Files prior to the installation of the app do not appear

Question

In my code I have a ListView that lists the pdf files in the "Documents" folder on the phone that is updated when you create one, but the ones that have been created previously do not appear, they are still in the documents folder and I can see them by entering the files on the phone , but they don't appear from the app.

This is my code:

class MainActivity : AppCompatActivity() {

    private lateinit var binding: ActivityMainBinding

    private var pdfFileNames = arrayOf<String>() // Lista de nombres de archivos PDF
    private lateinit var pdfAdapter: ArrayAdapter<String> // Adaptador para el ListView

    private lateinit var listView: ListView

    private val documentsDirectory = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOCUMENTS)

    @SuppressLint("MissingInflatedId")
    @Override
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        Log.d("MainActivity", "Iniciando la cámara")

        // CONFIGURAMOS VIEWBINDING
        binding = ActivityMainBinding.inflate(layoutInflater)
        setContentView(binding.root)

        // Inicializa los elementos de la interfaz
        listView = binding.listaPdf


        // Inicializa el adaptador para el ListView
        pdfAdapter = ArrayAdapter(this, android.R.layout.simple_list_item_1, pdfFileNames)
        listView.adapter = pdfAdapter


        listView.setOnItemClickListener { parent, view, position, id ->
            val selectedFileName = pdfFileNames[position] // Obtiene el nombre del archivo PDF seleccionado
            val selectedFile = File(documentsDirectory, selectedFileName) // Obtiene el archivo PDF correspondiente
            openPdf(selectedFile) // Abre el archivo PDF seleccionado
        }
    }

    override fun onResume() {
        super.onResume()
        loadPDFs()
    }

    
    //LISTA PDF   
    // Función para cargar los nombres de archivos PDF
    private fun loadPDFs() {
        if (documentsDirectory.exists() && documentsDirectory.isDirectory) {
            pdfFileNames = documentsDirectory
                .listFiles { file -> file.isFile && file.name.toLowerCase().endsWith(".pdf") }
                .map { it.name }
                .toTypedArray()

            if(pdfFileNames.isNotEmpty()){
                // Actualiza el adaptador del ListView
                pdfAdapter = ArrayAdapter(this, android.R.layout.simple_list_item_1, pdfFileNames)
                listView.adapter = pdfAdapter
            }else{
                Toast.makeText(this, "No se encontraron archivos pdf en la carpeta Documentos",Toast.LENGTH_SHORT).show()
            }
        }
    }

        
    //PDF
    private fun openPdf(pdfFile: File) {
        val intent = Intent(this, VisorPDF::class.java)
        intent.putExtra("pdf_path", pdfFile.absolutePath)
        startActivity(intent)
    }

I tried to call the function loadPDFs on the onCreate and onResume functions but it doesn`t works

EDIT 1: I have tried adding a log to see how many files it detects within the "/Documents" folder and it only counts the new files, with a total of 11 (8 from the previous installation and 3 pdf created from the new installation)

EDIT 2: I have checked if having the phone in Spanish language changes the name of the "/Documents" folder to "Documentos" but that does not happen, and both new and old files have the same path

Answer 1

Your app can only see files in Documents/ that this app installation created. If the user uninstalls and reinstalls your app, your newly-installed app installation cannot see the files created in Documents/ from your prior app installation.

You may be better served using ACTION_OPEN_DOCUMENT / ActivityResultContracts.OpenDocument, as that allows the user to access everything in Documents/, and elsewhere.