一个简单的HttpURLConnection多线程下载实例，没有做断点续传，没有实现线程池，会根据网络状况自动分配线程数
/**
* 简单的多线程下载（不支持断点,无线程池） * * @Title MulThreadDownload * @Description 简单的多线程下载 * @author Andy */ public class MulThreadDownload { /** 下载的URL */ private URL downloadUrl; /** 本地文件 */ private File localFile; /** 每个线程下载的数据长度 */ private int block; /** * * 多线程文件下载(根据网络状况自动分配线程数) * * @param path * 下载地址 * @param locDirPath * 本地目录 * @param downloadCallBack * 回调 * @param fileTypes * 指定文件类型（可选） * @throws Exception */ public void download(Context context, String path, String locDirPath, DownloadCallBack downloadCallBack, String... fileTypes) throws Exception { int threadCount = 3; try { ConnectivityManager connectivityManager = (ConnectivityManager) context .getSystemService(CONNECTIVITY_SERVICE); NetworkInfo info = connectivityManager.getActiveNetworkInfo(); if (info == null || !info.isConnectedOrConnecting()) { threadCount = 3; return; } switch (info.getType()) { case ConnectivityManager.TYPE_WIFI: case ConnectivityManager.TYPE_WIMAX: case ConnectivityManager.TYPE_ETHERNET: threadCount = 4; break; case ConnectivityManager.TYPE_MOBILE: switch (info.getSubtype()) { case TelephonyManager.NETWORK_TYPE_LTE: // 4G case TelephonyManager.NETWORK_TYPE_HSPAP: case TelephonyManager.NETWORK_TYPE_EHRPD: threadCount = 3; break; case TelephonyManager.NETWORK_TYPE_UMTS: // 3G case TelephonyManager.NETWORK_TYPE_CDMA: case TelephonyManager.NETWORK_TYPE_EVDO_0: case TelephonyManager.NETWORK_TYPE_EVDO_A: case TelephonyManager.NETWORK_TYPE_EVDO_B: threadCount = 2; break; case TelephonyManager.NETWORK_TYPE_GPRS: // 2G case TelephonyManager.NETWORK_TYPE_EDGE: threadCount = 1; break; default: threadCount = 3; } break; default: threadCount = 3; } } catch (Exception e) { threadCount = 3; } download(path, locDirPath, threadCount, downloadCallBack, fileTypes); } /** * * 多线程文件下载 * * @param path * 下载地址 * @param locDirPath * 本地目录 * @param threadCount * 线程数 * @param downloadCallBack * 回调 * @param fileTypes * 指定文件类型（可选） * @throws Exception */ public void download(final String path, final String locDirPath, final int threadCount, final DownloadCallBack downloadCallBack, final String... fileTypes) { System.out.println("线程" + "主线程开始=" + path); new Thread() { public void run() { try { downloadThread(path, locDirPath, threadCount, downloadCallBack, fileTypes); } catch (Exception e) { e.printStackTrace(); System.out.println("线程" + "子线程开始=" + e); downloadCallBack.error(); } }; }.start(); } /** * * 多线程文件下载 * * @param path * 下载地址 * @param locDirPath * 本地目录 * @param threadCount * 线程数 * @param downloadCallBack * 回调 * @param fileTypes * 指定文件类型 * @throws Exception */ private void downloadThread(String path, String locDirPath, final int threadCount, final DownloadCallBack downloadCallBack, String... fileTypes) throws Exception { downloadUrl = new URL(path); HttpURLConnection conn = (HttpURLConnection) downloadUrl .openConnection(); // 设置 GET 请求方式 conn.setRequestMethod("GET"); // 设置响应超时 conn.setConnectTimeout(5 * 1000); // 获取下载文件大小 final int len = conn.getContentLength(); System.out.println("线程" + "len=" + len); if (len <= 0) { // 未获取到正确的文件大小 downloadCallBack.contentLengthError(); return; } File dir = new File(locDirPath); if (!dir.exists()) { dir.mkdirs(); } /* 获取本地文件完整路径 */ final String locPath = getLocPath(path, locDirPath, fileTypes); /* 创建本地目标文件，并设置其大小为准备下载文件的总大小 */ localFile = new File(locPath + ".tmp"); RandomAccessFile accessFile = new RandomAccessFile(localFile, "rwd"); accessFile.setLength(len); accessFile.close(); /* 计算每条线程要下载的数据大小 */ block = len % threadCount == 0 ? len / threadCount : len / threadCount + 1; downloadCallBack.totalSize(len); /* 启动线程下载文件 */ for (int i = 0; i < threadCount; i++) { int threadId = i; long start = i * block; long end = start + block - 1; if (end >= len) { end = len - 1; } System.out.println("线程" + threadId + "开始"); new DownloadThread(threadId, start, end, new Callback() { @Override public void complete(int threadId) { completeNum++; System.out.println("线程" + threadId + "完成"+completeNum+":"+threadCount); if (completeNum == threadCount) { // 全部下载完成 localFile.renameTo(new File(locPath)); downloadCallBack.complete(locPath); } } @Override public void progress(int threadId, long size) { downloadSize += size; downloadCallBack.progress(len, downloadSize); } @Override public void error(int threadId) { System.out.println("线程" + threadId + "error"); downloadCallBack.error(); } }).start(); } } public interface DownloadCallBack { /** 异常，结束下载，ContentLength<=0 */ public void contentLengthError(); public void totalSize(long total); public void complete(String path); public void progress(long total, long size); public void error(); } int completeNum = 0; long downloadSize = 0; private String getLocPath(String path, String locDirPath, String... fileTypes) { String locPath; // 获取文件名 String locName = OSUtil.toMD5(path); // 文件类型 String fileType; if (fileTypes != null && fileTypes.length > 0) { fileType = fileTypes[0]; } else { // 获取path中的文件格式后缀 String[] s = path.split("\\."); fileType = s[s.length - 1]; } if (fileType != null && fileType.trim().length() > 0) { // 如果path带有文件后缀，则使用其作为后缀 locPath = locDirPath + File.separator + locName + "." + fileType; } else { locPath = locDirPath + File.separator + locName; } return locPath; } /** * 内部类： 文件下载线程类 */ private final class DownloadThread extends Thread { /* 线程 id */ private int threadId; /* 线程下载结果回调 */ private Callback callback; /* 开始下载的位置 */ private long startPosition; /* 结束下载的位置 */ private long endPosition; /** * 新建一个下载线程 * * @param threadid * 线程 id */ public DownloadThread(int threadId, long start, long end, Callback callback) { this.threadId = threadId; this.callback = callback; startPosition = start; endPosition = end; } @Override public void run() { RandomAccessFile accessFile = null; try { /* 设置从本地文件的什么位置开始写入数据 ,"rwd" 表示对文件具有读写删权限 */ accessFile = new RandomAccessFile(localFile, "rwd"); accessFile.seek(startPosition); HttpURLConnection conn = (HttpURLConnection) downloadUrl .openConnection(); conn.setRequestMethod("GET"); conn.setReadTimeout(5 * 1000); /* 为 HTTP 设置 Range 属性，可以指定服务器返回数据的范围 */ conn.setRequestProperty("Range", "bytes=" + startPosition + "-" + endPosition); /* 将数据写往本地文件 */ long size = writeTo(accessFile, conn); if (size >= endPosition - startPosition) { callback.complete(threadId); } } catch (Exception e) { e.printStackTrace(); } finally { try { if (accessFile != null) { accessFile.close(); } } catch (IOException ex) { ex.printStackTrace(); } } } /** * 将下载数据写往本地文件 */ private long writeTo(RandomAccessFile accessFile, HttpURLConnection conn) { InputStream is = null; long size = 0; try { is = conn.getInputStream(); byte[] buffer = new byte[1024]; int len = -1; while ((len = is.read(buffer)) != -1) { accessFile.write(buffer, 0, len); size += len; callback.progress(threadId, len); } } catch (IOException e) { e.printStackTrace(); } finally { try { if (is != null) { is.close(); } } catch (Exception ex) { ex.printStackTrace(); } } return size; } } interface Callback { public void complete(int threadId); public void progress(int threadId, long size); public void error(int threadId); } }