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近期穿戴设备发展得非常火。把相关技术也带旺了，当中一项是BLE（）。BLE是蓝牙4.0的核心Profile，主打功能是高速搜索，高速连接。超低功耗保持连接和数据传输，弱点是数据传输速率低，因为BLE的低功耗特点，因此普遍用于穿戴设备。Android 4.3才開始支持BLE API，所以请各位客官把本文代码执行在蓝牙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。
PS：我的i9100刷了4.4系统后，居然也能跟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的终端能够包括多个Service，一个Service能够包括多个Characteristic。一个Characteristic包括一个Value和多个Descriptor，一个Descriptor包括一个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，比如PERMISSION和PROPERTY，而当中最经常使用的是PROPERTY。本文所用的BLE蓝牙模块居然没有标准的Characteristic的PERMISSION。Characteristic的PROPERTY能够通过位运算符组合来设置读写属性，比如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。另一些必要的读写蓝牙方法，应该算是简化到大家一看就能够懂了。
本文代码能够到下载。接下来贴出本文执行的结果，首先是连接BLE设备后。枚举出设备全部Service、Characteristic、Descriptor，而且手机会往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（见PC串口助手的截图）：
04-21 18:28:25.465: E/DeviceScanActivity(12254): -->service type:PRIMARY04-21 18:28:25.465: E/DeviceScanActivity(12254): -->includedServices size:004-21 18:28:25.465: E/DeviceScanActivity(12254): -->service uuid:00001800-0000-1000-8000-00805f9b34fb04-21 18:28:25.465: E/DeviceScanActivity(12254): ---->char uuid:00002a00-0000-1000-8000-00805f9b34fb04-21 18:28:25.465: E/DeviceScanActivity(12254): ---->char permission:UNKNOW04-21 18:28:25.465: E/DeviceScanActivity(12254): ---->char property:READ04-21 18:28:25.465: E/DeviceScanActivity(12254): ---->char uuid:00002a01-0000-1000-8000-00805f9b34fb04-21 18:28:25.470: E/DeviceScanActivity(12254): ---->char permission:UNKNOW04-21 18:28:25.470: E/DeviceScanActivity(12254): ---->char property:READ04-21 18:28:25.470: E/DeviceScanActivity(12254): ---->char uuid:00002a02-0000-1000-8000-00805f9b34fb04-21 18:28:25.470: E/DeviceScanActivity(12254): ---->char permission:UNKNOW04-21 18:28:25.470: E/DeviceScanActivity(12254): ---->char property:READ|WRITE|04-21 18:28:25.470: E/DeviceScanActivity(12254): ---->char uuid:00002a03-0000-1000-8000-00805f9b34fb04-21 18:28:25.470: E/DeviceScanActivity(12254): ---->char permission:UNKNOW04-21 18:28:25.475: E/DeviceScanActivity(12254): ---->char property:READ|WRITE|04-21 18:28:25.475: E/DeviceScanActivity(12254): ---->char uuid:00002a04-0000-1000-8000-00805f9b34fb04-21 18:28:25.475: E/DeviceScanActivity(12254): ---->char permission:UNKNOW04-21 18:28:25.475: E/DeviceScanActivity(12254): ---->char property:READ04-21 18:28:25.475: E/DeviceScanActivity(12254): -->service type:PRIMARY04-21 18:28:25.475: E/DeviceScanActivity(12254): -->includedServices size:004-21 18:28:25.475: E/DeviceScanActivity(12254): -->service uuid:00001801-0000-1000-8000-00805f9b34fb04-21 18:28:25.480: E/DeviceScanActivity(12254): ---->char uuid:00002a05-0000-1000-8000-00805f9b34fb04-21 18:28:25.480: E/DeviceScanActivity(12254): ---->char permission:UNKNOW04-21 18:28:25.480: E/DeviceScanActivity(12254): ---->char property:INDICATE04-21 18:28:25.480: E/DeviceScanActivity(12254): -------->desc uuid:00002902-0000-1000-8000-00805f9b34fb04-21 18:28:25.480: E/DeviceScanActivity(12254): -------->desc permission:UNKNOW04-21 18:28:25.480: E/DeviceScanActivity(12254): -->service type:PRIMARY04-21 18:28:25.480: E/DeviceScanActivity(12254): -->includedServices size:004-21 18:28:25.480: E/DeviceScanActivity(12254): -->service uuid:0000ffe0-0000-1000-8000-00805f9b34fb04-21 18:28:25.480: E/DeviceScanActivity(12254): ---->char uuid:0000ffe1-0000-1000-8000-00805f9b34fb04-21 18:28:25.480: E/DeviceScanActivity(12254): ---->char permission:UNKNOW04-21 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:00002902-0000-1000-8000-00805f9b34fb04-21 18:28:25.490: E/DeviceScanActivity(12254): -------->desc permission:UNKNOW04-21 18:28:25.490: E/DeviceScanActivity(12254): -------->desc uuid:00002901-0000-1000-8000-00805f9b34fb04-21 18:28:25.490: E/DeviceScanActivity(12254): -------->desc permission:UNKNOW04-21 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
下面Log是PC上的串口工具通过BLE模块发送过来。由BluetoothGattCallback的 onCharacteristicChanged（）打出Log04-21 18:30:18.260: E/DeviceScanActivity(12254): onCharWrite BLE DEVICE write 0000ffe1-0000-1000-8000-00805f9b34fb -> send data to phone04-21 18:30:18.745: E/DeviceScanActivity(12254): onCharWrite BLE DEVICE write 0000ffe1-0000-1000-8000-00805f9b34fb -> send data to phone04-21 18:30:19.085: E/DeviceScanActivity(12254): onCharWrite BLE DEVICE write 0000ffe1-0000-1000-8000-00805f9b34fb -> send data to phone04-21 18:30:19.350: E/DeviceScanActivity(12254): onCharWrite BLE DEVICE write 0000ffe1-0000-1000-8000-00805f9b34fb -> send data to phone04-21 18:30:19.605: E/DeviceScanActivity(12254): onCharWrite BLE DEVICE write 0000ffe1-0000-1000-8000-00805f9b34fb -> send data to phone04-21 18:30:19.835: E/DeviceScanActivity(12254): onCharWrite BLE DEVICE write 0000ffe1-0000-1000-8000-00805f9b34fb -> send data to phone04-21 18:30:20.055: E/DeviceScanActivity(12254): onCharWrite BLE DEVICE write 0000ffe1-0000-1000-8000-00805f9b34fb -> send data to phone04-21 18:30:20.320: E/DeviceScanActivity(12254): onCharWrite BLE DEVICE write 0000ffe1-0000-1000-8000-00805f9b34fb -> send data to phone04-21 18:30:20.510: E/DeviceScanActivity(12254): onCharWrite BLE DEVICE write 0000ffe1-0000-1000-8000-00805f9b34fb -> send data to phone04-21 18:30:20.735: E/DeviceScanActivity(12254): onCharWrite BLE DEVICE write 0000ffe1-0000-1000-8000-00805f9b34fb -> send data to phone04-21 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; /**搜索BLE终端*/ private BluetoothAdapter mBluetoothAdapter; /**读写BLE终端*/ 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(); } /** * 搜索到BLE终端服务的事件 */ private BluetoothLeClass.OnServiceDiscoverListener mOnServiceDiscover = new OnServiceDiscoverListener(){ @Override public void onServiceDiscover(BluetoothGatt gatt) { displayGattServices(mBLE.getSupportedGattServices()); } }; /** * 收到BLE终端数据交互的事件 */ private BluetoothLeClass.OnDataAvailableListener mOnDataAvailable = new OnDataAvailableListener(){ /** * BLE终端数据被读的事件 */ @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())); } /** * 收到BLE终端写入数据回调 */ @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 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 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是能够跟蓝牙模块串口通信的Characteristic if(gattCharacteristic.getUuid().toString().equals(UUID_KEY_DATA)){ //測试读取当前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 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)); } } } }// }}