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Android实现网络多线程断点续传下载实例

程序员文章站 2024-03-05 08:20:48
我们编写的是andorid的http协议多线程断点下载应用程序。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,多线程断点需要什么功能? 1.多线程...

我们编写的是andorid的http协议多线程断点下载应用程序。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,多线程断点需要什么功能?

1.多线程下载,

2.支持断点。

使用多线程的好处:使用多线程下载会提升文件下载的速度。那么多线程下载文件的过程是:

(1)首先获得下载文件的长度,然后设置本地文件的长度。

httpurlconnection.getcontentlength();//获取下载文件的长度
randomaccessfile file = new randomaccessfile("qqwubisetup.exe","rwd");
file.setlength(filesize);//设置本地文件的长度

(2)根据文件长度和线程数计算每条线程下载的数据长度和下载位置。

如:文件的长度为6m,线程数为3,那么,每条线程下载的数据长度为2m,每条线程开始下载的位置如下图所示。

Android实现网络多线程断点续传下载实例

例如10m大小,使用3个线程来下载,
线程下载的数据长度   (10%3 == 0 ? 10/3:10/3+1) ,第1,2个线程下载长度是4m,第三个线程下载长度为2m
下载开始位置:线程id*每条线程下载的数据长度 = ?
下载结束位置:(线程id+1)*每条线程下载的数据长度-1=?

(3)使用http的range头字段指定每条线程从文件的什么位置开始下载,下载到什么位置为止,

如:指定从文件的2m位置开始下载,下载到位置(4m-1byte)为止
代码如下:httpurlconnection.setrequestproperty("range", "bytes=2097152-4194303");

(4)保存文件,使用randomaccessfile类指定每条线程从本地文件的什么位置开始写入数据。
 randomaccessfile threadfile = new randomaccessfile("qqwubisetup.exe ","rwd");
 threadfile.seek(2097152);//从文件的什么位置开始写入数据

程序结构如下图所示:

Android实现网络多线程断点续传下载实例

string.xml文件中代码:

 <?xml version="1.0" encoding="utf-8"?> 
<resources>

  <string name="hello">hello world, mainactivity!</string>

  <string name="app_name">android网络多线程断点下载</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>

  <string name="success">下载完成</string>

  <string name="error">下载失败</string>

</resources>

 main.xml文件中代码:

 <?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">
  <!-- 下载路径 -->

  <textview

    android:layout_width="fill_parent"

    android:layout_height="wrap_content"

    android:text="@string/path"/>

  <edittext 

    android:id="@+id/path" 

    android:text="http://www.winrar.com.cn/download/wrar380sc.exe" 

    android:layout_width="fill_parent" 

    android:layout_height="wrap_content">

  </edittext>

  <!-- 下载按钮 -->

  <button

    android:layout_width="wrap_content"

    android:layout_height="wrap_content"

    android:text="@string/downloadbutton"

    android:id="@+id/button"/>

  <!-- 进度条 -->

  <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>

androidmanifest.xml文件中代码:

 <?xml version="1.0" encoding="utf-8"?><manifest xmlns:android="http://schemas.android.com/apk/res/android"   package="com.android.downloader"   android:versioncode="1"   android:versionname="1.0">
  <uses-sdk android:minsdkversion="8" />

  <application android:icon="@drawable/icon" android:label="@string/app_name">
    <activity android:name=".mainactivity"
         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>
  
  <!-- 在sdcard中创建与删除文件权限 -->
  <uses-permission android:name="android.permission.mount_unmount_filesystems"/>
  
  <!-- 往sdcard写入数据权限 -->
  <uses-permission android:name="android.permission.write_external_storage"/>
  
  <!-- 访问internet权限 -->
  <uses-permission android:name="android.permission.internet"/>
</manifest>

 mainactivity中代码:

 package com.android.downloader;
import java.io.file;

 

import com.android.network.downloadprogresslistener;

import com.android.network.filedownloader;

 

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 mainactivity 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

   */

  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+ "%");

        

        if(progressbar.getprogress()==progressbar.getmax()){

          toast.maketext(mainactivity.this, r.string.success, 1).show();

        }

        break;

      case -1:

        toast.maketext(mainactivity.this, r.string.error, 1).show();

        break;

      }

    }

  };

  

  /** called when the activity is first created. */

  @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) {

        // todo auto-generated method stub

        string path = downloadpathtext.gettext().tostring();

        system.out.println(environment.getexternalstoragestate()+"------"+environment.media_mounted);

        

        if(environment.getexternalstoragestate().equals(environment.media_mounted)){

          download(path, environment.getexternalstoragedirectory());

        }else{

          toast.maketext(mainactivity.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

    * @param path

    * @param savedir

    */

  private void download(final string path, final file savedir) {

    new thread(new runnable() {      

      @override

      public void run() {

        filedownloader loader = new filedownloader(mainactivity.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();

  }
}

dbopenhelper中代码:

package com.android.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 = "down.db";

  private static final int version = 1;

  

  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);

  }

}

fileservice中代码:

package com.android.service;
import java.util.hashmap;

import java.util.map;

 

import android.content.context;

import android.database.cursor;

import android.database.sqlite.sqlitedatabase;

 

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();

  }
}

downloadprogresslistener中代码:

package com.android.network;
public interface downloadprogresslistener {
  public void ondownloadsize(int size);
} 

filedownloader中代码:

package com.android.network;
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.android.service.fileservice;
import android.content.context;
import android.util.log;
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());

    }

  }

 

  private static void print(string msg){

    log.i(tag, msg);

  }

}

downloadthread 中代码:

package com.android.network;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 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;
  
  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 {
        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);
      }
    }
  }
  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;
  }}

运行效果如下:

Android实现网络多线程断点续传下载实例