inno setup to browse and extract zip file at sepcific location - inno-setup

Question

I want to enable users to browse and extract zip files at a specific location.
Requirements/steps:
Display welcome page
Next display browse button to select installation directory(DisableDirPage=no)
Next display browse button to select zip file(JDK)
Extract JDK zip file selected in step 3 at location selected in step 2, that means JDK should be extracted in installation directory that user selects in step 2
Problems with my code:
After the first step my code directly jump into 3rd step and then it goes to 2nd.
The code to extract zip is not working if I pass method name as the parameter. If I pass the hardcoded value of the location it works. I don't know pascal and it basically seems to be a syntax related issue.
[SETUP]
AppName=My Program
AppVersion=1.5
DefaultDirName={pf}\My Program
DefaultGroupName=My Program
UninstallDisplayIcon={app}\MyProg.exe
DisableProgramGroupPage=no
DisableWelcomePage=no
DisableDirPage=no
Compression=lzma2
SolidCompression=yes
OutputDir=userdocs:Inno Setup Examples Output
[Files]
Source: "{code:GetLicensePath}"; DestDir: "{app}"; Flags: external
Source: "7za.exe"; DestDir: "D:\authorized\Builds\Solo\"; Flags: deleteafterinstall;
[Icons]
Name: "{group}\My Program"; Filename: "{app}\MyProg.exe"
[Run]
Filename: D:\authorized\Builds\Solo\7za.exe; Parameters: "x ""{{Code:GetZipPath}}"" -o""{app}\"" * -r -aoa"; Flags: runhidden runascurrentuser;
[Code]
var
Page: TInputFileWizardPage;
DataDir:String;
procedure InitializeWizard();
begin
Page :=
CreateInputFilePage(
wpWelcome,
'Select Zip File Location',
'Where is your Zip file located?',
'Select where Zip file is located, then click Next.');
Page.Add(
'Location of Zip file:',
'*.7z|*.rar|All files|*.*',
'.zip');
// Set initial value (optional)
Page.Values[0] := ExpandConstant('{%USERPROFILE}\Downloads\setup.7z');
;
end;
function GetZipPath(Param: string): string;
begin
DataDir := Page.Values[0];
end;
Could you help me, please?

Answer 1

The order of your custom page is determined by the first argument of the Create* function. So change wpWelcome to wpSelectDir.
Why double {{...}} - That’s likely the problem. Also code: should be lowercase.
Your scripted constant function does not really return anything. It should be:
Result := Page.Values[0];