turn interacts with the
 * Bluetooth LE API.
 */
public class DeviceControlActivity extends Activity {
    private final static String TAG = DeviceControlActivity.class.getSimpleName();

    public static final String EXTRAS_DEVICE_NAME = "DEVICE_NAME";
    public static final String EXTRAS_DEVICE_ADDRESS = "DEVICE_ADDRESS";

    private TextView mConnectionState;
    private TextView mDataField;
    private String mDeviceName;
    private String mDeviceAddress;
    private ExpandableListView mGattServicesList;
    private BluetoothLeService mBluetoothLeService;
    private ArrayList<ArrayList<BluetoothGattCharacteristic>> mGattCharacteristics =
            new ArrayList<ArrayList<BluetoothGattCharacteristic>>();
    private boolean mConnected = false;
    private BluetoothGattCharacteristic mNotifyCharacteristic;

    private final String LIST_NAME = "NAME";
    private final String LIST_UUID = "UUID";

    private BluetoothGattCharacteristic bluetoothGattCharacteristicHM_10;

    // Code to manage Service lifecycle.
    private final ServiceConnection mServiceConnection = new ServiceConnection() {

        @Override
        public void onServiceConnected(ComponentName componentName, IBinder service) {
            mBluetoothLeService = ((BluetoothLeService.LocalBinder) service).getService();
            if (!mBluetoothLeService.initialize()) {
                Log.e(TAG, "Unable to initialize Bluetooth");
                finish();
            }
            // Automatically connects to the device upon successful start-up initialization.
            mBluetoothLeService.connect(mDeviceAddress);
        }

        @Override
        public void onServiceDisconnected(ComponentName componentName) {
            mBluetoothLeService = null;
        }
    };

    // Handles various events fired by the Service.
    // ACTION_GATT_CONNECTED: connected to a GATT server.
    // ACTION_GATT_DISCONNECTED: disconnected from a GATT server.
    // ACTION_GATT_SERVICES_DISCOVERED: discovered GATT services.
    // ACTION_DATA_AVAILABLE: received data from the device.  This can be a result of read
    //                        or notification operations.
    private final BroadcastReceiver mGattUpdateReceiver = new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent intent) {
            final String action = intent.getAction();
            if (BluetoothLeService.ACTION_GATT_CONNECTED.equals(action)) {
                mConnected = true;
                updateConnectionState(R.string.connected);
                invalidateOptionsMenu();
            } else if (BluetoothLeService.ACTION_GATT_DISCONNECTED.equals(action)) {
                mConnected = false;
                updateConnectionState(R.string.disconnected);
                invalidateOptionsMenu();
                clearUI();
            } else if (BluetoothLeService.ACTION_GATT_SERVICES_DISCOVERED.equals(action)) {
                // Show all the supported services and characteristics on the user interface.
                displayGattServices(mBluetoothLeService.getSupportedGattServices());
            } else if (BluetoothLeService.ACTION_DATA_AVAILABLE.equals(action)) {
                displayData(intent.getStringExtra(BluetoothLeService.EXTRA_DATA));

                //Echo back received data, with something inserted
                final byte[] rxBytes = bluetoothGattCharacteristicHM_10.getValue();
                final byte[] insertSomething = {(byte)'\n'};
                byte[] txBytes = new byte[insertSomething.length + rxBytes.length];
                System.arraycopy(insertSomething, 0, txBytes, 0, insertSomething.length);
                System.arraycopy(rxBytes, 0, txBytes, insertSomething.length, rxBytes.length);

                if(bluetoothGattCharacteristicHM_10 != null){
                    bluetoothGattCharacteristicHM_10.setValue(txBytes);
                    mBluetoothLeService.writeCharacteristic(bluetoothGattCharacteristicHM_10);
                    mBluetoothLeService.setCharacteristicNotification(bluetoothGattCharacteristicHM_10,true);
                }

            }
        }
    };

    // If a given GATT characteristic is selected, check for supported features.  This sample
    // demonstrates 'Read' and 'Notify' features.  See
    // http://d.android.com/reference/android/bluetooth/BluetoothGatt.html for the complete
    // list of supported characteristic features.
    private final ExpandableListView.OnChildClickListener servicesListClickListner =
            new ExpandableListView.OnChildClickListener() {
                @Override
                public boolean onChildClick(ExpandableListView parent, View v, int groupPosition,
                                            int childPosition, long id) {
                    if (mGattCharacteristics != null) {
                        final BluetoothGattCharacteristic characteristic =
                                mGattCharacteristics.get(groupPosition).get(childPosition);
                        final int charaProp = characteristic.getProperties();
                        if ((charaProp | BluetoothGattCharacteristic.PROPERTY_READ) > 0) {
                            // If there is an active notification on a characteristic, clear
                            // it first so it doesn't update the data field on the user interface.
                            if (mNotifyCharacteristic != null) {
                                mBluetoothLeService.setCharacteristicNotification(
                                        mNotifyCharacteristic, false);
                                mNotifyCharacteristic = null;
                            }
                            mBluetoothLeService.readCharacteristic(characteristic);
                        }
                        if ((charaProp | BluetoothGattCharacteristic.PROPERTY_NOTIFY) > 0) {
                            mNotifyCharacteristic = characteristic;
                            mBluetoothLeService.setCharacteristicNotification(
                                    characteristic, true);
                        }
                        return true;
                    }
                    return false;
                }
    };

    private void clearUI() {
        mGattServicesList.setAdapter((SimpleExpandableListAdapter) null);
        mDataField.setText(R.string.no_data);
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.gatt_services_characteristics);

        final Intent intent = getIntent();
        mDeviceName = intent.getStringExtra(EXTRAS_DEVICE_NAME);
        mDeviceAddress = intent.getStringExtra(EXTRAS_DEVICE_ADDRESS);

        // Sets up UI references.
        ((TextView) findViewById(R.id.device_address)).setText(mDeviceAddress);
        mGattServicesList = (ExpandableListView) findViewById(R.id.gatt_services_list);
        mGattServicesList.setOnChildClickListener(servicesListClickListner);
        mConnectionState = (TextView) findViewById(R.id.connection_state);
        mDataField = (TextView) findViewById(R.id.data_value);

        getActionBar().setTitle(mDeviceName);
        getActionBar().setDisplayHomeAsUpEnabled(true);
        Intent gattServiceIntent = new Intent(this, BluetoothLeService.class);
        bindService(gattServiceIntent, mServiceConnection, BIND_AUTO_CREATE);
    }

    @Override
    protected void onResume() {
        super.onResume();
        registerReceiver(mGattUpdateReceiver, makeGattUpdateIntentFilter());
        if (mBluetoothLeService != null) {
            final boolean result = mBluetoothLeService.connect(mDeviceAddress);
            Log.d(TAG, "Connect request result=" + result);
        }
    }

    @Override
    protected void onPause() {
        super.onPause();
        unregisterReceiver(mGattUpdateReceiver);
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        unbindService(mServiceConnection);
        mBluetoothLeService = null;
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.gatt_services, menu);
        if (mConnected) {
            menu.findItem(R.id.menu_connect).setVisible(false);
            menu.findItem(R.id.menu_disconnect).setVisible(true);
        } else {
            menu.findItem(R.id.menu_connect).setVisible(true);
            menu.findItem(R.id.menu_disconnect).setVisible(false);
        }
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        switch(item.getItemId()) {
            case R.id.menu_connect:
                mBluetoothLeService.connect(mDeviceAddress);
                return true;
            case R.id.menu_disconnect:
                mBluetoothLeService.disconnect();
                return true;
            case android.R.id.home:
                onBackPressed();
                return true;
        }
        return super.onOptionsItemSelected(item);
    }

    private void updateConnectionState(final int resourceId) {
        runOnUiThread(new Runnable() {
            @Override
            public void run() {
                mConnectionState.setText(resourceId);
            }
        });
    }

    private void displayData(String data) {
        if (data != null) {
            mDataField.setText(data);
        }
    }

    // Demonstrates how to iterate through the supported GATT Services/Characteristics.
    // In this sample, we populate the data structure that is bound to the ExpandableListView
    // on the UI.
    private void displayGattServices(List<BluetoothGattService> gattServices) {

        UUID UUID_HM_10 =
                UUID.fromString(SampleGattAttributes.HM_10);

        if (gattServices == null) return;
        String uuid = null;
        String unknownServiceString = getResources().getString(R.string.unknown_service);
        String unknownCharaString = getResources().getString(R.string.unknown_characteristic);
        ArrayList<HashMap<String, String>> gattServiceData = new ArrayList<HashMap<String, String>>();
        ArrayList<ArrayList<HashMap<String, String>>> gattCharacteristicData
                = new ArrayList<ArrayList<HashMap<String, String>>>();
        mGattCharacteristics = new ArrayList<ArrayList<BluetoothGattCharacteristic>>();

        // Loops through available GATT Services.
        for (BluetoothGattService gattService : gattServices) {
            HashMap<String, String> currentServiceData = new HashMap<String, String>();
            uuid = gattService.getUuid().toString();
            currentServiceData.put(
                    LIST_NAME, SampleGattAttributes.lookup(uuid, unknownServiceString));
            currentServiceData.put(LIST_UUID, uuid);
            gattServiceData.add(currentServiceData);

            ArrayList<HashMap<String, String>> gattCharacteristicGroupData =
                    new ArrayList<HashMap<String, String>>();
            List<BluetoothGattCharacteristic> gattCharacteristics =
                    gattService.getCharacteristics();
            ArrayList<BluetoothGattCharacteristic> charas =
                    new ArrayList<BluetoothGattCharacteristic>();

            // Loops through available Characteristics.
            for (BluetoothGattCharacteristic gattCharacteristic : gattCharacteristics) {
                charas.add(gattCharacteristic);
                HashMap<String, String> currentCharaData = new HashMap<String, String>();
                uuid = gattCharacteristic.getUuid().toString();
                currentCharaData.put(
                        LIST_NAME, SampleGattAttributes.lookup(uuid, unknownCharaString));
                currentCharaData.put(LIST_UUID, uuid);
                gattCharacteristicGroupData.add(currentCharaData);

                //Check if it is "HM_10"
                if(uuid.equals(SampleGattAttributes.HM_10)){
                    bluetoothGattCharacteristicHM_10 = gattService.getCharacteristic(UUID_HM_10);

                }
            }
            mGattCharacteristics.add(charas);
            gattCharacteristicData.add(gattCharacteristicGroupData);
        }

        SimpleExpandableListAdapter gattServiceAdapter = new SimpleExpandableListAdapter(
                this,
                gattServiceData,
                android.R.layout.simple_expandable_list_item_2,
                new String[] {LIST_NAME, LIST_UUID},
                new int[] { android.R.id.text1, android.R.id.text2 },
                gattCharacteristicData,
                android.R.layout.simple_expandable_list_item_2,
                new String[] {LIST_NAME, LIST_UUID},
                new int[] { android.R.id.text1, android.R.id.text2 }
        );
        mGattServicesList.setAdapter(gattServiceAdapter);
    }

    private static IntentFilter makeGattUpdateIntentFilter() {
        final IntentFilter intentFilter = new IntentFilter();
        intentFilter.addAction(BluetoothLeService.ACTION_GATT_CONNECTED);
        intentFilter.addAction(BluetoothLeService.ACTION_GATT_DISCONNECTED);
        intentFilter.addAction(BluetoothLeService.ACTION_GATT_SERVICES_DISCOVERED);
        intentFilter.addAction(BluetoothLeService.ACTION_DATA_AVAILABLE);
        return intentFilter;
    }
}

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