TResourceStream 的进度条 (Delphi)

Question

如何将 ProgressBar 用于 SaveToFile 方法？实际上我想将资源保存到文件中，并在保存时将进度条从 0% 更新到 100%，我该怎么做？

Answer 1

您可以像下面的代码一样创建自己的 TResourceStream 后代。但对于大量资源（可能就是这种情况，否则您就不必看到进度）最好将其“包装”在单独的线程中。如果您需要帮助，请大声喊叫。

type
  TForm1 = class(TForm)
    Button: TButton;
    ProgressBar: TProgressBar;
    procedure ButtonClick(Sender: TObject);
  private
    procedure StreamProgress(Sender: TObject; Percentage: Single);
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

type
  TStreamProgressEvent = procedure(Sender: TObject;
    Percentage: Single) of object;

  TProgressResourceStream = class(TResourceStream)
  private
    FOnProgress: TStreamProgressEvent;
  public
    procedure SaveToFile(const FileName: TFileName);
    property OnProgress: TStreamProgressEvent read FOnProgress
      write FOnProgress;
  end;

{ TProgressResourceStream }

procedure TProgressResourceStream.SaveToFile(const FileName: TFileName);
var
  Count: Int64;
  Stream: TStream;
  BlockSize: Int64;
  P: PAnsiChar;
  WriteCount: Int64;
begin
  if Assigned(FOnProgress) then
  begin
    Count := Size;
    if Count <> 0 then
    begin
      Stream := TFileStream.Create(FileName, fmCreate);
      try
        if Count < 500 then
          BlockSize := 5
        else
          BlockSize := Count div 50;
        P := Memory;
        WriteCount := 0;
        while WriteCount < Count do
        begin
          if WriteCount < Count - BlockSize then
            Inc(WriteCount, Stream.Write(P^, BlockSize))
          else
            Inc(WriteCount, Stream.Write(P^, Count - WriteCount));
          Inc(P, BlockSize);
          FOnProgress(Self, WriteCount / Count);
        end;
      finally
        Stream.Free;
      end;
    end;
  end
  else
    inherited SaveToFile(FileName);
end;

{ TForm1 }

procedure TForm1.ButtonClick(Sender: TObject);
var
  Stream: TProgressResourceStream;
begin
  ProgressBar.Min := 0;
  Stream := TProgressResourceStream.Create(HInstance, 'TFORM1', RT_RCDATA);
  try
    Stream.OnProgress := StreamProgress;
    Stream.SaveToFile('TForm1.dat');
  finally
    Stream.Free;
  end;
end;

procedure TForm1.StreamProgress(Sender: TObject; Percentage: Single);
begin
  with ProgressBar do
    Position := Round(Percentage * Max);
end;

Answer 2

由于它继承自 TStream，因此您可以使用 Size 属性来获取总大小，使用 Position 属性来获取当前位置。您可以使用它们来“驱动”进度条。然后，您可以使用单独的 TFileStream 并从 TResourceStream 逐块写入文件，而不是使用 SaveToFile 写入文件。您可以对最后一部分使用 TStream.CopyFrom 方法。