Android 4.3(API Level 18)介绍了内置平台支持蓝牙低能量的核心做用,并提供了API,应用程序能够用它来发现设备,查询服务，和读写字符。与传统的蓝牙相比，Bluetooth Low Energy (BLE) 旨在提供显著下降功耗。这使得Android应用可以与具备BLE的低耗能设备进行通讯，例如，传感器、心率监视器,健身设备,等等。 BLE 权限 为了在应用程序中使用蓝牙功能,必须声明蓝牙蓝牙许可。您须要这个权限执行任何蓝牙通讯,如请求链接,接受链接,传输数据。 声明蓝牙权限须要在应用的manifest 文件中加以下代码： <uses-permission android:name="android.permission.BLUETOOTH"/> <uses-permission android:name="android.permission.BLUETOOTH_ADMIN"/> 若是你想声明应用程序仅BLE-capable设备可用,在你的应用程序的清单包括如下: <uses-feature android:name="android.hardware.bluetooth_le" android:required="true"/> 然而,若是你想让你的应用程序可用的设备不支持BLE,你应该仍是这个元素包含在您的应用程序的清单,但在运行时设置android:required=“false”。在运行时您能够决定BLE可用性经过使用PackageManager.hasSystemFeature(): //用这个检查设备是否支持BLE。 if (!getPackageManager().hasSystemFeature(PackageManager.FEATURE_BLUETOOTH_LE)) { Toast.makeText(this, R.string.ble_not_supported, Toast.LENGTH_SHORT).show(); finish(); } 设置BLE BLE在您的应用程序能够交互以前,你须要确认在设备上是支持BLE,若是是这样,确保启用。注意这检查须要设置< uses-feature…/ >为false。 若是不支持BLE,那么你应该禁用任何BLE特性。若是支持，可是已经禁用，你能够用你的应用启动它。完成这个设置须要两步，使用BluetoothAdapter。 1.获取luetoothAdapter。 BluetoothAdapter表明设备的蓝牙适配器。整个系统有一个蓝牙适配器,和您的应用程序可使用这个对象与它交互。下面的代码片断显示了如何获取适配器。使用getSystemService ()返回一个BluetoothManager实例,而后获取适配器。 Android 4.3(API LEVEL 18)引入了BluetoothManager: //初始化蓝牙适配器 final BluetoothManager bluetoothManager = (BluetoothManager) getSystemService(Context.BLUETOOTH_SERVICE); mBluetoothAdapter = bluetoothManager.getAdapter(); 2.启动蓝牙 接下来,您须要确保启用蓝牙。用isEnabled()检查蓝牙当前是否启动。若是这个方法返回false,那么蓝牙是关闭的。下面的代码片断检查是否启用蓝牙。若是没有,将提示用户去设置启用蓝牙。 if (mBluetoothAdapter == null || !mBluetoothAdapter.isEnabled()) { Intent enableBtIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE); startActivityForResult(enableBtIntent, REQUEST_ENABLE_BT); } 搜索蓝牙设备 搜索蓝牙设备使用startLeScan()方法。该方法以BluetoothAdapter.LeScanCallback做为参数,您必须实现这个回调,由于这是如何返回扫描结果。由于扫描很是耗电,你应该遵照以下规则： · 只要找到了设备就应该中止搜索。 · 不要在一个无限循环中搜索, 须要设置一个时间限制搜索. 下面代码做用是如何开始和结束搜索： public class DeviceScanActivity extends ListActivity { private BluetoothAdapter mBluetoothAdapter; private boolean mScanning; private Handler mHandler; // Stops scanning after 10 seconds. private static final long SCAN_PERIOD = 10000; ... private void scanLeDevice(final boolean enable) { if (enable) { // Stops scanning after a pre-defined scan period. mHandler.postDelayed(new Runnable() { @Override public void run() { mScanning = false; mBluetoothAdapter.stopLeScan(mLeScanCallback); } }, SCAN_PERIOD); mScanning = true; mBluetoothAdapter.startLeScan(mLeScanCallback); } else { mScanning = false; mBluetoothAdapter.stopLeScan(mLeScanCallback); } ... } ... } 若是你想只扫描特定类型的外围设备,你可使用startLeScan(UUID[],BluetoothAdapter.LeScanCallback),提供一个UUID对象数组,指定蓝牙服务应用程序所支持的。 这里使用BluetoothAdapter.LeScanCallback的实现用来显示蓝牙扫描结果: private LeDeviceListAdapter mLeDeviceListAdapter; ... // Device scan callback. private BluetoothAdapter.LeScanCallback mLeScanCallback = new BluetoothAdapter.LeScanCallback() { @Override public void onLeScan(final BluetoothDevice device, int rssi, byte[] scanRecord) { runOnUiThread(new Runnable() { @Override public void run() { mLeDeviceListAdapter.addDevice(device); mLeDeviceListAdapter.notifyDataSetChanged(); } }); } }; 注意：不能在同一时间扫描BLE和传统的蓝牙。 连接 GATT Server 与BLE设备交互的第一步是链接到它,更具体地说,链接到设备上的GATT服务器。链接到GATT服务器使用connectGatt()方法,这个方法取三个参数:一个上下文对象,(布尔指示是否自动链接到设备就可用),和BluetoothGattCallback回调函数。 mBluetoothGatt = device.connectGatt(this, false, mGattCallback); 这个链接到GATT服务端经过BLE设备,并返回一个BluetoothGatt实例,而后您可使用GATT客户端进行操做。调用者(Android应用程序)是GATT客户端。BluetoothGattCallback用于提供结果给客户端,如链接状态,以及任何进一步的GATT客户端操做。 在这个例子中,有幸得到应用程序提供了一个活动(DeviceControlActivity)链接,显示数据,并显示GATT服务和支持的设备特征。基于用户输入,此活动与一个服务交互称为BluetoothLeService,这服务与BLE设备交互是经过Android BLE API: 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. 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."); 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 // New services discovered 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); } } ... }; ... } 当一个特定的回调函数被触发，它调用适当的broadcastUpdate()辅助方法并将其传递一个action。注意,本节中的数据解析执行按照蓝牙心率测量概要文件规范: 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); } Back in DeviceControlActivity, these events are handled by a BroadcastReceiver: // 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)); } } }; 阅读BLE属性 一旦你的Android应用程序链接到一个GATT服务器和发现服务,它能够读取和写入属性。例如,这段代码遍历服务器的服务和数据并将它们显示在UI中: 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); } ... } ... } 接收GATT通知 当一个特定的设备上的特征变化须要BLE的应用通知。这个代码片断显示了如何设置一个通知特性,使用setCharacteristicNotification()方法: 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); 一旦通知做为一个特性被启用,若是远程设备上的特性变化将触发onCharacteristicChanged()回调。 @Override // Characteristic notification public void onCharacteristicChanged(BluetoothGatt gatt, BluetoothGattCharacteristic characteristic) { broadcastUpdate(ACTION_DATA_AVAILABLE, characteristic); } 关闭客户端应用 一旦应用程序完成使用BLE设备，应该调用close()方法去释放系统资源。 public void close() { if (mBluetoothGatt == null) { return; } mBluetoothGatt.close(); mBluetoothGatt = null; }