1 public String download(String urlStr) { 2         StringBuffer sb = new StringBuffer(); 3         String line = null; 4         BufferedReader buffer = null; 5         try { 6             // 创建一个URL对象 7             url = new URL(urlStr); 8             // 创建一个Http连接 9             HttpURLConnection urlConn = (HttpURLConnection) url10                     .openConnection();11             // 使用IO流读取数据12             buffer = new BufferedReader(new InputStreamReader(urlConn13                     .getInputStream()));14             while ((line = buffer.readLine()) != null) {15                 sb.append(line);16             }17         } catch (Exception e) {18             e.printStackTrace();19         } finally {20             try {21                 buffer.close();22             } catch (Exception e) {23                 e.printStackTrace();24             }25         }26         return sb.toString();27     }28 29     /**30      * 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31      */32     public int downFile(String urlStr, String path, String fileName) {33         InputStream inputStream = null;34         try {35             FileUtils fileUtils = new FileUtils();36             37             if (fileUtils.isFileExist(path + fileName)) {38                 return 1;39             } else {40                 inputStream = getInputStreamFromUrl(urlStr);41                 File resultFile = fileUtils.write2SDFromInput(path,fileName, inputStream);42                 if (resultFile == null) {43                     return -1;44                 }45             }46         } catch (Exception e) {47             e.printStackTrace();48             return -1;49         } finally {50             try {51                 inputStream.close();52             } catch (Exception e) {53                 e.printStackTrace();54             }55         }56         return 0;57     }58 59     /**60      * 根据URL得到输入流61      * 62      * @param urlStr63      * @return64      * @throws MalformedURLException65      * @throws IOException66      */67     public InputStream getInputStreamFromUrl(String urlStr)68             throws MalformedURLException, IOException {69         url = new URL(urlStr);70         HttpURLConnection urlConn = (HttpURLConnection) url.openConnection();71         InputStream inputStream = urlConn.getInputStream();72         return inputStream;73     }74 }

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);//写入数据            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;    }}