android－－ 通过HTTP协议实现断点续传下载

 */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

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;}@Overridepublic 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

package cn.itcast.net.download;public interface DownloadProgressListener {public void onDownloadSize(int size);}

DBOpenHelper.java

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);}@Overridepublic void onCreate(SQLiteDatabase db) {db.execSQL("CREATE TABLE IF NOT EXISTS filedownlog (id integer primary key autoincrement, downpath varchar(100), threadid INTEGER, downlength INTEGER)");}@Overridepublic void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {db.execSQL("DROP TABLE IF EXISTS filedownlog");onCreate(db);}}

FileService.java

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 positionSQLiteDatabase 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

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(){@Overridepublic 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() {@Overridepublic 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() {@Overridepublic 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() {@Overridepublic 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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