File Selector (.txt)

Question

I've been trying to get a code to list all the .txt files which are stored in a directory of a mobile phone.

It's my first time with Android Studio, so it's hard for me to achieve that. To test, firstly I am trying to do it with the files that I have created in the Download folder of the emulator (in the SD), but no matter how hard I try, the application keeps closing every time I load the code.

I've tried different codes but I am not progressing, so all help is welcome.

Here, I am going to put one of the codes I've tried so far (almost everything is taken from the Internet, source http://www.aprendeandroid.com/l8/listar_archivos.htm):

public class MainActivity extends AppCompatActivity {
    private ActivityResultRegistry listaFiles;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Tomar_datos = (Button) findViewById(R.id.Tomar_datos);
    }

    Button Tomar_datos;

    public void onClick(View view) {
        Intent i = new Intent();
        i.setClass(MainActivity.this, ListaFilesActivity.class);
        startActivity(i);
    }


    class ListaFilesActivity extends Activity {

        private List<String> item = null;

        @Override
        public void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            requestWindowFeature(Window.FEATURE_NO_TITLE); // para quitar titulo
            setContentView(R.layout.activity_main);

            item = new ArrayList<String>();

            File f = new File(Environment.getExternalStorageDirectory() + "/Download");
            File[] files = f.listFiles();

            for (int i = 0; i < files.length; i++) {
                File file = files[i];

                if (file.isDirectory())

                    item.add(file.getName() + "/");

                else

                    item.add(file.getName());
            }


            //Mostramos la ruta en el layout
            TextView ruta = (TextView) findViewById(R.id.ruta);
            ruta.setText(Environment.getExternalStorageDirectory() + "/Download");

            //Localizamos y llenamos la lista
            ListView lstOpciones = (ListView) findViewById(R.id.listaFiles);
            ArrayAdapter<String> fileList = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, item);
            lstOpciones.setAdapter(fileList);

            // Accion para realizar al pulsar sobre la lista
            lstOpciones.setOnItemClickListener(new OnItemClickListener() {

                @Override
                public void onItemClick(AdapterView<?> a, View v, int position, long id) {

                    // Devuelvo los datos a la activity principal
                    Intent data = new Intent();
                    data.putExtra("filename", item.get(position));
                    setResult(RESULT_OK, data);
                    finish();
                }
            });
        }
    }
}

Answer 1

Please just try this way of filter with list files may help you

File f = new File(Environment.getExternalStorageDirectory() + "/Download");
File[] textiles = f.listFiles(new FileFilter() {
            @Override
            public boolean accept(File file)
            {
                return (file.getPath().endsWith(".txt"));
            }
});

Or

List list;//list of file or path

private void listAllTextfiles(File directory) {
   
    final File[] files = folder.listFiles();//can add above filter for .txt file only

    if ( files != null ) {
        for ( File file : files ) {
            if ( file != null ) {
                if ( file.isDirectory() ){ 
                    listAllTextfiles(file);
                }
                else {  
                  list.add(file or path)
                }
            }
        }
    }
}