html网页生成工具,网站优化 ppt,铜川泰士公馆建设网站,小型手机网站建设多少钱蓝牙介绍 Android 4.3(API Level 18)介绍了内置平台支持蓝牙低能量的核心作用,并提供了API,应用程序可以用它来发现设备,查询服务#xff0c;和读写字符。与传统的蓝牙相比#xff0c;Bluetooth Low Energy (BLE) 旨在提供显著降低功耗。这使得Android应用能够与具有BLE的低耗…蓝牙介绍 Android 4.3(API Level 18)介绍了内置平台支持蓝牙低能量的核心作用,并提供了API,应用程序可以用它来发现设备,查询服务和读写字符。与传统的蓝牙相比Bluetooth Low Energy (BLE) 旨在提供显著降低功耗。这使得Android应用能够与具有BLE的低耗能设备进行通信例如传感器、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。您需要这个权限执行任何蓝牙通信,如请求连接,接受连接,传输数据。 声明蓝牙权限需要在应用的manifest 文件中加如下代码 uses-permission android:nameandroid.permission.BLUETOOTH/ uses-permission android:nameandroid.permission.BLUETOOTH_ADMIN/ 如果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以下: uses-feature android:nameandroid.hardware.bluetooth_le android:requiredtrue/ 然而,如果你想让你的应用程序可用的设备不支持BLE,你应该还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”。在运行时您可以决定BLE可用性通过使用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在您的应用程序可以交互之前,你需要确认在设备上是支持BLE,如果是这样,确保启用。注意这检查需要设置 uses-feature…/ 为false。 如果不支持BLE,那么你应该禁用任何BLE特性。如果支持但是已经禁用你可以用你的应用启动它。完成这个设置需要两步使用BluetoothAdapter。
1.获取luetoothAdapter。 BluetoothAdapter代表设备的蓝牙适配器。整个系统有一个蓝牙适配器,和您的应用程序可以使用这个对象与它交互。下面的代码片段显示了如何获取适配器。使用getSystemService ()返回一个BluetoothManager实例,然后获取适配器。
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,您需要确保启用蓝牙。用isEnabled()检查蓝牙当前是否启动。如果这个方法返回false,那么蓝牙是关闭的。下面的代码片段检查是否启用蓝牙。如果没有,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作为参数,您必须实现这个回调,因为这是如何返回扫描结果。因为扫描非常耗电,你应该遵守如下规则
· 只要找到了设备就应该停止搜索。
· 不要在一个无限循环中搜索, 需要设置一个时间限制搜索. 下面代码作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); } ... } ... } 如果你想只扫描特定类型的外围设备,你可以使用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。
链接 GATT Server 与BLE设备交互的第一步是连接到它,更具体地说,连接到设备上的GATT服务器。连接到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,(布尔指示是否自动连接到设备就可用),和BluetoothGattCallback回调函数。
mBluetoothGatt device.connectGatt(this, false, mGattCallback); 这个连接到GATT服务端通过BLE设备,并返回一个BluetoothGatt实例,然后您可以使用GATT客户端进行操作。调用者(Android应用程序)是GATT客户端。BluetoothGattCallback用于提供结果给客户端,如连接状态,以及任何进一步的GATT客户端操作。 在这个例子中,有幸获得应用程序提供了一个活动(DeviceControlActivity)连接,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设备交互是通过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应用程序连接到一个GATT服务器和发现服务,它可以读取和写入属性。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(ListBluetoothGattService gattServices) { if (gattServices null) return; String uuid null; String unknownServiceString getResources(). getString(R.string.unknown_service); String unknownCharaString getResources(). getString(R.string.unknown_characteristic); ArrayListHashMapString, String gattServiceData new ArrayListHashMapString, String(); ArrayListArrayListHashMapString, String gattCharacteristicData new ArrayListArrayListHashMapString, String(); mGattCharacteristics new ArrayListArrayListBluetoothGattCharacteristic(); // Loops through available GATT Services. for (BluetoothGattService gattService : gattServices) { HashMapString, String currentServiceData new HashMapString, String(); uuid gattService.getUuid().toString(); currentServiceData.put( LIST_NAME, SampleGattAttributes. lookup(uuid, unknownServiceString)); currentServiceData.put(LIST_UUID, uuid); gattServiceData.add(currentServiceData); ArrayListHashMapString, String gattCharacteristicGroupData new ArrayListHashMapString, String(); ListBluetoothGattCharacteristic gattCharacteristics gattService.getCharacteristics(); ArrayListBluetoothGattCharacteristic charas new ArrayListBluetoothGattCharacteristic(); // Loops through available Characteristics. for (BluetoothGattCharacteristic gattCharacteristic : gattCharacteristics) { charas.add(gattCharacteristic); HashMapString, String currentCharaData new HashMapString, 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需要BLE的应用通知。这个代码片段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); 一旦通知作为一个特性被启用,如果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; }
