开发入门
更新时间：2017-08-08 阅读：3814
目录
Android BLE
Android的4.3（API Level 18）引入了蓝牙低耗能的内置平台支持，提供相应的API，应用程序可以用它来发现设备，查询服务，和读/写特征。在对比传统蓝牙，蓝牙低功耗（BLE）被设计成更低的功耗，这允许Android应用使用具有低功率的设备，如接近传感器，心脏速率显示器，健身设备，等等BLE设备。
基本概念
- Generic Attribute Profile (GATT) GATT是在BLE连接中用以接收和发送属性数据的通用规格。
- Attribute Protocol (ATT) 属性协议是以UUID来标识属性的协议。
- Characteristic 特征包含一个值和0或n个描述该值的描述符。
- Descriptor 描述符是一个用以描述特征值的属性。
- Service 服务是是特征的集合。
角色和职责
角色分为中央（Central）和周边（peripheral），以Android手机和BLE心脏速率显示器为例，Android手机的角色就是中央，它的职责是控制BLE心脏速率显示器；而BLE心脏速率显示器的角色是周边，它的职责是响应Android手机的控制。
BLE权限
在BLE开发中，Android应用需要以下权限：
<uses-permission android:name="android.permission.BLUETOOTH"/>
<uses-permission android:name="android.permission.BLUETOOTH_ADMIN"/>
另外，应用判断存不存在BLE特性，可以在AndroidManifest.xml中加入：
<uses-feature android:name="android.hardware.bluetooth_le" android:required="true"/>
而在代码中，可以这样判断：
// 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)) {
Toast.makeText(this, R.string.ble_not_supported, Toast.LENGTH_SHORT).show();
finish();
}
BLE开发
设置BLE
1.获取BluetoothAdapter
// Initializes Bluetooth adapter.
final BluetoothManager bluetoothManager =
(BluetoothManager) getSystemService(Context.BLUETOOTH_SERVICE);
mBluetoothAdapter = bluetoothManager.getAdapter();
2.打开蓝牙
private BluetoothAdapter mBluetoothAdapter;
...
// Ensures Bluetooth is available on the device and it is enabled. If not,
// displays a dialog requesting user permission to enable Bluetooth.
if (mBluetoothAdapter == null || !mBluetoothAdapter.isEnabled()) {
Intent enableBtIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
startActivityForResult(enableBtIntent, REQUEST_ENABLE_BT);
}
查找BLE设备
要查找BLE设备，你要调用startLeScan()方法，这个方法以一个BluetoothAdapter.LeScanCallback对象作为参数。停止查找，你要调用stopLeScan（）方法，这个方法以一个BluetoothAdapter.LeScanCallback对象作为参数。
/**
* Activity for scanning and displaying available BLE devices.
*/
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);
}
...
}
...
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();
}
});
}
};
}
连接到GATT Server
连接设备调用connectGatt()方法，这个方法有3个参数，一个Context对象，一个表示自动连接的布尔值，一个BluetoothGattCallback对象：
mBluetoothGatt = device.connectGatt(this, false, mGattCallback);
BluetoothGattCallback是一个BLE连接状态的回调：
// 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);
}
}
...
};
读GATT属性
读GATT属性要调用readCharacteristic(）方法，这个方法有一个BluetoothGattCharacteristic对象作为参数：
public boolean readCharacteristic(UUID gatservice_uuid,UUID char_uuid){
synchronized(mGattLock){
try{
if(mBluetoothGatt==null || mBluetoothGattServiceList==null) return false;
BluetoothGattService bgs = mBluetoothGatt.getService(gatservice_uuid);
if(bgs==null) return false;
BluetoothGattCharacteristic bgc = bgs.getCharacteristic(char_uuid);
if(bgc==null) return false;
int properties = bgc.getProperties();
if(((properties&BluetoothGattCharacteristic.PROPERTY_READ ) == BluetoothGattCharacteristic.PROPERTY_READ ))
{
return mBluetoothGatt.readCharacteristic(bgc);
}else{
LOGD(gatservice_uuid+"->"+char_uuid+" can not read !");
return false;
}
}catch(Exception ex){
return false ;
}
}
}
写GATT属性
读GATT属性要调用writeCharacteristic(）方法，这个方法有一个BluetoothGattCharacteristic对象作为参数：
public boolean writeCharacteristic(UUID gatservice_uuid,UUID char_uuid,String value){
synchronized(mGattLock){
try{
if(mBluetoothGatt==null || mBluetoothGattServiceList==null) return false;
BluetoothGattService bgs = mBluetoothGatt.getService(gatservice_uuid);
if(bgs==null){
LOGD("bgs:"+bgs+"->"+" can not find ! write error");
return false;
}
BluetoothGattCharacteristic bgc = bgs.getCharacteristic(char_uuid);
if(bgc==null) {
LOGD("bgc:"+bgc+"->"+" can not find ! write error");
return false;
}
int properties = bgc.getProperties();
if( ( ( properties&BluetoothGattCharacteristic.PROPERTY_WRITE ) == BluetoothGattCharacteristic.PROPERTY_WRITE )
|| ( ( properties&BluetoothGattCharacteristic.PROPERTY_SIGNED_WRITE ) == BluetoothGattCharacteristic.PROPERTY_SIGNED_WRITE )
|| ( ( properties&BluetoothGattCharacteristic.PROPERTY_WRITE_NO_RESPONSE ) == BluetoothGattCharacteristic.PROPERTY_WRITE_NO_RESPONSE ) )
{
bgc.setValue(value);
return mBluetoothGatt.writeCharacteristic(bgc);
}else{
LOGD(gatservice_uuid+"->"+char_uuid+" can not write !");
return false;
}
}catch(Exception ex){
LOGD("writeCharacteristic mBluetoothGatt dead .");
return false ;
}
}
}
接收BLE通知
接收BLE通知要调用setCharacteristicNotification（）方法，这方法有一个BluetoothGattDescriptor对象作为参数：
private static String CLIENT_CHARACTERISTIC_CONFIG = "00002902-0000-1000-8000-00805f9b34fb";
public boolean setCharacteristicNotification(UUID gatservice_uuid,UUID char_uuid,boolean enable){
synchronized(mGattLock){
try{
if(mBluetoothGatt==null || mBluetoothGattServiceList==null) return false;
BluetoothGattService bgs = mBluetoothGatt.getService(gatservice_uuid);
if(bgs==null) return false;
BluetoothGattCharacteristic bgc = bgs.getCharacteristic(char_uuid);
if(bgc==null) return false;
int properties = bgc.getProperties();
if((properties&BluetoothGattCharacteristic.PROPERTY_NOTIFY ) == BluetoothGattCharacteristic.PROPERTY_NOTIFY )
{
if(mBluetoothGatt.setCharacteristicNotification(bgc,enable))
{
BluetoothGattDescriptor descriptor = bgc.getDescriptor(UUID.fromString(CLIENT_CHARACTERISTIC_CONFIG));
descriptor.setValue(BluetoothGattDescriptor.ENABLE_NOTIFICATION_VALUE);
return mBluetoothGatt.writeDescriptor(descriptor);
}else{
return false;
}
}else{
LOGD(gatservice_uuid+"->"+char_uuid+" can not notify !");
return false;
}
}catch(Exception ex){
LOGD("setCharacteristicNotification mBluetoothGatt dead .");
return false ;
}
}
}
关闭客户端应用
使用完BLE设备，需要调用close（）方法：
public void close() {
if (mBluetoothGatt == null) {
return;
}
mBluetoothGatt.close();
mBluetoothGatt = null;
}
