iOS蓝牙开发(CoreBluetooth)

目前在iOS中蓝牙开发框架主要有以下几种

GameKit.framework：iOS7之前的蓝牙通讯框架，从iOS7开始过期.
MultipeerConnectivity.framework：iOS7开始引入的新的蓝牙通讯开发框架，用于取代GameKit。
CoreBluetooth.framework：功能强大的蓝牙开发框架，要求设备必须支持蓝牙4.0。
前两个框架使用起来比较简单，但是缺点也比较明显：仅仅支持iOS设备，传输内容仅限于沙盒或者照片库中用户选择的文件，并且第一个框架只能在同一个应用之间进行传输（一个iOS设备安装应用A，另一个iOS设备上安装应用B是无法传输的）。CoreBluetooth就摆脱了这些束缚，它不再局限于iOS设备之间进行传输，你可以通过iOS设备向Android、Windows Phone以及其他安装有蓝牙4.0芯片的智能设备传输，因此也是目前智能家居、无线支付等热门智能设备所推崇的技术。本文主要介绍CoreBluetooth的相关开发流程.

CoreBluetooth开发模式

CoreBluetooth设计类似于客户端-服务器端的设计，peripheral和central, 可以理解成外设和中心。对应他们分别有一组相关的API和类.

CoreBluetooth架构

左侧叫做中心模式，以app作为中心，连接其他的外设的，而右侧称为外设模式，使用手机作为外设别其他中心设备操作的场景。
服务和特征，特征的属性(service and characteristic):
蓝牙设备添加若干服务，服务內添加若干特征，特征就是具体键值对，提供对数据的读取和写。蓝牙中心和外设数据的交换基于服务的特征.

外设和服务特征的关系

中心的开发

流程

建立中心角色
扫描外设（discover）
连接外设(connect)
扫描外设中的服务和特征(discover)
- 4.1 获取外设的services
- 4.2 获取外设的Characteristics,获取Characteristics的值，获取 Characteristics的Descriptor和Descriptor的值
与外设做数据交互(explore and interact)
订阅Characteristic的通知
断开连接(disconnect)

步骤
CoreBluetooth中不管是中心还是外设的开发,均是上面的流程,通过一步步的代理回调实现的,按照流程跟着走,一步一步实现代理.


 //初始化
 _centralManager = [[CBCentralManager alloc] initWithDelegate:self
 queue:nil
 options:@{CBCentralManagerOptionRestoreIdentifierKey:kRestoreIdentifierKey}];
 //监听中心设备状态
 -(void)centralManagerDidUpdateState:(CBCentralManager *)central{
 if (central.state == CBCentralManagerStatePoweredOn) {
 [self writeToLogWithText:@"中心设备已打开"];
 [_centralManager scanForPeripheralsWithServices:nil options:nil];
 } //中心设备CBCentralManagerStatePoweredOn状态下就可以开始搜索外设了
 }
 -(void)centralManager:(CBCentralManager *)central didDiscoverPeripheral:(CBPeripheral *)peripheral advertisementData:(NSDictionary *)advertisementData RSSI:(NSNumber *)RSSI{
 //搜索到指定的外设就可以开始连接外设了
 [_centralManager connectPeripheral:peripheral options:nil];
 }
 -(void)centralManager:(CBCentralManager *)central didConnectPeripheral:(CBPeripheral *)peripheral{
 //连接成功后开始搜索服务
 [peripheral discoverServices:nil];
 }
 -(void)peripheral:(CBPeripheral *)peripheral didDiscoverServices:(NSError *)error{
 //搜索服务成功后查找指定服务中的特征
 [peripheral discoverCharacteristics:nil forService:service];
 }
 -(void)peripheral:(CBPeripheral *)peripheral didDiscoverCharacteristicsForService:(nonnull CBService *)service error:(nullable NSError *)error{
 //发现可用特征后,就可以进行相应的操作了,主要有以下三种
 //情景一：读取
 if (characteristic.properties & CBCharacteristicPropertyRead) {
 if ([characteristic.UUID.UUIDString isEqualToString:kReadUUID]) {
 [peripheral readValueForCharacteristic:characteristic];
 if (characteristic.value) {
 NSString *value=[[NSString alloc]initWithData:characteristic.value encoding:NSUTF8StringEncoding];
 NSLog(@"读取到特征值：%@",value);
 }
 }
 }
   //情景二：通知
  if (characteristic.properties & CBCharacteristicPropertyNotify) {
      if ([characteristic.UUID.UUIDString isEqualToString:kNotifyUUID] || [characteristic.UUID.UUIDString isEqualToString:kWriteUUID]) {
          _curCharacter = characteristic;
          [peripheral setNotifyValue:YES forCharacteristic:characteristic];
          [self writeToLogWithText:@"已订阅特征通知"];
      }
  }
  
  //情景二：写数据
  if (characteristic.properties & CBCharacteristicPropertyWrite) {
      if ([characteristic.UUID.UUIDString isEqualToString:kWriteUUID]) {
          [peripheral writeValue:[@"hello,外设" dataUsingEncoding:NSUTF8StringEncoding] forCharacteristic:characteristic type:CBCharacteristicWriteWithResponse];
          [self writeToLogWithText:@"写数据给外设"];
          
          _curPeripherals = peripheral;
          _curCharacter = characteristic;
      }
  }

}
//根据不同的场景,会调用以下三个方法
-(void)peripheral:(CBPeripheral *)peripheral didUpdateNotificationStateForCharacteristic:(nonnull CBCharacteristic *)characteristic error:(nullable NSError *)error;
-(void)peripheral:(CBPeripheral *)peripheral didUpdateValueForCharacteristic:(nonnull CBCharacteristic *)characteristic error:(nullable NSError *)error;
-(void)peripheral:(CBPeripheral *)peripheral didWriteValueForCharacteristic:(nonnull CBCharacteristic *)characteristic error:(nullable NSError *)error;
}

外设的开发

流程

 
    
    打开peripheralManager，设置peripheralManager的委托

创建characteristics，characteristics的description 创建service，把characteristics添加到service中，再把service添加到peripheralManager中
开启广播advertising
对central的操作进行响应
- 4.1 读characteristics请求
- 4.2 写characteristics请求
- 4.4 订阅和取消订阅characteristics

步骤


 //初始化
 _peripheralManager = [[CBPeripheralManager alloc] initWithDelegate:self queue:nil];
 //启动外设
 -(void)peripheralManagerDidUpdateState:(CBPeripheralManager *)peripheral{
 switch (peripheral.state) {
 case CBPeripheralManagerStatePoweredOn:
 //CBPeripheralManagerStatePoweredOn下添加服务和特征
 [self setupService];
 }
 //创建服务,特征并添加服务到外围设备
 -(void)setupService{
 //可通知的特征
 // CBUUID *characteristicUUID = [CBUUID UUIDWithString:kNotifyUUID];
 // _characteristic = [[CBMutableCharacteristic alloc] initWithType:characteristicUUID properties:CBCharacteristicPropertyNotify value:nil permissions:CBAttributePermissionsReadable];
 //可读写的特征
 CBUUID *UUID2 = [CBUUID UUIDWithString:kWriteUUID];
 _characteristic = [[CBMutableCharacteristic alloc] initWithType:UUID2 properties:CBCharacteristicPropertyWrite|CBCharacteristicPropertyNotify value:nil permissions:CBAttributePermissionsWriteEncryptionRequired];
 //
 //只读的特征
 // CBUUID *UUID3 = [CBUUID UUIDWithString:kReadUUID];
 // NSData *characteristicValue = [@"aaron才" dataUsingEncoding:NSUTF8StringEncoding];
 // _characteristic = [[CBMutableCharacteristic alloc] initWithType:UUID3 properties:CBCharacteristicPropertyRead value:characteristicValue permissions:CBAttributePermissionsReadable];
 CBUUID *serviceUUID = [CBUUID UUIDWithString:kServiceUUID];
 _service = [[CBMutableService alloc] initWithType:serviceUUID primary:YES];
 [_service setCharacteristics:@[_characteristic]];
 [_peripheralManager addService:_service];
 }
 //添加服务后开始广播,等待中心设备的连接
 -(void)peripheralManager:(CBPeripheralManager *)peripheral didAddService:(CBService *)service error:(nullable NSError *)error{
 NSDictionary *dict = @{CBAdvertisementDataLocalNameKey:kPeripheralName};
 [_peripheralManager startAdvertising:dict];
 [self writeToLogWithText:@"向外围设备添加了服务"];
 }
 根据中心设备的响应,外设在代理中收到中心发来的信息,
 //订阅特征
 -(void)peripheralManager:(CBPeripheralManager *)peripheral central:(CBCentral *)central didSubscribeToCharacteristic:(CBCharacteristic *)characteristic;
 //取消订阅
 -(void)peripheralManager:(CBPeripheralManager *)peripheral central:(CBCentral *)central didUnsubscribeFromCharacteristic:(CBCharacteristic *)characteristic;
 //中心设备读外设数据
 -(void)peripheralManager:(CBPeripheralManager *)peripheral didReceiveReadRequest:(CBATTRequest *)request;
 //收到中心写来的数据
 -(void)peripheralManager:(CBPeripheralManager *)peripheral didReceiveWriteRequests:(NSArray *)requests;

UIBackgroundModes下的蓝牙数据传输

CoreBluetooth提供了非常友好的Background支持.按一下步骤,经过测试,app进入后台后,也能收到外设特征更新的值,据WWDC2013视频介绍,就算因为内存紧张,app在后台被杀掉,系统也会自动帮我们重新启动app进行蓝牙数据传输,不过这个就没测试到,不知道有没有人做过这方便的研究.

```
设置info.plist
```


 UIBackgroundModes
 
 bluetooth-central
 bluetooth-peripheral

初始化方式中添加``options:@{CBCentralManagerOptionRestoreIdentifierKey:kRestoreIdentifierKey}``


 _centralManager = [[CBCentralManager alloc] initWithDelegate:self
 queue:nil
 options:@{CBCentralManagerOptionRestoreIdentifierKey:kRestoreIdentifierKey}];

 
  
  (void)centralManager:(CBCentralManager *)central willRestoreState:(NSDictionary *)dict{ 
  
 // NSArray *scanServices = dict[CBCentralManagerRestoredStateScanServicesKey];
 // NSArray *scanOptions = dict[CBCentralManagerRestoredStateScanOptionsKey]; 
 NSArray *peripherals = dict[CBCentralManagerRestoredStatePeripheralsKey];
for (CBPeripheral *peripheral in peripherals) {
    [self.peripherals addObject:peripheral];
    peripheral.delegate = self;
}
 
 }

 
  
   (void)centralManagerDidUpdateState:(CBCentralManager *)central{
 if (central.state == CBCentralManagerStatePoweredOn) {
 [self writeToLogWithText:@"中心设备已打开"];
 [_centralManager scanForPeripheralsWithServices:nil options:nil];
   //03,检查是否restore connected peripherals
  for (CBPeripheral *peripheral in _peripherals) {
      if (peripheral.state == CBPeripheralStateConnected) {
          NSUInteger serviceIdx = [peripheral.services indexOfObjectPassingTest:^BOOL(CBService * _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stop) {
              return [obj.UUID isEqual:kServiceUUID];
          }];
          
          if (serviceIdx == NSNotFound) {
              [peripheral discoverServices:@[kServiceUUID]];
              continue;
          }
          
          CBService *service = peripheral.services[serviceIdx];
          NSUInteger charIdx = [service.characteristics indexOfObjectPassingTest:^BOOL(CBCharacteristic * _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stop) {
              return [obj.UUID isEqual:kNotifyUUID];
          }];
          
          if (charIdx == NSNotFound) {
              [peripheral discoverCharacteristics:@[kNotifyUUID] forService:service];
              continue;
          }
          
          CBCharacteristic *characteristic = service.characteristics[charIdx];
          if (!characteristic.isNotifying) {
              [peripheral setNotifyValue:YES forCharacteristic:characteristic];
          }
      }
  }
 }else{
 [_peripherals removeAllObjects];
 }
 }

 
  
   (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
 // Override point for customization after application launch.
 NSArray *peripheralManagerIdentifiers = launchOptions[UIApplicationLaunchOptionsBluetoothPeripheralsKey];
 NSArray *centraManagerIdentifiers = launchOptions[UIApplicationLaunchOptionsBluetoothCentralsKey];
 for (NSString *identifier in centraManagerIdentifiers) {
 if ([identifier isEqualToString:kRestoreIdentifierKey]) {
   }
 }
 return YES;
 }

Demo

不动手写代码的学框架都是耍流氓,为了更好的学习,我也是自己都敲了一遍代码,前文中的三种场景以及后台模式都实现了,可以实现中心设备和外设之前的订阅特征,读写数据等功能.希望大家都交流.下面是传送门以及界面展示
github传送门 CoreBluetoothDemo

主界面

![中心设备]IMG_3660.PNG](http://upload-images.jianshu.io/upload_images/1093584-e66b42d6c1c7133f.PNG?imageMogr2/auto-orient/strip%7CimageView2/2/w/1240)

外设