android应用多线程和http断点续传下载数据
程序员文章站
2022-04-10 22:52:37
...
断点续传的原理很简单，就是在Http的请求上和一般的下载有所不同而已。注：需要web容器的支持，现在绝大多数都支持此项
以例子说明断点续传。
例如使用本地的服务器127.0.0.1，文件名为data.zip。下载该文件所发出的头信息如下：
下面是用自己模拟一个"浏览器"来传递请求信息给Web服务器，要求从20120828字节开始。
请仔细查看一下，就会发现上面多了一行RANGE: bytes=20120828- 的信息
这一行的意思是告诉服务器下载data.zip这个文件从20120828字节开始传，前面的字节就不需要用传了。
服务器收到这个请求以后，返回的信息如下：
返回的代码也改为206了，而不再是200了。
知道了以上原理，就可以进行断点续传的编程了。
至于多线程，不多做介绍了，以下是实现的多线程断点续的部分代码：
文件下载类的主要代码
下载的线程类的主要代码
下载的调用如下：
其中downloadbar是一个进度条控件，SpecialActivity则是android中的一个控件
以例子说明断点续传。
例如使用本地的服务器127.0.0.1，文件名为data.zip。下载该文件所发出的头信息如下：
GET /data.zip HTTP/1.1 Accept: image/gif, image/x-xbitmap, image/jpeg, image/pjpeg, application/vnd.ms-excel, application/msword, application/vnd.ms-powerpoint, */* Accept-Language: zh-cn Accept-Encoding: gzip, deflate User-Agent: Mozilla/4.0 (compatible; MSIE 5.01; Windows NT 5.0) Connection: Keep-Alive在服务器端接收到请求后，会按要求寻找请求的文件，并提取文件的信息，然后返回给浏览器，返回信息如下：
200 Content-Length=105555555 Accept-Ranges=bytes Date=Sun, 28 Aug 2012 10:56:16 GMT ETag=W/"031a54e173c11:df5" Content-Type=application/octet-stream Server=Apache/1.3.14(Unix) Last-Modified= Sun, 28 Aug 2012 10:56:16 GMT断点续传，就是要将文件从已经下载的地方开始，继续下载。所在客户端在发给服务器的信息中，要指明下载开始的地方。
下面是用自己模拟一个"浏览器"来传递请求信息给Web服务器，要求从20120828字节开始。
GET /data.zip HTTP/1.0 User-Agent: Mozilla/4.0 (compatible; MSIE 5.01; Windows NT 5.0)RANGE: bytes=20120828-
请仔细查看一下，就会发现上面多了一行RANGE: bytes=20120828- 的信息
这一行的意思是告诉服务器下载data.zip这个文件从20120828字节开始传，前面的字节就不需要用传了。
服务器收到这个请求以后，返回的信息如下：
206 Content-Length=105555555 Content-Range=bytes 20120828-105555554/105555555 Date= Sun, 28 Aug 2012 11:04:18 GMT ETag=W/"031a54e173c11:df5" Content-Type=application/octet-stream Server=Apache/1.3.14(Unix) Last-Modified= Sun, 28 Aug 2012 10:56:16 GMT和前面服务器返回的信息比较一下，就会发现增加了一行：
Content-Range=bytes 20120828-10555554/10555555
返回的代码也改为206了，而不再是200了。
知道了以上原理，就可以进行断点续传的编程了。
至于多线程，不多做介绍了，以下是实现的多线程断点续的部分代码：
文件下载类的主要代码
private static final String TAG = "FileDownloader";
private Context context;
private DownloadDao downloadDao;
/* 已下载文件长度 */
private int downloadSize = 0;
/* 原始文件长度 */
private int fileSize = 0;
/* 线程数 */
private DownloadThread[] threads;
/* 本地保存文件 */
private File saveFile;
/* 缓存各线程下载的长度*/
private Map<Integer, Integer> data = new ConcurrentHashMap<Integer, Integer>();
/* 每条线程下载的长度 */
private int block;
/* 下载路径 */
private String downloadUrl;
/* 压缩包名称 */
private String filename;
/**
* 构建文件下载器
* @param downloadUrl 下载路径
* @param fileSaveDir 文件保存目录
* @param threadNum 下载线程数
*/
public FileDownloader(Context context, String downloadUrl, File fileSaveDir, int threadNum) {
try {
this.context = context;
this.downloadUrl = downloadUrl;
downloadDao = new DownloadDao(this.context);
URL url = new URL(this.downloadUrl);
if(!fileSaveDir.exists()) fileSaveDir.mkdirs();
this.threads = new DownloadThread[threadNum];
HttpURLConnection conn = (HttpURLConnection) url.openConnection();
conn.setConnectTimeout(10*1000);
//conn.setReadTimeout(50*1000);
conn.setRequestMethod("GET");
conn.setRequestProperty("Accept", "image/gif, image/jpeg, image/pjpeg, image/pjpeg, application/x-shockwave-flash, application/xaml+xml, application/vnd.ms-xpsdocument, application/x-ms-xbap, application/x-ms-application, application/vnd.ms-excel, application/vnd.ms-powerpoint, application/msword, */*");
conn.setRequestProperty("Accept-Language", "zh-CN");
conn.setRequestProperty("Referer", downloadUrl);
conn.setRequestProperty("Charset", "UTF-8");
conn.setRequestProperty("User-Agent", "Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 5.2; Trident/4.0; .NET CLR 1.1.4322; .NET CLR 2.0.50727; .NET CLR 3.0.04506.30; .NET CLR 3.0.4506.2152; .NET CLR 3.5.30729)");
conn.setRequestProperty("Connection", "Keep-Alive");
conn.connect();
printResponseHeader(conn);
Log.w("conn.getResponseCode()",String.valueOf(conn.getResponseCode()));
if (conn.getResponseCode()==200) {
this.fileSize = conn.getContentLength();//根据响应获取文件大小
if (this.fileSize <= 0) throw new RuntimeException("Unkown file size ");
this.filename = getFileName(conn);
this.saveFile = new File(fileSaveDir, filename);/* 保存文件 */
ArrayList<Map<String,String>> logdata = downloadDao.getData(downloadUrl);
if(logdata.size()>0){
for(int i=0; i<logdata.size(); i++){
int threadId = 0;
int pos = 0;
for(Map.Entry<String, String> entry : logdata.get(i).entrySet())
{
if(entry.getKey().equals("THREADID")){
threadId = Integer.parseInt(entry.getValue());
}else{
pos = Integer.parseInt(entry.getValue());
}
}
data.put(threadId,pos);
}
// for(Map.Entry<String, String> entry : logdata.get(0).entrySet())
// data.put(Integer.parseInt(entry.getKey()), Integer.parseInt(entry.getValue()));
}
this.block = (this.fileSize % this.threads.length)==0? this.fileSize / this.threads.length : this.fileSize / this.threads.length + 1;
if(this.data.size()==this.threads.length){
for (int i = 0; i < this.threads.length; i++) {
this.downloadSize += this.data.get(i+1);
}
Log.w(TAG, "已经下载的长度"+ this.downloadSize);
}
}else{
throw new RuntimeException("server no response ");
}
} catch (Exception e) {
Log.w(TAG, e.getMessage());
throw new RuntimeException("don't connection this url");
}
}
/**
* 获取文件名
*/
private String getFileName(HttpURLConnection conn) {
String filename = this.downloadUrl.substring(this.downloadUrl.lastIndexOf('/') + 1);
if(filename==null || "".equals(filename.trim())){//如果获取不到文件名称
for (int i = 0;; i++) {
String mine = conn.getHeaderField(i);
if (mine == null) break;
if("content-disposition".equals(conn.getHeaderFieldKey(i).toLowerCase())){
Matcher m = Pattern.compile(".*filename=(.*)").matcher(mine.toLowerCase());
if(m.find()) return m.group(1);
}
}
filename = UUID.randomUUID()+ ".tmp";//默认取一个文件名
}
return filename;
}
/**
* 开始下载文件
* @param listener 监听下载数量的变化,如果不需要了解实时下载的数量,可以设置为null
* @return 已下载文件大小
* @throws Exception
*/
public int download(DownloadProgressListener listener) throws Exception{
try {
RandomAccessFile randOut = new RandomAccessFile(this.saveFile, "rw");
if(this.fileSize>0) randOut.setLength(this.fileSize);
randOut.close();
URL url = new URL(this.downloadUrl);
if(this.data.size() != this.threads.length){
this.data.clear();
for (int i = 0; i < this.threads.length; i++) {
this.data.put(i+1, 0);
}
}
for (int i = 0; i < this.threads.length; i++) {
int downLength = this.data.get(i+1);
if(downLength < this.block && this.downloadSize<this.fileSize){ //该线程未完成下载时,继续下载
this.threads[i] = new DownloadThread(this, url, this.saveFile, this.block, this.data.get(i+1), i+1);
this.threads[i].setPriority(7);
this.threads[i].start();
}else{
this.threads[i] = null;
}
}
this.downloadDao.saveData(this.downloadUrl, this.data);
boolean notFinish = true;//下载未完成
while (notFinish) {// 循环判断是否下载完毕
Thread.sleep(900);
notFinish = false;//假定下载完成
for (int i = 0; i < this.threads.length; i++){
if (this.threads[i] != null && !this.threads[i].isFinish()) {
notFinish = true;//下载没有完成
if(this.threads[i].getDownLength() == -1){//如果下载失败,再重新下载
this.threads[i] = new DownloadThread(this, url, this.saveFile, this.block, this.data.get(i+1), i+1);
this.threads[i].setPriority(7);
this.threads[i].start();
}
}
}
Log.w("this.downloadSize", String.valueOf(this.downloadSize));
Log.w("this.fileSize", String.valueOf(this.fileSize));
if(this.downloadSize==this.fileSize){
//解压zip文件
/*listener.onDownloadSize(this.downloadSize,true);
String unZipfileName=this.saveFile.getPath();//压缩文件路径
this.unZip(unZipfileName, this.tempPath);
listener.onDownloadSize(this.downloadSize,false);*/
listener.onDownloadSize(this.downloadSize,false);
String unZipfileName=this.saveFile.getPath();//压缩文件路径
this.unZip(unZipfileName, this.tempPath);
listener.onDownloadSize(this.downloadSize,true);
}else{
listener.onDownloadSize(this.downloadSize,false);
}
}
downloadDao.deleteData(this.downloadUrl);
} catch (Exception e) {
Log.w(TAG, e.getMessage());
throw new Exception("file download fail");
}
return this.downloadSize;
}
/**
* 获取Http响应头字段
* @param http
* @return
*/
public static Map<String, String> getHttpResponseHeader(HttpURLConnection http) {
Map<String, String> header = new LinkedHashMap<String, String>();
for (int i = 0;; i++) {
String mine = http.getHeaderField(i);
if (mine == null) break;
header.put(http.getHeaderFieldKey(i), mine);
}
return header;
}
/**
* 打印Http头字段
* @param http
*/
public static void printResponseHeader(HttpURLConnection http){
Map<String, String> header = getHttpResponseHeader(http);
for(Map.Entry<String, String> entry : header.entrySet()){
String key = entry.getKey()!=null ? entry.getKey()+ ":" : "";
Log.w(TAG, key+ entry.getValue());
}
}
下载的线程类的主要代码
/**
* 下载线程类
* @author zhaidi
*
*/
public class DownloadThread extends Thread {
private static final String TAG = "DownloadThread";
private File saveFile;
private URL downUrl;
private int block;
/* 下载开始位置 */
private int threadId = -1;
private int downLength;
private boolean finish = false;
private FileUpOrDown downloader;
//private FileUpdater updater;
public DownloadThread(FileDownloader downloader, URL downUrl, File saveFile, int block, int downLength, int threadId) {
this.downUrl = downUrl;
this.saveFile = saveFile;
this.block = block;
this.downloader = downloader;
this.threadId = threadId;
this.downLength = downLength;
}
public DownloadThread(FileUpdater updater, URL downUrl, File saveFile, int block, int downLength, int threadId) {
this.downUrl = downUrl;
this.saveFile = saveFile;
this.block = block;
this.downloader = updater;
this.threadId = threadId;
this.downLength = downLength;
}
@Override
public void run() {
if(downLength < block){//未下载完成
try {
HttpURLConnection http = (HttpURLConnection) downUrl.openConnection();
http.setConnectTimeout(5 * 1000);
http.setRequestMethod("GET");
http.setRequestProperty("Accept", "image/gif, image/jpeg, image/pjpeg, image/pjpeg, application/x-shockwave-flash, application/xaml+xml, application/vnd.ms-xpsdocument, application/x-ms-xbap, application/x-ms-application, application/vnd.ms-excel, application/vnd.ms-powerpoint, application/msword, */*");
http.setRequestProperty("Accept-Language", "zh-CN");
http.setRequestProperty("Referer", downUrl.toString());
http.setRequestProperty("Charset", "UTF-8");
int startPos = block * (threadId - 1) + downLength;//开始位置
int endPos = block * threadId -1;//结束位置
http.setRequestProperty("Range", "bytes=" + startPos + "-"+ endPos);//设置获取实体数据的范围
http.setRequestProperty("User-Agent", "Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 5.2; Trident/4.0; .NET CLR 1.1.4322; .NET CLR 2.0.50727; .NET CLR 3.0.04506.30; .NET CLR 3.0.4506.2152; .NET CLR 3.5.30729)");
http.setRequestProperty("Connection", "Keep-Alive");
InputStream inStream = http.getInputStream();
byte[] buffer = new byte[1024];
int offset = 0;
print("Thread " + this.threadId + " start download from position "+ startPos);
RandomAccessFile threadfile = new RandomAccessFile(this.saveFile, "rwd");
threadfile.seek(startPos);
while ((offset = inStream.read(buffer, 0, 1024)) != -1) {
threadfile.write(buffer, 0, offset);
downLength += offset;
downloader.update(this.threadId, downLength);
downloader.saveLogFile();
downloader.append(offset);
}
threadfile.close();
inStream.close();
print("Thread " + this.threadId + " download finish");
this.finish = true;
} catch (Exception e) {
this.downLength = -1;
print("Thread "+ this.threadId+ ":"+ e);
}
}
}
private static void print(String msg){
Log.i(TAG, msg);
}
/**
* 下载是否完成
* @return
*/
public boolean isFinish() {
return finish;
}
/**
* 已经下载的内容大小
* @return 如果返回值为-1,代表下载失败
*/
public long getDownLength() {
return downLength;
}
}
下载的调用如下：
其中downloadbar是一个进度条控件，SpecialActivity则是android中的一个控件
FileDownloader loader = new FileDownloader(SpecialActivity.this, path, dir, 5);
int length = loader.getFileSize();//获取文件的长度
downloadbar.setMax(length);
loader.download(new DownloadProgressListener(){
@Override
/*public void onDownloadSize(int size) {//可以实时得到文件下载的长度
Message msg = new Message();
msg.what = 1;
msg.getData().putInt("size", size);
handler.sendMessage(msg);
}});*/
public void onDownloadSize(int size,boolean upzip) {//可以实时得到文件下载的长度
Message msg = new Message();
msg.what = 1;
msg.getData().putInt("size", size);
handler.sendMessage(msg);
}});