andorid 数据储存

<?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.application3.DataActivity1"
    android:orientation="vertical">

    <EditText
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/et_1"
        android:hint="Key"/>
    <EditText
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/et_2"
        android:hint="Value"/>
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content">
        <Button
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:text="保存"
            android:layout_weight="1"
            android:onClick="bt1_onClick"/>
        <Button
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:text="读取"
            android:layout_weight="1"
            android:onClick="bt2_onClick"/>

    </LinearLayout>


</LinearLayout>

package com.hanqi.application3;

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 DataActivity1 extends AppCompatActivity {
    EditText et1;
    EditText et2;
    SharedPreferences sp;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_data1);

        et1=(EditText)findViewById(R.id.et_1);
        et2=(EditText)findViewById(R.id.et_2);
        //1.获取sp的实例，制定了文件名和操作模式
        sp = getSharedPreferences("mydata",MODE_PRIVATE);

    }
    //保存
    public void bt1_onClick(View v)
    {
        //1.获取Key和Value
        String key = et1.getText().toString();
        String value = et2.getText().toString();
        if (key.length() ==0||value.length() == 0)
        {
            Toast.makeText(DataActivity1.this, "key或value不能为空", Toast.LENGTH_SHORT).show();
        }
        else {



        //2.取得Editor        edit编辑器
        SharedPreferences.Editor editor = sp.edit();
        //3.放入键值对
        editor.putString(key,value);
        //4.提交保存
        boolean b = editor.commit();
        if (b)
        {
            Toast.makeText(DataActivity1.this, "保存成功", Toast.LENGTH_SHORT).show();
        }
        else
        {
            Toast.makeText(DataActivity1.this, "保存失败", Toast.LENGTH_SHORT).show();
        }
        }

    }
    //读取
    public void bt2_onClick(View v)
    {

        //1.获取要读的key
        String key = et1.getText().toString();
        //2.读并设置文本框
        et2.setText(sp.getString(key,"没有发现key"));

    }

}