android 多线程断点续传下载

2022-03-29 00:14:18

今天跟大家一起分享下Android开发中比较难的一个环节,可能很多人看到这个标题就会感觉头很大,的确如果没有良好的编码能力和逻辑思维,这块是很难搞明白的,前面2次总结中已经为大家分享过有关技术的一些基本要领,我们先一起简单回顾下它的基本原理。

http://blog.csdn.net/shimiso/article/details/6763664 android 多线程断点续传下载一

http://blog.csdn.net/shimiso/article/details/6763986 android 多线程断点续传下载二

什么是多线程下载？

多线程下载其实就是迅雷,BT一些下载原理,通过多个线程同时和服务器连接,那么你就可以榨取到较高的带宽了,大致做法是将文件切割成N块,每块交给单独一个线程去下载,各自下载完成后将文件块组合成一个文件,程序上要完成做切割和组装的小算法

什么是断点续传?

断点续传,就是当我们下载未结束时候,退出保存下载进度,当下次打开继续下载的时接着上次的进度继续下载,不用每次下载都重新开始,那么有关断点续传的原理和实现手段,可参考我以前的一篇总结http://blog.csdn.net/shimiso/article/details/5956314 里面详细讲解http协议断点续传的原理,务必要看懂,否则你无法真正理解本节代码

怎么完成多线程断点续传?

将两者合二为一需要程序记住每个文件块的下载进度,并保存入库,当下载程序启动时候你需要判断程序是否已经下载过该文件,并取出各个文件块的保存记录,换算出下载进度继续下载,在这里你需要掌握Java多线程的基本知识,handler的使用,以及集合,算法,文件操作等基本技能,同时还要解决sqlite数据库的同步问题,因为它是不太怎么支持多线程操作的,控制不好经常会出现库被锁定的异常,同时在android2.3以后就不能activity中直接操作http,否则你将收到系统送上的NetworkOnMainThreadException异常,在UI体验上一定记住要使用异步完成,既然大致思路已经清楚,下面我们开始分析程序:

package cn.demo.DBHelper;

 import android.content.Context;

import android.database.sqlite.SQLiteDatabase;

import android.database.sqlite.SQLiteOpenHelper;

     /**

      * 建立一个数据库帮助类

      */

 public class DBHelper extends SQLiteOpenHelper {

     //download.db-->数据库名

     public DBHelper(Context context) {

         super(context, "download.db", null, );

     }

     /**

      * 在download.db数据库下创建一个download_info表存储下载信息

      */

     @Override

     public void onCreate(SQLiteDatabase db) {

         db.execSQL("create table download_info(_id integer PRIMARY KEY AUTOINCREMENT, thread_id integer, "

                 + "start_pos integer, end_pos integer, compelete_size integer,url char)");

     }

     @Override

     public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

     }

 }

数据库操作要借助单例和同步,来保证线程的执行顺序,以免多个线程争相抢用sqlite资源导致异常出现

package cn.demo.Dao;

import java.util.ArrayList;

import java.util.List;

import android.content.Context;

import android.database.Cursor;

import android.database.sqlite.SQLiteDatabase;

import cn.demo.DBHelper.DBHelper;

import cn.demo.entity.DownloadInfo;

/**

 *

 * 一个业务类

 */

public class Dao {

    private static Dao dao=null;

    private Context context;

    private  Dao(Context context) {

        this.context=context;

    }

    public static  Dao getInstance(Context context){

        if(dao==null){

            dao=new Dao(context);

        }

        return dao;

    }

    public  SQLiteDatabase getConnection() {

        SQLiteDatabase sqliteDatabase = null;

        try {

            sqliteDatabase= new DBHelper(context).getReadableDatabase();

        } catch (Exception e) {

        }

        return sqliteDatabase;

    }

    /**

     * 查看数据库中是否有数据

     */

    public synchronized boolean isHasInfors(String urlstr) {

        SQLiteDatabase database = getConnection();

        int count = -;

        Cursor cursor = null;

        try {

            String sql = "select count(*)  from download_info where url=?";

            cursor = database.rawQuery(sql, new String[] { urlstr });

            if (cursor.moveToFirst()) {

                count = cursor.getInt();

            }

        } catch (Exception e) {

            e.printStackTrace();

        } finally {

            if (null != database) {

                database.close();

            }

            if (null != cursor) {

                cursor.close();

            }

        }

        return count == ;

    }

    /**

     * 保存 下载的具体信息

     */

    public synchronized void saveInfos(List<DownloadInfo> infos) {

        SQLiteDatabase database = getConnection();

        try {

            for (DownloadInfo info : infos) {

                String sql = "insert into download_info(thread_id,start_pos, end_pos,compelete_size,url) values (?,?,?,?,?)";

                Object[] bindArgs = { info.getThreadId(), info.getStartPos(),

                        info.getEndPos(), info.getCompeleteSize(),

                        info.getUrl() };

                database.execSQL(sql, bindArgs);

            }

        } catch (Exception e) {

            e.printStackTrace();

        } finally {

            if (null != database) {

                database.close();

            }

        }

    }

    /**

     * 得到下载具体信息

     */

    public synchronized List<DownloadInfo> getInfos(String urlstr) {

        List<DownloadInfo> list = new ArrayList<DownloadInfo>();

        SQLiteDatabase database = getConnection();

        Cursor cursor = null;

        try {

            String sql = "select thread_id, start_pos, end_pos,compelete_size,url from download_info where url=?";

            cursor = database.rawQuery(sql, new String[] { urlstr });

            while (cursor.moveToNext()) {

                DownloadInfo info = new DownloadInfo(cursor.getInt(),

                        cursor.getInt(), cursor.getInt(), cursor.getInt(),

                        cursor.getString());

                list.add(info);

            }

        } catch (Exception e) {

            e.printStackTrace();

        } finally {

            if (null != database) {

                database.close();

            }

            if (null != cursor) {

                cursor.close();

            }

        }

        return list;

    }

    /**

     * 更新数据库中的下载信息

     */

    public synchronized void updataInfos(int threadId, int compeleteSize, String urlstr) {

        SQLiteDatabase database = getConnection();

        try {

            String sql = "update download_info set compelete_size=? where thread_id=? and url=?";

            Object[] bindArgs = { compeleteSize, threadId, urlstr };

            database.execSQL(sql, bindArgs);

        } catch (Exception e) {

            e.printStackTrace();

        } finally {

            if (null != database) {

                database.close();

            }

        }

    }

    /**

     * 下载完成后删除数据库中的数据

     */

    public synchronized void delete(String url) {

        SQLiteDatabase database = getConnection();

        try {

            database.delete("download_info", "url=?", new String[] { url });

        } catch (Exception e) {

            e.printStackTrace();

        } finally {

            if (null != database) {

                database.close();

            }

        }

    }

}

package cn.demo.download;

import java.util.List;

import java.util.Map;

import android.content.Context;

import android.view.LayoutInflater;

import android.view.View;

import android.view.View.OnClickListener;

import android.view.ViewGroup;

import android.widget.BaseAdapter;

import android.widget.Button;

import android.widget.TextView;

public class DownLoadAdapter extends BaseAdapter{

    private LayoutInflater mInflater;

    private List<Map<String, String>> data;

    private Context context;

    private OnClickListener click;

    public DownLoadAdapter(Context context,List<Map<String, String>> data) {

        this.context=context;

        mInflater = LayoutInflater.from(context);

        this.data=data;

    }

    public void refresh(List<Map<String, String>> data) {

        this.data=data;

        this.notifyDataSetChanged();

    }

    public void setOnclick(OnClickListener click) {

         this.click=click;

    }

    @Override

    public int getCount() {

        return data.size();

    }

    @Override

    public Object getItem(int position) {

        return data.get(position);

    }

    @Override

    public long getItemId(int position) {

        return position;

    }

    @Override

    public View getView(final int position, View convertView, ViewGroup parent) {

        final Map<String, String> bean=data.get(position);

        ViewHolder holder = null;

        if (convertView == null) {

            convertView = mInflater.inflate(R.layout.list_item, null);

            holder = new ViewHolder();

            holder.resouceName=(TextView) convertView.findViewById(R.id.tv_resouce_name);

            holder.startDownload=(Button) convertView.findViewById(R.id.btn_start);

            holder.pauseDownload=(Button) convertView.findViewById(R.id.btn_pause);

            convertView.setTag(holder);

        } else {

            holder = (ViewHolder) convertView.getTag();

        }

         holder.resouceName.setText(bean.get("name"));

        return convertView;

    }

    public OnClickListener getClick() {

        return click;

    }

    public void setClick(OnClickListener click) {

        this.click = click;

    }

    private class ViewHolder {

        public TextView resouceName;

        public Button startDownload;

        public Button pauseDownload;

    }

}

注意子线程不要影响主UI线程,灵活运用task和handler,各取所长,保证用户体验,handler通常在主线程中有利于专门负责处理UI的一些工作

package cn.demo.download;

 import java.util.ArrayList;

import java.util.HashMap;

import java.util.List;

import java.util.Map;

import android.app.ListActivity;

import android.os.AsyncTask;

import android.os.Bundle;

import android.os.Handler;

import android.os.Message;

import android.view.View;

import android.widget.Button;

import android.widget.LinearLayout;

import android.widget.LinearLayout.LayoutParams;

import android.widget.ProgressBar;

import android.widget.TextView;

import android.widget.Toast;

import cn.demo.entity.LoadInfo;

import cn.demo.service.Downloader;

 public class MainActivity extends ListActivity {

     // 固定下载的资源路径，这里可以设置网络上的地址

     private static final String URL = "http://download.haozip.com/";

     // 固定存放下载的音乐的路径：SD卡目录下

     private static final String SD_PATH = "/mnt/sdcard/";

     // 存放各个下载器

     private Map<String, Downloader> downloaders = new HashMap<String, Downloader>();

     // 存放与下载器对应的进度条

     private Map<String, ProgressBar> ProgressBars = new HashMap<String, ProgressBar>();

     /**

      * 利用消息处理机制适时更新进度条

      */

     private Handler mHandler = new Handler() {

         public void handleMessage(Message msg) {

             if (msg.what == ) {

                 String url = (String) msg.obj;

                 int length = msg.arg1;

                 ProgressBar bar = ProgressBars.get(url);

                 if (bar != null) {

                     // 设置进度条按读取的length长度更新

                     bar.incrementProgressBy(length);

                     if (bar.getProgress() == bar.getMax()) {

                         LinearLayout layout = (LinearLayout) bar.getParent();

                         TextView resouceName=(TextView)layout.findViewById(R.id.tv_resouce_name);

                         Toast.makeText(MainActivity.this, "["+resouceName.getText()+"]下载完成！", Toast.LENGTH_SHORT).show();

                         // 下载完成后清除进度条并将map中的数据清空

                         layout.removeView(bar);

                         ProgressBars.remove(url);

                         downloaders.get(url).delete(url);

                         downloaders.get(url).reset();

                         downloaders.remove(url);

                         Button btn_start=(Button)layout.findViewById(R.id.btn_start);

                         Button btn_pause=(Button)layout.findViewById(R.id.btn_pause);

                         btn_pause.setVisibility(View.GONE);

                         btn_start.setVisibility(View.GONE);

                     }

                 }

             }

         }

     };

     @Override

     public void onCreate(Bundle savedInstanceState) {

         super.onCreate(savedInstanceState);

         setContentView(R.layout.main);

         showListView();

     }

     // 显示listView，这里可以随便添加

     private void showListView() {

         List<Map<String, String>> data = new ArrayList<Map<String, String>>();

         Map<String, String> map = new HashMap<String, String>();

         map.put("name", "haozip_v3.1.exe");

         data.add(map);

         map = new HashMap<String, String>();

         map.put("name", "haozip_v3.1_hj.exe");

         data.add(map);

         map = new HashMap<String, String>();

         map.put("name", "haozip_v2.8_x64_tiny.exe");

         data.add(map);

         map = new HashMap<String, String>();

         map.put("name", "haozip_v2.8_tiny.exe");

         data.add(map);

         DownLoadAdapter adapter=new DownLoadAdapter(this,data);

         setListAdapter(adapter);

     }

     /**

      * 响应开始下载按钮的点击事件

      */

     public void startDownload(View v) {

         // 得到textView的内容

         LinearLayout layout = (LinearLayout) v.getParent();

         String resouceName = ((TextView) layout.findViewById(R.id.tv_resouce_name)).getText().toString();

         String urlstr = URL + resouceName;

         String localfile = SD_PATH + resouceName;

         //设置下载线程数为4，这里是我为了方便随便固定的

         String threadcount = "";

         DownloadTask downloadTask=new DownloadTask(v);

         downloadTask.execute(urlstr,localfile,threadcount);

     };

    class DownloadTask extends AsyncTask<String, Integer, LoadInfo>{

        Downloader downloader=null;

        View v=null;

        String urlstr=null;

        public DownloadTask(final View v){

            this.v=v;

        }

        @Override

        protected void onPreExecute() {

            Button btn_start=(Button)((View)v.getParent()).findViewById(R.id.btn_start);

            Button btn_pause=(Button)((View)v.getParent()).findViewById(R.id.btn_pause);

            btn_start.setVisibility(View.GONE);

            btn_pause.setVisibility(View.VISIBLE);

        }

        @Override

        protected LoadInfo doInBackground(String... params) {

            urlstr=params[];

            String localfile=params[];

            int threadcount=Integer.parseInt(params[]);

             // 初始化一个downloader下载器

             downloader = downloaders.get(urlstr);

             if (downloader == null) {

                 downloader = new Downloader(urlstr, localfile, threadcount, MainActivity.this, mHandler);

                 downloaders.put(urlstr, downloader);

             }

             if (downloader.isdownloading())

                 return null;

             // 得到下载信息类的个数组成集合

             return downloader.getDownloaderInfors();

        }

        @Override

        protected void onPostExecute(LoadInfo loadInfo) {

            if(loadInfo!=null){

                 // 显示进度条

                 showProgress(loadInfo, urlstr, v);

                 // 调用方法开始下载

                 downloader.download();

            }

        }

     };

     /**

      * 显示进度条

      */

     private void showProgress(LoadInfo loadInfo, String url, View v) {

         ProgressBar bar = ProgressBars.get(url);

         if (bar == null) {

             bar = new ProgressBar(this, null, android.R.attr.progressBarStyleHorizontal);

             bar.setMax(loadInfo.getFileSize());

             bar.setProgress(loadInfo.getComplete());

             ProgressBars.put(url, bar);

             LinearLayout.LayoutParams params = new LayoutParams(LayoutParams.FILL_PARENT, );

             ((LinearLayout) ((LinearLayout) v.getParent()).getParent()).addView(bar, params);

         }

     }

     /**

      * 响应暂停下载按钮的点击事件

      */

     public void pauseDownload(View v) {

         LinearLayout layout = (LinearLayout) v.getParent();

         String resouceName = ((TextView) layout.findViewById(R.id.tv_resouce_name)).getText().toString();

         String urlstr = URL + resouceName;

         downloaders.get(urlstr).pause();

         Button btn_start=(Button)((View)v.getParent()).findViewById(R.id.btn_start);

          Button btn_pause=(Button)((View)v.getParent()).findViewById(R.id.btn_pause);

         btn_pause.setVisibility(View.GONE);

         btn_start.setVisibility(View.VISIBLE);

     }

 }

这是一个信息的实体,记录了一些字典信息,可以认为是一个简单bean对象

package cn.demo.entity;

 /**

  *创建一个下载信息的实体类

  */

 public class DownloadInfo {

     private int threadId;//下载器id

     private int startPos;//开始点

     private int endPos;//结束点

     private int compeleteSize;//完成度

     private String url;//下载器网络标识

     public DownloadInfo(int threadId, int startPos, int endPos,

             int compeleteSize,String url) {

         this.threadId = threadId;

         this.startPos = startPos;

         this.endPos = endPos;

         this.compeleteSize = compeleteSize;

         this.url=url;

     }

     public DownloadInfo() {

     }

     public String getUrl() {

         return url;

     }

     public void setUrl(String url) {

         this.url = url;

     }

     public int getThreadId() {

         return threadId;

     }

     public void setThreadId(int threadId) {

         this.threadId = threadId;

     }

     public int getStartPos() {

         return startPos;

     }

     public void setStartPos(int startPos) {

         this.startPos = startPos;

     }

     public int getEndPos() {

         return endPos;

     }

     public void setEndPos(int endPos) {

         this.endPos = endPos;

     }

     public int getCompeleteSize() {

         return compeleteSize;

     }

     public void setCompeleteSize(int compeleteSize) {

         this.compeleteSize = compeleteSize;

     }

     @Override

     public String toString() {

         return "DownloadInfo [threadId=" + threadId

                 + ", startPos=" + startPos + ", endPos=" + endPos

                 + ", compeleteSize=" + compeleteSize +"]";

     }

 }

package cn.demo.entity;

 /**

  *自定义的一个记载下载器详细信息的类

  */

 public class LoadInfo {

     public int fileSize;//文件大小

     private int complete;//完成度

     private String urlstring;//下载器标识

     public LoadInfo(int fileSize, int complete, String urlstring) {

         this.fileSize = fileSize;

         this.complete = complete;

         this.urlstring = urlstring;

     }

     public LoadInfo() {

     }

     public int getFileSize() {

         return fileSize;

     }

     public void setFileSize(int fileSize) {

         this.fileSize = fileSize;

     }

     public int getComplete() {

         return complete;

     }

     public void setComplete(int complete) {

         this.complete = complete;

     }

     public String getUrlstring() {

         return urlstring;

     }

     public void setUrlstring(String urlstring) {

         this.urlstring = urlstring;

     }

     @Override

     public String toString() {

         return "LoadInfo [fileSize=" + fileSize + ", complete=" + complete

                 + ", urlstring=" + urlstring + "]";

     }

 }

这是一个核心类,专门用来处理下载的

package cn.demo.service;

 import java.io.File;

import java.io.InputStream;

import java.io.RandomAccessFile;

import java.net.HttpURLConnection;

import java.net.URL;

import java.util.ArrayList;

import java.util.List;

import android.content.Context;

import android.os.AsyncTask;

import android.os.Handler;

import android.os.Message;

import android.util.Log;

import cn.demo.Dao.Dao;

import cn.demo.entity.DownloadInfo;

import cn.demo.entity.LoadInfo;

 public class Downloader {

     private String urlstr;// 下载的地址

     private String localfile;// 保存路径

     private int threadcount;// 线程数

     private Handler mHandler;// 消息处理器

     private int fileSize;// 所要下载的文件的大小

     private Context context;

     private List<DownloadInfo> infos;// 存放下载信息类的集合

     private static final int INIT = ;//定义三种下载的状态：初始化状态，正在下载状态，暂停状态

     private static final int DOWNLOADING = ;

     private static final int PAUSE = ;

     private int state = INIT;

     public Downloader(String urlstr, String localfile, int threadcount,

             Context context, Handler mHandler) {

         this.urlstr = urlstr;

         this.localfile = localfile;

         this.threadcount = threadcount;

         this.mHandler = mHandler;

         this.context = context;

     }

     /**

      *判断是否正在下载

      */

     public boolean isdownloading() {

         return state == DOWNLOADING;

     }

     /**

      * 得到downloader里的信息

      * 首先进行判断是否是第一次下载，如果是第一次就要进行初始化，并将下载器的信息保存到数据库中

      * 如果不是第一次下载，那就要从数据库中读出之前下载的信息（起始位置，结束为止，文件大小等），并将下载信息返回给下载器

      */

     public LoadInfo getDownloaderInfors() {

         if (isFirst(urlstr)) {

             Log.v("TAG", "isFirst");

             init();

             int range = fileSize / threadcount;

             infos = new ArrayList<DownloadInfo>();

             for (int i = ; i < threadcount - ; i++) {

                 DownloadInfo info = new DownloadInfo(i, i * range, (i + )* range - , , urlstr);

                 infos.add(info);

             }

             DownloadInfo info = new DownloadInfo(threadcount - ,(threadcount - ) * range, fileSize - , , urlstr);

             infos.add(info);

             //保存infos中的数据到数据库

             Dao.getInstance(context).saveInfos(infos);

             //创建一个LoadInfo对象记载下载器的具体信息

             LoadInfo loadInfo = new LoadInfo(fileSize, , urlstr);

             return loadInfo;

         } else {

             //得到数据库中已有的urlstr的下载器的具体信息

             infos = Dao.getInstance(context).getInfos(urlstr);

             Log.v("TAG", "not isFirst size=" + infos.size());

             int size = ;

             int compeleteSize = ;

             for (DownloadInfo info : infos) {

                 compeleteSize += info.getCompeleteSize();

                 size += info.getEndPos() - info.getStartPos() + ;

             }

             return new LoadInfo(size, compeleteSize, urlstr);

         }

     }

     /**

      * 初始化

      */

     private void init() {

         try {

             URL url = new URL(urlstr);

             HttpURLConnection connection = (HttpURLConnection) url.openConnection();

             connection.setConnectTimeout();

             connection.setRequestMethod("GET");

             fileSize = connection.getContentLength();

             File file = new File(localfile);

             if (!file.exists()) {

                 file.createNewFile();

             }

             // 本地访问文件

             RandomAccessFile accessFile = new RandomAccessFile(file, "rwd");

             accessFile.setLength(fileSize);

             accessFile.close();

             connection.disconnect();

         } catch (Exception e) {

             e.printStackTrace();

         }

     }

     /**

      * 判断是否是第一次 下载

      */

     private boolean isFirst(String urlstr) {

         return Dao.getInstance(context).isHasInfors(urlstr);

     }

     /**

      * 利用线程开始下载数据

      */

     public void download() {

         if (infos != null) {

             if (state == DOWNLOADING)

                 return;

             state = DOWNLOADING;

             for (DownloadInfo info : infos) {

                 new MyThread(info.getThreadId(), info.getStartPos(),

                         info.getEndPos(), info.getCompeleteSize(),

                         info.getUrl()).start();

             }

         }

     }

     public class MyThread extends Thread {

         private int threadId;

         private int startPos;

         private int endPos;

         private int compeleteSize;

         private String urlstr;

         public MyThread(int threadId, int startPos, int endPos,

                 int compeleteSize, String urlstr) {

             this.threadId = threadId;

             this.startPos = startPos;

             this.endPos = endPos;

             this.compeleteSize = compeleteSize;

             this.urlstr = urlstr;

         }

         @Override

         public void run() {

             HttpURLConnection connection = null;

             RandomAccessFile randomAccessFile = null;

             InputStream is = null;

             try {

                 URL url = new URL(urlstr);

                 connection = (HttpURLConnection) url.openConnection();

                 connection.setConnectTimeout();

                 connection.setRequestMethod("GET");

                 // 设置范围，格式为Range：bytes x-y;

                 connection.setRequestProperty("Range", "bytes="+(startPos + compeleteSize) + "-" + endPos);

                 randomAccessFile = new RandomAccessFile(localfile, "rwd");

                 randomAccessFile.seek(startPos + compeleteSize);

                 // 将要下载的文件写到保存在保存路径下的文件中

                 is = connection.getInputStream();

                 byte[] buffer = new byte[];

                 int length = -;

                 while ((length = is.read(buffer)) != -) {

                     randomAccessFile.write(buffer, , length);

                     compeleteSize += length;

                     // 更新数据库中的下载信息

                     Dao.getInstance(context).updataInfos(threadId, compeleteSize, urlstr);

                     // 用消息将下载信息传给进度条，对进度条进行更新

                     Message message = Message.obtain();

                     message.what = ;

                     message.obj = urlstr;

                     message.arg1 = length;

                     mHandler.sendMessage(message);

                     if (state == PAUSE) {

                         return;

                     }

                 }

             } catch (Exception e) {

                 e.printStackTrace();

             }

         }

     }

     //删除数据库中urlstr对应的下载器信息

     public void delete(String urlstr) {

         Dao.getInstance(context).delete(urlstr);

     }

     //设置暂停

     public void pause() {

         state = PAUSE;

     }

     //重置下载状态

     public void reset() {

         state = INIT;

     }

 }

以下是些xml文件

<?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="wrap_content">

     <LinearLayout

            android:orientation="horizontal"

            android:layout_width="fill_parent"

            android:layout_height="wrap_content"

            android:layout_marginBottom="5dip">

         <TextView

             android:layout_width="fill_parent"

             android:layout_height="wrap_content"

             android:layout_weight=""

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

         <Button

             android:layout_width="fill_parent"

             android:layout_height="wrap_content"

             android:layout_weight=""

             android:text="下载"

             android:id="@+id/btn_start"

             android:onClick="startDownload"/>

         <Button

             android:layout_width="fill_parent"

             android:layout_height="wrap_content"

             android:layout_weight=""

             android:text="暂停"

             android:visibility="gone"

             android:id="@+id/btn_pause"

             android:onClick="pauseDownload"/>

       </LinearLayout>

 </LinearLayout>

<?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"

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

     <ListView android:id="@android:id/list"

         android:layout_width="fill_parent"

         android:layout_height="fill_parent">

     </ListView>

 </LinearLayout>

<manifest xmlns:android="http://schemas.android.com/apk/res/android"

    package="cn.demo.download"

    android:versionCode=""

    android:versionName="1.0">

    <uses-sdk android:minSdkVersion="" android:targetSdkVersion="" />

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

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

    <application android:label="@string/app_name"

        android:icon="@drawable/ic_launcher"

        android:theme="@style/AppTheme">

        <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>

</manifest>

运行效果如下

源码下载地址

http://blog.csdn.net/shimiso/article/details/49450551 android 多线程断点续传下载四-模仿下载助手

码农公寓

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