iOS蓝牙

前几个月做了一个蓝牙的项目，初次接触，也查了好多资料，算是有了个大概的了解，最近又做另一个蓝牙的项目，发现还是有很多地方不是很明白，也为了防止忘记，就写下来吧！

在CBCentralManager初始化的时候，一般放在另一个线程中：

    dispatch_queue_t centralQueue = dispatch_queue_create("myCentralQueue",DISPATCH_QUEUE_SERIAL);    _centralManager = [[CBCentralManager alloc] initWithDelegate:self queue:centralQueue];

初始化也可以使用如下的方法：

- (id)initWithDelegate:(id<CBCentralManagerDelegate>)delegate queue:(dispatch_queue_t)queue options:(NSDictionary *)options

如：

NSDictionary *options = [NSDictionary dictionaryWithObjectsAndKeys:[NSNumber numberWithBool:YES],CBCentralManagerOptionShowPowerAlertKey,@"zStrapRestoreIdentifier",CBCentralManagerOptionRestoreIdentifierKey,nil];myCenter = [[CBCentralManager alloc] initWithDelegate:self                                          queue:dispatch_queue_create("com.myBLEQueue", NULL)                                          options:options];

Central Manager Initialization Options 对应的有两项：
CBCentralManagerOptionShowPowerAlertKey
布尔值，表示的是在central manager初始化时，如果当前蓝牙没打开，是否弹出alert框。
CBCentralManagerOptionRestoreIdentifierKey
CBCentralManagerOptionRestoreIdentifierKey，字符串，一个唯一的标示符，用来蓝牙的恢复连接的。在后台的长连接中可能会用到。

就是说，如果蓝牙程序进入后台，程序会被挂起，可能由于memory pressure，程序被系统kill了，那么代理方法就不会执行了。这时候可以使用State Preservation & Restoration，这样程序会重新加载进入后台。

调试iOS蓝牙的时候，可以下个LightBlue，非常方便，网上也有仿写LightBlue的Demo，参考这两处：
https://github.com/chenee/DarkBlue

http://boxertan.github.io/blog/2014/07/07/xue-xi-ioslan-ya-ji-zhu-%2Cfang-xie-lightblue/

使用scanForPeripheralsWithServices:options: 来扫描外设

NSDictionary *option = [NSDictionary dictionaryWithObjectsAndKeys:[NSNumber numberWithBool:NO], CBCentralManagerScanOptionAllowDuplicatesKey,nil];[_centralManager scanForPeripheralsWithServices:nil options:option];

options是可选的，CBCentralManagerScanOptionAllowDuplicatesKey，bool值，为NO，表示不会重复扫描已经发现的设备。

连接外设使用connectPeripheral:options: 方法，options为可选，options可以为：
CBConnectPeripheralOptionNotifyOnConnectionKey
CBConnectPeripheralOptionNotifyOnDisconnectionKey
CBConnectPeripheralOptionNotifyOnNotificationKey

具体的意思参考文档

[myCenter connectPeripheral:peripheralInfo.peripheral options:@{    CBConnectPeripheralOptionNotifyOnConnectionKey: @YES,    CBConnectPeripheralOptionNotifyOnDisconnectionKey: @YES,    CBConnectPeripheralOptionNotifyOnNotificationKey: @YES}];

在蓝牙连接的过程中，代理方法centralManagerDidUpdateState: 会判断中央设备的状态

- (void)centralManagerDidUpdateState:(CBCentralManager *)central{    // Determine the state of the peripheral    if ([central state] == CBCentralManagerStatePoweredOff) {        NSLog(@"CoreBluetooth BLE hardware is powered off");    }    else if ([central state] == CBCentralManagerStatePoweredOn) {        NSLog(@"CoreBluetooth BLE hardware is powered on and ready");    }    else if ([central state] == CBCentralManagerStateUnauthorized) {        NSLog(@"CoreBluetooth BLE state is unauthorized");    }    else if ([central state] == CBCentralManagerStateUnknown) {        NSLog(@"CoreBluetooth BLE state is unknown");    }    else if ([central state] == CBCentralManagerStateUnsupported) {        NSLog(@"CoreBluetooth BLE hardware is unsupported on this platform");    }}

返现characteristic后可以读取它的值，也可以订阅它：

[self.peripheral readValueForCharacteristic:characteristic];[self.peripheral setNotifyValue:YES forCharacteristic:characteristic];

以上两个方法都会调用代理方法：didUpdateValueForCharacteristic:error: 

向外设的某个characteristic写入值，可以这样写

- (void)writeToperipheral:(CBPeripheral *)peripheral Service:(NSString *)serviceUUID characteristic:(NSString *)characteristicUUID data:(NSData *)data{    CBUUID *servUUID = [CBUUID UUIDWithString:serviceUUID];    CBUUID *charUUID = [CBUUID UUIDWithString:characteristicUUID];    CBService *service = nil;    CBCharacteristic *characteristic = nil;    for (CBService *ser in peripheral.services) {        if ([ser.UUID isEqual:servUUID]) {            service = ser;            break;        }    }    if (service) {        for (CBCharacteristic *charac in service.characteristics) {            if ([charac.UUID isEqual:charUUID]) {                characteristic = charac;                break;            }        }    }    if (characteristic) {        [peripheral writeValue:data forCharacteristic:characteristic type:CBCharacteristicWriteWithResponse];    }    else{        NSLog(@"not found that characteristic");    }}

NSData的值可以这样组织，这与你的需求有关并不一定：

char data;data = 0x15;NSData *d = [[NSData alloc] initWithBytes:&data length:1];

读取某个characteristic的值

- (void)readPeripheral:(CBPeripheral *)peripheral serviceUUID:(NSString *)serviceUUID characteristicUUID:(NSString *)characteristicUUID{    CBUUID *servUUID = [CBUUID UUIDWithString:serviceUUID];    CBUUID *charUUID = [CBUUID UUIDWithString:characteristicUUID];    CBService *service = nil;    CBCharacteristic *characteristic = nil;    for (CBService *ser in peripheral.services) {        if ([ser.UUID isEqual:servUUID]) {            service = ser;            break;        }    }    if (service) {        for (CBCharacteristic *charac in service.characteristics) {            if ([charac.UUID isEqual:charUUID]) {                characteristic = charac;                break;            }        }    }    if (characteristic) {        [peripheral readValueForCharacteristic:characteristic];    }else{        NSLog(@"----------未找到当前的characteristic");    }}

通过保存的identity来找到以前连接的设备
保存identity

NSUUID *uuid = peripheral.identifier;NSString *uuidString = uuid.UUIDString;[[NSUserDefaults standardUserDefaults] setObject:uuidString forKey:PERIPHERAL_UUID];[[NSUserDefaults standardUserDefaults] synchronize];

然后通过identity，来搜索设备：

NSString *uuidString = [[NSUserDefaults standardUserDefaults] stringForKey:PERIPHERAL_UUID];NSUUID *uuid = [[NSUUID alloc] initWithUUIDString:uuidString];_peripheralArr = [NSMutableArray arrayWithArray: [self.centralManager retrievePeripheralsWithIdentifiers:@[uuid]]];for (CBPeripheral *peripheral in _peripheralArr) {    self.peripheral = peripheral;    [self.centralManager connectPeripheral:peripheral options:nil];}

通过retrieveConnectedPeripheralsWithServices：函数来检索当前连接到系统的蓝牙设备：

NSArray *atmp = [NSArray arrayWithObjects:[CBUUID UUIDWithString:@"180A"], nil];NSArray *retrivedArray = [myCenter retrieveConnectedPeripheralsWithServices:atmp];NSLog(@"retrivedArray:\n%@",retrivedArray);for (CBPeripheral* peripheral in retrivedArray) {    [self addPeripheral:peripheral advertisementData:nil  RSSI:nil];}