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业务背景
正如上篇iOS端智能硬件BLE通信技术实现一文所述,整个蓝牙库的最初设计实现最初都是为硬件通信服务的,19年年前突然接到需求,希望通过车载上放置的蓝牙收音设备,让用户在唤醒设备后,直接将用户的语音指令转成app里面可执行的操作,如“XXX, 播放每日XX的歌”,“XXX,上/下一首”等一些当前app用户常用的操作,产品希望通过这类车载设备来扩大app现有用户的使用场景甚至探寻增加新用户的可能。
现有问题
其实原app中蓝牙通信目前已经有两套代码了,一套用于早先的蓝牙耳机,一套用于硬件A业务,硬件A业务由于是18年11月才并入现有app的,存在两套代码也无可厚非,现在又增加了新的车载设备,难道再编写一套为车载设备而设计的蓝牙通信方案吗?作为一个有节操的程序媛,当然不可能这么做了!!
首先跟嵌入式端同学约定:车载设备的通信协议复用原有硬件A的那一套,这样数据收发处理(发送拆包接收组包)的代码就能复用,但是负责管理蓝牙一系列通信行为(扫描、停止扫描、连接、发现服务、断开连接、接收蓝牙数据等)以及提供发送数据接口和回调收到的数据给用户的VBBluetoothManager
类, 耦合了扫描硬件A的标识符serviceUUID
, 读写硬件A特征值的标识符characteristicUUID
, 甚至有在已扫描到的设备列表中根据硬件名称或UUID
查找特定设备的接口,其中的很多接口都是为硬件A通信服务的,先看下原有部分代码:
// from VBBluetoothManager.m, 以下...表示省略其他无关代码
@interface VBBluetoothManager ()<VBDataBridgeDelegate,CBCentralManagerDelegate,CBPeripheralDelegate>
{
...
NSArray *_serviceUUIDs;
NSMutableArray *_characterUUIDs;
...
}
@implementation VBBluetoothManager
- (instancetype)init {
if (self = [super init]) {
...
_serviceUUIDs = @[[VBUUIDUtil UUIDWithType:VBUUIDService]];
_characterUUIDs = [NSMutableArray array];
NSArray<NSNumber *> *cases = [VBUUIDUtil cases];
for (NSNumber *type in cases) {
if ([type integerValue] != VBUUIDService) {
[_characterUUIDs addObject:[VBUUIDUtil UUIDWithType:[type integerValue]]];
}
}
...
}
return self;
}
#pragma mark - Public Methods
// 扫描外设
- (void)scanWithDurationWithTimeout:(NSTimeInterval)timeout resetPrevScan:(BOOL)isReset {
if (isReset) {
[self resetScan];
}
// 前台时不指定serviceUUID去扫描(兼容嵌入式旧版本,旧版本蓝牙名称很长,超过了蓝牙广播包的长度限制,导致根据serviceUUID无法扫描到)
// 后台的话bluetooth state reservation and restoration要求一定要指定serviceUUID
NSArray *services = ([UIApplication sharedApplication].applicationState == UIApplicationStateActive) ? nil : _serviceUUIDs;
[_central scanForPeripheralsWithServices: services options:@{CBCentralManagerScanOptionAllowDuplicatesKey: @NO}];
// 先将之前的扫描取消
[NSObject cancelPreviousPerformRequestsWithTarget:self selector:@selector(endScanForPeriphers) object:nil];
[self performSelector:@selector(endScanForPeriphers) withObject:nil afterDelay:timeout];
}
// 取消所有连接
- (void)cancelAllConnections {
_isManualDisconnect = YES;
for (CBPeripheral *peripheral in [_central retrieveConnectedPeripheralsWithServices:_serviceUUIDs]) {
[_central cancelPeripheralConnection:peripheral];
}
}
// 设备连接成功后,在发送数据前先发现服务
- (void)startDiscoverServiceForPeripheral:(CBPeripheral *)peripheral {
BOOL canSendData = [self canSendDataForPeripheral:peripheral];
peripheral.delegate = self;
if (canSendData) {
[self constructDataBridges:peripheral];
return;
}
[peripheral discoverServices:_serviceUUIDs];
}
#pragma mark - Private Methods
// 能否向外设发送数据
- (BOOL)canSendDataForPeripheral:(CBPeripheral *)peripheral {
BOOL isRxCharacterNotify = NO;
BOOL isCtsCharacterNotify = NO;
for (CBCharacteristic *character in [peripheral.services.firstObject characteristics]) {
VBUUIDType uuidType = [VBUUIDUtil typeForUUID:character.UUID];
switch (uuidType) {
case VBUUIDRxCharacteristic:
isRxCharacterNotify = character.isNotifying;
break;
case VBUUIDCtsCharacteristic:
isCtsCharacterNotify = character.isNotifying;
default:
break;
}
}
// 只有在cts和rx通道都开启的情况下,才能发送数据
BOOL canSendData = isRxCharacterNotify && isCtsCharacterNotify;
return canSendData;
}
// 根据外设实例构造数据加工处理的桥接类
- (void)constructDataBridges:(CBPeripheral *)peripheral {
CBService *primaryService = peripheral.services.firstObject;
NSArray<CBCharacteristic *> *characteristics = primaryService.characteristics;
if (!characteristics) {
return;
}
CBCharacteristic *txWriteCharacter;
CBCharacteristic *rxReceiveCharacter;
for (CBCharacteristic *character in characteristics) {
VBUUIDType uuidType = [VBUUIDUtil typeForUUID:character.UUID];
if (uuidType == VBUUIDNone) {
break;
} else if (uuidType == VBUUIDTxCharacteristic) {
txWriteCharacter = character;
} else {
if (uuidType == VBUUIDRxCharacteristic) {
rxReceiveCharacter = character;
}
if (!character.isNotifying) {
[peripheral setNotifyValue:YES forCharacteristic:character];
}
}
}
if (txWriteCharacter && rxReceiveCharacter) {
NSUInteger index = [self peripheralIndexAtDataBridges:peripheral];
// 移除旧的
if (index != NSNotFound) {
[_dataBridges removeObjectAtIndex:index];
}
VBDataBridge *bridge = [[VBDataBridge alloc] initWithPeripheral:peripheral writeCharacter:txWriteCharacter receiveCharacter:rxReceiveCharacter];
bridge.delegate = self;
[_dataBridges addObject:bridge];
}
}
#pragma mark - CBCentralManager delegate
- (void)centralManager:(CBCentralManager *)central didDiscoverPeripheral:(CBPeripheral *)peripheral advertisementData:(NSDictionary<NSString *,id> *)advertisementData RSSI:(NSNumber *)RSSI {
if (peripheral && ![_peripherals containsObject:peripheral] && [peripheral.name hasPrefix:@"硬件A的名称"]) {
[_peripherals addObject:peripheral];
for (id<VBBluetoothManagerDelegate> observer in _delegateObservers) {
NSAssert([NSThread isMainThread], @"非主线程");
if ([observer respondsToSelector:@selector(bluetoothManager:didFindNewPeripheral:)]) {
[observer bluetoothManager:self didFindNewPeripheral:peripheral];
}
}
}
}
#pragma mark - CBPeripheral delegate
// 1. 找到服务
- (void)peripheral:(CBPeripheral *)peripheral didDiscoverServices:(NSError *)error {
NSArray<CBService *> *services = peripheral.services;
if (!services) {
return;
}
for (CBService *service in services) {
[peripheral discoverCharacteristics:_characterUUIDs forService:service];
}
}
// 2. 找到特征
- (void)peripheral:(CBPeripheral *)peripheral didDiscoverCharacteristicsForService:(CBService *)service error:(NSError *)error {
[self constructDataBridges:peripheral];
}
...
@end
从以上未重构之前的VBBluetoothManager
类的代码可以看到:该类确实耦合了大量跟特定外设信息相关的代码,导致现在新增加一种车载外设,却无法走通同样的通信流程。
解决方案
1. 抽取公共属性和方法
Untitled.gif(1) ServiceUUIDs: 扫描外设时所用到的服务UUID数组;
(2) CharacterUUIDs: 读写数据特征和订阅特征的UUID数组;
(3) rxCharacterUUID: 嵌入式端告知的读数据的特征UUID,和txCharacterUUID一起用于构造数据加工处理类VBDataBridge实例,后者主要的作用是:收到数据处理的请求,交由VBDataBridge去决定是该接收类receiver去组装数据,还是sender类去拆包分次发送数据;
(4) txCharacterUUID: 嵌入式端告知的写数据的特征UUID,作用如上所述;
(5) peripheral: CBPeripheral
实例类, 用该实例包装生成自己的蓝牙外设类,判断当前能否发送数据(canSendData)、开启订阅特征(notifyCharacter)等都需从该实例中执行相应操作;
(6) peripheralType: 外设类型,已知的外设类型枚举;
(7) prefixName: 外设的名称前缀;
(8) canSendData: 能否向外设发送数据,只有写数据通道处于notifying状态才可写;
(9) notifyCharacterForService:completionBlock::开启可读取或订阅特征的通道,并把对应的特征值通过block传回给调用方。
typedef void(^NotifyCharacterBlock)(CBCharacteristic *txWriteCharacter, CBCharacteristic *rxReceiveCharacter);
typedef NS_ENUM(NSInteger, VBPeripheralType) {
VBPeripheralTypeUnknown,
VBPeripheralTypeVbox,
VBPeripheralTypeCarplay,
};
@protocol VBPeripheralProtocol <NSObject>
+ (NSString *)prefixName;
@end
// interface
@interface VBPeripheral : NSObject
@property (nonatomic, assign, readonly) VBPeripheralType type;
@property (nonatomic, strong) CBPeripheral *peripheral;
@property (nonatomic, copy, readonly) NSArray<CBUUID *> *services;
@property (nonatomic, copy, readonly) NSArray<CBUUID *> *characterUUIDs;
@property (nonatomic, copy, readonly) CBUUID *rxCharacterUUID;
@property (nonatomic, copy, readonly) CBUUID *txCharacterUUID;
+ (instancetype)peripheralWithCBPeripheral:(CBPeripheral *)peripheral;
- (BOOL)canSendData;
- (void)notifyCharactersForService:(CBService *)service completionBlock:(NotifyCharacterBlock)completion;
@end
// implementation
@implementation VBPeripheral
- (instancetype)initWithPeripheral:(CBPeripheral *)peripheral {
self = [super init];
if (self) {
_peripheral = peripheral;
}
return self;
}
+ (instancetype)peripheralWithCBPeripheral:(CBPeripheral *)peripheral {
if ([peripheral.name hasPrefix:[VBVboxPeripheral prefixName]]) {
return [[VBVboxPeripheral alloc] initWithPeripheral:peripheral];
} else if ([peripheral.name hasPrefix:[VBCarplayPeripheral prefixName]]) {
return [[VBCarplayPeripheral alloc] initWithPeripheral:peripheral];
} else {
return nil;
}
}
@end
2. 子类化对应外设模型
目前已知有两种蓝牙外设:硬件A和车载,每种设备有自己的服务和特征UUID,我们需要在具体的外设模型中实现上面抽象出来的属性和接口。
2.1 扩展VBUUIDType
枚举类型
typedef NS_ENUM(NSInteger, VBUUIDType)
{
VBUUIDNone = 0,
// 车载设备的UUID
VBCarplayServiceType = 0xFE00,
VBCarplayTxCharacteristicType= 0xFE01,
VBCarplayRxCharacteristicType = 0xFE02,
// 硬件设备的UUID
VBVboxServiceType = 0xFFF0,
VBVboxTxCharacteristicType = 0xFFF1, // 手机向硬件发送LE数据的链路
VBVboxRxCharacteristicType = 0xFFF2, // 手机从硬件接收LE数据的链路
VBVboxCtsCharacteristicType = 0xFFF3, // 标识手机是否可以继续向硬件发送数据的链路,
};
2.2 硬件A外设模型
// interface
#import "VBPeripheralProtocol.h"
@interface VBVboxPeripheral :VBPeripheral
@end
// implementation
@implementation VBVboxPeripheral
- (VBPeripheralType)type {
return VBPeripheralTypeVbox;
}
- (NSArray<CBUUID *> *)services {
CBUUID *vboxService = [VBUUIDUtil UUIDWithType: VBVboxServiceType];
return @[vboxService];
}
- (NSArray<CBUUID *> *)characterUUIDs {
CBUUID *ctsCharacterUUID = [VBUUIDUtil UUIDWithType:VBVboxCtsCharacteristicType];
return @[self.txCharacterUUID, self.rxCharacterUUID, ctsCharacterUUID];
}
- (CBUUID *)txCharacterUUID {
return [VBUUIDUtil UUIDWithType:VBVboxTxCharacteristicType];
}
- (CBUUID *)rxCharacterUUID {
return [VBUUIDUtil UUIDWithType:VBVboxRxCharacteristicType];
}
- (BOOL)canSendData {
BOOL isRxCharacterNotify = NO;
BOOL isCtsCharacterNotify = NO;
for (CBCharacteristic *character in [self.peripheral.services.firstObject characteristics]) {
VBUUIDType uuidType = [VBUUIDUtil typeForUUID:character.UUID];
switch (uuidType) {
case VBVboxRxCharacteristicType:
isRxCharacterNotify = character.isNotifying;
break;
case VBVboxCtsCharacteristicType:
isCtsCharacterNotify = character.isNotifying;
default:
break;
}
}
// 硬件设备只有在cts和rx都开启的情况下,才能发送数据
BOOL canSendData = isRxCharacterNotify && isCtsCharacterNotify;
return canSendData;
}
- (void)notifyCharactersForService:(CBService *)service completionBlock:(NotifyCharacterBlock)completion {
CBCharacteristic *txWriteCharacter;
CBCharacteristic *rxReceiveCharacter;
for (CBCharacteristic *character in service.characteristics)
{
VBUUIDType uuidType = [VBUUIDUtil typeForUUID:character.UUID];
switch (uuidType)
{
case VBVboxTxCharacteristicType:
txWriteCharacter = character;
break;
case VBVboxRxCharacteristicType:
rxReceiveCharacter = character;
[self.peripheral setNotifyValue:YES forCharacteristic:character];
break;
case VBVboxCtsCharacteristicType:
[self.peripheral setNotifyValue:YES forCharacteristic:character];
break;
default:
break;
}
}
completion(txWriteCharacter, rxReceiveCharacter);
}
+ (NSString *)prefixName {
return @"硬件A的名称";
}
@end
2.3 车载外设模型
// interface
#import "VBPeripheralProtocol.h"
@interface VBCarplayPeripheral :VBPeripheral
@end
// implementation
@implementation VBCarplayPeripheral
- (VBPeripheralType)type {
return VBPeripheralTypeCarplay;
}
- (NSArray<CBUUID *> *)services {
CBUUID *carplayService = [VBUUIDUtil UUIDWithType:VBCarplayServiceType];
return @[carplayService];
}
- (NSArray<CBUUID *> *)characterUUIDs {
return @[self.txCharacterUUID, self.rxCharacterUUID];
}
- (CBUUID *)txCharacterUUID {
return [VBUUIDUtil UUIDWithType:VBCarplayTxCharacteristicType];
}
- (CBUUID *)rxCharacterUUID {
return [VBUUIDUtil UUIDWithType:VBCarplayRxCharacteristicType];
}
- (BOOL)canSendData {
// 车载设备只要rx通道打开就能发送数据
BOOL isRxNotifying = NO;
for (CBCharacteristic *character in [self.peripheral.services.firstObject characteristics]) {
VBUUIDType uuidType = [VBUUIDUtil typeForUUID:character.UUID];
if (uuidType == VBCarplayRxCharacteristicType) {
isRxNotifying = character.isNotifying;
break;
}
}
return isRxNotifying;
}
- (void)notifyCharactersForService:(CBService *)service completionBlock:(NotifyCharacterBlock)completion {
CBCharacteristic *txWriteCharacter;
CBCharacteristic *rxReceiveCharacter;
for (CBCharacteristic *character in service.characteristics)
{
VBUUIDType uuidType = [VBUUIDUtil typeForUUID:character.UUID];
switch (uuidType)
{
case VBCarplayTxCharacteristicType:
txWriteCharacter = character;
break;
case VBCarplayRxCharacteristicType:
rxReceiveCharacter = character;
[self.peripheral setNotifyValue:YES forCharacteristic:character];
break;
default:
break;
}
}
completion(txWriteCharacter, rxReceiveCharacter);
}
+ (NSString *)prefixName {
return @"NeVSPS";
}
3. 重构VBBluetoothManager
类
在VBBluetoothManager
类的原有代码中,替换原先用到serviceUUIDs、characterUUIDs以及能否判断能否向外设发送代码的业务逻辑:
@interface VBBluetoothManager ()
{
NSArray<CBUUID *> *_serviceUUIDs;
}
@end
@implementation VBBluetoothManager
- (instancetype)init {
self = [super init];
if (self) {
...
_serviceUUIDs = @[
[VBUUIDUtil UUIDWithType: VBVboxServiceType],
[VBUUIDUtil UUIDWithType: VBCarplayServiceType]];
...
}
return self;
}
- (void)startDiscoverServiceForPeripheral:(CBPeripheral *)peripheral {
BOOL canSendData = [self canSendDataForPeripheral:peripheral];
NELogVerbose(@"%s %@", __func__, @(canSendData));
peripheral.delegate = self;
id<VBPeripheralProtocol> vbPeripheral = [VBPeripheral peripheralWithCBPeripheral:peripheral];
if ([vbPeripheral canSendData]) {
return;
}
[peripheral discoverServices:vbPeripheral.services];
}
- (void)centralManager:(CBCentralManager *)central didDiscoverPeripheral:(CBPeripheral *)peripheral advertisementData:(NSDictionary<NSString *,id> *)advertisementData RSSI:(NSNumber *)RSSI {
BOOL isVboxPeripheral = [peripheral.name hasPrefix:[VBVboxPeripheral prefixName]];
BOOL isCarplayPeripheral = [peripheral.name hasPrefix:[VBCarplayPeripheral prefixName]];
if (peripheral && ![_peripherals containsObject:peripheral] &&
(isVboxPeripheral || isCarplayPeripheral)) {
[_peripherals addObject:peripheral];
for (id<VBBluetoothManagerDelegate> observer in _delegateObservers) {
NSAssert([NSThread isMainThread], @"非主线程");
if ([observer respondsToSelector:@selector(bluetoothManager:didFindNewPeripheral:)]) {
[observer bluetoothManager:self didFindNewPeripheral:peripheral];
}
}
}
}
#pragma mark - CBPeripheral delegate
// 1. 找到服务
- (void)peripheral:(CBPeripheral *)peripheral didDiscoverServices:(NSError *)error {
id<VBPeripheralProtocol> vbPeripheral = [VBPeripheral peripheralWithCBPeripheral:peripheral];
for (CBService *service in peripheral.services) {
[peripheral discoverCharacteristics:vbPeripheral.characterUUIDs forService:service];
}
}
// 2. 找到特征
- (void)peripheral:(CBPeripheral *)peripheral didDiscoverCharacteristicsForService:(CBService *)service error:(NSError *)error {
id<VBPeripheralProtocol> vbPeripheral = [VBPeripheral peripheralWithCBPeripheral:peripheral];
[vbPeripheral notifyCharactersForService:service completionBlock:^(CBCharacteristic *txWriteCharacter, CBCharacteristic *rxReceiveCharacter) {
if (txWriteCharacter && rxReceiveCharacter) {
NSUInteger index = [self peripheralIndexAtDataBridges:peripheral];
// 移除旧的
if (index != NSNotFound) {
[_dataBridges removeObjectAtIndex:index];
}
VBDataBridge *bridge = [[VBDataBridge alloc] initWithPeripheral:peripheral writeCharacter:txWriteCharacter receiveCharacter:rxReceiveCharacter];
bridge.delegate = self;
[_dataBridges addObject:bridge];
}
}];
}
...
@end
至此,重构蓝牙管理类以支持多种设备的蓝牙数据通信工作就完成了,至于接收到数据之后,上层怎么处理又是另外一回事了,在此不谈。
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