Android通过HTTP协议实现断点续传下载

来源：互联网发布：网络直播评论性文章编辑：程序博客网时间：2024/06/06 01:52

 // FileDownloader.java                                                                      package cn.itcast.net.download;  
  
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 cn.itcast.service.FileService;  
  
import android.content.Context;  
import android.util.Log;  
/** 
 * 文件下载器 
 * FileDownloader loader = new FileDownloader(context, "http://browse.babasport.com/ejb3/ActivePort.exe", 
                new File("D:\\androidsoft\\test"), 2); 
        loader.getFileSize();//得到文件总大小 
        try { 
            loader.download(new DownloadProgressListener(){ 
                public void onDownloadSize(int size) { 
                    print("已经下载："+ size); 
                }            
            }); 
        } catch (Exception e) { 
            e.printStackTrace(); 
        } 
 */  
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  
     */  
    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.Java

[java] view plain copy
package cn.itcast.net.download;  
  
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;  
    }  
}  

DownloadProgressListener.java

[java] view plain copy
package cn.itcast.net.download;  
  
public interface DownloadProgressListener {  
    public void onDownloadSize(int size);  
}  

DBOpenHelper.java

[java] view plain copy
package cn.itcast.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 = "itcast.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.java

[java] view plain copy
package cn.itcast.service;  
  
import java.util.HashMap;  
import java.util.Map;  
  
import android.content.Context;  
import android.database.Cursor;  
import android.database.sqlite.SQLiteDatabase;  
/** 
 * 业务bean 
 * 
 */  
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();  
    }  
      
}  

DownloadActivity.java

[java] view plain copy
package cn.itcast.download;  
  
import java.io.File;  
  
import cn.itcast.net.download.DownloadProgressListener;  
import cn.itcast.net.download.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 DownloadActivity 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(DownloadActivity.this, R.string.success, 1).show();  
                }  
                break;  
  
            case -1:  
                Toast.makeText(DownloadActivity.this, R.string.error, 1).show();  
                break;  
            }  
        }  
    };  
      
    @Override  
    public void onCreate(Bundle savedInstanceState) {  
        super.onCreate(savedInstanceState);  
        setContentView(R.layout.main);  
          
        downloadpathText = (EditText) this.findViewById(R.id.downloadpath);  
        progressBar = (ProgressBar) this.findViewById(R.id.downloadbar);  
        resultView = (TextView) this.findViewById(R.id.result);  
        Button button = (Button) this.findViewById(R.id.button);  
        button.setOnClickListener(new View.OnClickListener() {            
            @Override  
            public void onClick(View v) {  
                String path = downloadpathText.getText().toString();  
                if(Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)){  
                    download(path, Environment.getExternalStorageDirectory());  
                }else{  
                    Toast.makeText(DownloadActivity.this, R.string.sdcarderror, 1).show();  
                }  
                  
            }  
        });  
    }  
    //主线程(UI线程)  
    //业务逻辑正确，但是该程序运行的时候有问题  
    //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  
    private void download(final String path, final File savedir) {  
        new Thread(new Runnable() {           
            @Override  
            public void run() {  
                FileDownloader loader = new FileDownloader(DownloadActivity.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();  
    }  
}  

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