断点续传

<uses-sdk android:minSdkVersion="8" android:targetSdkVersion="8" />
<uses-permission android:name="android.permission.INTERNET"/>　
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
//添加xutils包
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;

import java.util.ArrayList;
import java.util.List;
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 = -1;
        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(0);
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if (null != database) {
                database.close();
            }
            if (null != cursor) {
                cursor.close();
            }
        }
        return count == 0;
    }

    /**
     * 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(0),
                        cursor.getInt(1), cursor.getInt(2), cursor.getInt(3),
                        cursor.getString(4));
                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();
            }
        }
    }
}


import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;


public class DBHelper extends SQLiteOpenHelper{
    //download.db-->数据库名
    public DBHelper(Context context) {
        super(context, "download.db", null, 1);
    }

    /**
     * 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) {

    }
}
 
import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.Button;
import android.widget.TextView;
import android.view.View.OnClickListener;
import java.util.List;
import java.util.Map;


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;



    }

}
import android.content.Context;
import android.os.Handler;
import android.os.Message;
import android.util.Log;

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;


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 = 1;//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 = 2;
    private static final int PAUSE = 3;
    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 = 0; i < threadcount - 1; i++) {
                DownloadInfo info = new DownloadInfo(i, i * range, (i + 1)* range - 1, 0, urlstr);
                infos.add(info);
            }
            DownloadInfo info = new DownloadInfo(threadcount - 1,(threadcount - 1) * range, fileSize - 1, 0, 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, 0, 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 = 0;
            int compeleteSize = 0;
            for (DownloadInfo info : infos) {
                compeleteSize += info.getCompeleteSize();
                size += info.getEndPos() - info.getStartPos() + 1;
            }
            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(5000);
            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(5000);
                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[4096];
                int length = -1;
                while ((length = is.read(buffer)) != -1) {
                    randomAccessFile.write(buffer, 0, 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 = 1;
                    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;
    }
}
    

    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 +"]";
    }
}


 
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 + "]";
    }
}

   
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 java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
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 == 1) {
                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.activity_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 = "4";
        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[0];
            String localfile=params[1];
            int threadcount=Integer.parseInt(params[2]);
            // 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, 5);
            ((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);
    }

}
  //布局
<ListView android:id="@android:id/list"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent">
</ListView>
<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="1"
        android:text="aaaaaa"
        android:id="@+id/tv_resouce_name"/>

    <Button
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_weight="1"
        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="1"
        android:text="暂停"
        android:visibility="gone"
        android:id="@+id/btn_pause"
        android:onClick="pauseDownload"/>
</LinearLayout>