登陆界面用户名，密码存储以及再次登陆自动填充用户名、密码

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.example.dell.wodelianxi.denglucunchu"
    android:background="@drawable/beijing"
    android:orientation="vertical">

    <EditText
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="请输入用户名"
        android:id="@+id/et_user"/>

    <EditText
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:inputType="numberPassword"
        android:hint="请输入密码"
        android:id="@+id/et_pwd"/>
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content">
        <CheckBox
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="保存用户名、密码"
            android:layout_weight="1"
            android:id="@+id/cb_jizhu"/>
        <Button
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="注册"
            android:layout_weight="2"
            android:background="@drawable/zhuce"
            android:id="@+id/zhuce"/>

        <Button
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="登陆"
            android:layout_weight="2"
            android:background="@drawable/zhuce"
            android:id="@+id/denglu"
            android:onClick="denglu"/>
    </LinearLayout>


</LinearLayout>

package com.example.dell.wodelianxi;

import android.content.SharedPreferences;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.text.TextUtils;
import android.view.View;
import android.widget.CheckBox;
import android.widget.EditText;
import android.widget.Toast;

public class denglucunchu extends AppCompatActivity {

    EditText et_user;
    EditText et_pwd;
    CheckBox cb_jizhu;
    SharedPreferences sp;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_denglucunchu);

        sp = getSharedPreferences("info", MODE_PRIVATE);

        et_user = (EditText)findViewById(R.id.et_user);

        et_pwd = (EditText)findViewById(R.id.et_pwd);

        cb_jizhu = (CheckBox)findViewById(R.id.cb_jizhu);

        et_user.setText(sp.getString("user",null));

        et_pwd.setText(sp.getString("password",null));
    }

    public void denglu(View view)
    {
        if (cb_jizhu.isChecked())
        {



                SharedPreferences.Editor editor = sp.edit();

                String user = et_user.getText().toString();
                String password = et_pwd.getText().toString();
            if(TextUtils.isEmpty(user) || TextUtils.isEmpty(password))
            {
                Toast.makeText(denglucunchu.this, "用户名或密码不能为空", Toast.LENGTH_SHORT).show();

            }
            else {
                editor.putString("user", user);

                 editor.putString("password", password);

                //editor.putString(user,password);

            editor.commit();
                Toast.makeText(denglucunchu.this, "保存成功", Toast.LENGTH_SHORT).show();
            }
        }
        else
        {
            Toast.makeText(denglucunchu.this, "请保存用户名、密码", Toast.LENGTH_SHORT).show();
        }
    }
}