Android——数据存储（课堂代码整理：SharedPreferences存储和手机内部文件存储）

layout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: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.MainActivity"
    android:orientation="vertical">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Hello World!"
        android:id="@+id/tv_1"/>
    <Button
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="SP存储"
        android:onClick="bt_onClick"/>
    <Button
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="SP读取"
        android:onClick="bt1_onClick"/>
    <EditText
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="请输入……"
        android:id="@+id/et_1"/>
    <Button
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="写内部文件"
        android:onClick="bt2_onClick"/>
    <Button
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="读内部文件"
        android:onClick="bt3_onClick"/>
</LinearLayout>

java类：

package com.hanqi.testapp3;

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

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.PrintStream;

public class MainActivity extends AppCompatActivity {

    EditText et_1;
    TextView tv_1;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        et_1 = (EditText)findViewById(R.id.et_1);
        tv_1 = (TextView)findViewById(R.id.tv_1);
    }
    public void bt_onClick(View v)        //SharedPreferences存储
    {
        //1.得到SharedPreferences对象
        SharedPreferences sharedPreferences = getSharedPreferences("abc", MODE_APPEND);
        //2.得到编辑器
        SharedPreferences.Editor editor =sharedPreferences.edit();
        //3.使用Editor添加数据
//        editor.putString("a","abcdef");
//        editor.putLong("long",12345);
        editor.remove("a");
        //4.提交保存
        editor.commit();
        Toast.makeText(MainActivity.this, "保存数据成功", Toast.LENGTH_SHORT).show();
    }
    //读取
    public void bt1_onClick(View v)
    {
        SharedPreferences sp = getSharedPreferences("abc",MODE_PRIVATE);
        String str = sp.getString("a", "默认值");
        Toast.makeText(MainActivity.this, "key = a"+" value = "+str, Toast.LENGTH_SHORT).show();
    }
    //写内部文件(手机内部文件存储)
    public void bt2_onClick(View v)
    {
        //从内存里写入文件
        //1.得到内部的存储目录
        try {
            File file = getFilesDir();
            String path = file.getAbsolutePath();
            Toast.makeText(MainActivity.this, "path = "+path, Toast.LENGTH_SHORT).show();
            //2.用输出流写入文件
            FileOutputStream fos = openFileOutput("test.txt",MODE_APPEND);
            //3.写入文件内容
            PrintStream ps = new PrintStream(fos);

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

            ps.print(str);
//            ps.print("测试");
//            ps.println("自动换行");
            ps.close();

            fos.close();
            Toast.makeText(MainActivity.this, "保存成功", Toast.LENGTH_SHORT).show();
        }
        catch (Exception e)
        {
            Toast.makeText(MainActivity.this, "保存失败", Toast.LENGTH_SHORT).show();
        }

    }
    public void bt3_onClick(View v)
    {
        try {
            //输入流
            FileInputStream fis = openFileInput("test.txt");
            //1.定义byte[]
            byte[] b = new byte[1024];
            int i = 0;//读到的数据长度
            String str1 = "";
            //2.循环读
            while ((i = fis.read(b))>0)
            {
                String str = new String(b,0,i);
                str1 += str;
            }
            fis.close();
            tv_1.setText(str1);
        }
        catch (Exception e)
        {

        }
    }
}