delphi多线程文件复制怎么实现

在Delphi中，可以使用TThread类来实现多线程文件复制。以下是一个示例代码：

unit Unit1;  interface  uses   Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,   Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls;  type   TCopyThread = class(TThread)   private     FSourceFile: string;     FDestFile: string;   protected     procedure Execute; override;   public     constructor Create(const SourceFile, DestFile: string);   end;    TForm1 = class(TForm)     Button1: TButton;     procedure Button1Click(Sender: TObject);   private     FCopyThread: TCopyThread;     procedure CopyProgress(const BytesCopied, TotalBytes: Int64);   end;  var   Form1: TForm1;  implementation  {$R *.dfm}  constructor TCopyThread.Create(const SourceFile, DestFile: string); begin   inherited Create(True);   FSourceFile := SourceFile;   FDestFile := DestFile; end;  procedure TCopyThread.Execute; var   SourceStream, DestStream: TFileStream;   Buffer: array[0..8191] of Byte;   BytesRead, BytesWritten: Integer; begin   SourceStream := TFileStream.Create(FSourceFile, fmOpenRead or fmShareDenyWrite);   try     DestStream := TFileStream.Create(FDestFile, fmCreate);     try       repeat         BytesRead := SourceStream.Read(Buffer, SizeOf(Buffer));         if BytesRead > 0 then         begin           BytesWritten := DestStream.Write(Buffer, BytesRead);           if BytesWritten <> BytesRead then             Break;           Synchronize(procedure           begin             // 更新进度显示             Form1.CopyProgress(SourceStream.Position, SourceStream.Size);           end);         end;       until BytesRead = 0;     finally       DestStream.Free;     end;   finally     SourceStream.Free;   end; end;  procedure TForm1.Button1Click(Sender: TObject); begin   if FCopyThread = nil then   begin     FCopyThread := TCopyThread.Create('source.txt', 'dest.txt');     FCopyThread.FreeOnTerminate := True;     FCopyThread.Start;     Button1.Caption := '取消';   end   else   begin     FCopyThread.Terminate;     FCopyThread := nil;     Button1.Caption := '开始';   end; end;  procedure TForm1.CopyProgress(const BytesCopied, TotalBytes: Int64); begin   // 更新进度显示   Caption := Format('Copying %d/%d bytes', [BytesCopied, TotalBytes]); end;  end. 

以上代码实现了一个简单的多线程文件复制功能。在按钮点击事件中，会创建一个TCopyThread对象并启动线程进行文件复制。在TCopyThread.Execute方法中，会使用TFileStream读取源文件内容，并写入到目标文件中。在每次写入数据后，通过Synchronize方法来在主线程中更新进度显示。

在窗体上放置一个按钮，并将按钮的OnClick事件绑定到Button1Click方法。运行程序后，点击按钮即可开始或取消文件复制操作。同时，窗体的标题栏会实时显示复制进度。

注意：在复制大文件时，可能会导致界面假死。为了避免这种情况，可以考虑在复制过程中使用进度条或者其他方式显示进度。