制作一个登录界面，以SP方式存储用户名。用户下次登录时自动显示上次填写的用户名

制作一个登录界面，以SP方式存储用户名。用户下次登录时自动显示上次填写的用户名

<?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"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="com.hanqi.testapp3.JiyidengluActivity"
    android:orientation="vertical">

    <EditText
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="用户名"
        android:id="@+id/et_1"/>
    <EditText
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="登录密码"
        android:id="@+id/et_2"
        android:inputType="textPassword"/>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content">

        <Button
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="登陆"
            android:onClick="bt2_OnClick"/>
    </LinearLayout>

</LinearLayout>

package com.hanqi.testapp3;

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

public class JiyidengluActivity extends AppCompatActivity {

    EditText et_1;
    EditText et_2;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_jiyidenglu);

        et_1=(EditText)findViewById(R.id.et_1);
        et_2=(EditText)findViewById(R.id.et_2);

        //读
        SharedPreferences sp=getSharedPreferences("defg",MODE_APPEND);

        String str=sp.getString("d",null);

        et_1.setText(str);
    }

    public void bt2_OnClick(View v)
    {
        EditText et_1=(EditText)findViewById(R.id.et_1);

        String yonghuming=et_1.getText().toString();

        if (yonghuming==null||yonghuming.trim().length()==0)
        {
            Toast.makeText(JiyidengluActivity.this, "请输入正确的用户名", Toast.LENGTH_SHORT).show();

            return;
        }

        else {

            //提取保存
            SharedPreferences sharedPreferences = getSharedPreferences("defg", MODE_APPEND);

            SharedPreferences.Editor editor = sharedPreferences.edit();

            editor.putString("d",yonghuming);

            editor.commit();

            Toast.makeText(JiyidengluActivity.this, "保存数据成功", Toast.LENGTH_SHORT).show();
        }
    }
}