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)
         {

         }
     }
 }