使用SharedPreferences将姓名和年龄信息保存在文件中，并读取信息

第一个是XML文件：

<?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:id="@+id/activity_main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context="com.example.zhoushasha.myapplication.MainActivity">

    <EditText
        android:id="@+id/et1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:hint="请输入姓名"
        android:textSize="25dp"/>
    <EditText
        android:id="@+id/et2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:hint="请输入年龄"
        android:textSize="25dp"/>
    <LinearLayout
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_weight="0">
        <Button
            android:id="@+id/bt1"
            android:layout_width="208dp"
            android:layout_height="wrap_content"
            android:text="写入"
            android:textSize="25dp"/>

        <Button
            android:id="@+id/bt2"
            android:layout_width="168dp"
            android:layout_height="wrap_content"
            android:text="读出"
            android:textSize="25dp"/>
    </LinearLayout>
</LinearLayout>

第二个是Java文件：

package com.example.zhoushasha.myapplication;

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

public class MainActivity extends AppCompatActivity {
    private EditText nameText;
    private EditText ageText;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        nameText = (EditText)this.findViewById(R.id.et1);
        ageText = (EditText)this.findViewById(R.id.et2);
        Button button = (Button)this.findViewById(R.id.bt1);
        Button showButton = (Button)this.findViewById(R.id.bt2);
        button.setOnClickListener(listener);
        showButton.setOnClickListener(listener);

        // 回显
        SharedPreferences sharedPreferences=getSharedPreferences("王艳",
                Activity.MODE_PRIVATE);
        String nameValue = sharedPreferences.getString("name", "");
        int ageValue = sharedPreferences.getInt("age",18);
        nameText.setText(nameValue);
        ageText.setText(String.valueOf(ageValue));
    }

    private View.OnClickListener listener = new View.OnClickListener(){
        public void onClick(View v) {
            Button button = (Button)v;
            //ljq123文件存放在/data/data/<package name>/shared_prefs目录下
            SharedPreferences sharedPreferences=getSharedPreferences("王艳",
                    Activity.MODE_PRIVATE );
            switch (button.getId()) {
                case R.id.bt1:
                    String name = nameText.getText().toString();
                    int age = Integer.parseInt(ageText.getText().toString());
                    Editor editor = sharedPreferences.edit(); //获取编辑器
                    editor.putString("name","王艳");
                    editor.putInt("age", age);
                    editor.commit();//提交修改
                    Toast.makeText( MainActivity.this, "保存成功", Toast.LENGTH_LONG).show();
                    break;
                case R.id.bt2:
                    String nameValue = sharedPreferences.getString("name", "");
                    int ageValue = sharedPreferences.getInt("age", 1);
                    Toast.makeText(MainActivity.this,"姓名："+nameValue + "，年龄：" + ageValue,Toast.LENGTH_LONG).show();

                    break;
            }
        }
    };
}


这样就可以使程序正常运行。