android下载简单工具类

功能是实现下载文件，图片或MP3等，为了简单起见使用单线程，此代码为MarsAndroid教程的复制品，放在此处，留着参考。

首先是一个得到字节流随后保存到内存卡上的工具类：

package com.example.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，即/SDCARD，后边加"/"为了之后方便

        SDpath=Environment.getExternalStorageDirectory()+"/";

    }

    /**

     * 在SD卡上创建文件

     * @param fileName

     * @return File

     * @throws IOException

     */

    public File creatSDFile(String fileName) throws IOException{

        File file=new File(SDpath+fileName);

        file.createNewFile();

        return file;

    }

    /**

     * 在SDCARD创建目录

     * @param dirName

     * @return

     */

    public File creatSDDir(String dirName){

        File dir=new File(SDpath+dirName);

        dir.mkdir();

        return dir;

    }

    public boolean isFileExist(String fileName){

        File file=new File(fileName);

        return file.exists();

    }

    /**

     * 将一个InputStream里的数据写入SD卡

     */

    public File write2SDFromInput(String path,String fileName,InputStream is){

        File file=null;

        OutputStream os=null;

        try{

            creatSDDir(path);

            file=creatSDFile(path+fileName);

            os=new FileOutputStream(file);

            byte buffer[]=new byte[4*1024];//4kb

            while((is.read(buffer))!=-1){

                os.write(buffer);

            }

            os.flush();

            System.out.println("write to "+path+"sucess!");

        }catch(Exception e){

            e.printStackTrace();

        }finally{

            try{

                os.close();

            }catch(Exception e){

                e.printStackTrace();

            }            

        }

        return file;

    }

    

    

    



}

随后是文件下载类：

package com.example.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;

    //此方法返回文本，但并未保存到SD卡

    public String downloadText(String urlstr){

        StringBuffer sb=new StringBuffer();

        String line=null;

        BufferedReader br=null;

        try{

            url=new URL(urlstr);

            HttpURLConnection con= (HttpURLConnection)url.openConnection();

            br=new BufferedReader(new InputStreamReader(con.getInputStream()));

            while((line=br.readLine())!=null){

                sb.append(line);

            }

        }catch(Exception e){

            e.printStackTrace();

        }finally{

            try {

                br.close();

            } catch (IOException e) {

                // TODO Auto-generated catch block

                e.printStackTrace();

            }

        }

        return sb.toString();

    }

    /**

     * 

     * @param urlstr

     * @param path

     * @param fileName

     * @return -1-error,0-success,1-file exist

     */

    public int downloadMP3(String urlstr,String path,String fileName){

        InputStream is=null;

        try{

            FileUtils fileUtils=new FileUtils();

            if(fileUtils.isFileExist(path+fileName)){

                return 1;

            }else{

                is=getInputStreamFromUrl(urlstr);

                File resultfile=fileUtils.write2SDFromInput(path, fileName, is);

                if(resultfile==null){

                    return -1;

                }

            }

        }catch(Exception e){

            e.printStackTrace();

            return -1;

        }finally{

            try {

                is.close();

            } catch (IOException e) {

                // TODO Auto-generated catch block

                e.printStackTrace();

            }

        }

        return 0;

    }

    private InputStream getInputStreamFromUrl(String urlstr) 

            throws MalformedURLException,IOException{

        URL url=new URL(urlstr);

        HttpURLConnection con=(HttpURLConnection)url.openConnection();

        InputStream is=con.getInputStream();

        return is;

    }



}