SharedPreferences存储用户名

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.a"
    android:orientation="vertical">

    <EditText
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="用户名"
        android:id="@+id/et_yhm"/>

    <EditText
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="密码"
        android:id="@+id/et_mm"/>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content">
        <Button
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:text="登陆"
            android:onClick="bt_denglu"/>
        <Button
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:text="注册"/>
    </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 a extends AppCompatActivity {

    EditText et_yhm;
    EditText et_mm;

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

        et_yhm = (EditText)findViewById(R.id.et_yhm);
        et_mm = (EditText)findViewById(R.id.et_mm);

        SharedPreferences sp = getSharedPreferences("name",MODE_APPEND);

        String name = sp.getString("name",null);

        et_yhm.setText(name);
    }

    public void bt_denglu(View v)
    {
        String yhm = et_yhm.getText().toString();

        SharedPreferences sharedPreferences = getSharedPreferences("name", MODE_APPEND);

        SharedPreferences.Editor editor = sharedPreferences.edit();

        editor.putString("name",yhm);

        editor.commit();

        Toast.makeText(a.this, "登陆成功", Toast.LENGTH_SHORT).show();
    }
}