Bluetooth LE Gatt Example, scan BLE devices

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The Title : Bluetooth LE Gatt Example, scan BLE devices
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Bluetooth LE Gatt Example, scan BLE devices

Last post show the first step to enable Bluetooth, this post show how to scan BLE devices in range.


We will re-use the BluetoothLeService.java in Android example code "Bluetooth Le Gatt example". Modify to suit our case.

BluetoothLeService.java
/*
* 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.blogspot.android_er.androidblegatt;

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.os.ParcelUuid;
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 =
"android-er.ACTION_GATT_CONNECTED";
public final static String ACTION_GATT_DISCONNECTED =
"android-er.ACTION_GATT_DISCONNECTED";
public final static String ACTION_GATT_SERVICES_DISCOVERED =
"android-er.ACTION_GATT_SERVICES_DISCOVERED";
public final static String ACTION_DATA_AVAILABLE =
"android-er.ACTION_DATA_AVAILABLE";
public final static String EXTRA_DATA =
"android-er.EXTRA_DATA";

public static String String_GENUINO101_ledService =
"19B10000-E8F2-537E-4F6C-D104768A1214";
public final static ParcelUuid ParcelUuid_GENUINO101_ledService =
ParcelUuid.fromString(String_GENUINO101_ledService);
public final static UUID UUID_GENUINO101_ledService =
UUID.fromString(String_GENUINO101_ledService);


public static String String_GENUINO101_switchChar =
"19B10001-E8F2-537E-4F6C-D104768A1214";
public final static UUID UUID_GENUINO101_switchChare =
UUID.fromString(String_GENUINO101_switchChar);


// 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());
}
}
*/


//remove special handling for time being
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 Genuino 101 ledService.
if (UUID_GENUINO101_ledService.equals(characteristic.getUuid())) {
BluetoothGattDescriptor descriptor = characteristic.getDescriptor(
UUID_GENUINO101_switchChare);
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();
}
}


Edit AndroidManifest.xml to add service of ".BluetoothLeService".
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.blogspot.android_er.androidblegatt">

<uses-feature android:name="android.hardware.bluetooth_le" android:required="true"/>
<uses-permission android:name="android.permission.BLUETOOTH"/>
<uses-permission android:name="android.permission.BLUETOOTH_ADMIN"/>
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION"/>

<application
android:allowBackup="true"
android:icon="@mipmap/ic_launcher"
android:label="@string/app_name"
android:supportsRtl="true"
android:theme="@style/AppTheme">
<activity android:name=".MainActivity">
<intent-filter>
<action android:name="android.intent.action.MAIN" />

<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<service android:name=".BluetoothLeService" android:enabled="true"/>
</application>

</manifest>

Edit activity_main.xml to add a Button to start scanning, and a ListView to display the result.
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:padding="16dp"
android:orientation="vertical"
tools:context="com.blogspot.android_er.androidblegatt.MainActivity">

<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center_horizontal"
android:autoLink="web"
android:text="http://android-er.blogspot.com/"
android:textStyle="bold" />

<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center_horizontal"
android:autoLink="web"
android:text="Bluetooth LE Gatt Example"
android:textStyle="italic" />

<Button
android:id="@+id/scan"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Scan"/>
<ListView
android:id="@+id/lelist"
android:layout_width="match_parent"
android:layout_height="match_parent"/>
</LinearLayout>


MainActivity.java
package com.blogspot.android_er.androidblegatt;

import android.app.Activity;
import android.app.AlertDialog;
import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothDevice;
import android.bluetooth.BluetoothManager;
import android.bluetooth.le.BluetoothLeScanner;
import android.bluetooth.le.ScanCallback;
import android.bluetooth.le.ScanResult;
import android.content.Context;
import android.content.DialogInterface;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.os.Bundle;
import android.os.Handler;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.Toast;

import java.util.ArrayList;
import java.util.List;

public class MainActivity extends AppCompatActivity {

private BluetoothAdapter mBluetoothAdapter;
private BluetoothLeScanner mBluetoothLeScanner;

private boolean mScanning;

private static final int RQS_ENABLE_BLUETOOTH = 1;

Button btnScan;
ListView listViewLE;

List<BluetoothDevice> listBluetoothDevice;
ListAdapter adapterLeScanResult;

private Handler mHandler;
private static final long SCAN_PERIOD = 10000;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);

// Check if BLE is supported on the device.
if (!getPackageManager().hasSystemFeature(PackageManager.FEATURE_BLUETOOTH_LE)) {
Toast.makeText(this,
"BLUETOOTH_LE not supported in this device!",
Toast.LENGTH_SHORT).show();
finish();
}

getBluetoothAdapterAndLeScanner();

// Checks if Bluetooth is supported on the device.
if (mBluetoothAdapter == null) {
Toast.makeText(this,
"bluetoothManager.getAdapter()==null",
Toast.LENGTH_SHORT).show();
finish();
return;
}

btnScan = (Button)findViewById(R.id.scan);
btnScan.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
scanLeDevice(true);
}
});
listViewLE = (ListView)findViewById(R.id.lelist);

listBluetoothDevice = new ArrayList<>();
adapterLeScanResult = new ArrayAdapter<BluetoothDevice>(
this, android.R.layout.simple_list_item_1, listBluetoothDevice);
listViewLE.setAdapter(adapterLeScanResult);
listViewLE.setOnItemClickListener(scanResultOnItemClickListener);

mHandler = new Handler();

}

AdapterView.OnItemClickListener scanResultOnItemClickListener =
new AdapterView.OnItemClickListener(){

@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
final BluetoothDevice device = (BluetoothDevice) parent.getItemAtPosition(position);

String msg = device.getAddress() + "\n"
+ device.getBluetoothClass().toString() + "\n"
+ getBTDevieType(device);

new AlertDialog.Builder(MainActivity.this)
.setTitle(device.getName())
.setMessage(msg)
.setPositiveButton("OK", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {

}
})
.show();

}
};

private String getBTDevieType(BluetoothDevice d){
String type = "";

switch (d.getType()){
case BluetoothDevice.DEVICE_TYPE_CLASSIC:
type = "DEVICE_TYPE_CLASSIC";
break;
case BluetoothDevice.DEVICE_TYPE_DUAL:
type = "DEVICE_TYPE_DUAL";
break;
case BluetoothDevice.DEVICE_TYPE_LE:
type = "DEVICE_TYPE_LE";
break;
case BluetoothDevice.DEVICE_TYPE_UNKNOWN:
type = "DEVICE_TYPE_UNKNOWN";
break;
default:
type = "unknown...";
}

return type;
}

@Override
protected void onResume() {
super.onResume();

if (!mBluetoothAdapter.isEnabled()) {
if (!mBluetoothAdapter.isEnabled()) {
Intent enableBtIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
startActivityForResult(enableBtIntent, RQS_ENABLE_BLUETOOTH);
}
}
}

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {

if (requestCode == RQS_ENABLE_BLUETOOTH && resultCode == Activity.RESULT_CANCELED) {
finish();
return;
}

getBluetoothAdapterAndLeScanner();

// Checks if Bluetooth is supported on the device.
if (mBluetoothAdapter == null) {
Toast.makeText(this,
"bluetoothManager.getAdapter()==null",
Toast.LENGTH_SHORT).show();
finish();
return;
}

super.onActivityResult(requestCode, resultCode, data);
}

private void getBluetoothAdapterAndLeScanner(){
// Get BluetoothAdapter and BluetoothLeScanner.
final BluetoothManager bluetoothManager =
(BluetoothManager) getSystemService(Context.BLUETOOTH_SERVICE);
mBluetoothAdapter = bluetoothManager.getAdapter();
mBluetoothLeScanner = mBluetoothAdapter.getBluetoothLeScanner();

mScanning = false;
}

/*
to call startScan (ScanCallback callback),
Requires BLUETOOTH_ADMIN permission.
Must hold ACCESS_COARSE_LOCATION or ACCESS_FINE_LOCATION permission to get results.
*/
private void scanLeDevice(final boolean enable) {
if (enable) {
listBluetoothDevice.clear();
listViewLE.invalidateViews();

// Stops scanning after a pre-defined scan period.
mHandler.postDelayed(new Runnable() {
@Override
public void run() {
mBluetoothLeScanner.stopScan(scanCallback);
listViewLE.invalidateViews();

Toast.makeText(MainActivity.this,
"Scan timeout",
Toast.LENGTH_LONG).show();

mScanning = false;
btnScan.setEnabled(true);
}
}, SCAN_PERIOD);

mBluetoothLeScanner.startScan(scanCallback);
mScanning = true;
btnScan.setEnabled(false);
} else {
mBluetoothLeScanner.stopScan(scanCallback);
mScanning = false;
btnScan.setEnabled(true);
}
}

private ScanCallback scanCallback = new ScanCallback() {
@Override
public void onScanResult(int callbackType, ScanResult result) {
super.onScanResult(callbackType, result);

addBluetoothDevice(result.getDevice());
}

@Override
public void onBatchScanResults(List<ScanResult> results) {
super.onBatchScanResults(results);
for(ScanResult result : results){
addBluetoothDevice(result.getDevice());
}
}

@Override
public void onScanFailed(int errorCode) {
super.onScanFailed(errorCode);
Toast.makeText(MainActivity.this,
"onScanFailed: " + String.valueOf(errorCode),
Toast.LENGTH_LONG).show();
}

private void addBluetoothDevice(BluetoothDevice device){
if(!listBluetoothDevice.contains(device)){
listBluetoothDevice.add(device);
listViewLE.invalidateViews();
}
}
};
}


As shown in this video; there are three bluetooth devices running in range. This example recognize Genuino 101 and HM-10 (BLE module), but not HC-06 (classic Bluetooth module).



Next:
Scan specified BLE devices with ScanFilter

~ Bluetooth LE Gatt Example, step-by-step



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