利用Api读写外部存储卡数据

public class MainActivity extends Activity {    private EditText et_name;private EditText et_pass;@Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);                et_name = (EditText) findViewById(R.id.et_name);    et_pass = (EditText) findViewById(R.id.et_pass);            readAccount();            }    public void readAccount(){    if(Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)){    File file = new File("sdcard/info.txt");    if(file.exists()){    try {FileInputStream fis = new FileInputStream(file);//把字节流转换成字符流BufferedReader br = new BufferedReader(new InputStreamReader(fis));//读取txt文件里的用户名和密码String text = br.readLine();String[] s = text.split("##");    et_name.setText(s[0]);    et_pass.setText(s[1]);} catch (Exception e) {// TODO Auto-generated catch blocke.printStackTrace();}    }    }    }    public void login(View v){        String name = et_name.getText().toString();    String pass = et_pass.getText().toString();        CheckBox cb = (CheckBox) findViewById(R.id.cb);    //判断选框是否被勾选    if(cb.isChecked()){    //MEDIA_UNKNOWN:不能识别sd卡    //MEDIA_REMOVED:没有sd卡    //MEDIA_UNMOUNTED:sd卡存在但是没有挂载    //MEDIA_CHECKING:sd卡正在准备    //MEDIA_MOUNTED：sd卡已经挂载，可用    if(Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)){        //返回一个File对象，其路径是sd卡的真实路径     File file = new File(Environment.getExternalStorageDirectory(), "info.txt");//    File file = new File("sdcard/info.txt");    FileOutputStream fos;try {fos = new FileOutputStream(file);fos.write((name + "##" + pass).getBytes());fos.close();} catch (Exception e) {// TODO Auto-generated catch blocke.printStackTrace();}    }    else{    Toast.makeText(this, "sd卡不可用哟亲么么哒", 0).show();    }    }        //创建并显示吐司对话框    Toast.makeText(this, "登录成功", 0).show();    }    }