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:name="android.permission.BLUETOOTH"/>
<uses-permission android:name="android.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:name="android.hardware.bluetooth_le" android:required="true"/>
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(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;
}
c#学习笔记06--函数02--变量的作用域01--其他结构中变量的作用域)
的使用来实现定时的执行任务)
