Android 文件，I/O操作小结

一、权限：

 

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

二、下载：

• public class HttpDownloader { 
•      
•     private URL url = null;  
•      
•     /** 
•      * 根据URL下载文件,前提是这个文件当中的内容是文本,函数的返回值就是文本当中的内容 
•      * 1.创建一个URL对象 
•      * 2.通过URL对象,创建一个HttpURLConnection对象 
•      * 3.得到InputStream 
•      * 4.从InputStream当中读取数据 
•      * @param urlStr 
•      * @return 
•      */ 
•     public String download(String urlStr){ 
•         StringBuffer sb = new StringBuffer(); 
•         String line = null; 
•         BufferedReader buffer = null; 
•         try { 
•             url = new URL(urlStr); 
•             HttpURLConnection urlConn = (HttpURLConnection)url.openConnection(); 
•             buffer = new BufferedReader(new InputStreamReader(urlConn.getInputStream())); 
•             while( (line = buffer.readLine()) != null){ 
•                 sb.append(line); 
•             } 
•              
•         }  
•         catch (Exception e) { 
•             e.printStackTrace(); 
•         } 
•         finally{ 
•             try { 
•                 buffer.close(); 
•             } catch (IOException e) { 
•                 e.printStackTrace(); 
•             } 
•         } 
•         return sb.toString(); 
•     } 
•  
•     /** 
•      *  
•      * @param urlStr 
•      * @param path 
•      * @param fileName 
•      * @return  
•      *      -1:文件下载出错 
•      *       0:文件下载成功 
•      *       1:文件已经存在 
•      */ 
•     public int downFile(String urlStr, String path, String fileName){ 
•         InputStream inputStream = null; 
•         try { 
•             FileUtils fileUtils = new FileUtils(); 
•              
•             if(fileUtils.isFileExist(path + fileName)){ 
•                 return 1; 
•             } else { 
•                 inputStream = getInputStreamFromURL(urlStr); 
•                 File resultFile = fileUtils.write2SDFromInput(path, fileName, inputStream); 
•                 if(resultFile == null){ 
•                     return -1; 
•                 } 
•             } 
•         }  
•         catch (Exception e) { 
•             e.printStackTrace(); 
•             return -1; 
•         } 
•         finally{ 
•             try { 
•                 inputStream.close(); 
•             } catch (IOException e) { 
•                 e.printStackTrace(); 
•             } 
•         } 
•         return 0; 
•     } 
•      
•     /** 
•      * 根据URL得到输入流 
•      * @param urlStr 
•      * @return 
•      */ 
•     public InputStream getInputStreamFromURL(String urlStr) { 
•         HttpURLConnection urlConn = null; 
•         InputStream inputStream = null; 
•         try { 
•             url = new URL(urlStr); 
•             urlConn = (HttpURLConnection)url.openConnection(); 
•             inputStream = urlConn.getInputStream(); 
•              
•         } catch (MalformedURLException e) { 
•             e.printStackTrace(); 
•         } catch (IOException e) { 
•             e.printStackTrace(); 
•         } 
•          
•         return inputStream; 
•     } 
• } 

 三、流操作

• public class FileUtils { 
•     private String SDPATH; 
•      
•     private int FILESIZE = 4 * 1024;  
•      
•     public String getSDPATH(){ 
•         return SDPATH; 
•     } 
•      
•     public FileUtils(){ 
•         //得到当前外部存储设备的目录( /SDCARD ) 
•         SDPATH = Environment.getExternalStorageDirectory() + "/"; 
•     } 
•      
•     /** 
•      * 在SD卡上创建文件 
•      * @param fileName 
•      * @return 
•      * @throws IOException 
•      */ 
•     public File createSDFile(String fileName) throws IOException{ 
•         File file = new File(SDPATH + fileName); 
•         file.createNewFile(); 
•         return file; 
•     } 
•      
•     /** 
•      * 在SD卡上创建目录 
•      * @param dirName 
•      * @return 
•      */ 
•     public File createSDDir(String dirName){ 
•         File dir = new File(SDPATH + dirName); 
•         dir.mkdir(); 
•         return dir; 
•     } 
•      
•     /** 
•      * 判断SD卡上的文件夹是否存在 
•      * @param fileName 
•      * @return 
•      */ 
•     public boolean isFileExist(String fileName){ 
•         File file = new File(SDPATH + fileName); 
•         return file.exists(); 
•     } 
•      
•     /** 
•      * 将一个InputStream里面的数据写入到SD卡中 
•      * @param path 
•      * @param fileName 
•      * @param input 
•      * @return 
•      */ 
•     public File write2SDFromInput(String path,String fileName,InputStream input){ 
•         File file = null; 
•         OutputStream output = null; 
•         try { 
•             createSDDir(path); 
•             file = createSDFile(path + fileName); 
•             output = new FileOutputStream(file); 
•             byte[] buffer = new byte[FILESIZE]; 
•             while((input.read(buffer)) != -1){ 
•                 output.write(buffer); 
•             } 
•             output.flush(); 
•         }  
•         catch (Exception e) { 
•             e.printStackTrace(); 
•         } 
•         finally{ 
•             try { 
•                 output.close(); 
•             } catch (IOException e) { 
•                 e.printStackTrace(); 
•             } 
•         } 
•         return file; 
•     } 
•  
• }