内部存储 openFileInputStream openFileOutputStream

 package com.qianfeng.gp08_day24_internalstorage;

 import java.io.FileInputStream;
 import java.io.FileNotFoundException;
 import java.io.FileOutputStream;
 import java.io.IOException;
 import java.util.Arrays;

 import android.os.Bundle;
 import android.app.Activity;
 import android.app.AlertDialog;
 import android.content.Context;
 import android.content.DialogInterface;
 import android.content.DialogInterface.OnClickListener;
 import android.view.Menu;
 import android.view.MenuItem;
 import android.view.View;
 import android.widget.ArrayAdapter;
 import android.widget.EditText;

 /**
  * 内部存储： SharedPreferences属于内部存储
  *        openFileOutput()  openFileInput()
  *        其实还是以文件的形式存储数据，IO
  *                                   /shared_prefs/
  * 内部存储的文件的存放位置  /data/data/(包名)/files/
  *
  */
 public class MainActivity extends Activity {

     private EditText edit_fileName,edit_content;

     //点击菜单项，弹出对话框，列出所有的内部存储空间中的文件
     private AlertDialog  fileDialog;
     private ArrayAdapter<String> adapter;

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

         edit_fileName = (EditText) findViewById(R.id.edit_fileName);
         edit_content = (EditText) findViewById(R.id.edit_fileContent);

         initDialog();
     }

     //初始化对话框的功能
     public void initDialog()
     {
         adapter  = new ArrayAdapter<String>(this,R.layout.item_layout);
         //得到内部存储空间中的所有的文件名 fileList()
         adapter.addAll(Arrays.asList(fileList()));

         fileDialog = new AlertDialog.Builder(this)
                                     .setTitle("文件选择对话框")
                                     .setIcon(R.drawable.ic_launcher)
                                     .setAdapter(adapter, new OnClickListener() {

                                         @Override
                                         public void onClick(DialogInterface dialog, int which) {
                                             //得到文件名
                                             String filename = adapter.getItem(which);
                                             edit_fileName.setText(filename);
                                             // 读取文件
                                             try {
                                                 readData(null);
                                             } catch (IOException e) {
                                                 e.printStackTrace();
                                             }
                                         }
                                     })
                                     .create();

     }

     public void saveFile(View v) throws IOException//把数据保存到内部存储空间的文件中
     {
         //获取文件名和文件内容
         String filename = edit_fileName.getText().toString().trim();
         String filecontent = edit_content.getText().toString().trim();

         FileOutputStream fos = openFileOutput(filename, Context.MODE_PRIVATE);
         fos.write(filecontent.getBytes());

         fos.close();
     }

     public void readData(View v) throws IOException
     {
         //获取被读取的文件名
         String filename = edit_fileName.getText().toString().trim();

         //读取文件
         FileInputStream fis = openFileInput(filename);
         byte[] arr = new byte[fis.available()];
         int len = fis.read(arr);
         edit_content.setText(new String(arr,0,len));
         fis.close();
     }

     @Override
     public boolean onCreateOptionsMenu(Menu menu) {
         getMenuInflater().inflate(R.menu.main, menu);
         return true;
     }
     @Override
     public boolean onOptionsItemSelected(MenuItem item) {
         if(item.getItemId()==R.id.action_selectFile)
         {
             fileDialog.show();
         }
         return super.onOptionsItemSelected(item);
     }

 }

MainActivity

 <RelativeLayout 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=".MainActivity" >

     <EditText
         android:id="@+id/edit_fileName"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:hint="输入文件名" />

     <Button
         android:id="@+id/btn_open"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:onClick="readData"
         android:layout_toRightOf="@id/edit_fileName"
         android:text="打开" />

     <Button
         android:id="@+id/btn_save"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:layout_toRightOf="@id/btn_open"
         android:onClick="saveFile"
         android:text="保存" />
     <EditText
         android:id="@+id/edit_fileContent"
         android:layout_width="match_parent"
         android:layout_height="match_parent"
         android:layout_below="@id/btn_save"
         android:background="@android:drawable/edit_text"
         android:hint="文件内容" />

 </RelativeLayout>

activity_main

 <?xml version="1.0" encoding="utf-8"?>
 <TextView xmlns:android="http://schemas.android.com/apk/res/android"
     android:layout_width="match_parent"
     android:layout_height="wrap_content"
     android:textSize="20sp"
     android:textColor="#000"
     />
     

item——layout