iOS app内使用蓝牙对系统蓝牙已连接的外设的搜索和连接

本来以为对手机系统蓝牙已连接的设备的搜索、连接、通信是使用ExternalAccessory框架的。后来和硬件部的沟通，才发现ExternalAccessory框架是对Lightning接口的硬件或者蓝牙(2.1)的设备才管用。我们使用的是ble协议的蓝牙，所以不能使用ExternalAccessory框架。只能继续找办法。后来发现CBCentralManager类就能实现。下面是CBCentralManager对系统蓝牙已连接外设的搜索、连接的一个简单的Demo代码。(连接成功自然就能发送指令了，通信前要不要发送内部协商的握手指令就看自己了)

#import "ViewController.h"
#import <CoreBluetooth/CoreBluetooth.h>
#import "XJConstants.h"

@interface ViewController ()<CBCentralManagerDelegate, CBPeripheralDelegate>
/** 系统蓝牙管理类 */
@property (nonatomic, strong) CBCentralManager *bleCentral; 
/** 找到的指定的设备 */
@property (nonatomic, strong) CBPeripheral *findPeripheral;

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    self.view.backgroundColor = [UIColor whiteColor];
    // 创建蓝牙操作线程
    dispatch_queue_t queue = dispatch_queue_create("xj.ble.thread", DISPATCH_QUEUE_CONCURRENT);
    // 创建系统蓝牙管理类
    _bleCentral = [[CBCentralManager alloc] initWithDelegate:self queue:queue];
    
}


#pragma mark - CBCentralManagerDelegate
/** 蓝牙连接状态改变 */
- (void)centralManagerDidUpdateState:(CBCentralManager *)central{
    XJBleLog(@"蓝牙状态改变  %ld",central.state);
    // 如果蓝牙不是开启状态
    if(central.state != CBManagerStatePoweredOn){ return; }

    // 自定义的服务ID。注意这里是服务ID，不是设备的[peripheral.identifier UUIDString]这个值
    CBUUID* serviceId = [CBUUID UUIDWithString:@"自定义的服务ID"];
    // 根据自定义的服务ID找出手机系统已连接的设备
    NSArray<CBPeripheral*>* peripheralArray = [_bleCentral retrieveConnectedPeripheralsWithServices:@[serviceId]];
    // 如果没有发现已经连接的设备
    if(peripheralArray.count == 0){
        XJBleLog(@"没有发现已连接的设备");
        //  -------------------- 扫描设备 -------------------
        // 设置 不重复扫描已发现设备
       NSDictionary *option = @{ CBCentralManagerScanOptionAllowDuplicatesKey : [NSNumber numberWithBool:NO] };
       // 开始扫描
       [_bleCentral scanForPeripheralsWithServices:nil options:option];
    }else{
        // 遍历系统已连接的设备
        for (CBPeripheral* peripheral in peripheralArray) {
            NSString* deviceId = [peripheral.identifier UUIDString];
            // 这里必须保存这个引用才可以连接设备成功，不然会连接失败
            self.findPeripheral = peripheral;
            XJBleLog(@"存在设备 - peripheral.name:  %@  连接状态：%ld  设备ID: %@ ",peripheral.name, peripheral.state, deviceId);
            [_bleCentral connectPeripheral:peripheral options:nil];
        }
    }
    

}

/**
 * 发现外设
 * advertisementData  是广播的值，一般携带设备名，serviceUUIDs等信息
 * RSSI绝对值越大，表示信号越差，设备离的越远。如果想装换成百分比强度，（RSSI+100）/100
 */
- (void)centralManager:(CBCentralManager *)central didDiscoverPeripheral:(CBPeripheral *)peripheral advertisementData:(NSDictionary<NSString *, id> *)advertisementData RSSI:(NSNumber *)RSSI{
    // 设备id
    NSString* deviceId = [peripheral.identifier UUIDString];
    // 设备名称
    NSString* deviceName = peripheral.name;
    // 根据设备名找到指定设备
    if([deviceName isEqualToString:@"自定义的设备名"]){
        XJBleLog(@"发现设备 - peripheral.name:  %@  RSSI: %@  设备ID: %@",peripheral.name, RSSI, deviceId);
        // 这里必须保存这个引用才可以连接设备成功，不然会连接失败
        self.findPeripheral = peripheral;
        [_bleCentral connectPeripheral:peripheral options:nil];
    }
}

/** 连接外设成功 */
- (void)centralManager:(CBCentralManager *)central didConnectPeripheral:(CBPeripheral *)peripheral{
    // 设备id
    NSString* deviceId = [peripheral.identifier UUIDString];
    NSString* deviceName = peripheral.name;
    XJBleLog(@"连接设备成功 - peripheral.name:  %@  连接状态：%ld  设备ID: %@ ",deviceName, peripheral.state, deviceId);
    // 注意这里是服务ID，不是设备的[peripheral.identifier UUIDString]这个值
    CBUUID* serviceId = [CBUUID UUIDWithString:@"自定义的服务ID"];
    NSArray<CBPeripheral*>* peripheralArray = [_bleCentral retrieveConnectedPeripheralsWithServices:@[serviceId]];
    for (CBPeripheral* peripheral in peripheralArray) {
        XJBleLog(@"------已连接的设备 - peripheral.name:  %@  连接状态：%ld  设备ID: %@ ",peripheral.name, peripheral.state, deviceId);
    }
}

/** 连接外设失败 */
- (void)centralManager:(CBCentralManager *)central didFailToConnectPeripheral:(CBPeripheral *)peripheral error:(nullable NSError *)error{}

/** 已经断开连接 */
- (void)centralManager:(CBCentralManager *)central didDisconnectPeripheral:(CBPeripheral *)peripheral error:(nullable NSError *)error{}

#pragma mark - CBPeripheralDelegate
/** 发现服务 */
- (void)peripheral:(CBPeripheral *)peripheral didDiscoverServices:(NSError *)error{}

/** 发现特征 */
- (void)peripheral:(CBPeripheral *)peripheral didDiscoverCharacteristicsForService:(CBService *)service error:(NSError *)error{}

/** 订阅的特征值的value发生改变的回调 */
// read  外设 --> 中心 (由控制类去解析返回的数据)
- (void)peripheral:(CBPeripheral *)peripheral didUpdateValueForCharacteristic:(CBCharacteristic *)characteristic error:(NSError *)error{}

/**
 * 当写入某个特征值后 外设代理执行的回调
 * 发送类型必须是CBCharacteristicWriteWithResponse才会回调
 */
- (void)peripheral:(CBPeripheral *)peripheral didWriteValueForCharacteristic:(CBCharacteristic *)characteristic error:(NSError *)error{}

/**
 * 读取信号强度回调的方法
 * peripheral 调用 readRSSI方法触发该代理
 */
-(void)peripheral:(CBPeripheral *)peripheral didReadRSSI:(NSNumber *)RSSI error:(NSError *)error{}


@end