16. 文件的保存与读取

一. 概述

此例子将文本文件存入data/data/files中，只有本程序能够读取。

二. 实现

1. 保存文件

/** * Save content to a file 

 * @param fileName the name of the file 

 * @param fileContent the content of the file 

 * @throws IOException 

 */ 

 public void save(String fileName, String fileContent) throws IOException { 

 FileOutputStream out = context.openFileOutput(fileName, 

Context.MODE_APPEND); 

 out.write(fileContent.getBytes()); 

 out.flush(); 

 out.close(); 

 }

2. 读取文件

/** * read the content in data/data/com.like.app/files 

 * @param fileName the name of the file 

 * @param fileContent the content of the file 

 * @return return the content of the file 

 * @throws IOException 

 */ 

 public String read(String fileName, String fileContent) throws IOException { 

 FileInputStream inputStream = context.openFileInput(fileName); 

 ByteArrayOutputStream outputStream = new ByteArrayOutputStream(); 

 byte[] buffer = new byte[1024]; 

 int len = 0; 

 while((len = inputStream.read(buffer)) != -1) { 

 outputStream.write(buffer, 0, len); 

 } 

 byte[] data = outputStream.toByteArray(); 

 outputStream.close();

 inputStream.close();

 return new String(data);

 }

3. 保存文件至SD卡

(1) 在操作SD卡之前，需要加入权限

<uses-permission android:name="android.permission.MOUNT_UNMOUNT_FILESYSTEMS" /> 

 <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

(2) 方法实现

/** * save file to sdcard 

 * @param fileName the name of the file 

 * @param fileContent the content of the file 

 * @throws IOException 

 */ 

 public void saveToSdcard(String fileName, String fileContent) throws IOException {

 //getExtrnalStorageDirectory() 获取sdcard路径 

 File file = new File(Environment.getExternalStorageDirectory(), fileName); 

 FileOutputStream outputStream = new FileOutputStream(file); 

 outputStream.write(fileContent.getBytes()); outputStream.close();

 }

4. 从SD卡读取文件

/** * read content from sdcard 

 * @param fileName the name of the file 

 * @param fileContent the content of the file 

 * @return return the content of the file 

 * @throws IOException 

 */ 

 public String readFromSdcard(String fileName, String fileContent) 

throws IOException { 

 FileInputStream inputStream = new FileInputStream(

new File(Environment.getExternalStorageDirectory(), fileName)); 

 ByteArrayOutputStream outputStream = new ByteArrayOutputStream(); 

 byte[] buffer = new byte[1024]; 

 int len = 0; while((len = inputStream.read(buffer)) != -1) { 

 outputStream.write(buffer, 0, len);

 } 

 byte[] data = outputStream.toByteArray(); 

 outputStream.close(); 

 inputStream.close(); 

 return new String(data); 

 }