iOS蓝牙连接

iOS蓝牙连接其实不难，可以参照官方的例子教程或者使用github的开源库babyBluetooth。

iOS蓝牙连接的流程如下：

通过服务的UUID扫描外部设备 -> 连接外部设备 -> 连接成功后扫描设备的服务 -> 发现服务后，扫描该服务的Characteristics -> 扫描到Characteristics后，进行读、写、订阅 -> 读和订阅后，有数据回来，会回调一个代理方法didUpdateValueForCharacteristic获得数据。

下面介绍一下官方教程的代码，因为iOS是作为主端，所以只介绍主端的代码，从端的代码示例代码也有，可以参考，并不难。

官方教程的代码下载链接

主端官方的例子主要是参照BTLECentralViewController.m这个文件。iOS原生的蓝牙基本是使用了代理方法的结构来处理蓝牙功能。基本上流程的一步对应一个代理方法。

创建CBCentralManager对象，并设置好它的代理。

_centralManager = [[CBCentralManager alloc] initWithDelegate:self queue:nil];

使用CBCentralManager扫描外部设备,这个需要传递外部设备的服务的UUID，如果不传递的话，那么就会扫描所有设备。代码如下，

- (void)scan
{
    [self.centralManager scanForPeripheralsWithServices:@[[CBUUID UUIDWithString:TRANSFER_SERVICE_UUID]]
                                                options:@{ CBCentralManagerScanOptionAllowDuplicatesKey : @YES }];
    
    NSLog(@"Scanning started");
}

发现设备后会回调一个代理方法，

- (void)centralManager:(CBCentralManager *)central didDiscoverPeripheral:(CBPeripheral *)peripheral advertisementData:(NSDictionary *)advertisementData RSSI:(NSNumber *)RSSI

在这个方法里面连接设备

[self.centralManager connectPeripheral:peripheral options:nil];

设备连接成功后会回调一个方法，先停止扫描，然后在这个方法里面扫描设备的服务。如果不传服务的UUID，那么会扫描所有服务。

- (void)centralManager:(CBCentralManager *)central didConnectPeripheral:(CBPeripheral *)peripheral
{
    NSLog(@"Peripheral Connected");
    
    // Stop scanning
    [self.centralManager stopScan];
    NSLog(@"Scanning stopped");
    
    // Clear the data that we may already have
    [self.data setLength:0];

    // Make sure we get the discovery callbacks
    peripheral.delegate = self;
    
    // Search only for services that match our UUID
    [peripheral discoverServices:@[[CBUUID UUIDWithString:TRANSFER_SERVICE_UUID]]];
}

扫描到服务后继续调用另外回调方法，在这个方法扫描Characteristics

- (void)peripheral:(CBPeripheral *)peripheral didDiscoverServices:(NSError *)error
{
    if (error) {
        NSLog(@"Error discovering services: %@", [error localizedDescription]);
        [self cleanup];
        return;
    }
    
    // Discover the characteristic we want...
    
    // Loop through the newly filled peripheral.services array, just in case there's more than one.
    for (CBService *service in peripheral.services) {
        [peripheral discoverCharacteristics:@[[CBUUID UUIDWithString:TRANSFER_CHARACTERISTIC_UUID]] forService:service];
    }
}

发现Characteristics后继续回调另外一个方法。这里面可以判断一下Characteristics的UUID，对需要订阅的Characteristics进行订阅，或者读写数据。

- (void)peripheral:(CBPeripheral *)peripheral didDiscoverCharacteristicsForService:(CBService *)service error:(NSError *)error
{
    // Deal with errors (if any)
    if (error) {
        NSLog(@"Error discovering characteristics: %@", [error localizedDescription]);
        [self cleanup];
        return;
    }
    // Again, we loop through the array, just in case.
    for (CBCharacteristic *characteristic in service.characteristics) {
        // And check if it's the right one
        if ([characteristic.UUID isEqual:[CBUUID UUIDWithString:TRANSFER_CHARACTERISTIC_UUID]]) {
            //订阅characteristic If it is, subscribe to it
            [peripheral setNotifyValue:YES forCharacteristic:characteristic];
        }
    }
//读取characteristic
//[peripheral readValueForCharacteristic:characteristic];
    // Once this is complete, we just need to wait for the data to come in.
}

如果读取或者订阅的Characteristic有更新，那么就会调用下面的方法。

- (void)peripheral:(CBPeripheral *)peripheral didUpdateValueForCharacteristic:(CBCharacteristic *)characteristic error:(NSError *)error
{
    if (error) {
        NSLog(@"Error discovering characteristics: %@", [error localizedDescription]);
        return;
    }
    //获得数据
    NSData *data = characteristic.value;
}

如果要断开连接，调用下面方法

[self.centralManager cancelPeripheralConnection:peripheral];