使用多線程斷點續(xù)傳下載器在下載的時候多個線程并發(fā)可以占用服務器端更多資源， 從而加快下載速度，在下載過程中記錄每個線程已拷貝數(shù)據(jù)的數(shù)量，如果下載中斷，比如無信號斷線、電量不足等情況下，這就需要使用到斷點續(xù)傳功能，下次啟動 時從記錄位置繼續(xù)下載，可避免重復部分的下載。這里采用數(shù)據(jù)庫來記錄下載的進度。
斷點續(xù)傳
1.斷點續(xù)傳需要在下載過程中記錄每條線程的下載進度
2.每次下載開始之前先讀取數(shù)據(jù)庫，查詢是否有未完成的記錄，有就繼續(xù)下載，沒有則創(chuàng)建新記錄插入數(shù)據(jù)庫
3.在每次向文件中寫入數(shù)據(jù)之后，在數(shù)據(jù)庫中更新下載進度
4.下載完成之后刪除數(shù)據(jù)庫中下載記錄
Handler傳輸數(shù)據(jù)
這個主要用來記錄百分比，每下載一部分數(shù)據(jù)就通知主線程來記錄時間
1.主線程中創(chuàng)建的View只能在主線程中修改，其他線程只能通過和主線程通信，在主線程中改變View數(shù)據(jù)
2.我們使用Handler可以處理這種需求
主線程中創(chuàng)建Handler，重寫handleMessage()方法
新線程中使用Handler發(fā)送消息，主線程即可收到消息，并且執(zhí)行handleMessage()方法
使用多線程的好處：使用多線程下載會提升文件下載的速度。那么多線程下載文件的過程是：
(1)首先獲得下載文件的長度，然后設置本地文件的長度。
HttpURLConnection.getContentLength();//獲取下載文件的長度
RandomAccessFile file = new RandomAccessFile("QQWubiSetup.exe","rwd");
file.setLength(filesize);//設置本地文件的長度
(2)根據(jù)文件長度和線程數(shù)計算每條線程下載的數(shù)據(jù)長度和下載位置。
如：文件的長度為6M，線程數(shù)為3，那么，每條線程下載的數(shù)據(jù)長度為2M，每條線程開始下載的位置如下圖所示。
例如10M大小，使用3個線程來下載，
線程下載的數(shù)據(jù)長度 (10%3 == 0 ？ 10/3:10/3+1) ,第1，2個線程下載長度是4M，第三個線程下載長度為2M
下載開始位置：線程id*每條線程下載的數(shù)據(jù)長度 = ?
下載結束位置：（線程id+1）*每條線程下載的數(shù)據(jù)長度-1=?
(3)使用Http的Range頭字段指定每條線程從文件的什么位置開始下載，下載到什么位置為止，
如：指定從文件的2M位置開始下載，下載到位置(4M-1byte)為止
代碼如下：HttpURLConnection.setRequestProperty("Range", "bytes=2097152-4194303");
(4)保存文件，使用RandomAccessFile類指定每條線程從本地文件的什么位置開始寫入數(shù)據(jù)。
RandomAccessFile threadfile = new RandomAccessFile("QQWubiSetup.exe ","rwd");
threadfile.seek(2097152);//從文件的什么位置開始寫入數(shù)據(jù)
string.xml文件中代碼：
1 <?xml version="1.0" encoding="utf-8"?>
2 <resources>
3 <string name="hello">Hello World, MainActivity!</string>
4 <string name="app_name">Android網(wǎng)絡多線程斷點下載</string>
5 <string name="path">下載路徑</string>
6 <string name="downloadbutton">下載</string>
7 <string name="sdcarderror">SDCard不存在或者寫保護</string>
8 <string name="success">下載完成</string>
9 <string name="error">下載失敗</string>
10 </resources>
main.xml文件中代碼：
1 <?xml version="1.0" encoding="utf-8"?>
2 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
3 android:orientation="vertical"
4 android:layout_width="fill_parent"
5 android:layout_height="fill_parent">
6 <!-- 下載路徑 -->
7 <TextView
8 android:layout_width="fill_parent"
9 android:layout_height="wrap_content"
10 android:text="@string/path"/>
11 <EditText
12 android:id="@+id/path"
13 android:text="http://www.winrar.com.cn/download/wrar380sc.exe"
14 android:layout_width="fill_parent"
15 android:layout_height="wrap_content">
16 </EditText>
17 <!-- 下載按鈕 -->
18 <Button
19 android:layout_width="wrap_content"
20 android:layout_height="wrap_content"
21 android:text="@string/downloadbutton"
22 android:id="@+id/button"/>
23 <!-- 進度條 -->
24 <ProgressBar
25 android:layout_width="fill_parent"
26 android:layout_height="20dip"
27 style="?android:attr/progressBarStyleHorizontal"
28 android:id="@+id/downloadbar" />
29 <TextView
30 android:layout_width="fill_parent"
31 android:layout_height="wrap_content"
32 android:gravity="center"
33 android:id="@+id/resultView" />
34 </LinearLayout>
AndroidManifest.xml文件中代碼：
1 <?xml version="1.0" encoding="utf-8"?>
2 <manifest xmlns:android="http://schemas.android.com/apk/res/android" package="com.android.downloader" android:versionCode="1" android:versionName="1.0">
3 <uses-sdk android:minSdkVersion="8" />
4
5 <application android:icon="@drawable/icon" android:label="@string/app_name">
6 <activity android:name=".MainActivity"
7 android:label="@string/app_name">
8 <intent-filter>
9 <action android:name="android.intent.action.MAIN" />
10 <category android:name="android.intent.category.LAUNCHER" />
11 </intent-filter>
12 </activity>
13
14 </application>
15
16 <!-- 在SDCard中創(chuàng)建與刪除文件權限 -->
17 <uses-permission android:name="android.permission.MOUNT_UNMOUNT_FILESYSTEMS"/>
18
19 <!-- 往SDCard寫入數(shù)據(jù)權限 -->
20 <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
21
22 <!-- 訪問internet權限 -->
23 <uses-permission android:name="android.permission.INTERNET"/>
24 </manifest>
MainActivity中代碼：
1 package com.android.downloader;
2 import java.io.File;
3
4 import com.android.network.DownloadProgressListener;
5 import com.android.network.FileDownloader;
6
7 import android.app.Activity;
8 import android.os.Bundle;
9 import android.os.Environment;
10 import android.os.Handler;
11 import android.os.Message;
12 import android.view.View;
13 import android.widget.Button;
14 import android.widget.EditText;
15 import android.widget.ProgressBar;
16 import android.widget.TextView;
17 import android.widget.Toast;
18
19 public class MainActivity extends Activity {
20 private EditText downloadpathText;
21 private TextView resultView;
22 private ProgressBar progressBar;
23
24 /**
25 * 當Handler被創(chuàng)建會關聯(lián)到創(chuàng)建它的當前線程的消息隊列，該類用于往消息隊列發(fā)送消息
26 * 消息隊列中的消息由當前線程內(nèi)部進行處理
27 */
28 private Handler handler = new Handler(){
29
30 @Override
31 public void handleMessage(Message msg) {
32 switch (msg.what) {
33 case 1:
34 progressBar.setProgress(msg.getData().getInt("size"));
35 float num = (float)progressBar.getProgress()/(float)progressBar.getMax();
36 int result = (int)(num*100);
37 resultView.setText(result+ "%");
38
39 if(progressBar.getProgress()==progressBar.getMax()){
40 Toast.makeText(MainActivity.this, R.string.success, 1).show();
41 }
42 break;
43 case -1:
44 Toast.makeText(MainActivity.this, R.string.error, 1).show();
45 break;
46 }
47 }
48 };
49
50 /** Called when the activity is first created. */
51 @Override
52 public void onCreate(Bundle savedInstanceState) {
53 super.onCreate(savedInstanceState);
54 setContentView(R.layout.main);
55
56 downloadpathText = (EditText) this.findViewById(R.id.path);
57 progressBar = (ProgressBar) this.findViewById(R.id.downloadbar);
58 resultView = (TextView) this.findViewById(R.id.resultView);
59 Button button = (Button) this.findViewById(R.id.button);
60
61 button.setOnClickListener(new View.OnClickListener() {
62
63 @Override
64 public void onClick(View v) {
65 // TODO Auto-generated method stub
66 String path = downloadpathText.getText().toString();
67 System.out.println(Environment.getExternalStorageState()+"------"+Environment.MEDIA_MOUNTED);
68
69 if(Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)){
70 download(path, Environment.getExternalStorageDirectory());
71 }else{
72 Toast.makeText(MainActivity.this, R.string.sdcarderror, 1).show();
73 }
74 }
75 });
76 }
77
78 /**
79 * 主線程(UI線程)
80 * 對于顯示控件的界面更新只是由UI線程負責，如果是在非UI線程更新控件的屬性值，更新后的顯示界面不會反映到屏幕上
81 * @param path
82 * @param savedir
83 */
84 private void download(final String path, final File savedir) {
85 new Thread(new Runnable() {
86 @Override
87 public void run() {
88 FileDownloader loader = new FileDownloader(MainActivity.this, path, savedir, 3);
89 progressBar.setMax(loader.getFileSize());//設置進度條的最大刻度為文件的長度
90
91 try {
92 loader.download(new DownloadProgressListener() {
93 @Override
94 public void onDownloadSize(int size) {//實時獲知文件已經(jīng)下載的數(shù)據(jù)長度
95 Message msg = new Message();
96 msg.what = 1;
97 msg.getData().putInt("size", size);
98 handler.sendMessage(msg);//發(fā)送消息
99 }
100 });
101 } catch (Exception e) {
102 handler.obtainMessage(-1).sendToTarget();
103 }
104 }
105 }).start();
106 }
107 }
DBOpenHelper中代碼：
1 package com.android.service;
2 import android.content.Context;
3 import android.database.sqlite.SQLiteDatabase;
4 import android.database.sqlite.SQLiteOpenHelper;
5
6 public class DBOpenHelper extends SQLiteOpenHelper {
7 private static final String DBNAME = "down.db";
8 private static final int VERSION = 1;
9
10 public DBOpenHelper(Context context) {
11 super(context, DBNAME, null, VERSION);
12 }
13
14 @Override
15 public void onCreate(SQLiteDatabase db) {
16 db.execSQL("CREATE TABLE IF NOT EXISTS filedownlog (id integer primary key autoincrement, downpath varchar(100), threadid INTEGER, downlength INTEGER)");
17 }
18
19 @Override
20 public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
21 db.execSQL("DROP TABLE IF EXISTS filedownlog");
22 onCreate(db);
23 }
24 }
FileService中代碼：
1 package com.android.service;
2 import java.util.HashMap;
3 import java.util.Map;
4
5 import android.content.Context;
6 import android.database.Cursor;
7 import android.database.sqlite.SQLiteDatabase;
8
9 public class FileService {
10 private DBOpenHelper openHelper;
11
12 public FileService(Context context) {
13 openHelper = new DBOpenHelper(context);
14 }
15
16 /**
17 * 獲取每條線程已經(jīng)下載的文件長度
18 * @param path
19 * @return
20 */
21 public Map<Integer, Integer> getData(String path){
22 SQLiteDatabase db = openHelper.getReadableDatabase();
23 Cursor cursor = db.rawQuery("select threadid, downlength from filedownlog where downpath=?", new String[]{path});
24 Map<Integer, Integer> data = new HashMap<Integer, Integer>();
25
26 while(cursor.moveToNext()){
27 data.put(cursor.getInt(0), cursor.getInt(1));
28 }
29
30 cursor.close();
31 db.close();
32 return data;
33 }
34
35 /**
36 * 保存每條線程已經(jīng)下載的文件長度
37 * @param path
38 * @param map
39 */
40 public void save(String path, Map<Integer, Integer> map){//int threadid, int position
41 SQLiteDatabase db = openHelper.getWritableDatabase();
42 db.beginTransaction();
43
44 try{
45 for(Map.Entry<Integer, Integer> entry : map.entrySet()){
46 db.execSQL("insert into filedownlog(downpath, threadid, downlength) values(?,?,?)",
47 new Object[]{path, entry.getKey(), entry.getValue()});
48 }
49 db.setTransactionSuccessful();
50 }finally{
51 db.endTransaction();
52 }
53
54 db.close();
55 }
56
57 /**
58 * 實時更新每條線程已經(jīng)下載的文件長度
59 * @param path
60 * @param map
61 */
62 public void update(String path, Map<Integer, Integer> map){
63 SQLiteDatabase db = openHelper.getWritableDatabase();
64 db.beginTransaction();
65
66 try{
67 for(Map.Entry<Integer, Integer> entry : map.entrySet()){
68 db.execSQL("update filedownlog set downlength=? where downpath=? and threadid=?",
69 new Object[]{entry.getValue(), path, entry.getKey()});
70 }
71
72 db.setTransactionSuccessful();
73 }finally{
74 db.endTransaction();
75 }
76
77 db.close();
78 }
79
80 /**
81 * 當文件下載完成后，刪除對應的下載記錄
82 * @param path
83 */
84 public void delete(String path){
85 SQLiteDatabase db = openHelper.getWritableDatabase();
86 db.execSQL("delete from filedownlog where downpath=?", new Object[]{path});
87 db.close();
88 }
89 }
DownloadProgressListener中代碼：
1 package com.android.network;
2 public interface DownloadProgressListener {
3 public void onDownloadSize(int size);
4 }
FileDownloader中代碼：
1 package com.android.network;
2 import java.io.File;
3 import java.io.RandomAccessFile;
4 import java.net.HttpURLConnection;
5 import java.net.URL;
6 import java.util.LinkedHashMap;
7 import java.util.Map;
8 import java.util.UUID;
9 import java.util.concurrent.ConcurrentHashMap;
10 import java.util.regex.Matcher;
11 import java.util.regex.Pattern;
12
13 import com.android.service.FileService;
14
15 import android.content.Context;
16 import android.util.Log;
17
18 public class FileDownloader {
19 private static final String TAG = "FileDownloader";
20 private Context context;
21 private FileService fileService;
22
23 /* 已下載文件長度 */
24 private int downloadSize = 0;
25
26 /* 原始文件長度 */
27 private int fileSize = 0;
28
29 /* 線程數(shù) */
30 private DownloadThread[] threads;
31
32 /* 本地保存文件 */
33 private File saveFile;
34
35 /* 緩存各線程下載的長度*/
36 private Map<Integer, Integer> data = new ConcurrentHashMap<Integer, Integer>();
37
38 /* 每條線程下載的長度 */
39 private int block;
40
41 /* 下載路徑 */
42 private String downloadUrl;
43
44 /**
45 * 獲取線程數(shù)
46 */
47 public int getThreadSize() {
48 return threads.length;
49 }
50
51 /**
52 * 獲取文件大小
53 * @return
54 */
55 public int getFileSize() {
56 return fileSize;
57 }
58
59 /**
60 * 累計已下載大小
61 * @param size
62 */
63 protected synchronized void append(int size) {
64 downloadSize += size;
65 }
66
67 /**
68 * 更新指定線程最后下載的位置
69 * @param threadId 線程id
70 * @param pos 最后下載的位置
71 */
72 protected synchronized void update(int threadId, int pos) {
73 this.data.put(threadId, pos);
74 this.fileService.update(this.downloadUrl, this.data);
75 }
76
77 /**
78 * 構建文件下載器
79 * @param downloadUrl 下載路徑
80 * @param fileSaveDir 文件保存目錄
81 * @param threadNum 下載線程數(shù)
82 */
83 public FileDownloader(Context context, String downloadUrl, File fileSaveDir, int threadNum) {
84 try {
85 this.context = context;
86 this.downloadUrl = downloadUrl;
87 fileService = new FileService(this.context);
88 URL url = new URL(this.downloadUrl);
89 if(!fileSaveDir.exists()) fileSaveDir.mkdirs();
90 this.threads = new DownloadThread[threadNum];
91
92 HttpURLConnection conn = (HttpURLConnection) url.openConnection();
93 conn.setConnectTimeout(5*1000);
94 conn.setRequestMethod("GET");
95 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, */*");
96 conn.setRequestProperty("Accept-Language", "zh-CN");
97 conn.setRequestProperty("Referer", downloadUrl);
98 conn.setRequestProperty("Charset", "UTF-8");
99 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)");
100 conn.setRequestProperty("Connection", "Keep-Alive");
101 conn.connect();
102 printResponseHeader(conn);
103
104 if (conn.getResponseCode()==200) {
105 this.fileSize = conn.getContentLength();//根據(jù)響應獲取文件大小
106 if (this.fileSize <= 0) throw new RuntimeException("Unkown file size ");
107
108 String filename = getFileName(conn);//獲取文件名稱
109 this.saveFile = new File(fileSaveDir, filename);//構建保存文件
110 Map<Integer, Integer> logdata = fileService.getData(downloadUrl);//獲取下載記錄
111
112 if(logdata.size()>0){//如果存在下載記錄
113 for(Map.Entry<Integer, Integer> entry : logdata.entrySet())
114 data.put(entry.getKey(), entry.getValue());//把各條線程已經(jīng)下載的數(shù)據(jù)長度放入data中
115 }
116
117 if(this.data.size()==this.threads.length){//下面計算所有線程已經(jīng)下載的數(shù)據(jù)長度
118 for (int i = 0; i < this.threads.length; i++) {
119 this.downloadSize += this.data.get(i+1);
120 }
121
122 print("已經(jīng)下載的長度"+ this.downloadSize);
123 }
124
125 //計算每條線程下載的數(shù)據(jù)長度
126 this.block = (this.fileSize % this.threads.length)==0? this.fileSize / this.threads.length : this.fileSize / this.threads.length + 1;
127 }else{
128 throw new RuntimeException("server no response ");
129 }
130 } catch (Exception e) {
131 print(e.toString());
132 throw new RuntimeException("don't connection this url");
133 }
134 }
135
136 /**
137 * 獲取文件名
138 * @param conn
139 * @return
140 */
141 private String getFileName(HttpURLConnection conn) {
142 String filename = this.downloadUrl.substring(this.downloadUrl.lastIndexOf('/') + 1);
143
144 if(filename==null || "".equals(filename.trim())){//如果獲取不到文件名稱
145 for (int i = 0;; i++) {
146 String mine = conn.getHeaderField(i);
147
148 if (mine == null) break;
149
150 if("content-disposition".equals(conn.getHeaderFieldKey(i).toLowerCase())){
151 Matcher m = Pattern.compile(".*filename=(.*)").matcher(mine.toLowerCase());
152 if(m.find()) return m.group(1);
153 }
154 }
155
156 filename = UUID.randomUUID()+ ".tmp";//默認取一個文件名
157 }
158
159 return filename;
160 }
161
162 /**
163 * 開始下載文件
164 * @param listener 監(jiān)聽下載數(shù)量的變化,如果不需要了解實時下載的數(shù)量,可以設置為null
165 * @return 已下載文件大小
166 * @throws Exception
167 */
168 public int download(DownloadProgressListener listener) throws Exception{
169 try {
170 RandomAccessFile randOut = new RandomAccessFile(this.saveFile, "rw");
171 if(this.fileSize>0) randOut.setLength(this.fileSize);
172 randOut.close();
173 URL url = new URL(this.downloadUrl);
174
175 if(this.data.size() != this.threads.length){
176 this.data.clear();
177
178 for (int i = 0; i < this.threads.length; i++) {
179 this.data.put(i+1, 0);//初始化每條線程已經(jīng)下載的數(shù)據(jù)長度為0
180 }
181 }
182
183 for (int i = 0; i < this.threads.length; i++) {//開啟線程進行下載
184 int downLength = this.data.get(i+1);
185
186 if(downLength < this.block && this.downloadSize<this.fileSize){//判斷線程是否已經(jīng)完成下載,否則繼續(xù)下載
187 this.threads[i] = new DownloadThread(this, url, this.saveFile, this.block, this.data.get(i+1), i+1);
188 this.threads[i].setPriority(7);
189 this.threads[i].start();
190 }else{
191 this.threads[i] = null;
192 }
193 }
194
195 this.fileService.save(this.downloadUrl, this.data);
196 boolean notFinish = true;//下載未完成
197
198 while (notFinish) {// 循環(huán)判斷所有線程是否完成下載
199 Thread.sleep(900);
200 notFinish = false;//假定全部線程下載完成
201
202 for (int i = 0; i < this.threads.length; i++){
203 if (this.threads[i] != null && !this.threads[i].isFinish()) {//如果發(fā)現(xiàn)線程未完成下載
204 notFinish = true;//設置標志為下載沒有完成
205
206 if(this.threads[i].getDownLength() == -1){//如果下載失敗,再重新下載
207 this.threads[i] = new DownloadThread(this, url, this.saveFile, this.block, this.data.get(i+1), i+1);
208 this.threads[i].setPriority(7);
209 this.threads[i].start();
210 }
211 }
212 }
213
214 if(listener!=null) listener.onDownloadSize(this.downloadSize);//通知目前已經(jīng)下載完成的數(shù)據(jù)長度
215 }
216
217 fileService.delete(this.downloadUrl);
218 } catch (Exception e) {
219 print(e.toString());
220 throw new Exception("file download fail");
221 }
222 return this.downloadSize;
223 }
224
225 /**
226 * 獲取Http響應頭字段
227 * @param http
228 * @return
229 */
230 public static Map<String, String> getHttpResponseHeader(HttpURLConnection http) {
231 Map<String, String> header = new LinkedHashMap<String, String>();
232
233 for (int i = 0;; i++) {
234 String mine = http.getHeaderField(i);
235 if (mine == null) break;
236 header.put(http.getHeaderFieldKey(i), mine);
237 }
238
239 return header;
240 }
241
242 /**
243 * 打印Http頭字段
244 * @param http
245 */
246 public static void printResponseHeader(HttpURLConnection http){
247 Map<String, String> header = getHttpResponseHeader(http);
248
249 for(Map.Entry<String, String> entry : header.entrySet()){
250 String key = entry.getKey()!=null ? entry.getKey()+ ":" : "";
251 print(key+ entry.getValue());
252 }
253 }
254
255 private static void print(String msg){
256 Log.i(TAG, msg);
257 }
258 }
DownloadThread 中代碼：
1 package com.android.network;
2 import java.io.File;
3 import java.io.InputStream;
4 import java.io.RandomAccessFile;
5 import java.net.HttpURLConnection;
6 import java.net.URL;
7
8 import android.util.Log;
9
10 public class DownloadThread extends Thread {
11 private static final String TAG = "DownloadThread";
12 private File saveFile;
13 private URL downUrl;
14 private int block;
15
16 /* 下載開始位置 */
17 private int threadId = -1;
18 private int downLength;
19 private boolean finish = false;
20 private FileDownloader downloader;
21
22 public DownloadThread(FileDownloader downloader, URL downUrl, File saveFile, int block, int downLength, int threadId) {
23 this.downUrl = downUrl;
24 this.saveFile = saveFile;
25 this.block = block;
26 this.downloader = downloader;
27 this.threadId = threadId;
28 this.downLength = downLength;
29 }
30
31 @Override
32 public void run() {
33 if(downLength < block){//未下載完成
34 try {
35 HttpURLConnection http = (HttpURLConnection) downUrl.openConnection();
36 http.setConnectTimeout(5 * 1000);
37 http.setRequestMethod("GET");
38 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, */*");
39 http.setRequestProperty("Accept-Language", "zh-CN");
40 http.setRequestProperty("Referer", downUrl.toString());
41 http.setRequestProperty("Charset", "UTF-8");
42 int startPos = block * (threadId - 1) + downLength;//開始位置
43 int endPos = block * threadId -1;//結束位置
44 http.setRequestProperty("Range", "bytes=" + startPos + "-"+ endPos);//設置獲取實體數(shù)據(jù)的范圍
45 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)");
46 http.setRequestProperty("Connection", "Keep-Alive");
47
48 InputStream inStream = http.getInputStream();
49 byte[] buffer = new byte[1024];
50 int offset = 0;
51 print("Thread " + this.threadId + " start download from position "+ startPos);
52 RandomAccessFile threadfile = new RandomAccessFile(this.saveFile, "rwd");
53 threadfile.seek(startPos);
54
55 while ((offset = inStream.read(buffer, 0, 1024)) != -1) {
56 threadfile.write(buffer, 0, offset);
57 downLength += offset;
58 downloader.update(this.threadId, downLength);
59 downloader.append(offset);
60 }
61
62 threadfile.close();
63 inStream.close();
64 print("Thread " + this.threadId + " download finish");
65 this.finish = true;
66 } catch (Exception e) {
67 this.downLength = -1;
68 print("Thread "+ this.threadId+ ":"+ e);
69 }
70 }
71 }
72
73 private static void print(String msg){
74 Log.i(TAG, msg);
75 }
76
77 /**
78 * 下載是否完成
79 * @return
80 */
81 public boolean isFinish() {
82 return finish;
83 }
84
85 /**
86 * 已經(jīng)下載的內(nèi)容大小
87 * @return 如果返回值為-1,代表下載失敗
88 */
89 public long getDownLength() {
90 return downLength;
91 }
92 }