文件下载类 HttpDownloader,内存卡操作类 FileUtils

转载自：http://www.cnblogs.com/luzhiyuan/archive/2012/05/05/2485347.html

HttpDownloader代码

package mars.utils;
 
 import java.io.BufferedReader;
 import java.io.File;
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.InputStreamReader;
 import java.net.HttpURLConnection;
 import java.net.MalformedURLException;
 import java.net.URL;
 
 
 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件当中的内容
      * 1.创建一个URL对象
      * 2.通过URL对象，创建一个HttpURLConnection对象
      * 3.得到InputStram
      * 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 {
             // 创建一个URL对象
             url = new URL(urlStr);
             // 创建一个Http连接
             HttpURLConnection urlConn = (HttpURLConnection) url
                     .openConnection();
             // 使用IO流读取数据
             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 (Exception e) {
                 e.printStackTrace();
             }
         }
         return sb.toString();
     }
 
     /**
      * 该函数返回整形 -1：代表下载文件出错 0：代表下载文件成功 1：代表文件已经存在
      */
     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 (Exception e) {
                 e.printStackTrace();
             }
         }
         return 0;
     }
 
     /**
      * 根据URL得到输入流
      * 
      * @param urlStr
      * @return
      * @throws MalformedURLException
      * @throws IOException
      */
     public InputStream getInputStreamFromUrl(String urlStr)
             throws MalformedURLException, IOException {
         url = new URL(urlStr);
         HttpURLConnection urlConn = (HttpURLConnection) url.openConnection();
         InputStream inputStream = urlConn.getInputStream();
         return inputStream;
     }
 }

FileUtils代码

package mars.utils;
 
 import java.io.File;
 import java.io.FileOutputStream;
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.OutputStream;
 
 import android.os.Environment;
 
 public class FileUtils {
     private String SDPATH;
 
     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
      * 
      * @throws IOException
      */
     public File creatSDFile(String fileName) throws IOException {
         File file = new File(SDPATH + fileName);
         file.createNewFile();
         return file;
     }
     
     /**
      * 在SD卡上创建目录
      * 
      * @param dirName
      */
     public File creatSDDir(String dirName) {
         File dir = new File(SDPATH + dirName);
         dir.mkdirs();
         return dir;
     }
 
     /**
      * 判断SD卡上的文件夹是否存在
      */
     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
      */
     public File write2SDFromInput(String path,String fileName,InputStream input){
         File file = null;
         OutputStream output = null;
         try{
             creatSDDir(path);
             file = creatSDFile(path + fileName);
             output = new FileOutputStream(file);
             byte buffer [] = new byte[4 * 1024];
             while((input.read(buffer)) != -1){
                 output.write(buffer);
             }
             output.flush();
         }
         catch(Exception e){
             e.printStackTrace();
         }
         finally{
             try{
                 output.close();
             }
             catch(Exception e){
                 e.printStackTrace();
             }
         }
         return file;
     }
 
 }