Android-低功耗蓝牙BLE（Bluetooth Low Energy）开发

本文主要是介绍Android-低功耗蓝牙BLE（Bluetooth Low Energy）开发，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

1.前言

1、Android 4.3 (API Level 18)才开始提供低功耗蓝牙开发API；
2、根据API可以发现设备、查询服务、读写characteristics；
3、顾名思义，BLE出现旨在显著地降低能耗，这就使得app可以和一些低功耗设备交互，例如：接近传感器、心率监视器,健身设备,等等。

2.关键术语和概念

Generic Attribute Profile (GATT)：GATT协议定义了一个通用的规范，这个规范用于在BLE 连接上发送和接收一些短消息；
Attribute Protocol (ATT)：GATT 建立在ATT上面,ATT是一种最优化的协议对于BLE设备；
Characteristic：这个东西可以被看成一个类来描述一些交互的信息；
Descriptor:描述符，定义一些属性来描述Characteristic的值；
Service:用来搜集Characteristic的服务，例如：心率监测器搜集一些心率测量相关的Characteristic数据；

3.manifest 权限配置
声明权限

<uses-permission android:name="android.permission.BLUETOOTH"/>
<uses-permission android:name="android.permission.BLUETOOTH_ADMIN"/>

静态声明以下语句表示app是否支持BLE，required=”true”表支持，反之则不支持；

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

之后在代码检查设备是否支持BLE

// Use this check to determine whether BLE is supported on the device. Then
// you can selectively disable BLE-related features.
if (!getPackageManager().hasSystemFeature(PackageManager.FEATURE_BLUETOOTH_LE)) { //不支持 todo...
}else{ //支持 todo...
}

4. 配置BLE

前提是设备支持BLE；
如果可能出现为false的情况下，我们有必要在代码中动态检查是否支持BLE；

//初始化蓝牙适配器，核心类
final BluetoothManager bluetoothManager =(BluetoothManager) getSystemService(Context.BLUETOOTH_SERVICE);
mBluetoothAdapter = bluetoothManager.getAdapter();

private BluetoothAdapter mBluetoothAdapter;
...
//如果蓝牙适配器==null 或者 蓝牙没有打开，代码请求打开蓝牙
if (mBluetoothAdapter == null || !mBluetoothAdapter.isEnabled()) {Intent enableBtIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);startActivityForResult(enableBtIntent, REQUEST_ENABLE_BT);
}

5.搜索设备

因为扫描设备比较耗电，所以一旦你发现了想要的设备，立即停止扫描；
千万不要不停地循环扫描，而是设置扫描的时间，因为之前可用的设备可能离开BLE的范围，这时候还在循环扫描比较浪费电；
注意：我们不能同时扫描 低功耗蓝牙设备（BLE） 和 传统蓝牙设备；

//startScan有很多个重载的方法 
mBluetoothAdapter.startScan(BluetoothAdapter.LeScanCallback);mBluetoothAdapter.startScan (List<ScanFilter> filters, ScanSettings settings, ScanCallback callback);...

/*** Activity 示例：扫描和展示可用BLE设备*/
public class DeviceScanActivity extends ListActivity {private BluetoothAdapter mBluetoothAdapter;private boolean mScanning;private Handler mHandler;// 扫描时间 10秒private static final long SCAN_PERIOD = 10000;...private void scanLeDevice(final boolean enable) {if (enable) {// 通过Handler延迟任务，取消扫描mHandler.postDelayed(new Runnable() {@Overridepublic void run() {mScanning = false;mBluetoothAdapter.stopLeScan(mLeScanCallback);}}, SCAN_PERIOD);mScanning = true;//开始扫描mBluetoothAdapter.startLeScan(mLeScanCallback);//扫描指定UUID的设备使用面这个方法startLeScan(UUID[], BluetoothAdapter.LeScanCallback)} else {mScanning = false;//停止扫描mBluetoothAdapter.stopLeScan(mLeScanCallback);}...}
...
}

//BluetoothAdapter.LeScanCallback实现
private LeDeviceListAdapter mLeDeviceListAdapter;
...
// 扫描设备后回调接口
private BluetoothAdapter.LeScanCallback mLeScanCallback =new BluetoothAdapter.LeScanCallback() {@Overridepublic void onLeScan(final BluetoothDevice device, int rssi,byte[] scanRecord) {//device 扫描到的设备}
};

6. 连接到服务（GATT Server）

//参数一 Context
//参数二 Boolean 是否尝试自动连接当BLE设备变得可用的时候
//参数三 BluetoothGattCallbac 回调接口
mBluetoothGatt = device.connectGatt(Context, Boolean, BluetoothGattCallback);

// A service that interacts with the BLE device via the Android BLE API.
//开启服务，通过Android BLE API 实现和BLE设备的交互
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.HEART_RATE_MEASUREMENT);// Various callback methods defined by the BLE API.//BLE API 定义了多种回调方法private final BluetoothGattCallback mGattCallback =new BluetoothGattCallback() {@Overridepublic void onConnectionStateChange(BluetoothGatt gatt, int status,int newState) {String intentAction;if (newState == BluetoothProfile.STATE_CONNECTED) { //连上GATT服务intentAction = ACTION_GATT_CONNECTED;mConnectionState = STATE_CONNECTED;broadcastUpdate(intentAction);Log.i(TAG, "Connected to GATT server.");Log.i(TAG, "Attempting to start service discovery:" +mBluetoothGatt.discoverServices());} else if (newState == BluetoothProfile.STATE_DISCONNECTED) {//断开服务连接intentAction = ACTION_GATT_DISCONNECTED;mConnectionState = STATE_DISCONNECTED;Log.i(TAG, "Disconnected from GATT server.");broadcastUpdate(intentAction);}}@Override// New services discovered//新的服务被发现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// Result of a characteristic read operation//public void onCharacteristicRead(BluetoothGatt gatt,BluetoothGattCharacteristic characteristic,int status) {if (status == BluetoothGatt.GATT_SUCCESS) {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.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());}}sendBroadcast(intent);
}

通过广播接收者处理这些事件

// 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() {@Overridepublic 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));}}
};

7.连上服务后，可以读取数据了

public class DeviceControlActivity extends Activity {...// 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) {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);}mGattCharacteristics.add(charas);gattCharacteristicData.add(gattCharacteristicGroupData);}...}
...
}

8.接收GATT通知

private BluetoothGatt mBluetoothGatt;
BluetoothGattCharacteristic characteristic;
boolean enabled;
...
mBluetoothGatt.setCharacteristicNotification(characteristic, enabled);
...
BluetoothGattDescriptor descriptor = characteristic.getDescriptor(UUID.fromString(SampleGattAttributes.CLIENT_CHARACTERISTIC_CONFIG));
descriptor.setValue(BluetoothGattDescriptor.ENABLE_NOTIFICATION_VALUE);
mBluetoothGatt.writeDescriptor(descriptor);

onCharacteristicChanged() 回调用来监听远程设备characteristic changes

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

8.App和BLE设备交互完成，需要释放资源

public void close() {if (mBluetoothGatt == null) {return;}mBluetoothGatt.close();mBluetoothGatt = null;
}

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Android-低功耗蓝牙BLE（Bluetooth Low Energy）开发

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