在Android平台下通过HTTP协议实现断点续传下载。

来源:互联网 发布:mysql价格 编辑:程序博客网 时间:2024/05/16 13:45

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?难在哪里?

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。

 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HttpRange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。

RandomAccessFilethreadfile = 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:

 string.xml文件中代码:

复制代码
<?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>
复制代码

main.xml文件中代码:

复制代码
<?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>
复制代码

  AndroidManifest.xml文件中代码:

复制代码
<?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>  
复制代码

MainActivity中代码:

复制代码
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();    }}  
复制代码

DBOpenHelper中代码:

复制代码
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);    }}
复制代码

FileService中代码:

复制代码
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();    }
复制代码

DownloadProgressListener中代码:

package com.android.network;public interface DownloadProgressListener {    public void onDownloadSize(int size);

FileDownloader中代码:

复制代码
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);    }}
复制代码

DownloadThread 中代码:

复制代码
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;    }
原创粉丝点击