公司业务有涉及到订单模块，客户需要连接蓝牙打印机打印订单小票。所以本文就记录一下iOS蓝牙打印的相关知识以及实际开发中遇到的问题解决方案。
1.前言
如果需要手机连接蓝牙设备就有两种方案：1.蓝牙设备生产厂商通过MFi认证（蓝牙软件开发者使用苹果标准的Bluetooth profiles可以不用申请MFi开发认证）。2.蓝牙芯片升级支持Bluetooth4.0（BLE)协议
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以下内容只适合蓝牙4.0，如我们碰到过客户设备蓝牙版本是2.0的情况，咨询生厂厂家技术支持后得到这样的回复。
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2. 蓝牙基础知识
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两组API分别对应不同的业务场景：
（1）左侧的是“中心模式”，就是以你的APP作为中心，连接其他的外设；中心模式也是本文使用的模式。
（2）右侧的是“外设模式”，使用手机作为外设识别其他中心设备操作的场景。
每个蓝牙4.0的设备都是通过服务和特征来展示自己的，一个设备包含一个或多个服务，每个服务下面又包含若干个特征。特征是与外界交互的最小单位。
下图展示的是蓝牙打印中心模式的整体流程。
image.png
3.蓝牙打印开发步骤
3.1 建立蓝牙管理中心角色
创建Central管理器时，管理器对象会调用代理对象的centralManagerDidUpdateState:方法，需要实现这个方法来确保本地设备支持BLE（CBCentralManagerDelegate）
#pragma mark -CBCentralManagerDelegate
- (void)centralManagerDidUpdateState:(CBCentralManager *)central
{
NSString * state = nil;
switch ([central state])
{
case CBCentralManagerStateUnsupported:
state = @"The platform/hardware doesn't support Bluetooth Low Energy.";
break;
case CBCentralManagerStateUnauthorized:
state = @"The app is not authorized to use Bluetooth Low Energy.";
break;
case CBCentralManagerStatePoweredOff:
state = @"Bluetooth is currently powered off.";
break;
case CBCentralManagerStatePoweredOn:
{
state = @"work";
[self startDeviceDiscovery];
break;
}
case CBCentralManagerStateUnknown:
default:
;
}
NSLog(@"Central manager state: %@", state);
}
3.2 搜索可用的蓝牙设备外设
调用CBCentralManager的scanForPeripheralsWithServices方法来扫描周围正在发出广播的外设。每找到一个外设会调centralManager:didDiscoverPeripheral:advertisementData:RSSI: 方法。该方法会CBPeripheral返回找到的外设，所以可以使用数组将找到的外设保存。
- (void)centralManager:(CBCentralManager *)central didDiscoverPeripheral:(CBPeripheral *)peripheral advertisementData:(NSDictionary *)advertisementData RSSI:(NSNumber *)RSSI{
if (peripheral)
{
NSLog(@"foundDevice. name[%s],RSSI[%d]\n",peripheral.name.UTF8String,peripheral.RSSI.intValue);
{
//self.peripheral = peripheral;
//发现设备后即可连接该设备 调用完该方法后会调用代理CBCentralManagerDelegate的- (void)centralManager:(CBCentralManager *)central didConnectPeripheral:(CBPeripheral *)peripheral表示连接上了设别
//如果不能连接会调用 - (void)centralManager:(CBCentralManager *)central didFailToConnectPeripheral:(CBPeripheral *)peripheral error:(NSError *)error
//[centralManager connectPeripheral:peripheral options:@{CBConnectPeripheralOptionNotifyOnConnectionKey : YES}];
if (![self.deviceList containsObject:peripheral])
[self.deviceList addObject:peripheral];
[_reDiscoveryView removeFromSuperview];
[self.deviceListTableView reloadData];
}
}
}
3.3连接蓝牙外设
当连接成功后，会回调方法centralManager:didConnectPeripheral:。在这个方法中，可以去记录当前的连接状态等数据。
- (void)centralManager:(CBCentralManager *)central didConnectPeripheral:(CBPeripheral *)peripheral
{
NSLog(@"has connected");
peripheral.delegate = self;
[[CentralManager sharedInstance].connectedDeviceArr addObject:peripheral];
NSIndexPath *indexPath = [NSIndexPath indexPathForItem:[self.deviceList indexOfObject:peripheral] inSection:0];
BluetoothDeviceCell * cell = [self.deviceListTableView cellForRowAtIndexPath:indexPath];
cell.connectedStatus = YES;
//此时设备已经连接上了找到该设备上的指定服务 调用完该方法后会调用代理CBPeripheralDelegate（现在开始调用另一个代理的方法了）的
//- (void)peripheral:(CBPeripheral *)peripheral didDiscoverServices:(NSError *)error
for (CBPeripheral *aPeripheral in [CentralManager sharedInstance].connectedDeviceArr) {
[aPeripheral discoverServices:@[[CBUUID UUIDWithString:kServiceUUID]]];
[aPeripheral discoverServices:@[[CBUUID UUIDWithString:kServiceUUID_cj]]];
}
}
如果连接失败，则会调用：
- (void)centralManager:(CBCentralManager *)central didFailToConnectPeripheral:(CBPeripheral *)peripheral error:(NSError *)error{
//连接发生错误
NSLog(@"connected periphheral failed");
}
3.4扫描外设服务和特征
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当与外设成功建立连接以后，就可以通信了。第一步是先找到当前外设提供的 service。调用CBPeripheralDelegatel的discoverServices:方法可以找到当前外设的所有 service。
- (void)peripheral:(CBPeripheral *)peripheral didDiscoverServices:(NSError *)error
{
if (error==nil)
{
//在这个方法中要查找到需要的服务 然后调用discoverCharacteristics方法查找需要的特性
//该discoverCharacteristics方法调用完后会调用代理CBPeripheralDelegate的
//- (void)peripheral:(CBPeripheral *)peripheral didDiscoverCharacteristicsForService:(CBService *)service error:(NSError *)error
for (CBService *service in peripheral.services)
{
if ([service.UUID isEqual:[CBUUID UUIDWithString:kServiceUUID]])
{
[CentralManager sharedInstance].cjFlag=0;
//[peripheral discoverCharacteristics:@[[CBUUID UUIDWithString:kCharacteristicUUID]] forService:service];
[peripheral discoverCharacteristics:nil forService:service];
}
else if ([service.UUID isEqual:[CBUUID UUIDWithString:kServiceUUID_cj]])
{
//[peripheral discoverCharacteristics:@[[CBUUID UUIDWithString:kCharacteristicUUID]] forService:service];
[CentralManager sharedInstance].cjFlag=1;
[peripheral discoverCharacteristics:nil forService:service];
}
}
}
}
在上面的方法中查找到需要的服务，然后调用discoverCharacteristics方法查找需要的特性:
- (void)discoverCharacteristics:(nullable NSArray *)characteristicUUIDs forService:(CBService *)service;
上述方法调用完后会调用代理方法didDiscoverCharacteristicsForService
- (void)peripheral:(CBPeripheral *)peripheral didDiscoverCharacteristicsForService:(CBService *)service error:(NSError *)error{
if (error==nil) {
//在这个方法中要找到我们所需的服务的特性 然后调用setNotifyValue方法告知我们要监测这个服务特性的状态变化
//当setNotifyValue方法调用后调用代理CBPeripheralDelegate的- (void)peripheral:(CBPeripheral *)peripheral didUpdateNotificationStateForCharacteristic:(CBCharacteristic *)characteristic error:(NSError *)error
for (CBCharacteristic *characteristic in service.characteristics)
{
if ([characteristic.UUID isEqual:[CBUUID UUIDWithString:kWriteCharacteristicUUID]])
{
[peripheral setNotifyValue:YES forCharacteristic:characteristic];
[CentralManager sharedInstance].activeWriteCharacteristic = characteristic;
}
else
if ([characteristic.UUID isEqual:[CBUUID UUIDWithString:kReadCharacteristicUUID]])
{
[peripheral setNotifyValue:YES forCharacteristic:characteristic];
[CentralManager sharedInstance].activeReadCharacteristic = characteristic;
}
else if ([characteristic.UUID isEqual:[CBUUID UUIDWithString:kFlowControlCharacteristicUUID]]) {
[peripheral setNotifyValue:YES forCharacteristic:characteristic];
[CentralManager sharedInstance].activeFlowControlCharacteristic = characteristic;
[CentralManager sharedInstance].credit = 0;
[CentralManager sharedInstance].response = 1;
}
else if ([characteristic.UUID isEqual:[CBUUID UUIDWithString:kWriteCharacteristicUUID_cj]]) {
[peripheral setNotifyValue:YES forCharacteristic:characteristic];
[CentralManager sharedInstance].activeWriteCharacteristic = characteristic;
}else if ([characteristic.UUID isEqual:[CBUUID UUIDWithString:kReadCharacteristicUUID_cj]]) {
[peripheral setNotifyValue:YES forCharacteristic:characteristic];
[CentralManager sharedInstance].activeReadCharacteristic = characteristic;
}
[self.deviceListTableView reloadData];
[self.scanConnectActivityInd stopAnimating];
self.tempActiveDevice = peripheral;
}
}
}
3.5 与外设进行数据交互
1）read方法时，回调updataValue；nofify时，notification回调一次后，updataValue再开始调，且不只一次；
2）接收 characteristic 数据的方式有两种：
在需要接收数据的时候，调用 readValueForCharacteristic:，这种是需要主动去接收的。
用 setNotifyValue:forCharacteristic: 方法订阅，当有数据发送时，可以直接在回调中接收。
向 characteristic 写数据
写数据其实是一个很常见的需求，如果 characteristic 可写，你可以通过CBPeripheral类的writeValue:forCharacteristic:type:方法来向设备写入NSData数据。
- (void)peripheral:(CBPeripheral *)peripheral didDiscoverCharacteristicsForService:(CBService *)service error:(NSError *)error{
if (error==nil) {
//在这个方法中要找到我们所需的服务的特性 然后调用setNotifyValue方法告知我们要监测这个服务特性的状态变化
//当setNotifyValue方法调用后调用代理CBPeripheralDelegate的- (void)peripheral:(CBPeripheral *)peripheral didUpdateNotificationStateForCharacteristic:(CBCharacteristic *)characteristic error:(NSError *)error
......
}
[[CentralManager sharedInstance].activeDevice writeValue:[NSData dataWithBytes:buf length:l] forCharacteristic:[CentralManager sharedInstance].activeWriteCharacteristic type:CBCharacteristicWriteWithResponse];
3.6 断开连接
首先调用CBCentralManager的cancelPeripheralConnection方法去断开连接
- (void)cancelPeripheralConnection:(CBPeripheral *)peripheral;
如果成功断开连接，调用didDisconnectPeripheral方法
- (void)centralManager:(CBCentralManager *)central didDisconnectPeripheral:(CBPeripheral *)peripheral error:(NSError *)error
{
NSLog(@"Peripheral Disconnected");
[[CentralManager sharedInstance].connectedDeviceArr removeObject:peripheral];
if ([[CentralManager sharedInstance].selectedDeviceList containsObject:peripheral]) {
[[CentralManager sharedInstance].selectedDeviceList removeObject:peripheral];
}
[self.deviceListTableView reloadData];
NSIndexPath *indexPath = [NSIndexPath indexPathForItem:[self.deviceList indexOfObject:peripheral] inSection:0];
BluetoothDeviceCell * cell = [self.deviceListTableView cellForRowAtIndexPath:indexPath];
cell.connectedStatus = NO;
// [self selectPrintDevice:cell];
}