最近做了一个智能硬件开发(针灸仪)的项目，有一部分涉及到低功耗蓝牙的开发，就是通过蓝牙和设备进行数据的交互，比如控制改设备的LED的开关，设备的开关机，设置设备的时间和温度等，下面就项目中遇到的坑一一说明：首先给出官网对于BLE开发的讲解,https://developer.Android.com/guide/topics/connectivity/bluetooth-le.html#terms官方demo：https://github.com/googlesamples/android-BluetoothLeGatt，demo也比较好理解，主要是四个类，其中，DeviceControlActivity通过启动BluetoothLeService用来进行与蓝牙外围设备的交互。(注意，因为本人是将UI做了更改，并放到了fragment中，所以部分代码跟demo不一致，请主动忽略，关注蓝牙核心代码)

BLE开发所需要的知识，通过官方demo，我们会发现很多service，点击service后，每个service下面是Characteristic，每个service和Characteristic都对应一个唯一的UUID。所以，在做BLE时候，首先你应该找出你的蓝牙外围设备uuid，不然会很头疼，这个UUID也可能是硬件给你的，也可以你自己试出来，当然自己试出来是个很烦的过程。自己试的方法就是根据demo，加上一份读写的协议，然后，排着点击，显示出来的蓝牙列表进行测试，看是否和协议对应。另外，BluetoothLeService类不用做太多的更改。

一，蓝牙设备的扫描

这一部分基本上很简单，只要设备上电以后，这部分代码执行后，便可以扫描出设备，并获得BluetoothDevice对象

public void scanLeDevice(final boolean enable) {

LogUtils.debug(TAG, "-----------开始扫描蓝牙=" + enable);

if (enable) {

// Stops scanning after a pre-defined scan period.

mHandler.postDelayed(new Runnable() {

@Override

public void run() {

stopScanOuter();

}

}, SCAN_PERIOD);

LogUtils.debug("----------startLeScan--");

mScanning = true;

mBluetoothAdapter.startLeScan(this);

} else {

mScanning = false;

mBluetoothAdapter.stopLeScan(this);

}

}

上面代码为开始扫描周围已上电的设备，当发现设备后，BluetoothAdapter.LeScanCallback会执行onLeScan回调，将BluetoothDevice返回，

@Override

public void onLeScan(final BluetoothDevice device, int rssi, byte[] scanRecord) {

Fragment dcfrag = getActivity().getSupportFragmentManager().findFragmentByTag("MyDeviceFragment");

if(dcfrag != null && dcfrag.isVisible()) {

getActivity().runOnUiThread(new Runnable() {

@Override

public void run() {

LogUtils.debug(TAG, "---------获得设备" + device);

mLeDeviceListAdapter.addDevice(device);

mLeDeviceListAdapter.notifyDataSetChanged();

}

});

}

}

到此，我们便可以得到扫描到的蓝牙设备，但是目前仅仅是扫描到，并不代表已经连接上蓝牙设备。

二，蓝牙设备的连接

1，绑定service

private final ServiceConnection mServiceConnection = new ServiceConnection() {

@Override

public void onServiceConnected(ComponentName componentName, IBinder service) {

LogUtils.debug(TAG, "开始绑定service onServiceConnected"+device+"---name="+device.getName()+"--address="+device.getAddress());

mDeviceAddress = device.getAddress();

mDeviceName = device.getName();

mBluetoothLeService = ((BluetoothLeService.LocalBinder) service).getService();

if (!mBluetoothLeService.initialize()) {

Log.i(TAG, "Unable to initialize Bluetooth");

}

// Automatically connects to the device upon successful start-up initialization.

mBluetoothLeService.connect(mDeviceAddress);

}

@Override

public void onServiceDisconnected(ComponentName componentName) {

LogUtils.debug(TAG, "--------onServiceDisconnected service无法绑定了");

mBluetoothLeService = null;

}

};

public void mybindService(){

LogUtils.debug(TAG, "---------开始执行onCreate---bindservice");

Intent gattServiceIntent = new Intent(getActivity(), BluetoothLeService.class);

getActivity().bindService(gattServiceIntent, mServiceConnection, getActivity().BIND_AUTO_CREATE);

}

2，连接蓝牙

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)) {

LogUtils.debug(TAG, "--mGattUpdateReceiver ACTION_GATT_CONNECTED");

mConnected = true;

LogUtils.debug(TAG, "--------ACTION_GATT_CONNECTED devicename"+mDeviceName);

Fragment dcfrag = getActivity().getSupportFragmentManager().findFragmentByTag("ConnectFragment");

if((dcfrag != null && dcfrag.isVisible())){

//暂时写死在这可以连接的BLE设备

if(mDeviceName == null || !deviceFilter(mDeviceName)){

connectService.switchFragment(false, mDeviceName);

}else{

connectService.switchFragment(true, mDeviceName);

}

}

} else if (BluetoothLeService.ACTION_GATT_DISCONNECTED.equals(action)) {

LogUtils.debug(TAG, "--mGattUpdateReceiver ACTION_GATT_DISCONNECTED");

mConnected = false;

Fragment dcfrag = getActivity().getSupportFragmentManager().findFragmentByTag("ConnectFragment");

if((dcfrag != null && dcfrag.isVisible()))

connectService.switchFragment(false, mDeviceName);

Fragment contfrag = getActivity().getSupportFragmentManager().findFragmentByTag("ControlorFragment");

if((contfrag != null && contfrag.isVisible())){

transfertoControler.closeButton(false, false);

}

} else if (BluetoothLeService.ACTION_GATT_SERVICES_DISCOVERED.equals(action)) {

LogUtils.debug(TAG, "--mGattUpdateReceiver ACTION_GATT_SERVICES_DISCOVERED");

initMoxibustionService(

mBluetoothLeService.getSupportedGatteService(

SampleGattAttributes.SERVIECE_NOTIFY_DATA));

initMoxibustionService(

mBluetoothLeService.getSupportedGatteService(

SampleGattAttributes.SERVIECE_WRITE_DATA));

// Show all the supported services and characteristics on the user interface.

// displayGattServices(mBluetoothLeService.getSupportedGattServices());

} else if (BluetoothLeService.ACTION_DATA_AVAILABLE.equals(action)) {

LogUtils.debug(TAG, "--mGattUpdateReceiver ACTION_DATA_AVAILABLE");

// byte[] data = intent.getByteArrayExtra(BluetoothLeService.EXTRA_DATA);

// StringBuilder stringBuilder = new StringBuilder(data.length);

// for(byte byteChar : data)

// stringBuilder.append(String.format("0x%02X ", byteChar));

// String log = stringBuilder.toString();

// LogUtils.debug(TAG, "---字节数组为="+ log);

parsedata(intent.getByteArrayExtra(BluetoothLeService.EXTRA_DATA));

} else if (BluetoothLeService.ACTION_DATA_SEND_CONFIRM.equals(action)) {

// ECHO from android

LogUtils.debug(TAG, "write ok!");

}

}

};

public void myConnetService(){

getActivity().registerReceiver(mGattUpdateReceiver, makeGattUpdateIntentFilter());

LogUtils.debug(TAG, "------mBluetoothLeService myConnetService" + mBluetoothLeService);

if (mBluetoothLeService != null) {

final boolean result = mBluetoothLeService.connect(mDeviceAddress);

LogUtils.debug(TAG, "Connect request result=" + result);

}

}

当连接上蓝牙后，我们会得到ACTION_GATT_CONNECTED的广播，然后是ACTION_GATT_SERVICES_DISCOVERED，这个时候我们需要对service进行初始化，以便能够读写数据，以下为初始化代码(注意，初始化时候我们需要用到读写service的UUID)

private void initMoxibustionService(BluetoothGattService gattService) {

String uuid = "";

if (gattService == null)

{

LogUtils.debug(TAG, "gattService is null");

return;

}

List gattCharacteristics = gattService.getCharacteristics();

for (BluetoothGattCharacteristic gattCharacteristic : gattCharacteristics) {

uuid = gattCharacteristic.getUuid().toString();

if (SampleGattAttributes.CHARACTER_NOTIFY_DATA.substring(0,8).equals(uuid.substring(0, 8))) {

mNotifyCharacteristic = gattCharacteristic;

mBluetoothLeService.setCharacteristicNotification(

mNotifyCharacteristic, true);

LogUtils.debug(TAG, "NOTIFY_DATA");

LogUtils.debug(TAG, "getProperties()=" + mNotifyCharacteristic.getProperties());

} else if (SampleGattAttributes.CHARACTER_WRITE_DATA.substring(0,8).equals(uuid.subSequence(0, 8))) {

// mCommandCharacteristic = gattCharacteristic;

//写数据的服务和characteristic

mCommandCharacteristic = mBluetoothLeService.getSupportedGatteService(SampleGattAttributes.SERVIECE_WRITE_DATA)

.getCharacteristic(UUID.fromString(SampleGattAttributes.CHARACTER_WRITE_DATA));

LogUtils.debug(TAG, "WRITE_CMD");

LogUtils.debug(TAG, "getProperties()=" + mCommandCharacteristic.getProperties());

mCommandCharacteristic.setWriteType(

BluetoothGattCharacteristic.WRITE_TYPE_DEFAULT);

LogUtils.debug(TAG, "getProperties()=" + mCommandCharacteristic.getProperties());

}

}

}

CHARACTER_NOTIFY_DATA和CHARACTER_WRITE_DATA为读和写数据的CHARACTER的UUID，如下，注意这四个UUID

3，解析数据

至此，如果顺利的话，我们就可以得到ACTION_DATA_AVAILABLE的广播，也就拿到了从蓝牙设备获得的byte数组，大多数协议里，每个字节代表一个命令。这里涉及到Java中byte值与int值的转换。因为Java中，所有的值都是singed性的，最高位为符号位，所以，大家请自行补下该部分的知识，对于有符号数，它的值相当于取补码，此处将不详述，

上面为读数据，下面我们说写数据，比如，如下的开关机命令，

// 01 10 01 01 92 07 17

public void controlpower(boolean isOpen){

if (mCommandCharacteristic == null) return;

if (mBluetoothLeService == null) return;

byte[] setDataAfter;

if(isOpen){

byte[] setDataBefore = {0x01, 0x10, 0x01, 0x01};

byte[] trans = inttobyte(integrityCheck(setDataBefore));

byte[] transV = Arrays.copyOfRange(trans, 2, 4);

byte[] setData = byteMerger(setDataBefore, reverse(transV));

byte[] dd = {0x17};

setDataAfter = byteMerger(setData, dd);

LogUtils.debug(TAG, "---setDataAfter[4]="+setDataAfter[4]+",setDataAfter[5]="+setDataAfter[5]);

}else{

byte[] setDataBefore = {0x01, 0x10, 0x01, 0x00};

byte[] trans = inttobyte(integrityCheck(setDataBefore));

byte[] transV = Arrays.copyOfRange(trans, 2, 4);

byte[] setData = byteMerger(setDataBefore, reverse(transV));

byte[] dd = {0x17};

setDataAfter = byteMerger(setData, dd);

printDataHex(setDataAfter);

}

mCommandCharacteristic.setValue(setDataAfter);

mBluetoothLeService.writeCharacteristic(mCommandCharacteristic);

}

mCommandCharacteristic.setValue(setDataAfter);

mBluetoothLeService.writeCharacteristic(mCommandCharacteristic);

这两行代码，是核心代码，但是，我们要进行字节数组的正确传递，这里，给大家贴出来几个很有可能用到的方法，

CRC算法Java版：

//crc java

public int integrityCheck(byte[] bytes) {

int wCrc = 0xffff;

for (byte srcData : bytes) {

int data = byteToInt(srcData);

for(int j = 0; j < 8; j++) {

if ((((wCrc & 0x8000) >> 8) ^ ((data << j) & 0x80)) != 0) {

wCrc = (wCrc << 1) ^ 0x1021;

} else {

wCrc = wCrc << 1;

}

}

}

wCrc = (wCrc << 8) | (wCrc >> 8 & 0xff);

return wCrc & 0xffff;

}

public static int byteToInt(byte b) {

return b & 0xff;

}

// int to byte

public static byte[] inttobyte(int value) {

byte b0 = (byte) ((value >> 24) & 0xFF);

byte b1 = (byte) ((value >> 16) & 0xFF);

byte b2 = (byte) ((value >> 8) & 0xFF);

byte b3 = (byte) (value & 0xFF);

byte[] bytes = { b0, b1, b2, b3 };

return bytes;

}

//打印字节数组

public void printDataHex(byte[] data) {

if(SENTLOG){

StringBuilder stringBuilder = new StringBuilder(data.length);

for(byte byteChar : data)

stringBuilder.append(String.format("0x%02X ", byteChar));

String log = stringBuilder.toString();

LogUtils.debug(TAG, "---发送到蓝牙的字节数组为="+ log);

}

}

//数组倒序

public byte[] reverse(byte[] rt){

for (int i = 0; i < rt.length / 2; i++) {

byte temp = rt[i];

rt[i] = rt[rt.length - 1 - i];

rt[rt.length - 1 - i] = temp;

}

return rt;

}

//java 合并两个byte数组

public static byte[] byteMerger(byte[] byte_1, byte[] byte_2){

byte[] byte_3 = new byte[byte_1.length+byte_2.length];

System.arraycopy(byte_1, 0, byte_3, 0, byte_1.length);

System.arraycopy(byte_2, 0, byte_3, byte_1.length, byte_2.length);

return byte_3;

}

写的比较简单，但是关键代码都有了，大家可以参考下！~