外部存储上的FileWriting（在文本文件中写入多个数据）

Question

我想在文本文件中写入多个数据（移动加速度计读数）。 即所有读数，当我开始app时，直到我按下SAVE按钮。 我如何修改此代码来收集数据，这只会给出一次按下SAVE时X，Y，Z的读数。 这是显示读数的OnSensorChange函数：

  public void onSensorChanged(SensorEvent event) {

        acceleration.setText("X: " + event.values[0] +
                        "\n Y: " + event.values[1] +
                        "\n Z: " + event.values[2]

        );

And here is saving file code :

                String state;
                state= Environment.getExternalStorageState();
                if(Environment.MEDIA_MOUNTED.equals(state))
                {
                    File Root= Environment.getExternalStorageDirectory();
                    File dir=new File(Root.getAbsolutePath()+"/myappfile");
                    if(!dir.exists()) {
                        dir.mkdir();
                    }
                    File file =new File(dir,"file.txt");
                    String Message=acceleration.getText().toString();

                    try {
                        FileOutputStream fileOutputStream=new
FileOutputStream(file);
                        fileOutputStream.write(Message.getBytes());
                        fileOutputStream.close();
                        acceleration.setText("");
                        Toast.makeText(getApplicationContext(),"SAVED",Toast.LENGTH_LONG).show();

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


                }
                else
                {
                    Toast.makeText(getApplicationContext(),"not found",Toast.LENGTH_LONG).show();
                }