本文从以下三方面讲解下蓝牙开发
1、蓝牙相关基本知识
2、蓝牙相关类图
3、蓝牙交互流程
一、蓝牙相关基本知识
涉及到蓝牙开发，首先有几个问题是需要我们理解的
1、任何设备既可以是中心设备、也可以是外围设备
2、外设 和 中心设备 之间通过特征建立一个双向的数据通道
3、CBCentralManager主要操作中心设备，处理链接上外设之前的操作，链接上外设后，主要靠CBPeripheral（主要操作外设）处理外设相关操作（服务、特征、数据读写）
4、中心设备管理 CBCentralManager
中心控制类，主要管理中心设备，以及处理跟外设（外围设备）相关操作，主要是扫描、链接、断开外设。
操作中心设备的核心类。
很重要的协议CBCentralManagerDelegate，包含中心设备状态（是否打开蓝牙）回调、发现外设回调、链接外设成功回调、链接外设失败回调、外设链接断开回调等方法。
一个中心设备可以链接多个外围设备。
5、外围设备 CBPeripheral
外设类，包含设备的基础属性，名字，uuid等信息。向外设写入数据。
当中心设备连接到外设后，需要通过外设对象的代理方法进行数据交互。
操作外围设备的核心类。
很重要的协议CBPeripheralDelegate，包含发现服务回调、发现特征回调、特征的通知设置改变回调、特征更新回调、特征已写入数据回调等方法。
一个设备包含多个服务、一个服务包含多个特征、一个特征又包含多个描述。
6、外围设备管理 CBPeripheralManager
设备的控制，主要可以为设备设置Service以及Characteristic，可以手动配置特定的服务和特征值，也可看作可以自定义蓝牙协议，例如将手机作为外设时可以为自己的手机蓝牙设置服务和特征值。CBCentralManager更适合将自己的软件作为中心。
用的较少
7、服务 CBService
服务对象是用来管理外设提供的一些数据服务的。
一个服务可以包含多个特征
8、特征 CBCharacteristic
通过绑定服务中的特征值来进行数据的读写操作。
特征就是具体键值对，提供数据的地方。
每个特征属性分为这么几种：读，写，通知等几种方式。
有时读、写、通知可以是同一个特征，也可以读、写、通知各用一个特征表示。
一个特征可以包含多个描述。
一般我们操作到特征这一层
9、描述 CBDescriptor
每个characteristic可以对应一个或多个Description 供用户描述characteristic的信息或属性。
10、CBAttribute
CBService，CBCharacteristic，CBDescriptor 类都继承自 CBAttribute，
它们有一个共同的属性 CBUUID，用来作为唯一的标识。
二、蓝牙相关类图
下面用类图简述下：
一个中心设备可以连接多个外设，一个外设包含多个服务，一个服务包含多个特征，一个特征包含多个描述
服务、特征、描述都用CBUUID唯一标识
三、蓝牙交互流程
下面简述下以手机作为中心设备、其它作为外围设备的交互流程，大致流程如图所示
下面是操作详解
1、创建中心设备管理对象（初始化中心设备）
CBCentralManager 的创建是异步的，如果初始化完成之后没有被当前创建它的类所持有，就会在下一次 RunLoop 迭代的时候释放。
创建线程写nil，为主线程。
初始化成功后，就会触发 CBCentralManagerDelegate 中的中心设备状态更新方法：centralManagerDidUpdateState:
NSDictionary *options = @{CBCentralManagerOptionShowPowerAlertKey:@NO};
self.centralManager = [[CBCentralManager alloc] initWithDelegate:self queue:nil options:options];
/*! * @method initWithDelegate:queue:options: * * @param delegate The delegate that will receive central role events. * @param queue The dispatch queue on which the events will be dispatched. * @param options An optional dictionary specifying options for the manager. * * @discussion The initialization call. The events of the central role will be dispatched on the provided queue. * If <i>nil</i>, the main queue will be used. * * @seealso CBCentralManagerOptionShowPowerAlertKey * @seealso CBCentralManagerOptionRestoreIdentifierKey * */ - (instancetype)initWithDelegate:(nullable id<CBCentralManagerDelegate>)delegate queue:(nullable dispatch_queue_t)queue options:(nullable NSDictionary<NSString *, id> *)options NS_AVAILABLE(10_9, 7_0) NS_DESIGNATED_INITIALIZER;
@protocol CBCentralManagerDelegate <NSObject> @required /*! * @method centralManagerDidUpdateState: * * @param central The central manager whose state has changed. * * @discussion Invoked whenever the central manager's state has been updated. Commands should only be issued when the state is * <code>CBCentralManagerStatePoweredOn</code>. A state below <code>CBCentralManagerStatePoweredOn</code> * implies that scanning has stopped and any connected peripherals have been disconnected. If the state moves below * <code>CBCentralManagerStatePoweredOff</code>, all <code>CBPeripheral</code> objects obtained from this central * manager become invalid and must be retrieved or discovered again. * * @see state * */ - (void)centralManagerDidUpdateState:(CBCentralManager *)central;
2、扫描外围设备
在CBCentralManagerDelegate 中的中心设备状态更新方法：centralManagerDidUpdateState:中，
当中心设备处于CBManagerStatePoweredOn 状态的时候开始扫描周边设备（可以使用指定的 UUID 发现特定的 Service，也可以传入 nil，表示发现所有周边的蓝牙设备，不过还是建议只发现自己需要服务的设备）。
扫描外设：scanForPeripheralsWithServices:options:
该操作由CBCentralManager对象通过scanForPeripheralsWithServices:options:方法实现
case CBManagerStatePoweredOn: //蓝牙正常开启 [self startScan]; break;
- (void)startScan { // [self.centralManager scanForPeripheralsWithServices:nil options:@{CBCentralManagerScanOptionAllowDuplicatesKey : @YES }]; // 扫描所有设备 当指定设备不好使时可以使用该方法 // [self.centralManager scanForPeripheralsWithServices:nil options:nil]; // 扫描指定设备 快速 [self.centralManager scanForPeripheralsWithServices:@[[CBUUID UUIDWithString:self.peripheralServiceUUID]] options:nil]; [self startTime]; }
/*! * @method scanForPeripheralsWithServices:options: * * @param serviceUUIDs A list of <code>CBUUID</code> objects representing the service(s) to scan for. * @param options An optional dictionary specifying options for the scan. * * @discussion Starts scanning for peripherals that are advertising any of the services listed in <i>serviceUUIDs</i>. Although strongly discouraged, * if <i>serviceUUIDs</i> is <i>nil</i> all discovered peripherals will be returned. If the central is already scanning with different * <i>serviceUUIDs</i> or <i>options</i>, the provided parameters will replace them. * Applications that have specified the <code>bluetooth-central</code> background mode are allowed to scan while backgrounded, with two * caveats: the scan must specify one or more service types in <i>serviceUUIDs</i>, and the <code>CBCentralManagerScanOptionAllowDuplicatesKey</code> * scan option will be ignored. * * @see centralManager:didDiscoverPeripheral:advertisementData:RSSI: * @seealso CBCentralManagerScanOptionAllowDuplicatesKey * @seealso CBCentralManagerScanOptionSolicitedServiceUUIDsKey * */ - (void)scanForPeripheralsWithServices:(nullable NSArray<CBUUID *> *)serviceUUIDs options:(nullable NSDictionary<NSString *, id> *)options;
3、发现外围设备
CBCentralManager对象执行扫描外设方法scanForPeripheralsWithServices:options:后
会触发 CBCentralManagerDelegate 中的方法：（发现外设）centralManager:didDiscoverPeripheral:advertisementData:RSSI:
如果在扫描时指定了明确的服务，那么此时该方法里的外设就是包含该服务的外设，
如果传入的是nil，那么此时该方法里的外设就是周边所有打开的蓝牙设备。
/*! * @method centralManager:didDiscoverPeripheral:advertisementData:RSSI: * * @param central The central manager providing this update. * @param peripheral A <code>CBPeripheral</code> object. * @param advertisementData A dictionary containing any advertisement and scan response data. * @param RSSI The current RSSI of <i>peripheral</i>, in dBm. A value of <code>127</code> is reserved and indicates the RSSI * was not available. * * @discussion This method is invoked while scanning, upon the discovery of <i>peripheral</i> by <i>central</i>. A discovered peripheral must * be retained in order to use it; otherwise, it is assumed to not be of interest and will be cleaned up by the central manager. For * a list of <i>advertisementData</i> keys, see {@link CBAdvertisementDataLocalNameKey} and other similar constants. * * @seealso CBAdvertisementData.h * */ - (void)centralManager:(CBCentralManager *)central didDiscoverPeripheral:(CBPeripheral *)peripheral advertisementData:(NSDictionary<NSString *, id> *)advertisementData RSSI:(NSNumber *)RSSI;
4、链接外设
在CBCentralManagerDelegate 中的发现外设方法：centralManager:didDiscoverPeripheral:advertisementData:RSSI:中，
我们会链接外设：connectPeripheral:options:
该操作由CBCentralManager对象通过connectPeripheral:options:方法实现
我们通过名称或者厂商数据来确定我们需要链接的外设（过滤外设），找到后停止扫描，然后链接该外设，即链接指定外设
[central connectPeripheral:peripheral options:nil];
/*! * @method connectPeripheral:options: * * @param peripheral The <code>CBPeripheral</code> to be connected. * @param options An optional dictionary specifying connection behavior options. * * @discussion Initiates a connection to <i>peripheral</i>. Connection attempts never time out and, depending on the outcome, will result * in a call to either {@link centralManager:didConnectPeripheral:} or {@link centralManager:didFailToConnectPeripheral:error:}. * Pending attempts are cancelled automatically upon deallocation of <i>peripheral</i>, and explicitly via {@link cancelPeripheralConnection}. * * @see centralManager:didConnectPeripheral: * @see centralManager:didFailToConnectPeripheral:error: * @seealso CBConnectPeripheralOptionNotifyOnConnectionKey * @seealso CBConnectPeripheralOptionNotifyOnDisconnectionKey * @seealso CBConnectPeripheralOptionNotifyOnNotificationKey * @seealso CBConnectPeripheralOptionEnableTransportBridgingKey * @seealso CBConnectPeripheralOptionRequiresANCS * */ - (void)connectPeripheral:(CBPeripheral *)peripheral options:(nullable NSDictionary<NSString *, id> *)options;
5、链接外设结果回调
CBCentralManager对象执行链接外设方法connectPeripheral:options:后
会触发 CBCentralManagerDelegate 中的方法：
链接外设成功回调：centralManager:didConnectPeripheral:
/*! * @method centralManager:didConnectPeripheral: * * @param central The central manager providing this information. * @param peripheral The <code>CBPeripheral</code> that has connected. * * @discussion This method is invoked when a connection initiated by {@link connectPeripheral:options:} has succeeded. * */ - (void)centralManager:(CBCentralManager *)central didConnectPeripheral:(CBPeripheral *)peripheral;
链接外设失败回调：centralManager:didFailToConnectPeripheral:error:
/*! * @method centralManager:didFailToConnectPeripheral:error: * * @param central The central manager providing this information. * @param peripheral The <code>CBPeripheral</code> that has failed to connect. * @param error The cause of the failure. * * @discussion This method is invoked when a connection initiated by {@link connectPeripheral:options:} has failed to complete. As connection attempts do not * timeout, the failure of a connection is atypical and usually indicative of a transient issue. * */ - (void)centralManager:(CBCentralManager *)central didFailToConnectPeripheral:(CBPeripheral *)peripheral error:(nullable NSError *)error;
6、查找服务
在CBCentralManagerDelegate 中的链接外设成功回调方法：centralManager:didConnectPeripheral:中，
我们会查找服务：discoverServices:
该操作由CBPeripheral对象通过discoverServices:方法实现
[peripheral discoverServices:@[[CBUUID UUIDWithString:self.peripheralServiceUUID]]];
/*! * @method discoverServices: * * @param serviceUUIDs A list of <code>CBUUID</code> objects representing the service types to be discovered. If <i>nil</i>, * all services will be discovered. * * @discussion Discovers available service(s) on the peripheral. * * @see peripheral:didDiscoverServices: */ - (void)discoverServices:(nullable NSArray<CBUUID *> *)serviceUUIDs;
7、发现服务
CBPeripheral对象执行查找服务方法discoverServices:后，
会触发 CBPeripheralDelegate 中的发现服务方法：peripheral:didDiscoverServices:
/*! * @method peripheral:didDiscoverServices: * * @param peripheral The peripheral providing this information. * @param error If an error occurred, the cause of the failure. * * @discussion This method returns the result of a @link discoverServices: @/link call. If the service(s) were read successfully, they can be retrieved via * <i>peripheral</i>'s @link services @/link property. * */ - (void)peripheral:(CBPeripheral *)peripheral didDiscoverServices:(nullable NSError *)error;
8、查找特征
在 CBPeripheralDelegate 中的发现服务方法：peripheral:didDiscoverServices:中，
我们会查找特征：discoverCharacteristics:forService:
该操作由CBPeripheral对象通过discoverCharacteristics:forService:方法实现
[peripheral discoverCharacteristics:@[[CBUUID UUIDWithString:self.peripheralCharacteristicRTXUUID]] forService:service];
/*! * @method discoverCharacteristics:forService: * * @param characteristicUUIDs A list of <code>CBUUID</code> objects representing the characteristic types to be discovered. If <i>nil</i>, * all characteristics of <i>service</i> will be discovered. * @param service A GATT service. * * @discussion Discovers the specified characteristic(s) of <i>service</i>. * * @see peripheral:didDiscoverCharacteristicsForService:error: */ - (void)discoverCharacteristics:(nullable NSArray<CBUUID *> *)characteristicUUIDs forService:(CBService *)service;
9、发现特征
CBPeripheral对象执行查找特征方法discoverCharacteristics:forService:后，
会触发CBPeripheralDelegate 中的发现特征方法：peripheral:didDiscoverCharacteristicsForService:error:
/*! * @method peripheral:didDiscoverCharacteristicsForService:error: * * @param peripheral The peripheral providing this information. * @param service The <code>CBService</code> object containing the characteristic(s). * @param error If an error occurred, the cause of the failure. * * @discussion This method returns the result of a @link discoverCharacteristics:forService: @/link call. If the characteristic(s) were read successfully, * they can be retrieved via <i>service</i>'s <code>characteristics</code> property. */ - (void)peripheral:(CBPeripheral *)peripheral didDiscoverCharacteristicsForService:(CBService *)service error:(nullable NSError *)error;
10、写特征、通知特征（读取）、读特征
在 CBPeripheralDelegate 中的发现特征方法：peripheral:didDiscoverCharacteristicsForService:error:中，
我们会处理特征（读、写、通知），一般会保存写入特征，方便后期写入数据，打开使能通知，方便读取数据
写：
保存写特征，方便后期写入数据。
读：
通知特征和读特征都是为了读取，一般我们使用的都是通知，
使用通知的时候，要打开使能通知（订阅），
该操作由CBPeripheral对象通过setNotifyValue:forCharacteristic:方法打开指定通知特征
通知特征发送的数据在didUpdateValueForCharacteristic方法里接受（读取）
该操作会回调CBPeripheralDelegate 中的方法peripheral:didUpdateNotificationStateForCharacteristic:error:
通过characteristic.isNotifying知晓通知状态
/*! * @method peripheral:didUpdateNotificationStateForCharacteristic:error: * * @param peripheral The peripheral providing this information. * @param characteristic A <code>CBCharacteristic</code> object. * @param error If an error occurred, the cause of the failure. * * @discussion This method returns the result of a @link setNotifyValue:forCharacteristic: @/link call. */ - (void)peripheral:(CBPeripheral *)peripheral didUpdateNotificationStateForCharacteristic:(CBCharacteristic *)characteristic error:(nullable NSError *)error;
for (CBCharacteristic *characteristic in service.characteristics) { // if ([characteristic.UUID isEqual:[CBUUID UUIDWithString:self.peripheralCharacteristicTXUUID]]) { // // 打开使能通知 （订阅）该特征发送的数据在didUpdateValueForCharacteristic方法里接受（读取） // [peripheral setNotifyValue:YES forCharacteristic:characteristic]; // } else if ([characteristic.UUID isEqual:[CBUUID UUIDWithString:self.peripheralCharacteristicRXUUID]]) { // // 保存外设接受特征（写入特征） // self.characteristicRX = characteristic;
11、写入数据
写入方法：writeValue:forCharacteristic:type:
写入操作由CBPeripheral对象通过writeValue:forCharacteristic:type:方法写入指定写入特征
[self.peripheral writeValue:peripheralRXData forCharacteristic:self.characteristicRX type:
CBCharacteristicWriteWithResponse];
/*! * @method writeValue:forCharacteristic:type: * * @param data The value to write. * @param characteristic The characteristic whose characteristic value will be written. * @param type The type of write to be executed. * * @discussion Writes <i>value</i> to <i>characteristic</i>'s characteristic value. * If the <code>CBCharacteristicWriteWithResponse</code> type is specified, {@link peripheral:didWriteValueForCharacteristic:error:} * is called with the result of the write request. * If the <code>CBCharacteristicWriteWithoutResponse</code> type is specified, and canSendWriteWithoutResponse is false, the delivery * of the data is best-effort and may not be guaranteed. * * @see peripheral:didWriteValueForCharacteristic:error: * @see peripheralIsReadyToSendWriteWithoutResponse: * @see canSendWriteWithoutResponse * @see CBCharacteristicWriteType */ - (void)writeValue:(NSData *)data forCharacteristic:(CBCharacteristic *)characteristic type:(CBCharacteristicWriteType)type;
写入数据有两种方式：
/* 32 typedef NS_ENUM(NSInteger, CBCharacteristicWriteType) { 33 CBCharacteristicWriteWithResponse = 0,//写数据并且接收成功与否回执 34 CBCharacteristicWriteWithoutResponse,//写数据不接收回执 35 }; 36 */
如果写入类型为CBCharacteristicWriteWithResponse 回调CBPeripheralDelegate 中的方法：
peripheral:didWriteValueForCharacteristic:error:，
如果写入类型为CBCharacteristicWriteWithoutResponse不回调此方法，
该方法只是告知写入数据是否成功
/*! * @method peripheral:didWriteValueForCharacteristic:error: * * @param peripheral The peripheral providing this information. * @param characteristic A <code>CBCharacteristic</code> object. * @param error If an error occurred, the cause of the failure. * * @discussion This method returns the result of a {@link writeValue:forCharacteristic:type:} call, when the <code>CBCharacteristicWriteWithResponse</code> type is used. */ - (void)peripheral:(CBPeripheral *)peripheral didWriteValueForCharacteristic:(CBCharacteristic *)characteristic error:(nullable NSError *)error;
写入数据后外设响应数据在特征值更新方法didUpdateValueForCharacteristic:error:中读取
12、读取数据
读取外设发送给中心设备的数据，
无论是read的回调，还是notify（订阅）的回调都是CBPeripheralDelegate 中的方法：
特征值更新：didUpdateValueForCharacteristic:error:
/*! * @method peripheral:didUpdateValueForCharacteristic:error: * * @param peripheral The peripheral providing this information. * @param characteristic A <code>CBCharacteristic</code> object. * @param error If an error occurred, the cause of the failure. * * @discussion This method is invoked after a @link readValueForCharacteristic: @/link call, or upon receipt of a notification/indication. */ - (void)peripheral:(CBPeripheral *)peripheral didUpdateValueForCharacteristic:(CBCharacteristic *)characteristic error:(nullable NSError *)error;
13、断开链接
断开链接：cancelPeripheralConnection:
断开链接操作由CBCentralManager对象通过cancelPeripheralConnection:方法实现
该方法不会触发CBCentralManagerDelegate 中的方法：
断开外设（仅在异常断开时会触发）：centralManager:didDisconnectPeripheral:error:
/*! * @method cancelPeripheralConnection: * * @param peripheral A <code>CBPeripheral</code>. * * @discussion Cancels an active or pending connection to <i>peripheral</i>. Note that this is non-blocking, and any <code>CBPeripheral</code> * commands that are still pending to <i>peripheral</i> may or may not complete. * * @see centralManager:didDisconnectPeripheral:error: * */ - (void)cancelPeripheralConnection:(CBPeripheral *)peripheral;
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