Inno Setup，检测Java版本

使用Inno Setup安装Java应用程序时，我希望安装程序检查是否存在Java 7或更高版本，并在需要时进行安装。但是显然，我当前的代码无法在某些客户端的计算机上检测到Java 8。不过，我无法重现该错误。您看到我可能会想念的东西吗？也许这段代码不适用于最近的Windows？

基本上，我只检查Java> = 1.7的注册表。

[Code]

function InitializeSetup(): Boolean;
var
 ErrorCode: Integer;
 JavaInstalled : Boolean;
 ResultMsg : Boolean;
 Versions: TArrayOfString;
 I: Integer;
 regRoot: Integer;
begin
 { Check which view of registry should be taken: }
 regRoot := HKLM
 begin
  if IsWin64 then
  begin
   regRoot := HKLM64
  end;
 end;
 if (RegGetSubkeyNames(regRoot, 'SOFTWARE\JavaSoft\Java Runtime Environment', Versions)) or (RegGetSubkeyNames(regRoot, 'SOFTWARE\JavaSoft\Java Development Kit', Versions)) then
 begin
  for I := 0 to GetArrayLength(Versions)-1 do
   if JavaInstalled = true then
   begin
    //do nothing
   end else
   begin
    if ( Versions[I][2]='.' ) and ( ( StrToInt(Versions[I][1]) > 1 ) or ( ( StrToInt(Versions[I][1]) = 1 ) and ( StrToInt(Versions[I][3]) >= 7 ) ) ) then
    begin
     JavaInstalled := true;
    end else
    begin
     JavaInstalled := false;
    end;
   end;
 end else
 begin
  JavaInstalled := false;
 end;

 if JavaInstalled then
 begin
  Result := true;
 end else
 begin
  ResultMsg := MsgBox(ExpandConstant('{cm:JavaRequired}'), mbConfirmation, MB_YESNO) = idYes;
  if ResultMsg = false then
  begin
   Result := false;
  end else
  begin
   Result := true;
   ShellExec('open', 'http://www.java.com/getjava/', '','',SW_SHOWNORMAL,ewNoWait,ErrorCode);
  end;
 end;
end;

编辑：这是基于马丁的答案的最终结果。

[Code]
function CutJavaVersionPart(var V: string): Integer;
var
  S: string;
  P: Integer;
begin
  if Length(V) = 0 then
  begin
    Result := 0;
  end
    else
  begin
    P := Pos('.', V);
    if P = 0 then P := Pos('_', V);

    if P > 0 then
    begin
      S := Copy(V, 1, P - 1);
      Delete(V, 1, P);
    end
      else
    begin
      S := V;
      V := '';
    end;
    Result := StrToIntDef(S, 0);
  end;
end;

function MaxJavaVersion(V1, V2: string): string;
var
  Part1, Part2: Integer;
  Buf1, Buf2: string;
begin
  Buf1 := V1;
  Buf2 := V2;
  Result := '';
  while (Result = '') and
        ((Buf1 <> '') or (Buf2 <> '')) do
  begin
    Part1 := CutJavaVersionPart(Buf1);
    Part2 := CutJavaVersionPart(Buf2);
    if Part1 > Part2 then Result := V1
      else
    if Part2 > Part1 then Result := V2;
  end;
end;

function GetJavaVersion(): string;
var
  TempFile: string;
  ResultCode: Integer;
  S: AnsiString;
  P: Integer;
begin
  TempFile := ExpandConstant('{tmp}\javaversion.txt');
  if (not ExecAsOriginalUser(
            ExpandConstant('{cmd}'), '/c java -version 2> "' + TempFile + '"', '',
            SW_HIDE, ewWaitUntilTerminated, ResultCode)) or
     (ResultCode <> 0) then
  begin
    Log('Failed to execute java -version');
  end
    else
  if not LoadStringFromFile(TempFile, S) then
  begin
    Log(Format('Error reading file %s', [TempFile]));
  end
    else
  if Copy(S, 1, 14) <> 'java version "' then
  begin
    Log('Output of the java -version not as expected');
  end
    else
  begin
    Delete(S, 1, 14);
    P := Pos('"', S);
    if P = 0 then
    begin
      Log('Output of the java -version not as expected');
    end
      else
    begin
      SetLength(S, P - 1);
      Result := S;
    end;
  end;

  DeleteFile(TempFile);
end;

function HasJava1Dot7OrNewer: Boolean;
begin
  Result := (MaxJavaVersion('1.6.9', GetJavaVersion) <> '1.6.9');
end;

function InitializeSetup(): Boolean;
var
  ErrorCode: Integer;
begin
  Result := HasJava1Dot7OrNewer;
  if not Result then
  begin
    Result := MsgBox(ExpandConstant('{cm:JavaRequired}'), mbConfirmation, MB_YESNO) = idYes;
    if Result then
    begin
      ShellExec(
        'open', 'https://www.java.com/getjava/', '', '', SW_SHOWNORMAL, ewNoWait, ErrorCode);
    end;
  end;
end;