Android 多任务多线程断点下载

让我们看一下代码的实现方法。

package com.smart.db;

import java.util.HashMap;

import java.util.Map;

import android.content.Context;

import android.database.Cursor;

import android.database.sqlite.SQLiteDatabase;

/**

* 业务bean

*

*/

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 SmartFileDownlog 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 SmartFileDownlog(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 SmartFileDownlog 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 SmartFileDownlog where downpath=?", new Object[]{path});

db.close();

}

}

package com.smart.impl;

import java.io.File;

import java.io.RandomAccessFile;

import java.net.HttpURLConnection;

import java.net.URL;

import java.util.LinkedHashMap;

import java.util.Map;

import java.util.UUID;

import java.util.concurrent.ConcurrentHashMap;

import java.util.regex.Matcher;

import java.util.regex.Pattern;

import android.content.Context;

import android.util.Log;

import com.smart.db.FileService;

/**

* 文件下载器

* @author lihuoming@sohu.com

*/

public class SmartFileDownloader {

private static final String TAG = "SmartFileDownloader";

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 SmartDownloadThread[] 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 void update(int threadId, int pos) {

this.data.put(threadId, pos);

}

/**

* 保存记录文件

*/

protected synchronized void saveLogFile() {

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 SmartFileDownloader(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 SmartDownloadThread[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);

this.saveFile = new File(fileSaveDir, filename);/* 保存文件 */

Map<Integer, Integer> logdata = fileService.getData(downloadUrl);

if(logdata.size()>0){

for(Map.Entry<Integer, Integer> entry : logdata.entrySet())

data.put(entry.getKey(), 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);

}

print("已经下载的长度"+ this.downloadSize);

}

}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

*/

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(SmartDownloadProgressListener 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();//清除数据

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 = new SmartDownloadThread(this, url, this.saveFile, this.block, this.data.get(i+1), i+1);

this.threads.setPriority(7);

this.threads.start();

}else{

this.threads = null;

}

}

this.fileService.save(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 != null && !this.threads.isFinish()) {

notFinish = true;//下载没有完成

if(this.threads.getDownLength() == -1){//如果下载失败,再重新下载

this.threads = new SmartDownloadThread(this, url, this.saveFile, this.block, this.data.get(i+1), i+1);

this.threads.setPriority(7);

this.threads.start();

}

}

}

if(listener!=null) listener.onDownloadSize(this.downloadSize);

}

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

private static void print(String msg){

Log.i(TAG, msg);

}

}

package com.smart.impl;

import java.io.File;

import java.io.InputStream;

import java.io.RandomAccessFile;

import java.net.HttpURLConnection;

import java.net.URL;

import android.util.Log;

public class SmartDownloadThread extends Thread {

private static final String TAG = "SmartDownloadThread";

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 SmartFileDownloader downloader;

public SmartDownloadThread(SmartFileDownloader 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 {

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;

}

}

package com.smart.activoty.download;

import java.io.File;

import android.app.Activity;

import android.os.Bundle;

import android.os.Environment;

import android.os.Handler;

import android.os.Message;

import android.view.View;

import android.widget.Button;

import android.widget.EditText;

import android.widget.ProgressBar;

import android.widget.TextView;

import android.widget.Toast;

import com.smart.impl.SmartDownloadProgressListener;

import com.smart.impl.SmartFileDownloader;

public class SmartDownloadActivity extends Activity {

private ProgressBar downloadbar;

private EditText pathText;

private TextView resultView;

private Handler handler = new Handler(){

@Override//信息

public void handleMessage(Message msg) {

switch (msg.what) {

case 1:

int size = msg.getData().getInt("size");

downloadbar.setProgress(size);

float result = (float)downloadbar.getProgress()/ (float)downloadbar.getMax();

int p = (int)(result*100);

resultView.setText(p+"%");

if(downloadbar.getProgress()==downloadbar.getMax())

Toast.makeText(SmartDownloadActivity.this, R.string.success, 1).show();

break;

case -1:

Toast.makeText(SmartDownloadActivity.this, R.string.error, 1).show();

break;

}

}

};

@Override

public void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.main);

Button button = (Button)this.findViewById(R.id.button);

downloadbar = (ProgressBar)this.findViewById(R.id.downloadbar);

pathText = (EditText)this.findViewById(R.id.path);

resultView = (TextView)this.findViewById(R.id.result);

button.setOnClickListener(new View.OnClickListener() {

@Override

public void onClick(View v) {

String path = pathText.getText().toString();

if(Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)){

File dir = Environment.getExternalStorageDirectory();//文件保存目录

download(path, dir);

}else{

Toast.makeText(SmartDownloadActivity.this, R.string.sdcarderror, 1).show();

}

}

});

}

//对于UI控件的更新只能由主线程(UI线程)负责，如果在非UI线程更新UI控件，更新的结果不会反映在屏幕上，某些控件还会出错

private void download(final String path, final File dir){

new Thread(new Runnable() {

@Override

public void run() {

try {

SmartFileDownloader loader = new SmartFileDownloader(SmartDownloadActivity.this, path, dir, 3);

int length = loader.getFileSize();//获取文件的长度

downloadbar.setMax(length);

loader.download(new SmartDownloadProgressListener(){

@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);

}});

} catch (Exception e) {

Message msg = new Message();//信息提示

msg.what = -1;

msg.getData().putString("error", "下载失败");//如果下载错误，显示提示失败！

handler.sendMessage(msg);

}

}

}).start();//开始

}

}

转自：http://www.apkbus.com/android-15380-1-1.html