Inno Setup：如何实现下载文件哈希错误的美观任务对话框展示

I get it, the default error message for hash mismatches during downloads is pretty barebones and not user-friendly. Let's fix that by catching the exception, extracting critical details (filename, expected/found hashes), and displaying them in a clean, informative task dialog.

Modified NextButtonClick Function #

Replace your existing except block with the code below to add the customized error handling:

function NextButtonClick(CurPageID: integer): boolean;
var
  ExpectedHash, FoundHash, FileName: string;
  MsgParts: TArrayOfString;
begin
  Result := True;
  if (CurPageID = wpSelectTasks) then
  begin
    DownloadPage.Clear;
    if (WizardIsTaskSelected('downloadhelp')) then
      AddFileForDownload('{#HelpDocSetupURL}', 'HelpDocSetup.exe', '{#GetSHA256OfFile("..\HelpNDoc\CHM\Output\MSAHelpDocumentationSetup.exe")}');
  end
  else if (CurPageID = wpReady) then
  begin
    DownloadPage.Show;
    try
      try
        DownloadPage.Download;
        Result := True;
      except
        // Initialize fallback values
        ExpectedHash := 'N/A';
        FoundHash := 'N/A';
        FileName := 'Unknown file';

        // Get the failed filename from DownloadPage's failed files list
        if DownloadPage.FailedFiles.Count > 0 then
          FileName := ExtractFileName(DownloadPage.FailedFiles[0]);

        // Parse the exception message to extract hash values
        MsgParts := SplitString(GetExceptionMessage, ': ');
        if Length(MsgParts) >= 2 then
        begin
          MsgParts := SplitString(MsgParts[1], ', ');
          if Length(MsgParts) >= 2 then
          begin
            // Strip the "expected " prefix to get the raw hash
            ExpectedHash := Trim(Copy(MsgParts[0], 10, MaxInt));
            // Strip the "found " prefix to get the raw hash
            FoundHash := Trim(Copy(MsgParts[1], 7, MaxInt));
          end;
        end;

        // Display the customized task dialog with all details
        SuppressibleTaskDialogMsgBox(
          Format('Unable to download %s', [FileName]),
          Format('The file checksum does not match:'#13#10 +
                 'Expected SHA-256 hash: %s'#13#10 +
                 'Found SHA-256 hash: %s', [ExpectedHash, FoundHash]),
          mbError, MB_OK, ['OK'], 0, IDOK);
        
        Result := False;
      end;
    finally
      DownloadPage.Hide;
    end;
  end;
end;

Key Details Explained #

• Failed File Context: We use DownloadPage.FailedFiles to fetch the name of the problematic file—this lets the user know exactly which download failed, adding critical context.
• Exception Message Parsing: The default error message follows your ErrorFileHash2 template. We split this string to pull out the expected and actual hash values, so we can display them clearly instead of a generic message.
• Clean Dialog Layout: Using SuppressibleTaskDialogMsgBox creates a modern dialog with a clear title and formatted details (line breaks separate the hash values for easy readability).

Notes #

• Ensure you're using Inno Setup 5.6 or later—SplitString is a built-in function available from this version onwards.
• If you've modified the ErrorFileHash2 message template, adjust the string parsing logic (like the Copy offsets) to match your custom message format.

内容的提问来源于stack exchange，提问作者Andrew Truckle