最近穿戴设备发展得很火，把相关技术也带旺了，其中一项是BLE（Bluetooth Low Energy）。BLE是蓝牙4.0的核心Profile，主打功能是快速搜索，快速连接，超低功耗保持连接和传输数据，弱点是数据传输速率低，由于BLE的低功耗特点，因此普遍用于穿戴设备。Android 4.3才开始支持BLE API，所以请各位客官把本文代码运行在蓝牙4.0和Android 4.3及其以上的系统，另外本文所用的BLE终端是一个蓝牙4.0的串口蓝牙模块。
注：笔者的i9100刷了4.4系统后，竟然也能跟BLE蓝牙模块通信。
BLE分为三部分Service、Characteristic、Descriptor，这三部分都由UUID作为唯一标示符。一个蓝牙4.0的终端可以包含多个Service，一个Service可以包含多个Characteristic，一个Characteristic包含一个Value和多个Descriptor，一个Descriptor包含一个Value。一般来说，Characteristic是手机与BLE终端交换数据的关键，Characteristic有较多的跟权限相关的字段，例如PERMISSION和PROPERTY，而其中最常用的是PROPERTY，本文所用的BLE蓝牙模块竟然没有标准的Characteristic的PERMISSION。Characteristic的PROPERTY可以通过位运算符组合来设置读写属性，例如READ|WRITE、READ|WRITE_NO_RESPONSE|NOTIFY，因此读取PROPERTY后要分解成所用的组合（本文代码已含此分解方法）。
本文代码改自Android 4.3 Sample的BluetoothLeGatt，把冗余代码去掉，获取的BLE设备信息都通过Log，还有一些必要的读写蓝牙方法，应该算是简化到大家一看就可以懂了。本文完整代码可以点击此处本站下载。
接下来贴出本文运行的结果，首先是连接BLE设备后，枚举出设备所有Service、Characteristic、Descriptor，并且手机会往Characteristic uuid=0000ffe1-0000-1000-8000-00805f9b34fb写入“send data->”字符串，BLE终端收到数据通过串口传到PC串口助手：
04-21 18:28:25.465: E/DeviceScanActivity(12254): -->service type:PRIMARY
04-21 18:28:25.465: E/DeviceScanActivity(12254): -->includedServices size:0
04-21 18:28:25.465: E/DeviceScanActivity(12254): -->service uuid:00001800-0000-1000-8000-00805f9b34fb
04-21 18:28:25.465: E/DeviceScanActivity(12254): ---->char uuid:00002a00-0000-1000-8000-00805f9b34fb
04-21 18:28:25.465: E/DeviceScanActivity(12254): ---->char permission:UNKNOW
04-21 18:28:25.465: E/DeviceScanActivity(12254): ---->char property:READ
04-21 18:28:25.465: E/DeviceScanActivity(12254): ---->char uuid:00002a01-0000-1000-8000-00805f9b34fb
04-21 18:28:25.470: E/DeviceScanActivity(12254): ---->char permission:UNKNOW
04-21 18:28:25.470: E/DeviceScanActivity(12254): ---->char property:READ
04-21 18:28:25.470: E/DeviceScanActivity(12254): ---->char uuid:00002a02-0000-1000-8000-00805f9b34fb
04-21 18:28:25.470: E/DeviceScanActivity(12254): ---->char permission:UNKNOW
04-21 18:28:25.470: E/DeviceScanActivity(12254): ---->char property:READ|WRITE|
04-21 18:28:25.470: E/DeviceScanActivity(12254): ---->char uuid:00002a03-0000-1000-8000-00805f9b34fb
04-21 18:28:25.470: E/DeviceScanActivity(12254): ---->char permission:UNKNOW
04-21 18:28:25.475: E/DeviceScanActivity(12254): ---->char property:READ|WRITE|
04-21 18:28:25.475: E/DeviceScanActivity(12254): ---->char uuid:00002a04-0000-1000-8000-00805f9b34fb
04-21 18:28:25.475: E/DeviceScanActivity(12254): ---->char permission:UNKNOW
04-21 18:28:25.475: E/DeviceScanActivity(12254): ---->char property:READ
04-21 18:28:25.475: E/DeviceScanActivity(12254): -->service type:PRIMARY
04-21 18:28:25.475: E/DeviceScanActivity(12254): -->includedServices size:0
04-21 18:28:25.475: E/DeviceScanActivity(12254): -->service uuid:00001801-0000-1000-8000-00805f9b34fb
04-21 18:28:25.480: E/DeviceScanActivity(12254): ---->char uuid:00002a05-0000-1000-8000-00805f9b34fb
04-21 18:28:25.480: E/DeviceScanActivity(12254): ---->char permission:UNKNOW
04-21 18:28:25.480: E/DeviceScanActivity(12254): ---->char property:INDICATE
04-21 18:28:25.480: E/DeviceScanActivity(12254): -------->desc uuid:00002902-0000-1000-8000-00805f9b34fb
04-21 18:28:25.480: E/DeviceScanActivity(12254): -------->desc permission:UNKNOW
04-21 18:28:25.480: E/DeviceScanActivity(12254): -->service type:PRIMARY
04-21 18:28:25.480: E/DeviceScanActivity(12254): -->includedServices size:0
04-21 18:28:25.480: E/DeviceScanActivity(12254): -->service uuid:0000ffe0-0000-1000-8000-00805f9b34fb
04-21 18:28:25.480: E/DeviceScanActivity(12254): ---->char uuid:0000ffe1-0000-1000-8000-00805f9b34fb
04-21 18:28:25.480: E/DeviceScanActivity(12254): ---->char permission:UNKNOW
04-21 18:28:25.480: E/DeviceScanActivity(12254): ---->char property:READ|WRITE_NO_RESPONSE|NOTIFY|
04-21 18:28:25.490: E/DeviceScanActivity(12254): -------->desc uuid:00002902-0000-1000-8000-00805f9b34fb
04-21 18:28:25.490: E/DeviceScanActivity(12254): -------->desc permission:UNKNOW
04-21 18:28:25.490: E/DeviceScanActivity(12254): -------->desc uuid:00002901-0000-1000-8000-00805f9b34fb
04-21 18:28:25.490: E/DeviceScanActivity(12254): -------->desc permission:UNKNOW
04-21 18:28:26.025: E/DeviceScanActivity(12254): onCharRead BLE DEVICE read 0000ffe1-0000-1000-8000-00805f9b34fb -> 00
这里红字是由BluetoothGattCallback的onCharacteristicRead()回调而打出Log
以下Log是PC上的串口工具通过BLE模块发送过来，由BluetoothGattCallback的 onCharacteristicChanged（）打出Log
04-21 18:30:18.260: E/DeviceScanActivity(12254): onCharWrite BLE DEVICE write 0000ffe1-0000-1000-8000-00805f9b34fb -> send data to phone
04-21 18:30:18.745: E/DeviceScanActivity(12254): onCharWrite BLE DEVICE write 0000ffe1-0000-1000-8000-00805f9b34fb -> send data to phone
04-21 18:30:19.085: E/DeviceScanActivity(12254): onCharWrite BLE DEVICE write 0000ffe1-0000-1000-8000-00805f9b34fb -> send data to phone
04-21 18:30:19.350: E/DeviceScanActivity(12254): onCharWrite BLE DEVICE write 0000ffe1-0000-1000-8000-00805f9b34fb -> send data to phone
04-21 18:30:19.605: E/DeviceScanActivity(12254): onCharWrite BLE DEVICE write 0000ffe1-0000-1000-8000-00805f9b34fb -> send data to phone
04-21 18:30:19.835: E/DeviceScanActivity(12254): onCharWrite BLE DEVICE write 0000ffe1-0000-1000-8000-00805f9b34fb -> send data to phone
04-21 18:30:20.055: E/DeviceScanActivity(12254): onCharWrite BLE DEVICE write 0000ffe1-0000-1000-8000-00805f9b34fb -> send data to phone
04-21 18:30:20.320: E/DeviceScanActivity(12254): onCharWrite BLE DEVICE write 0000ffe1-0000-1000-8000-00805f9b34fb -> send data to phone
04-21 18:30:20.510: E/DeviceScanActivity(12254): onCharWrite BLE DEVICE write 0000ffe1-0000-1000-8000-00805f9b34fb -> send data to phone
04-21 18:30:20.735: E/DeviceScanActivity(12254): onCharWrite BLE DEVICE write 0000ffe1-0000-1000-8000-00805f9b34fb -> send data to phone
04-21 18:30:21.000: E/DeviceScanActivity(12254): onCharWrite BLE DEVICE write 0000ffe1-0000-1000-8000-00805f9b34fb -> send data to phone
接下来贴出本文核心代码：
public class DeviceScanActivity extends ListActivity {
private final static String TAG = DeviceScanActivity.class.getSimpleName();
private final static String UUID_KEY_DATA = "0000ffe1-0000-1000-8000-00805f9b34fb";
private LeDeviceListAdapter mLeDeviceListAdapter;
private BluetoothAdapter mBluetoothAdapter;
private BluetoothLeClass mBLE;
private boolean mScanning;
private Handler mHandler;
// Stops scanning after 10 seconds.
private static final long SCAN_PERIOD = 10000;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
getActionBar().setTitle(R.string.title_devices);
mHandler = new Handler();
// 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();
}
// Initializes a Bluetooth adapter. For API level 18 and above, get a reference to
// BluetoothAdapter through BluetoothManager.
final BluetoothManager bluetoothManager =
(BluetoothManager) getSystemService(Context.BLUETOOTH_SERVICE);
mBluetoothAdapter = bluetoothManager.getAdapter();
// Checks if Bluetooth is supported on the device.
if (mBluetoothAdapter == null) {
Toast.makeText(this, R.string.error_bluetooth_not_supported, Toast.LENGTH_SHORT).show();
finish();
return;
}
//开启蓝牙
mBluetoothAdapter.enable();
mBLE = new BluetoothLeClass(this);
if (!mBLE.initialize()) {
Log.e(TAG, "Unable to initialize Bluetooth");
finish();
}
//发现BLE终端的Service时回调
mBLE.setOnServiceDiscoverListener(mOnServiceDiscover);
//收到BLE终端数据交互的事件
mBLE.setOnDataAvailableListener(mOnDataAvailable);
}
@Override
protected void onResume() {
super.onResume();
// Initializes list view adapter.
mLeDeviceListAdapter = new LeDeviceListAdapter(this);
setListAdapter(mLeDeviceListAdapter);
scanLeDevice(true);
}
@Override
protected void onPause() {
super.onPause();
scanLeDevice(false);
mLeDeviceListAdapter.clear();
mBLE.disconnect();
}
@Override
protected void onStop() {
super.onStop();
mBLE.close();
}
@Override
protected void onListItemClick(ListView l, View v, int position, long id) {
final BluetoothDevice device = mLeDeviceListAdapter.getDevice(position);
if (device == null) return;
if (mScanning) {
mBluetoothAdapter.stopLeScan(mLeScanCallback);
mScanning = false;
}
mBLE.connect(device.getAddress());
}
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);
invalidateOptionsMenu();
}
}, SCAN_PERIOD);
mScanning = true;
mBluetoothAdapter.startLeScan(mLeScanCallback);
} else {
mScanning = false;
mBluetoothAdapter.stopLeScan(mLeScanCallback);
}
invalidateOptionsMenu();
}
private BluetoothLeClass.OnServiceDiscoverListener mOnServiceDiscover = new OnServiceDiscoverListener(){
@Override
public void onServiceDiscover(BluetoothGatt gatt) {
displayGattServices(mBLE.getSupportedGattServices());
}
};
private BluetoothLeClass.OnDataAvailableListener mOnDataAvailable = new OnDataAvailableListener(){
@Override
public void onCharacteristicRead(BluetoothGatt gatt,
BluetoothGattCharacteristic characteristic, int status) {
if (status == BluetoothGatt.GATT_SUCCESS)
Log.e(TAG,"onCharRead "+gatt.getDevice().getName()
+" read "
+characteristic.getUuid().toString()
+" -> "
+Utils.bytesToHexString(characteristic.getValue()));
}
@Override
public void onCharacteristicWrite(BluetoothGatt gatt,
BluetoothGattCharacteristic characteristic) {
Log.e(TAG,"onCharWrite "+gatt.getDevice().getName()
+" write "
+characteristic.getUuid().toString()
+" -> "
+new String(characteristic.getValue()));
}
};
// 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();
}
});
}
};
private void displayGattServices(List<BluetoothGattService> gattServices) {
if (gattServices == null) return;
for (BluetoothGattService gattService : gattServices) {
//-----Service的字段信息-----//
int type = gattService.getType();
Log.e(TAG,"-->service type:"+Utils.getServiceType(type));
Log.e(TAG,"-->includedServices size:"+gattService.getIncludedServices().size());
Log.e(TAG,"-->service uuid:"+gattService.getUuid());
//-----Characteristics的字段信息-----//
List<BluetoothGattCharacteristic> gattCharacteristics =gattService.getCharacteristics();
for (final BluetoothGattCharacteristic gattCharacteristic: gattCharacteristics) {
Log.e(TAG,"---->char uuid:"+gattCharacteristic.getUuid());
int permission = gattCharacteristic.getPermissions();
Log.e(TAG,"---->char permission:"+Utils.getCharPermission(permission));
int property = gattCharacteristic.getProperties();
Log.e(TAG,"---->char property:"+Utils.getCharPropertie(property));
byte[] data = gattCharacteristic.getValue();
if (data != null && data.length > 0) {
Log.e(TAG,"---->char value:"+new String(data));
}
//UUID_KEY_DATA是可以跟蓝牙模块串口通信的Characteristic
if(gattCharacteristic.getUuid().toString().equals(UUID_KEY_DATA)){
//测试读取当前Characteristic数据，会触发mOnDataAvailable.onCharacteristicRead()
mHandler.postDelayed(new Runnable() {
@Override
public void run() {
mBLE.readCharacteristic(gattCharacteristic);
}
}, 500);
//接受Characteristic被写的通知,收到蓝牙模块的数据后会触发mOnDataAvailable.onCharacteristicWrite()
mBLE.setCharacteristicNotification(gattCharacteristic, true);
//设置数据内容
gattCharacteristic.setValue("send data->");
//往蓝牙模块写入数据
mBLE.writeCharacteristic(gattCharacteristic);
}
//-----Descriptors的字段信息-----//
List<BluetoothGattDescriptor> gattDescriptors = gattCharacteristic.getDescriptors();
for (BluetoothGattDescriptor gattDescriptor : gattDescriptors) {
Log.e(TAG, "-------->desc uuid:" + gattDescriptor.getUuid());
int descPermission = gattDescriptor.getPermissions();
Log.e(TAG,"-------->desc permission:"+ Utils.getDescPermission(descPermission));
byte[] desData = gattDescriptor.getValue();
if (desData != null && desData.length > 0) {
Log.e(TAG, "-------->desc value:"+ new String(desData));
}
}
}
}//
}
}
感兴趣的读者可以动手测试一下代码的运行情况，希望能对大家的Android项目开发有所帮助。
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