创新设置:检查新更新

分类: 技术问答 • 2022-06-07 19:00:14

问题描述：

在阅读了这篇文章如何从Internet资源中读取文本文件?之后，我已经将代码修改为适合我的代码需要，但我有一些问题.

After reading this post How to read a text file from the Internet resource?, I've adapted the code to what I need but I have some problems.

我想做的是，当我运行安装程序时，它会检查是否有新的更新. 1)如果没有新的更新，则不显示任何消息. 2)如果有新更新，请显示一条消息，询问您是否要下载它.

What I want to do is that when I run the setup, it checks for new updates. 1) If there isn't a new update, don't show any message. 2) And if there is a new update, show a message asking whether you want to download it or not.

这是我的代码:

procedure InitializeWizard;
var
  DxLastVersion: string;
  DxSetupVersion: String;

begin
  if DownloadFile('http://dex.wotanksmods.com/latestver.txt', DxLastVersion)  then
    MsgBox(DxLastVersion, mbInformation, MB_YESNO)
  else
    MsgBox(DxLastVersion, mbError, MB_OK)
end;

非常感谢您.

答

由于您已决定使用通用的版本字符串模式，因此需要一个函数来解析和比较您的设置中的版本字符串从您的网站下载.而且由于Inno Setup中没有内置此类功能，因此您需要拥有自己的功能.

Since you've decided to use a common version string pattern, you'll need a function which will parse and compare a version string of your setup and the one downloaded from your site. And because there is no such function built-in in Inno Setup, you'll need to have your own one.

我已经看到了一些用于比较版本字符串的函数，例如 this script 中使用的那个，但我已经决定写我自己的.它可以检测到无效的版本字符串，并将缺少的版本块视为0，这将导致如下所示的版本字符串比较相等:

I've seen a few functions for comparing version strings, like e.g. the one used in this script, but I've decided to write my own. It can detect an invalid version string, and treats the missing version chunks as to be 0, which causes comparison of version strings like follows to be equal:

1.2.3
1.2.3.0.0.0

以下脚本可能会满足您的要求(安装版本由 AppVersion 指令):

The following script might do what you want (the setup version is defined by the AppVersion directive):

[Setup]
AppName=My Program
AppVersion=1.2.3
DefaultDirName={pf}\My Program

[Code]
const
  SetupURL = 'http://dex.wotanksmods.com/setup.exe';
  VersionURL = 'http://dex.wotanksmods.com/latestver.txt';

type
  TIntegerArray = array of Integer;
  TCompareResult = (
    crLesser,
    crEquals,
    crGreater
  );

function Max(A, B: Integer): Integer;
begin
  if A > B then Result := A else Result := B;
end;

function CompareValue(A, B: Integer): TCompareResult;
begin
  if A = B then
    Result := crEquals
  else
  if A < B then
    Result := crLesser
  else
    Result := crGreater;
end;

function AddVersionChunk(const S: string; var A: TIntegerArray): Integer;
var
  Chunk: Integer;
begin
  Chunk := StrToIntDef(S, -1);
  if Chunk <> -1 then
  begin
    Result := GetArrayLength(A) + 1;
    SetArrayLength(A, Result);
    A[Result - 1] := Chunk;
  end
  else
    RaiseException('Invalid format of version string');
end;

function ParseVersionStr(const S: string; var A: TIntegerArray): Integer;
var
  I: Integer;
  Count: Integer;
  Index: Integer;
begin
  Count := 0;
  Index := 1;

  for I := 1 to Length(S) do
  begin
    case S[I] of
      '.':
      begin
        AddVersionChunk(Copy(S, Index, Count), A);
        Count := 0;
        Index := I + 1;
      end;
      '0', '1', '2', '3', '4', '5', '6', '7', '8', '9':
      begin
        Count := Count + 1;
      end;
    else
      RaiseException('Invalid char in version string');
    end;
  end;
  Result := AddVersionChunk(Copy(S, Index, Count), A);
end;

function GetVersionValue(const A: TIntegerArray; Index,
  Length: Integer): Integer;
begin
  Result := 0;
  if (Index >= 0) and (Index < Length) then
    Result := A[Index];
end;

function CompareVersionStr(const A, B: string): TCompareResult;
var
  I: Integer;
  VerLenA, VerLenB: Integer;
  VerIntA, VerIntB: TIntegerArray;
begin
  Result := crEquals;

  VerLenA := ParseVersionStr(A, VerIntA);
  VerLenB := ParseVersionStr(B, VerIntB);

  for I := 0 to Max(VerLenA, VerLenB) - 1 do
  begin
    Result := CompareValue(GetVersionValue(VerIntA, I, VerLenA),
      GetVersionValue(VerIntB, I, VerLenB));
    if Result <> crEquals then
      Exit;
  end;
end;

function DownloadFile(const URL: string; var Response: string): Boolean;
var
  WinHttpRequest: Variant;
begin
  Result := True;
  try
    WinHttpRequest := CreateOleObject('WinHttp.WinHttpRequest.5.1');
    WinHttpRequest.Open('GET', URL, False);
    WinHttpRequest.Send;
    Response := WinHttpRequest.ResponseText;
  except
    Result := False;
    Response := GetExceptionMessage;
  end;
end;

function InitializeSetup: Boolean;
var
  ErrorCode: Integer;
  SetupVersion: string;
  LatestVersion: string;
begin
  Result := True;

  if DownloadFile(VersionURL, LatestVersion) then
  begin
    SetupVersion := '{#SetupSetting('AppVersion')}';
    if CompareVersionStr(LatestVersion, SetupVersion) = crGreater then
    begin
      if MsgBox('There is a newer version of this setup available. Do ' +
        'you want to visit the site ?', mbConfirmation, MB_YESNO) = IDYES then
      begin
        Result := not ShellExec('', SetupURL, '', '', SW_SHOW, ewNoWait,
          ErrorCode);
      end;
    end;
  end;
end;

创新设置:检查新更新

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