安卓SharedPreferences类的使用

package com.lidaochen.phonecall;

import android.content.Intent;
import android.content.SharedPreferences;
import android.net.Uri;
import android.os.Environment;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.text.TextUtils;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.CheckBox;
import android.widget.EditText;
import android.widget.TabHost;
import android.widget.ThemedSpinnerAdapter;
import android.widget.Toast;

import java.util.Map;

public class MainActivity extends AppCompatActivity{
    private EditText et_userName;
    private EditText et_pwd;
    private CheckBox cb;
    private SharedPreferences sp;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        // 初始化sp实例
        sp = getSharedPreferences("test", 0);

        // 1.获取控件
        et_userName = (EditText)findViewById(R.id.et_username);
        et_pwd = (EditText)findViewById(R.id.et_pwd);
        cb = (CheckBox)findViewById(R.id.cb);
        // 把我们需要的数据在test.xml中显示出来，然后在控件上显示出来
        String name = sp.getString("name", "");
        String pwd = sp.getString("pwd", "");
        // 将数据显示在控件上
        et_userName.setText(name);
        et_pwd.setText(pwd);
    }
    // 按钮点击事件
    public void login(View v)
    {
        // 获取userName和pwd
        String name = et_userName.getText().toString().trim();
        String pwd = et_pwd.getText().toString().trim();
        // 判断name和pwd是否为空
        if(TextUtils.isEmpty(name) || TextUtils.isEmpty(pwd))
        {
            Toast.makeText(MainActivity.this, "用户名或密码不能为空", Toast.LENGTH_LONG).show();
        }
        else
        {
            System.out.println("登录之后要干的事情！");
            if(cb.isChecked())
            {
               // 获取sp的编辑器
                SharedPreferences.Editor edit = sp.edit();
                edit.putString("name", name);
                edit.putString("pwd", pwd);
                // 把edit进行提交
                edit.commit();
                Toast.makeText(MainActivity.this, "保存成功！", Toast.LENGTH_LONG).show();
            }
            else
            {
                Toast.makeText(MainActivity.this, "请勾选复选框", Toast.LENGTH_LONG).show();
            }
        }
    }
}