Android（五）数据存储之五网络多线程断点下载 -

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Android（五）数据存储之五网络多线程断点下载

们编写的是Andorid的HTTP多线程断点下载应用程序。因为之间我们学习的学习积累，直接使用单线程下载HTTP文件对我们来说是一件非常简单的事。那么，多线程断点下载的难点在哪里？1.多线程下载，2.支持断点。 
多线程下载： <img title="2010-03-03 传智播客—Android（五）数据存储之五网络多线程断点下载 - 长城 - 长城" src="http://lh4.ggpht.com/_FMPy3IVGHrs/S49SK45xqaI/AAAAAAAABms/B6bk9kJo_vU/632BF46FE91E9326216CA04E22AF3F9E09350A1C.jpg?imgmax=800" border="0" alt="2010-03-03 传智播客—Android（五）数据存储之五网络多线程断点下载 - 长城 - 长城" width="435" height="91">
如何才能从文件的指定位置处开始下载文件？（比如从50MB开始）这一点我们可以通过HTTP请求信息头来设置，还记得HTTP请求信息头的“Range”属性吗？
断点：
首要问题（多线程下载）已经被我们解决了，支持断点下载想必大家也已经想到了。就是将下载的进度保存到文件中，但在Android中却不能这么做。通过老黎的试验，在Android平台中，我们需要向文件中写出下载的文件数据，还需要向另一个文件中写出下载进度，这样会出错。这样会导致有一个文件的内容没有被写出。所以我们就不能以文件的方式来保存下载进度，但可以通过数据库的方式保存下载进度。
这两大问题我们已经有了解决思路，那么就开始动手编写吧！
1.创建Android工程
Project name:MulThreadDownloader
BuildTarget:Android2.1
Application name：多线程断点下载
Package name:com.changcheng.download
Create Activity:MulThreadDownloader
Min SDK Version:7
2.AndroidManifest.xml
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.changcheng.download"
android:versionCode="1"
android:versionName="1.0">
<application android:icon="@drawable/icon" android:label="@string/app_name">
<activity android:name=".MulThreadDownloader"
android:label="@string/app_name">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
<uses-sdk android:minSdkVersion="7" />

<uses-permission android:name="android.permission.MOUNT_UNMOUNT_FILESYSTEMS"/>

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>

<uses-permission android:name="android.permission.INTERNET"/>
</manifest>
3.strings.xml
<?xml version="1.0" encoding="utf-8"?>
<resources>
<string name="hello">Hello World, DownloadActivity!</string>
<string name="app_name">多线程断点下载</string>
<string name="path">下载路径</string>
<string name="downloadbutton">下载</string>
<string name="sdcarderror">SDCard不存在或者写保护</string>
</resources>
4.main.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
>

<TextView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="@string/path"
/>
<EditText
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="http://www.winrar.com.cn/download/wrar380sc.exe"
android:id="@+id/path"
/>

<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/downloadbutton"
android:id="@+id/button"
/>

<ProgressBar
android:layout_width="fill_parent"
android:layout_height="20dip"
style="?android:attr/progressBarStyleHorizontal"
android:id="@+id/downloadbar"/>

<TextView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:gravity="center"
android:id="@+id/resultView"
/>
</LinearLayout>
5.MulThreadDownloader
package com.changcheng.download;
import java.io.File;
import com.changcheng.net.download.DownloadProgressListener;
import com.changcheng.net.download.FileDownloader;
import com.changcheng.download.R;
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;
public class MulThreadDownloader extends Activity {
private EditText pathText;
private ProgressBar progressBar;
private TextView resultView;
private Handler handler = new Handler(){
@Override
public void handleMessage(Message msg) {
if(!Thread.currentThread().isInterrupted()){
switch (msg.what) {
case 1:
// 获取当前文件下载的进度
int size = msg.getData().getInt("size");
progressBar.setProgress(size);
int result = (int)(((float)size/(float)progressBar.getMax()) * 100);
resultView.setText(result+ "%");
if(progressBar.getMax() == size){
Toast.makeText(MulThreadDownloader.this, "文件下载完成", 1).show();
}
break;
case -1:
String error = msg.getData().getString("error");
Toast.makeText(MulThreadDownloader.this, error, 1).show();
break;
}
}
super.handleMessage(msg);
}
};
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
pathText = (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 = pathText.getText().toString();
if(Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)){
//下载文件需要很长的时间，主线程是不能够长时间被阻塞，如果主线程被长时间阻塞，那么Android被回收应用
download(path, Environment.getExternalStorageDirectory());
}else{
Toast.makeText(MulThreadDownloader.this, R.string.sdcarderror, 1).show();
}
}
});
}
/**
* 下载文件
* @param path 下载路径
* @param saveDir 文件保存目录
*/
//对于Android的UI控件，只能由主线程负责显示界面的更新，其他线程不能直接更新UI控件的显示
public void download(final String path, final File saveDir){
new Thread(new Runnable() {
@Override
public void run() {
FileDownloader downer = new FileDownloader(MulThreadDownloader.this, path, saveDir, 3);
progressBar.setMax(downer.getFileSize());//设置进度条的最大刻度
try {
downer.download(new DownloadProgressListener(){
@Override
public void onDownloadSize(int size) {
Message msg = new Message();
msg.what = 1;
msg.getData().putInt("size", size);
handler.sendMessage(msg);//发送消息
}});
} catch (Exception e) {
Message msg = new Message();
msg.what = -1;
msg.getData().putString("error", "下载失败");
handler.sendMessage(msg);
}
}
}).start();
}
}
6.FileDownload
package com.changcheng.net.download;
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 com.changcheng.download.service.FileService;
import android.content.Context;
import android.util.Log;
/**
* 文件下载器
* @author lihuoming@sohu.com
*
*/
public class FileDownloader {
private Context context;
private FileService fileService;
private static final String TAG = "FileDownloader";
/* 已下载文件大小 */
private int downloadSize = 0;
/* 原始文件大小 */
private int fileSize = 0;
/* 线程数 */
private DownloadThread[] threads;
/* 下载路径 */
private URL url;
/* 本地保存文件 */
private File saveFile;
/* 下载记录文件 */
private File logFile;
/* 缓存各线程最后下载的位置*/
private Map<Integer, Integer> data = new ConcurrentHashMap<Integer, Integer>();
/* 每条线程下载的大小 */
private int block;
private String downloadUrl;//下载路径
/**
* 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 FileDownloader(Context context, String downloadUrl, File fileSaveDir, int threadNum) {
try {
this.context = context;
this.downloadUrl = downloadUrl;
fileService = new FileService(context);
this.url = new URL(downloadUrl);
if(!fileSaveDir.exists()) fileSaveDir.mkdirs();
this.threads = new DownloadThread[threadNum];
HttpURLConnection conn = (HttpURLConnection) url.openConnection();
conn.setConnectTimeout(6*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("无法获知文件大小 ");
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){
data.putAll(logdata);
}
this.block = 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)-(this.block * i);
}
print("已经下载的长度"+ this.downloadSize);
}
}else{
throw new RuntimeException("服务器响应错误 ");
}
} catch (Exception e) {
print(e.toString());
throw new RuntimeException("连接不到下载路径 ");
}
}
/**
* 获取文件名
*/
private String getFileName(HttpURLConnection conn) {
String filename = this.url.toString().substring(this.url.toString().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 {
if(this.data.size() != this.threads.length){
this.data.clear();
for (int i = 0; i < this.threads.length; i++) {
this.data.put(i+1, this.block * i);
}
}
for (int i = 0; i < this.threads.length; i++) {
int downLength = this.data.get(i+1) - (this.block * i);
if(downLength < this.block && this.data.get(i+1)<this.fileSize){ //该线程未完成下载时,继续下载
RandomAccessFile randOut = new RandomAccessFile(this.saveFile, "rw");
if(this.fileSize>0) randOut.setLength(this.fileSize);
randOut.seek(this.data.get(i+1));
this.threads[i] = new DownloadThread(this, this.url, randOut, 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
RandomAccessFile randOut = new RandomAccessFile(this.saveFile, "rw");
randOut.seek(this.data.get(i+1));
this.threads[i] = new DownloadThread(this, this.url, randOut, 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);
}
fileService.delete(this.downloadUrl);
} catch (Exception e) {
print(e.toString());
throw new Exception("下载失败");
}
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());
}
}
private static void print(String msg){
Log.i(TAG, msg);
}
}
7.DownloadProgressListener
package com.changcheng.net.download;
public interface DownloadProgressListener {
public void onDownloadSize(int size);
}
8.FileService
package com.changcheng.download.service;
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);
}
/**
* 获取线程最后下载位置
* @param path
* @return
*/
public Map<Integer, Integer> getData(String path){
SQLiteDatabase db = openHelper.getReadableDatabase();
Cursor cursor = db.rawQuery("select threadid, position from filedown 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;
}
/**
* 保存下载线程初始位置
* @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 filedown(downpath, threadid, position) values(?,?,?)",
new Object[]{path, entry.getKey(), entry.getValue()});
}
db.setTransactionSuccessful();
}finally{
db.endTransaction();
}
db.close();
}
/**
* 实时更新线程的最后下载位置
* @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 filedown set position=? 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，清掉该文件对应的下载记录
* @param path
*/
public void delete(String path){
SQLiteDatabase db = openHelper.getWritableDatabase();
db.execSQL("delete from filedown where downpath=?", new Object[]{path});
db.close();
}
}
9.DownloadThread
package com.changcheng.net.download;
import java.io.InputStream;
import java.io.RandomAccessFile;
import java.net.HttpURLConnection;
import java.net.URL;
import android.util.Log;
public class DownloadThread extends Thread {
private static final String TAG = "DownloadThread";
private RandomAccessFile saveFile;
private URL downUrl;
private int block;
/* 下载开始位置 */
private int threadId = -1;
private int startPos;
private int downLength;
private boolean finish = false;
private FileDownloader downloader;
public DownloadThread(FileDownloader downloader, URL downUrl, RandomAccessFile saveFile, int block, int startPos, int threadId) {
this.downUrl = downUrl;
this.saveFile = saveFile;
this.block = block;
this.startPos = startPos;
this.downloader = downloader;
this.threadId = threadId;
this.downLength = startPos - (block * (threadId - 1));
}
@Override
public void run() {
if(downLength < block){//未下载完成
try {
HttpURLConnection http = (HttpURLConnection) downUrl.openConnection();
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");
http.setRequestProperty("Range", "bytes=" + this.startPos + "-");
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();
int max = block>1024 ? 1024 : (block>10 ? 10 : 1);
byte[] buffer = new byte[max];
int offset = 0;
print("线程 " + this.threadId + "从位置"+ this.startPos+ "开始下载 ");
while (downLength < block && (offset = inStream.read(buffer, 0, max)) != -1) {
saveFile.write(buffer, 0, offset);
downLength += offset;
downloader.update(this.threadId, block * (threadId - 1) + downLength);
downloader.saveLogFile();
downloader.append(offset);
int spare = block-downLength;//求剩下的字节数
if(spare < max) max = (int) spare;
}
saveFile.close();
inStream.close();
print("线程 " + this.threadId + "完成下载 ");
this.finish = true;
this.interrupt();
} catch (Exception e) {
this.downLength = -1;
print("线程"+ 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;
}
}
11.DBOpenHelper
package com.changcheng.download.service;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
public class DBOpenHelper extends SQLiteOpenHelper {
private static final String DBNAME = "download.db";
private static final int VERSION = 2;
public DBOpenHelper(Context context) {
super(context, DBNAME, null, VERSION);
}
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL("CREATE TABLE IF NOT EXISTS filedown (id integer primary key autoincrement, downpath varchar(100), threadid INTEGER, position INTEGER)");
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("DROP TABLE IF EXISTS filedown");
onCreate(db);
}
}
结束！

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