Cómo crear un archivo de texto e insertar datos en ese archivo en Android

Revisa la documentación de android . De hecho, no es muy diferente al manejo de archivos java io estándar, por lo que también puede verificar esa documentación.

Un ejemplo de la documentación de Android:

String FILENAME = "hello_file";
String string = "hello world!";

FileOutputStream fos = openFileOutput(FILENAME, Context.MODE_PRIVATE);
fos.write(string.getBytes());
fos.close();

Si desea crear un archivo y escribir y anexar datos a él muchas veces, a continuación, utilice el siguiente código, se creará el archivo si no sale y anexará datos si existe.

 SimpleDateFormat formatter = new SimpleDateFormat("yyyy_MM_dd");
        Date now = new Date();
        String fileName = formatter.format(now) + ".txt";//like 2016_01_12.txt


         try
            {
                File root = new File(Environment.getExternalStorageDirectory()+File.separator+"Music_Folder", "Report Files");
                //File root = new File(Environment.getExternalStorageDirectory(), "Notes");
                if (!root.exists()) 
                {
                    root.mkdirs();
                }
                File gpxfile = new File(root, fileName);


                FileWriter writer = new FileWriter(gpxfile,true);
                writer.append(sBody+"\n\n");
                writer.flush();
                writer.close();
                Toast.makeText(this, "Data has been written to Report File", Toast.LENGTH_SHORT).show();
            }
            catch(IOException e)
            {
                 e.printStackTrace();

            }

First create a Project With PdfCreation in Android Studio

Then Follow below steps:

1.Download itextpdf-5.3.2.jar library from this link [https://sourceforge.net/projects/itext/files/iText/iText5.3.2/][1] and then
2.Add to app>libs>itextpdf-5.3.2.jar
3.Right click on jar file then click on add to library
4. Document document = new Document(PageSize.A4); // Create Directory in External Storage
        String root = Environment.getExternalStorageDirectory().toString();
        File myDir = new File(root + "/PDF");
        System.out.print(myDir.toString());
        myDir.mkdirs(); // Create Pdf Writer for Writting into New Created Document
        try {
            PdfWriter.getInstance(document, new FileOutputStream(FILE));
        } catch (DocumentException e) {
            e.printStackTrace();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } // Open Document for Writting into document
        document.open(); // User Define Method
        addMetaData(document);
        try {
            addTitlePage(document);
        } catch (DocumentException e) {
            e.printStackTrace();
        } // Close Document after writting all content
        document.close();

5.   public void addMetaData(Document document)
    {
        document.addTitle("RESUME");
        document.addSubject("Person Info");
        document.addKeywords("Personal, Education, Skills");
                document.addAuthor("TAG");
        document.addCreator("TAG");
    }
    public void addTitlePage(Document document) throws DocumentException
    { // Font Style for Document
        Font catFont = new Font(Font.FontFamily.TIMES_ROMAN, 18, Font.BOLD);
        Font titleFont = new Font(Font.FontFamily.TIMES_ROMAN, 22, Font.BOLD
                | Font.UNDERLINE, BaseColor.GRAY);
        Font smallBold = new Font(Font.FontFamily.TIMES_ROMAN, 12, Font.BOLD);
        Font normal = new Font(Font.FontFamily.TIMES_ROMAN, 12, Font.NORMAL); // Start New Paragraph
        Paragraph prHead = new Paragraph(); // Set Font in this Paragraph
        prHead.setFont(titleFont); // Add item into Paragraph
        prHead.add("RESUME – Name\n"); // Create Table into Document with 1 Row
        PdfPTable myTable = new PdfPTable(1); // 100.0f mean width of table is same as Document size
        myTable.setWidthPercentage(100.0f); // Create New Cell into Table
        PdfPCell myCell = new PdfPCell(new Paragraph(""));
        myCell.setBorder(Rectangle.BOTTOM); // Add Cell into Table
        myTable.addCell(myCell);
        prHead.setFont(catFont);
        prHead.add("\nName1 Name2\n");
        prHead.setAlignment(Element.ALIGN_CENTER); // Add all above details into Document
        document.add(prHead);
        document.add(myTable);
        document.add(myTable); // Now Start another New Paragraph
        Paragraph prPersinalInfo = new Paragraph();
        prPersinalInfo.setFont(smallBold);
        prPersinalInfo.add("Address 1\n");
        prPersinalInfo.add("Address 2\n");
        prPersinalInfo.add("City: SanFran. State: CA\n");
        prPersinalInfo.add("Country: USA Zip Code: 000001\n");
        prPersinalInfo.add("Mobile: 9999999999 Fax: 1111111 Email: [email protected] \n");
        prPersinalInfo.setAlignment(Element.ALIGN_CENTER);
        document.add(prPersinalInfo);
        document.add(myTable);
        document.add(myTable);
        Paragraph prProfile = new Paragraph();
        prProfile.setFont(smallBold);
        prProfile.add("\n \n Profile : \n ");
        prProfile.setFont(normal);
        prProfile.add("\nI am Mr. XYZ. I am Android Application Developer at TAG.");
        prProfile.setFont(smallBold);
        document.add(prProfile); // Create new Page in PDF
        document.newPage();
    }