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;    }}

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