用偏好设置保存和获取用户名，密码

    private void saveLoginInfo(String username,String password){
        SharedPreferences preferences =getSharedPreferences(getString(R.string.pref_login_info), Context.MODE_PRIVATE);
        SharedPreferences.Editor editor = preferences.edit();
        editor.putString(getString(R.string.pref_login_user_name_key), username);
        editor.putString(getString(R.string.pref_login_pass_word_key), CommonUtils.getMD5String(password));
        editor.apply();
    }
    private Map readLoginInfo(){
        SharedPreferences preferences = getSharedPreferences(getString(R.string.pref_login_info), Context.MODE_PRIVATE);
        String username=preferences.getString(getString(R.string.pref_login_user_name_key), "");
        String password=preferences.getString(getString(R.string.pref_login_pass_word_key), "");
        Map<String, String> info = new HashMap<String, String>();
        info.put("UserName", username);
        info.put("UserPwd", password);
        return info;
    }