Android 實現斷點續傳

斷點續傳：

斷點續傳指的是在下載或上傳時，將下載或上傳任務（一個文件或一個壓縮包）人為的劃分為幾個部分，每一個部分采用一個線程進行上傳或下載，如果碰到網絡故障，可以從已經上傳或下載的部分開始繼續上傳下載以後未上傳下載的部分，而沒有必要從頭開始上傳下載。用途可以節省時間，提高速度。
測試服務器是否支持斷點續傳的方法：

浏覽器測試：

看看某個請求的響應頭信息裡面是否包含：
Accept-Ranges bytes
比如請求hao123，相應頭信息裡面包含：

Accept-Ranges bytes
Cache-Control max-age=0
Content-Encoding gzip
Content-Length 59107
Content-Type text/html;charset=UTF-8
Date Fri, 03 Jan 2014 02:40:27 GMT
Etag "1946829081"
Expires Fri, 03 Jan 2014 02:40:27 GMT
LFY cq01.13
Last-Modified Fri, 03 Jan 2014 02:40:00 GMT
SFY cq01.14
Server BWS/1.0
Set-Cookie hz=0; path=/; domain=www.hao123.com
Vary Accept-Encoding

表明支持斷點續傳

curl測試：

curl –-range 100-200 http://192.168.9.155/johnny/testzip.zip > download_1
看下載文件的大小是否是100字節。
如果服務器支持斷點續傳，那麼在請求頭信息裡面加上屬性就可以了：
RANGE: bytes=1000-

這一行就是告訴服務器這個文件從1000字節開始傳，前面就不要傳了。

Java代碼實現：

DownLoaderTask.java

package com.johnny.testdownloadbreakpoint;

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.RandomAccessFile;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLConnection;

import android.app.AlertDialog;
import android.app.AlertDialog.Builder;
import android.app.ProgressDialog;
import android.content.Context;
import android.content.DialogInterface;
import android.content.DialogInterface.OnCancelListener;
import android.content.DialogInterface.OnClickListener;
import android.os.AsyncTask;
import android.util.Log;

public class DownLoaderTask extends AsyncTask {
	private final String TAG = "DownLoaderTask";
	private URL mUrl;
	private File mFile;
	private ProgressDialog mDialog;
	private int mProgress = 0;
	private ProgressReportingOutputStream mOutputStream;
	private Context mContext;
	public DownLoaderTask(String url,String out,Context context){
		super();
		if(context!=null){
			mDialog = new ProgressDialog(context);
			mContext = context;
		}
		else{
			mDialog = null;
		}
		
		try {
			mUrl = new URL(url);
			String fileName = new File(mUrl.getFile()).getName();
			mFile = new File(out, fileName);
			Log.d(TAG, "out="+out+", name="+fileName+",mUrl.getFile()="+mUrl.getFile());
		} catch (MalformedURLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		
	}
	
	@Override
	protected void onPreExecute() {
		// TODO Auto-generated method stub
		//super.onPreExecute();
		if(mDialog!=null){
			mDialog.setTitle("Downloading...");
			mDialog.setMessage(mFile.getName());
			mDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
			mDialog.setOnCancelListener(new OnCancelListener() {
				
				@Override
				public void onCancel(DialogInterface dialog) {
					// TODO Auto-generated method stub
					cancel(true);
				}
			});
			mDialog.show();
		}
	}

	@Override
	protected Long doInBackground(Void... params) {
		// TODO Auto-generated method stub
		if(!checkURL()){
			Log.e(TAG, "url can not access.....");
			return 0l;
		}
		return download();
	}

	@Override
	protected void onProgressUpdate(Integer... values) {
		// TODO Auto-generated method stub
		//super.onProgressUpdate(values);
		if(mDialog==null)
			return;
		if(values.length>1){
			int contentLength = values[1];
			if(contentLength==-1){
				mDialog.setIndeterminate(true);
			}
			else{
				mDialog.setMax(contentLength);
			}
		}
		else{
			mDialog.setProgress(values[0].intValue());
		}
	}

	@Override
	protected void onPostExecute(Long result) {
		// TODO Auto-generated method stub
		//super.onPostExecute(result);
		if(mDialog!=null&&mDialog.isShowing()){
			mDialog.dismiss();
		}
		if(isCancelled())
			return;
	}

	private long download(){
		URLConnection connection = null;
		int bytesCopied = 0;
		try {
			connection = mUrl.openConnection();
			int length = connection.getContentLength();
			if(mFile.exists()&&length == mFile.length()){
				Log.d(TAG, "file "+mFile.getName()+" already exits!!");
				return 0l;
			}
			else if(mFile.exists()&&length > mFile.length()){
				Log.d(TAG, "Downdoad from breakpoint : size is = "+mFile.length()+", total is "+length);
				publishProgress(0,length);
				mProgress=(int) mFile.length();
				URLConnection connection1=mUrl.openConnection();
				connection1.setRequestProperty("RANGE", "bytes="+ mFile.length() +"-");
				bytesCopied=copyFromBreakPoint(connection1.getInputStream(),mFile);
				if(bytesCopied!=length&&length!=-1){
					Log.d(TAG, "Download incomplete bytesCopied="+mFile.length()+", length"+length);
				}
			}
			else if(!mFile.exists()){
				mOutputStream = new ProgressReportingOutputStream(mFile);
				publishProgress(0,length);
				bytesCopied =copy(connection.getInputStream(),mOutputStream);
				if(bytesCopied!=length&&length!=-1){
					Log.d(TAG, "Download incomplete bytesCopied="+bytesCopied+", length"+length);
				}
				mOutputStream.close();
			}
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		return bytesCopied;
	}
	private int copy(InputStream input, OutputStream output){
		byte[] buffer = new byte[1024*8];
		BufferedInputStream in = new BufferedInputStream(input, 1024*8);
		BufferedOutputStream out  = new BufferedOutputStream(output, 1024*8);
		int count =0,n=0;
		try {
			while((n=in.read(buffer, 0, 1024*8))!=-1){
				out.write(buffer, 0, n);
				count+=n;
				
				if(isCancelled()){
					Log.e(TAG, "stop downloading .....");
					//out.flush();
					//out.close();
					//in.close();
					break;
				}
				
			}
			out.flush();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}finally{
			try {
				out.close();
			} catch (IOException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
			try {
				in.close();
			} catch (IOException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
		}
		return count;
	}
	private int copyFromBreakPoint(InputStream input, File output){
		byte[] buffer = new byte[1024*8];
		int count =0,n=0;
		try {
			RandomAccessFile fos = new RandomAccessFile(output, "rw");
			
			fos.seek(output.length());
			while(true){
				n=input.read(buffer);
				if(n<=0){
					break;
				}
				fos.write(buffer, 0, n);
			    mProgress += n;
			    publishProgress(mProgress);
			}
			input.close();
			fos.close();
			
		} catch (FileNotFoundException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		
		return 0;
	}
	private boolean checkURL(){
		boolean ret = false;
		try {
			HttpURLConnection conn = (HttpURLConnection) mUrl.openConnection();
			if(conn.getResponseCode()==200)
				ret=true;
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		return ret;
	}
	private final class ProgressReportingOutputStream extends FileOutputStream{

		public ProgressReportingOutputStream(File file)
				throws FileNotFoundException {
			super(file);
			// TODO Auto-generated constructor stub
		}

		@Override
		public void write(byte[] buffer, int byteOffset, int byteCount)
				throws IOException {
			// TODO Auto-generated method stub
			super.write(buffer, byteOffset, byteCount);
		    mProgress += byteCount;
		    publishProgress(mProgress);
		}
		
	}
}

MainActivity.java

package com.johnny.testdownloadbreakpoint;

import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;

public class MainActivity extends Activity {

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		doDownLoadWork();
	}

	@Override
	public boolean onCreateOptionsMenu(Menu menu) {
		// Inflate the menu; this adds items to the action bar if it is present.
		getMenuInflater().inflate(R.menu.main, menu);
		return true;
	}
	private void doDownLoadWork(){
		DownLoaderTask task = new DownLoaderTask("http://192.168.9.155/johnny/H264+MP3.flv", "/storage/emulated/legacy/", this);
		//DownLoaderTask task = new DownLoaderTask("http://192.168.9.155/johnny/test.h264", getCacheDir().getAbsolutePath()+"/", this);
		task.execute();
	}

}