在上一节中,我们简单介绍了如何创建多任务下载,但那种还不能拿来实用,这一集我们重点通过代码为大家展示如何创建多线程断点续传下载,这在实际项目中很常用.
main.xml:
[html] view
plaincopy
<?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"
>
<edittext
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:id="@+id/edittext"
android:text="http://gongxue.cn/yingyinkuaiche/uploadfiles_9323/201008/2010082909434077.mp3"
/>
<linearlayout
android:orientation="horizontal"
<button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/downbutton"
android:text="download"
/>
android:id="@+id/pausebutton"
android:enabled="false"
android:text="pause"
</linearlayout>
<progressbar
android:layout_height="18dp"
style="?android:attr/progressbarstylehorizontal"
android:id="@+id/progressbar"
<textview
android:layout_width="fill_parent"
android:id="@+id/textview"
android:gravity="center"
</linearlayout>
string.xml:
<resources>
<string name="hello">hello world, main!</string>
<string name="app_name">多线程断点续传下载</string>
</resources>
androidmanifest.xml:
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="sms.multithreaddownload"
android:versioncode="1"
android:versionname="1.0">
<application android:icon="@drawable/icon" android:label="@string/app_name">
<activity android:name=".main"
android:label="@string/app_name">
<intent-filter>
<action android:name="android.intent.action.main" />
<category android:name="android.intent.category.launcher" />
</intent-filter>
</activity>
<uses-library android:name="android.test.runner" />
</application>
<uses-sdk android:minsdkversion="8" />
<instrumentation
android:targetpackage="sms.multithreaddownload"
android:name="android.test.instrumentationtestrunner" />
<!-- 访问网络的权限 -->
<uses-permission android:name="android.permission.internet"/>
<!-- sdcard写数据的权限 -->
<uses-permission android:name="android.permission.write_external_storage"/>
</manifest>
activity程序:
[java] view
package sms.multithreaddownload;
import java.io.file;
import sms.multithreaddownload.bean.downloadlistener;
import sms.multithreaddownload.service.downloadservice;
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.view.view.onclicklistener;
import android.widget.button;
import android.widget.edittext;
import android.widget.progressbar;
import android.widget.textview;
import android.widget.toast;
public class main extends activity {
private edittext path;
private textview progress;
private progressbar progressbar;
private handler handler = new uihandler();
private downloadservice servcie;
private button downbutton;
private button pausebutton;
private final class uihandler extends handler {
@override
public void handlemessage(message msg) {
switch (msg.what) {
case 1:
int downloaded_size = msg.getdata().getint("size");
progressbar.setprogress(downloaded_size);
int result = (int) ((float) downloaded_size / progressbar.getmax() * 100);
progress.settext(result + "%");
if (progressbar.getmax() == progressbar.getprogress()) {
toast.maketext(getapplicationcontext(), "下载完成", toast.length_long).show();
}
}
}
}
@override
public void oncreate(bundle savedinstancestate) {
super.oncreate(savedinstancestate);
setcontentview(r.layout.main);
path = (edittext) this.findviewbyid(r.id.edittext);
progress = (textview) this.findviewbyid(r.id.textview);
progressbar = (progressbar) this.findviewbyid(r.id.progressbar);
downbutton = (button) this.findviewbyid(r.id.downbutton);
pausebutton = (button) this.findviewbyid(r.id.pausebutton);
downbutton.setonclicklistener(new downloadbutton());
pausebutton.setonclicklistener(new pausebutton());
private final class downloadbutton implements view.onclicklistener {
public void onclick(view v) {
downloadtask task;
try {
task = new downloadtask(path.gettext().tostring());
servcie.ispause = false;
v.setenabled(false);
pausebutton.setenabled(true);
new thread(task).start();
} catch (exception e) {
e.printstacktrace();
public class pausebutton implements onclicklistener {
servcie.ispause = true;
v.setenabled(false);
downbutton.setenabled(true);
public void pause(view v) {
private final class downloadtask implements runnable {
public downloadtask(string target) throws exception {
if (environment.getexternalstoragestate().equals(environment.media_mounted)) {
file destination = environment.getexternalstoragedirectory();
servcie = new downloadservice(target, destination, 3, getapplicationcontext());
progressbar.setmax(servcie.filesize);
} else {
toast.maketext(getapplicationcontext(), "sd卡不存在或写保护!", toast.length_long).show();
public void run() {
servcie.download(new downloadlistener() {
@override
public void ondownload(int downloaded_size) {
message message = new message();
message.what = 1;
message.getdata().putint("size", downloaded_size);
handler.sendmessage(message);
});
}
工具类:
package sms.multithreaddownload.bean;
import android.content.context;
import android.database.sqlite.sqlitedatabase;
import android.database.sqlite.sqliteopenhelper;
public class dbhelper extends sqliteopenhelper {
public dbhelper(context context) {
super(context, "multidownload.db", null, 1);
public void oncreate(sqlitedatabase db) {
db.execsql("create table filedownloading(_id integer primary key autoincrement,downpath varchar(100),threadid integer,downlength integer)");
public void onupgrade(sqlitedatabase db, int oldversion, int newversion) {
// todo auto-generated method stub
public interface downloadlistener {
public void ondownload(int downloaded_size);
import java.io.inputstream;
import java.io.randomaccessfile;
import java.net.httpurlconnection;
import java.net.url;
import android.util.log;
public final class multithreaddownload implements runnable {
public int id;
private randomaccessfile savedfile;
private string path;
/* 当前已下载量 */
public int currentdownloadsize = 0;
/* 下载状态 */
public boolean finished;
/* 用于监视下载状态 */
private final downloadservice downloadservice;
/* 线程下载任务的起始点 */
public int start;
/* 线程下载任务的结束点 */
private int end;
public multithreaddownload(int id, file savedfile, int block, string path, integer downlength, downloadservice downloadservice) throws exception {
this.id = id;
this.path = path;
if (downlength != null) this.currentdownloadsize = downlength;
this.savedfile = new randomaccessfile(savedfile, "rwd");
this.downloadservice = downloadservice;
start = id * block + currentdownloadsize;
end = (id + 1) * block;
public void run() {
try {
httpurlconnection conn = (httpurlconnection) new url(path).openconnection();
conn.setconnecttimeout(5000);
conn.setrequestmethod("get");
conn.setrequestproperty("range", "bytes=" + start + "-" + end); // 设置获取数据的范围
inputstream in = conn.getinputstream();
byte[] buffer = new byte[1024];
int len = 0;
savedfile.seek(start);
while (!downloadservice.ispause && (len = in.read(buffer)) != -1) {
savedfile.write(buffer, 0, len);
currentdownloadsize += len;
savedfile.close();
in.close();
conn.disconnect();
if (!downloadservice.ispause) log.i(downloadservice.tag, "thread " + (this.id + 1) + "finished");
finished = true;
} catch (exception e) {
e.printstacktrace();
throw new runtimeexception("file downloading error!");
service类:
package sms.multithreaddownload.service;
import java.util.hashmap;
import java.util.list;
import java.util.map;
import java.util.map.entry;
import java.util.uuid;
import java.util.concurrent.concurrenthashmap;
import java.util.regex.matcher;
import java.util.regex.pattern;
import sms.multithreaddownload.bean.dbhelper;
import sms.multithreaddownload.bean.multithreaddownload;
import android.database.cursor;
public class downloadservice {
public static final string tag = "tag";
/* 用于查询数据库 */
private dbhelper dbhelper;
/* 要下载的文件大小 */
public int filesize;
/* 每条线程需要下载的数据量 */
private int block;
/* 保存文件地目录 */
private file savedfile;
/* 下载地址 */
/* 是否停止下载 */
public boolean ispause;
/* 线程数 */
private multithreaddownload[] threads;
/* 各线程已经下载的数据量 */
private map<integer, integer> downloadedlength = new concurrenthashmap<integer, integer>();
public downloadservice(string target, file destination, int thread_size, context context) throws exception {
dbhelper = new dbhelper(context);
this.threads = new multithreaddownload[thread_size];
this.path = target;
url url = new url(target);
httpurlconnection conn = (httpurlconnection) url.openconnection();
conn.setconnecttimeout(5000);
conn.setrequestmethod("get");
if (conn.getresponsecode() != 200) {
throw new runtimeexception("server no response!");
filesize = conn.getcontentlength();
if (filesize <= 0) {
throw new runtimeexception("file is incorrect!");
string filename = getfilename(conn);
if (!destination.exists()) destination.mkdirs();
// 构建一个同样大小的文件
this.savedfile = new file(destination, filename);
randomaccessfile doout = new randomaccessfile(savedfile, "rwd");
doout.setlength(filesize);
doout.close();
conn.disconnect();
// 计算每条线程需要下载的数据长度
this.block = filesize % thread_size == 0 ? filesize / thread_size : filesize / thread_size + 1;
// 查询已经下载的记录
downloadedlength = this.getdownloadedlength(path);
private map<integer, integer> getdownloadedlength(string path) {
sqlitedatabase db = dbhelper.getreadabledatabase();
string sql = "select threadid,downlength from filedownloading where downpath=?";
cursor cursor = db.rawquery(sql, new string[] { path });
map<integer, integer> data = new hashmap<integer, integer>();
while (cursor.movetonext()) {
data.put(cursor.getint(0), cursor.getint(1));
db.close();
return data;
private string getfilename(httpurlconnection conn) {
string filename = path.substring(path.lastindexof("/") + 1, path.length());
if (filename == null || "".equals(filename.trim())) {
string content_disposition = null;
for (entry<string, list<string>> entry : conn.getheaderfields().entryset()) {
if ("content-disposition".equalsignorecase(entry.getkey())) {
content_disposition = entry.getvalue().tostring();
}
matcher matcher = pattern.compile(".*filename=(.*)").matcher(content_disposition);
if (matcher.find()) filename = matcher.group(1);
filename = uuid.randomuuid().tostring() + ".tmp"; // 默认名
return filename;
public void download(downloadlistener listener) throws exception {
this.deletedownloading(); // 先删除上次的记录,再重新添加
for (int i = 0; i < threads.length; i++) {
threads[i] = new multithreaddownload(i, savedfile, block, path, downloadedlength.get(i), this);
new thread(threads[i]).start();
this.savedownloading(threads);
while (!isfinish(threads)) {
thread.sleep(900);
if (listener != null) listener.ondownload(getdownloadedsize(threads));
this.updatedownloading(threads);
if (!this.ispause) this.deletedownloading();// 完成下载之后删除本次下载记录
private void savedownloading(multithreaddownload[] threads) {
sqlitedatabase db = dbhelper.getwritabledatabase();
db.begintransaction();
for (multithreaddownload thread : threads) {
string sql = "insert into filedownloading(downpath,threadid,downlength) values(?,?,?)";
db.execsql(sql, new object[] { path, thread.id, 0 });
db.settransactionsuccessful();
} finally {
db.endtransaction();
db.close();
private void deletedownloading() {
string sql = "delete from filedownloading where downpath=?";
db.execsql(sql, new object[] { path });
private void updatedownloading(multithreaddownload[] threads) {
string sql = "update filedownloading set downlength=? where threadid=? and downpath=?";
db.execsql(sql, new string[] { thread.currentdownloadsize + "", thread.id + "", path });
private int getdownloadedsize(multithreaddownload[] threads) {
int sum = 0;
for (int len = threads.length, i = 0; i < len; i++) {
sum += threads[i].currentdownloadsize;
return sum;
private boolean isfinish(multithreaddownload[] threads) {
for (int len = threads.length, i = 0; i < len; i++) {
if (!threads[i].finished) {
return false;
return true;
return false;
运行效果:
源码下载地址