SharedPreferences sp = getSharedPreferences("atw",MODE_PRIVATE);//创建对象，
String readstring = sp.getString("isFirst", "false");//默认false
if (readstring.equals("false")){
SharedPreferences.Editor editor = sp.edit();//获取编辑对象
editor.putString("isFirst","true");//keyname是储存数据的键值名，同一个对象可以保存多个键值
editor.commit();//提交保存修改
}