谁给解释一下这段代码？
{***************************************************************************** *本单元说明：串口通信封装类 ****************************************************************************}unit COMDevIO; interface uses SysUtils, Forms, CPort; type TOnDataReceived = procedure(const AStr: string) of object; type TCOMDevIO = class private //串口通信对象 fPort: TComPort; //串口通信接收对象 fPortDataPacket: TComDataPacket; //数据接收回调函数 fOnDataReceived: TOnDataReceived; private //数据接收处理 procedure PortDataPacketPacket(Sender: TObject; const Str: String); public //创建 constructor Create(ACOM: Byte); //设置通信参数 procedure setParameters(ACOM: Byte; ABaudRate: TBaudRate = br9600; ADataBits: TDataBits = dbSeven; AParityBit: TParityBits = prOdd; AParityCheck: Boolean = True; AStopBit: TStopBits = sbTwoStopBits); //设置通信超时 procedure setWriteTotal(t: Integer); //打开串口 function openCOM(ACOM: Byte): Boolean; //关闭串口 procedure close; //发送数据 function sendData(const AStr: string): Boolean; //设置数据接收函数 procedure setOnDataReceived(AOnDataReceived: TOnDataReceived); end; implementation uses LogUnit; { TCOMDevIO } constructor TCOMDevIO.Create(ACOM: Byte);begin fPort := TComPort.Create(Application.MainForm); if ACOM > 0 then begin fPort.Port := 'COM' + IntToStr(ACOM); end; fPort.BaudRate := br9600; fPort.DataBits := dbSeven; fPort.StopBits := sbTwoStopBits; fPort.Parity.Bits := prOdd; fPort.Parity.Check := TRUE; fPort.DiscardNull := FALSE ; fPort.EventChar := #13; fPort.Events := [evRxChar]; fPort.Timeouts.ReadInterval := -1; fPort.Timeouts.ReadTotalMultiplier := 0; fPort.Timeouts.ReadTotalConstant := 0; fPort.Timeouts.WriteTotalConstant := 1000; fPort.Timeouts.WriteTotalMultiplier := 100; fPortDataPacket := TComDataPacket.Create(fPort); fPortDataPacket.OnPacket := PortDataPacketPacket; fPortDataPacket.ComPort := fPort; fPortDataPacket.MaxBufferSize := 1024; fPortDataPacket.CaseInsensitive := False; fPortDataPacket.IncludeStrings := False; fPort.SyncMethod := smThreadSync;end; procedure TCOMDevIO.setParameters(ACOM: Byte; ABaudRate: TBaudRate = br9600; ADataBits: TDataBits = dbSeven; AParityBit: TParityBits = prOdd; AParityCheck: Boolean = True; AStopBit: TStopBits = sbTwoStopBits);begin // note: 尽量不要在已打开串口的情况下修改参数 fPort.BaudRate := ABaudRate; fPort.DataBits := ADataBits; fPort.Parity.Bits := AParityBit; fPort.Parity.Check := AParityCheck; fPort.StopBits := AStopBit;end; procedure TCOMDevIO.setWriteTotal(t: Integer);begin fPort.Timeouts.WriteTotalConstant := t;end; function TCOMDevIO.openCOM(ACOM: Byte): Boolean;var Port: TPort;begin Result := False; Port := 'COM' + IntToStr(ACOM); fPort.Close; if fPort.Port <> Port then begin // note: 如果以前串口已经打开，执行下面的语句会更换串口号后打开串口 fPort.Port := Port; end; try fPort.Open; Result := fPort.Connected; except On E: Exception do begin WriteLog(Format('无法打开串口:%d, %s', [ACOM, E.Message])); end; end;end; procedure TCOMDevIO.close;begin fPort.Close;end; procedure TCOMDevIO.PortDataPacketPacket(Sender: TObject; const Str: String);begin if Assigned(fOnDataReceived) then begin fOnDataReceived(Str); end;end; function TCOMDevIO.sendData(const AStr: string): Boolean;begin Result := False; try if not fPort.Connected then begin Exit; end; fPort.WriteStr(AStr); // ErrorLog('TCOMDevIO.SendData:'+TransHexStr(AStr)); Result := True; except On E: Exception do begin WriteLog('向串口发送数据出现异常: '+E.Message); end; end;end; procedure TCOMDevIO.setOnDataReceived(AOnDataReceived: TOnDataReceived);begin fOnDataReceived := AOnDataReceived;end; end.
这不就是个操作串口的吗，有什么好解释的，而且注释也能看明白
TOnDataReceived 是个方法类型，用作事件，没有执行，是因为这个事件时有外部关联的，当外部对这个事件做了定以后，就会触发，就行button的OnClick
[解决办法]
在这里是一个回调函数,是封装在另外的地方，比如在dll中
当setOnDataReceived这个方法触发时，就会执行dll中对应的这个函数
即procedure xx(const AStr: string);
[解决办法]
首先,你要理解,串口对象是用来做什么事情的.比如打印的接口,一些硬件的驱动等.
然后,要使用某对象,最简单的思路就是:对象的创建(Create)->对象的初始化设置参数(setParameters)->对象的应用(此为串口,如果打开就返回此串口,如果没打开,就重新注册生成新的串口,这相当与设计模式中的单例模式,一个类(此处是串口)只能有一个该类的实例(串口对象))->对象的销毁.
按照这个思路再重新理解你的代码.