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。
更多请参考：
苹果官方文档
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);
}
