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);
    }

}

<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>

<?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"
    />