Android多线程.断点续传下载

多线程，可断点续传的demo！最早写于2010.7！

/**

 * @brief  主界面    
 * @author lixp
 */
public class HomeActivity extends Activity {
    private EditText downloadpathText;
    private TextView resultView;
    private ProgressBar progressBar;
    
    /**
     * 当Handler被创建会关联到创建它的当前线程的消息队列，该类用于往消息队列发送消息
     * 消息队列中的消息由当前线程内部进行处理
     * 使用Handler更新UI界面信息。
     */
    private Handler handler = new Handler(){
    @Override
public void handleMessage(Message msg) {
switch (msg.what) {
case 1:
progressBar.setProgress(msg.getData().getInt("size"));
float num = (float)progressBar.getProgress()/(float)progressBar.getMax();
int result = (int)(num*100);
resultView.setText(result+ "%");

//显示下载成功信息
if(progressBar.getProgress()==progressBar.getMax()){
Toast.makeText(HomeActivity.this, R.string.success, 1).show();
}
break;
case -1:
//显示下载错误信息
Toast.makeText(HomeActivity.this, R.string.error, 1).show();
break;
 }
 }
};
    
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        
        downloadpathText = (EditText) this.findViewById(R.id.path);
        progressBar = (ProgressBar) this.findViewById(R.id.downloadbar);
        resultView = (TextView) this.findViewById(R.id.resultView);
        
        Button button = (Button) this.findViewById(R.id.button);
        button.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
String path = downloadpathText.getText().toString();
System.out.println(Environment.getExternalStorageState()+"------"+Environment.MEDIA_MOUNTED);

if(Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)){
//开始下载文件
download(path, Environment.getExternalStorageDirectory());
}else{
//显示SDCard错误信息
Toast.makeText(HomeActivity.this, R.string.sdcarderror, 1).show();
}
}
});
}
    
  /**
  * 主线程(UI线程)
  * 对于显示控件的界面更新只是由UI线程负责，如果是在非UI线程更新控件的属性值，更新后的显示界面不会反映到屏幕上
  * 如果想让更新后的显示界面反映到屏幕上，需要用Handler设置。
  * @param path   lixp
  * @param savedir
  */
    private void download(final String path, final File savedir) {
    new Thread(new Runnable() {
@Override
public void run() {
//开启3个线程进行下载
FileDownloader loader = new FileDownloader(HomeActivity.this, path, savedir, 3);
    progressBar.setMax(loader.getFileSize());//设置进度条的最大刻度为文件的长度
   
try {
loader.download(new DownloadProgressListener() {
@Override
public void onDownloadSize(int size) {//实时获知文件已经下载的数据长度
Message msg = new Message();
msg.what = 1;
msg.getData().putInt("size", size);
handler.sendMessage(msg);//发送消息
}
});
} catch (Exception e) {
handler.obtainMessage(-1).sendToTarget();
}
}
}).start();
}

}

二.

/**
 * 下载线程类
 * @author lixp
 */
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 FileDownloader downloader;

/**
* @param downloader:下载器
* @param downUrl:下载地址
* @param saveFile:下载路径
* 
*/
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;
}

@Override
public void run() {
if(downLength < block){//未下载完成
try {
//使用Get方式下载
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.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);
}
}
}
/**
* 下载是否完成
*/
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;
}
}

三.//lixp
public class FileDownloader {
private static final String TAG = "FileDownloader";
private Context context;
private FileService fileService;

/* 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;
/**
* 获取线程数
*/
public int getThreadSize() {
return threads.length;
}
/**
* 获取文件大小
* @return
*/
public int getFileSize() {
return fileSize;
}

/**
* 累计已下载大小
* @param size
*/
protected synchronized void append(int size) {
downloadSize += size;
}

/**
* 更新指定线程最后下载的位置
* @param threadId 线程id
* @param pos 最后下载的位置
*/
protected synchronized void update(int threadId, int pos) {
this.data.put(threadId, pos);
this.fileService.update(this.downloadUrl, this.data);
}

/**
* 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;
fileService = new FileService(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(5*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);

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 ");

String filename = getFileName(conn);//获取文件名称
this.saveFile = new File(fileSaveDir, filename);//构建保存文件
Map<Integer, Integer> logdata = fileService.getData(downloadUrl);//获取下载记录

if(logdata.size()>0){//如果存在下载记录
for(Map.Entry<Integer, Integer> entry : logdata.entrySet())
data.put(entry.getKey(), entry.getValue());//把各条线程已经下载的数据长度放入data中
}

if(this.data.size()==this.threads.length){//下面计算所有线程已经下载的数据长度
for (int i = 0; i < this.threads.length; i++) {
this.downloadSize += this.data.get(i+1);
}

print("已经下载的长度"+ this.downloadSize);
}

//计算每条线程下载的数据长度
this.block = (this.fileSize % this.threads.length)==0? this.fileSize / this.threads.length : this.fileSize / this.threads.length + 1;
}else{
throw new RuntimeException("server no response ");
}
} catch (Exception e) {
print(e.toString());
throw new RuntimeException("don't connection this url");
}
}

/**
* 获取文件名
* @param conn
* @return
*/
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);//初始化每条线程已经下载的数据长度为0
}
}

for (int i = 0; i < this.threads.length; i++) {//开启线程进行下载
int downLength = this.data.get(i+1);

if(downLength < this.block && this.downloadSize<this.fileSize){//判断线程是否已经完成下载,否则继续下载
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.fileService.save(this.downloadUrl, this.data);
boolean notFinish = true;//下载未完成

while (notFinish) {// 循环判断所有线程是否完成下载
Thread.sleep(900);
notFinish = false;//假定全部线程下载完成

for (int i = 0; i < this.threads.length; i++){
if (this.threads[i] != null && !this.threads[i].isFinish()) {//如果发现线程未完成下载
notFinish = true;//设置标志为下载没有完成

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();
}
}
}

if(listener!=null) listener.onDownloadSize(this.downloadSize);//通知目前已经下载完成的数据长度
}

fileService.delete(this.downloadUrl);
} catch (Exception e) {
print(e.toString());
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()+ ":" : "";
print(key+ entry.getValue());
}
}

/**
* 打印日志信息
* @param msg
*/
private static void print(String msg){
Log.i(TAG, msg);
}
}

四.**
 * 数据库操作类
 * @author lixp
 */
public class DBOpenHelper extends SQLiteOpenHelper {
private static final String DBNAME = "down.db";
private static final int VERSION = 1;

/**
* 构造器
* @param context
*/
public DBOpenHelper(Context context) {
super(context, DBNAME, null, VERSION);
}

@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL("CREATE TABLE IF NOT EXISTS filedownlog (id integer primary key autoincrement, downpath varchar(100), threadid INTEGER, downlength INTEGER)");
}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("DROP TABLE IF EXISTS filedownlog");
onCreate(db);
}
}

五.//下载工具类
public class FileService {
private DBOpenHelper openHelper;
public FileService(Context context) {
openHelper = new DBOpenHelper(context);
}
/**
* 获取每条线程已经下载的文件长度
* @param path
* @return
*/
public Map<Integer, Integer> getData(String path){
SQLiteDatabase db = openHelper.getReadableDatabase();
Cursor cursor = db.rawQuery("select threadid, downlength from filedownlog where downpath=?", new String[]{path});
Map<Integer, Integer> data = new HashMap<Integer, Integer>();

while(cursor.moveToNext()){
data.put(cursor.getInt(0), cursor.getInt(1));
}

cursor.close();
db.close();
return data;
}

/**
* 保存每条线程已经下载的文件长度
* @param path
* @param map
*/
public void save(String path,  Map<Integer, Integer> map){//int threadid, int position
SQLiteDatabase db = openHelper.getWritableDatabase();
db.beginTransaction();

try{
for(Map.Entry<Integer, Integer> entry : map.entrySet()){
db.execSQL("insert into filedownlog(downpath, threadid, downlength) values(?,?,?)",
new Object[]{path, entry.getKey(), entry.getValue()});
}
db.setTransactionSuccessful();
}finally{
db.endTransaction();
}
db.close();
}

/**
* 实时更新每条线程已经下载的文件长度
* @param path
* @param map
*/
public void update(String path, Map<Integer, Integer> map){
SQLiteDatabase db = openHelper.getWritableDatabase();
db.beginTransaction();

try{
for(Map.Entry<Integer, Integer> entry : map.entrySet()){
db.execSQL("update filedownlog set downlength=? where downpath=? and threadid=?",
new Object[]{entry.getValue(), path, entry.getKey()});
}
db.setTransactionSuccessful();
}finally{
db.endTransaction();
}
db.close();
}

/**
* 当文件下载完成后，删除对应的下载记录
* @param path
*/
public void delete(String path){
SQLiteDatabase db = openHelper.getWritableDatabase();
db.execSQL("delete from filedownlog where downpath=?", new Object[]{path});
db.close();
}
}