Application does not create file in external memory

Question

I’m using the following code:

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_pdftest);
        Button Btgerar = (Button) findViewById(R.id.gerarpdf);
        Btgerar.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                CriarPDF();
            }
        });
    }
    public void CriarPDF() {
        String FILE = Environment.getExternalStorageDirectory().toString() + "/PDF/" + "Ficha.pdf";
        EditText txt = (EditText) findViewById(R.id.editText);
        // Create New Blank Document
        Document document = new Document(PageSize.A4);

        // Create Directory in External Storage
        String root = Environment.getExternalStorageDirectory().toString();
        File myDir = new File(root + "/PDF");
        myDir.mkdirs();

        // Create Pdf Writer for Writting into New Created Document
        try {
            PdfWriter.getInstance(document, new FileOutputStream(FILE));

        // Open Document for Writting into document
            document.open();
            document.add(new Paragraph(txt.getText().toString()));


        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (DocumentException e) {
            e.printStackTrace();
        }

        // Close Document after writting all content
        document.close();
        Toast.makeText(this, "PDF File is Created. Location : " + FILE,
                Toast.LENGTH_LONG).show();

        // Create new Page in PDF
        document.newPage();


    }
}

And I’ve also stated on Android Manifest:

uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE

• build Gradle version :
• compileSdkVersion 24
• buildToolsVersion '24.0.0'
• minSdkVersion 8
• targetSdkVersion 24

The program runs normally on my cell, but after generation of the pdf file I can’t find anywhere.