Mac开发之MIDI通讯

笔者最近在做Mac软件与MIDI 设备通讯的项目，苦于国内没有教程和实战，摸爬滚打很久才终于整通，现分享于大家。

下文代码实例：
MIDI Demo

关于MIDI通讯需要了解的一些基本名词，因为iOS 开发或者是Mac OS 开发基本上都没见过这种，所以为了好理解先列出来一些基本的：

维护客户端对象（MIDIClientRef）
输入端口（MIDIInputPortCreate）
输出端口（MIDIOutputPortCreate）
客户端拥有的MIDI连接端口（MIDIPortRef）
返回系统中的一个数据源一般后面类似数组接（N）（MIDIGetSource）
可以理解为MIDI数据包格式，常见数据需要处理成这样传至MIDI设备（MIDIPacketList）
传值至MIDI设备（MIDISend）

MIDI 大概流程及代码

.h 文件：

#import <Foundation/Foundation.h>
#import <CoreMIDI/CoreMIDI.h>

@protocol MidiGetDataDelegate <NSObject>   // 下位机返回数据代理
- (void)responeMidiGetData:(NSData *)getData;
@end

@interface MIDIManager : NSObject
{
    MIDIClientRef client;
    MIDIPortRef inputPort;
    MIDIPortRef outputPort;
    //用于存储MIDI源ID的唯一ID数组
    MIDIUniqueID idArray[256];
    
}

- (void)responeMidiGetData:(id<MidiGetDataDelegate>)delegate;

//返回数据缓存区
@property (nonatomic, strong) NSMutableData * muData;
@property (nonatomic, weak) id<MidiGetDataDelegate> infoDelegate;

//创建MIDI 输入端口 输出端口
- (id)initWithClientName: (NSString *)clientName inPort: (NSString *)iPort outPort: (NSString *)oPort;

//传数据到下位机
- (void)sendData:(NSData *)data;

//获取设备名字
- (NSString *)getDeviceName;

@end

.m 文件：

#import "MIDIManager.h"

@implementation MIDIManager

- (id)initWithClientName:(NSString *)clientName inPort:(NSString *)iPort outPort:(NSString *)oPort {
    if (self = [super init]) {
        
        _muData = [NSMutableData data];
        [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(receiveData:)name:@"receiveData" object:nil];
        
        // 如果存在，请处理旧的MIDI客户端
        if (client != (MIDIObjectRef)NULL) MIDIClientDispose(client);
        
        // 创建一个MIDI客户端
        MIDIClientCreate(CFSTR("Client"), MyMIDIStateChangedHander, (__bridge void *)(self), &client);
        
        
        // 列举所有MIDI来源
        ItemCount sourceCount = MIDIGetNumberOfSources();
        NSAssert(sourceCount < sizeof(idArray), @"ID buffer size is smaller than the nuber of MIDI sources.");
        
        // 将MIDI源连接到输入端口
        MIDIEndpointRef source = MIDIGetSource(0);
        MIDIObjectGetIntegerProperty(source, kMIDIPropertyUniqueID, &idArray[0]);
        MIDIOutputPortCreate(client, (__bridge CFStringRef)oPort, &outputPort);
        MIDIInputPortCreate(client, (__bridge CFStringRef)iPort, MyMIDIReadProc, (__bridge void *)(self), &inputPort);
        MIDIPortConnectSource(outputPort, source, &idArray[0]);
        MIDIPortConnectSource(inputPort, source, &idArray[0]);

    }
    return self;
}

//传数据到下位机
- (void)sendData:(NSData *)data
{
    NSLog(@"传至下位机数据内容 %@",data);
    
    // 传数据到MIDI源
    
    MIDIEndpointRef outputEndpoint = MIDIGetDestination(0);
    
    Byte *sendData = (Byte*)[data bytes];
    
    char buffer[1024];
    MIDIPacketList *packets = (MIDIPacketList *)buffer;
    
    MIDIPacket *packet = MIDIPacketListInit(packets);
    
    packet = MIDIPacketListAdd(packets, 1024, packet, 0, data.length, sendData);
    
    [self sendDataToMIDI:outputPort :outputEndpoint :packets];
   
}


//传数据到MIDI
-(void)sendDataToMIDI:(MIDIPortRef )inputPort :(MIDIEndpointRef)outputEndpoint :(MIDIPacketList *)packets
{
    MIDISend(inputPort, outputEndpoint, packets);
}

//获取设备名字
- (NSString *)getDeviceName
{
    MIDIEndpointRef source = MIDIGetSource(0);
    // 从MIDI源检索信息
    CFStringRef name;
    MIDIObjectGetStringProperty(source, kMIDIPropertyDisplayName, &name);
    
    NSString *deviceName = [NSString stringWithFormat:@"(%08X)", idArray[0]];
    return deviceName;
}

//监控MIDI设备状态
static void MyMIDIStateChangedHander(const MIDINotification *message, void *refCon)
{
    // 只处理添加和删除操作
    if (message->messageID != kMIDIMsgObjectAdded && message->messageID != kMIDIMsgObjectRemoved) return;
    
    // 只有过程源操作
    const MIDIObjectAddRemoveNotification *addRemoveDetail = (const MIDIObjectAddRemoveNotification*)message;
    if (addRemoveDetail->childType != kMIDIObjectType_Source) return;
    // 向应用程序委托发送更新消息(在主线程上)
    NSLog(@"%@",@"检测到MIDI状态的变化");
}

//接收MIDI数据
static void MyMIDIReadProc(const MIDIPacketList *packetList, void *readProcRefCon, void *srcConnRefCon)
{
    
    NSLog(@"我拿到MIDI返回的数据");
    
    // 处理所有传入的数据包.
    MIDIPacket *packet = (MIDIPacket *) packetList->packet;
    NSData *receiveData = [[NSData alloc] initWithBytes:packet->data length:packet->length];
    
    NSNotification *notification =[NSNotification notificationWithName:@"receiveData" object:receiveData userInfo:nil];
    [[NSNotificationCenter defaultCenter] postNotification:notification];

}

- (void)receiveData:(NSNotification *)nottext
{
    //清除 aa之前的数据
    Byte *testByte = (Byte*)[nottext.object bytes];
    NSString *bytesStr = [NSString stringWithFormat:@"%1x", testByte[0]];
    if ([bytesStr  isEqual: @"aa"]) {
        [self emptyData];
    }
    
    //添加 到数据集
    [_muData appendData:nottext.object];
    
    if ([self.infoDelegate respondsToSelector:@selector(responeMidiGetData:)]) {
        [self.infoDelegate responeMidiGetData:_muData];
    }
    return;
}

- (void)emptyData
{
    [_muData resetBytesInRange:NSMakeRange(0, _muData.length)];
    [_muData setLength:0];
}

- (void)responeMidiGetData:(id<MidiGetDataDelegate>)delegate
{
    self.infoDelegate = delegate;
}

@end

VC 中创建与使用（记得添加头文件）：

    //创建MIDI
    midi = [[MIDIManager alloc]initWithClientName:@"Client" inPort:@"portName" outPort:@"portName"];
    midi.infoDelegate = self;//加载返回数据代理
    NSLog(@"MIDI设备名字 ： %@",[midi getDeviceName]);

MIDI 传值

    Byte testData[] = {0xAA,0x55,0xff,0xff};
    NSData *testSendData = [[NSData alloc] initWithBytes:testData length:4];
    [midi sendData:testSendData];

MIDI接收

//MIDI返回数据代理
- (void)responeMidiGetData:(NSData *)getData
{
    NSLog(@"我是通过代理拿到的数据 %@",getData);
}