protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        writeToFile("test.txt", "abcdefg");
        String str = readFromFile("test.txt");
        setTitle(str);
    }

    private String readFromFile(String FILENAME) {
        try{
            FileInputStream fin = openFileInput(FILENAME);
            byte[] buff = new byte[fin.available()];
            fin.read(buff);
            String str = new String(buff);
            return str;
        }catch (Exception e){
            return null;
        }
    }

    private void writeToFile(String FILENAME, String string) {
        try {
            FileOutputStream fos = openFileOutput(FILENAME, Context.MODE_PRIVATE);
            fos.write(string.getBytes());
            fos.close();
        }catch (Exception e){
        }
    }