[Android] สอบถามวิธีนำค่าที่เก็บได้จากTextview มาใช้เป็น filename

String Activity = textX.getText().toString();
final String trainfname =  Activity + ".txt";

  protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_train);

        root = android.os.Environment.getExternalStorageDirectory();
        dir = new File(root.getAbsolutePath() + "/trainmyapp");
        dir.mkdirs();

        FilesSensor = new File(dir , trainfname);


        btstart = (Button) findViewById(R.id.btstart);
        btstop = (Button) findViewById(R.id.btstop);
        textX = (TextView) findViewById(R.id.textX);
        textT = (TextView) findViewById(R.id.textT);
        textD = (TextView) findViewById(R.id.textD);

        sensorManager = (SensorManager) getSystemService(Context.SENSOR_SERVICE);
        sensor = sensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER);

    }