Android http协议实现文件下载

用http协议下载文件，主要用到的是httpURLConnection对象，主要的步骤如下：

1. 创建HttpURLConnection对象

2.获得一个InputStream对象

3.修改权限：访问网络和写SDK卡，在Manifest.xml声明：

<uses-permission android:name="android.permission.INTERNET"/>  //允许网络访问<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/> //允许写入SDK卡

String urlDownload = "";urlDownload = "http://www.baidu.com/img/baidu_sylogo1.gif";URL url = new URL(urlDownload );   // 打开连接   URLConnection con = url.openConnection();// 输入流   InputStream is = con.getInputStream();

如上面的代码所示，指定一个下载的目标链接，我们上面指定了一个图片地址。然后构建一个URL对象，调用该对象的openConnection方法来建立一个数据通路（连接）。代码的最后一行使用 con.getInputStream，拿到一个输入流对象，通过这个流对象我们就可以读取到这个文件的内容了。下面要做的，就是读取这个流，将流写入我们的本地文件。不过在这之前，我们还要说下这个方法：

//获得文件的长度int contentLength = con.getContentLength();System.out.println("长度 :"+contentLength);

获得文件长度的方法。ContentLength是不很熟啊。它是http协议里描述头(head)部分的描述属性之一。实际这里是发送了一个http请求，分析了返回（response)里数据内容。

我们常常会把文件下载到手机的存储卡里，所以还会用到获得存储卡路径的方法：

// 获得存储卡路径，构成 保存文件的目标路径String dirName = "";dirName = Environment.getExternalStorageDirectory()+"/MyDownload/";File f = new File(dirName);if(!f.exists()){    f.mkdir();}

Environment.getExternalStorageDirectory() 方法会返回一个字符串，指示了存储卡的路径。我们拼接字符串出一个准备存放下载文件的文件夹。并先判断文件夹是是否存在，如果不存在，则新建一个文件夹。

做完了上面的准备后，基本就能实现下载了。我们看看主要的完整代码。

下载前的准备工作：

//要下载的文件路径String urlDownload = "";//urlDownload =  "http://192.168.3.39/text.txt";urlDownload = "http://www.baidu.com/img/baidu_sylogo1.gif";// 获得存储卡路径，构成 保存文件的目标路径String dirName = "";dirName = Environment.getExternalStorageDirectory()+"/MyDownload/";File f = new File(dirName);if(!f.exists()){    f.mkdir();}

下载的操作：

//准备拼接新的文件名（保存在存储卡后的文件名）String newFilename = _urlStr.substring(_urlStr.lastIndexOf("/")+1);newFilename = _dirName + newFilename;File file = new File(newFilename);//如果目标文件已经存在，则删除。产生覆盖旧文件的效果if(file.exists()){    file.delete();}try {         // 构造URL            URL url = new URL(_urlStr);            // 打开连接            URLConnection con = url.openConnection();         //获得文件的长度         int contentLength = con.getContentLength();         System.out.println("长度 :"+contentLength);         // 输入流            InputStream is = con.getInputStream();           // 1K的数据缓冲            byte[] bs = new byte[1024];            // 读取到的数据长度            int len;            // 输出的文件流            OutputStream os = new FileOutputStream(newFilename);            // 开始读取            while ((len = is.read(bs)) != -1) {                os.write(bs, 0, len);            }           // 完毕，关闭所有链接            os.close();           is.close();          } catch (Exception e) {        e.printStackTrace();}

下面是封装的一些方法我的部分代码如下：

   //从服务器下载图片到本地    private void getPhotoFromServer(List<Advert> adverts){    //读取服务器ip地址    String serverip = NetworkUtil.getDns(); //直接读取服务器的ip地址    //String serverURL = serverURLAll.substring(serverURLAll.indexOf(":")+3, serverURLAll.lastIndexOf(":")); //最好还是直接从数据库或者其他地方读取ip地址    Log.d(TAG, "server ip is " + serverip);    //整合成完整的广告图片存放地址目录    String urlDownload = "http://" + serverip +":8080/proPicRecord/";    //广告图片本地sd卡存放目录    String dirName = "/sdcard/advert/";    //判断本地存放广告图片的目录是否存，不存在则新建文件夹    File f = new File(dirName);    if(!f.exists())    {       f.mkdir();    }     //服务器上广告图片完整路径名，供下载用    String urlDownloadAll = "";    //准备拼接新的文件名（保存在存储卡后的文件名）    for(int i=0; adverts!=null && i<adverts.size(); i++){            Advert advert = adverts.get(i);            //下载路径添加上广告图片名字            urlDownloadAll = urlDownload + advert.getUrl();            Log.d(TAG, "The whole server download url is " + urlDownloadAll);                    //获取广告图片的名字，其实使用advert.getUrl()也可            String newFilename = urlDownloadAll.substring(urlDownloadAll.lastIndexOf("/")+1);           //本地播放广告图片的完整路径           newFilename = dirName + newFilename;           Log.d(TAG, "The local url is" + newFilename);           File file = new File(newFilename);           //如果目标文件已经存在，则删除，产生覆盖旧文件的效果（此处以后可以扩展为已经存在图片不再重新下载功能）          if(file.exists())          {              file.delete();          }          try{                  //构造URL              URL url = new URL(urlDownloadAll);              //打开连接              URLConnection con = url.openConnection();              //获得文件的长度              //int contentLength = con.getContentLength();              //System.out.println("长度 :"+contentLength);              //输入流              InputStream is = con.getInputStream();              //1K的数据缓冲              byte[] bs = new byte[1024];              //读取到的数据长度              int len;              //输出的文件流              OutputStream os = new FileOutputStream(newFilename);              //开始读取              while ((len = is.read(bs)) != -1) {                  os.write(bs, 0, len);              }               //完毕，关闭所有链接               os.close();               is.close();          }catch(Exception e){              e.printStackTrace();         }     }  }

单个文件下载：

package page.util;import java.io.BufferedReader;import java.io.File;import java.io.IOException;import java.io.InputStream;import java.io.InputStreamReader;import java.net.HttpURLConnection;import java.net.MalformedURLException;import java.net.URL;public class HttpDownloaderUtil{ private URL url=null;  /**  * 根据URL下载文本文件,以行读取文件  */ public String download(String urlStr){  StringBuffer sb = new StringBuffer();  String line = null;  BufferedReader buffer = null;  try{      url = new URL(urlStr);       HttpURLConnection urlConn = (HttpURLConnection)url.openConnection();       buffer = new BufferedReader(new InputStreamReader(urlConn.getInputStream()));       while((line = buffer.readLine())!=null)       {            sb.append(line);       }  }catch(Exception e)  {       e.printStackTrace();  }finally{       try{            buffer.close();       }catch(Exception e){            e.printStackTrace();   }  }  return sb.toString(); } /**  * 下载文件并写SD卡  * @param urlStr  * @param path  * @param fileName  * @return 0-success,-1-fail,1-existed  */ public int downFile(String urlStr,String path,String fileName){  InputStream inputStream= null;  try{       FileUtil fileUtil = new FileUtil();       if(fileUtil.isFileExist(path+fileName))            return 1;       else{            inputStream = getInputStreamFromUrl(urlStr);            File resultFile = fileUtil.write2SDFromInput(path, fileName, inputStream);            if(resultFile == null)             return -1;       }     }catch(Exception e){       e.printStackTrace();  }finally{       try{            inputStream.close();       }catch(Exception e){            e.printStackTrace();       }  }  return 0; } public InputStream getInputStreamFromUrl(String urlStr) throws MalformedURLException,IOException{  url = new URL(urlStr);  HttpURLConnection urlCon =(HttpURLConnection)url.openConnection();  InputStream inputStream = urlCon.getInputStream();  return inputStream; }}

文件处理的工具类：

package page.util;import java.io.File;import java.io.FileOutputStream;import java.io.IOException;import java.io.InputStream;import java.io.OutputStream;import android.os.Environment;public class FileUtil{ private String SDPATH;  public String getSDPATH(){  return SDPATH; }  public FileUtil(){  SDPATH= Environment.getExternalStorageDirectory()+"/"; }  public File createSDFile(String fileName) throws IOException{  File file = new File(SDPATH+fileName);  file.createNewFile();  return file; } public File createSDDir(String dirName) {  File dir = new File(SDPATH+dirName);  dir.mkdir();  return dir; } public boolean isFileExist(String fileName){  File file = new File(SDPATH+fileName);  return file.exists(); } public File write2SDFromInput(String path,String fileName,InputStream input){  File file = null;  OutputStream output = null;  try{      createSDDir(path);      file = createSDFile(path+fileName);      output = new FileOutputStream(file);       byte buffer[] = new byte[4*1024];      while((input.read(buffer))!=-1){         output.write(buffer);      }      output.flush();      }catch(Exception e){          e.printStackTrace();      }finally{         try{             output.close();         }         catch(Exception e){            e.printStackTrace();         }      }      return file;  }}

DownLoaderTask.java

package com.johnny.testzipanddownload;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.net.MalformedURLException;import java.net.URL;import java.net.URLConnection;import android.app.ProgressDialog;import android.content.Context;import android.content.DialogInterface;import android.content.DialogInterface.OnCancelListener;import android.os.AsyncTask;import android.util.Log;public class DownLoaderTask extends AsyncTask<Void, Integer, Long> { 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  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;  ((MainActivity)mContext).showUnzipDialog(); } 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;   }   mOutputStream = new ProgressReportingOutputStream(mFile);   publishProgress(0,length);   bytesCopied =copy(connection.getInputStream(),mOutputStream);   if(bytesCopied!=length&&length!=-1){    Log.e(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;   }   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 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);  } }}

解压：
ZipExtractorTask .java

package com.johnny.testzipanddownload;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.util.Enumeration;import java.util.zip.ZipEntry;import java.util.zip.ZipException;import java.util.zip.ZipFile;import android.app.ProgressDialog;import android.content.Context;import android.content.DialogInterface;import android.content.DialogInterface.OnCancelListener;import android.os.AsyncTask;import android.util.Log;public class ZipExtractorTask extends AsyncTask<Void, Integer, Long> { private final String TAG = "ZipExtractorTask"; private final File mInput; private final File mOutput; private final ProgressDialog mDialog; private int mProgress = 0; private final Context mContext; private boolean mReplaceAll; public ZipExtractorTask(String in, String out, Context context, boolean replaceAll){  super();  mInput = new File(in);  mOutput = new File(out);  if(!mOutput.exists()){   if(!mOutput.mkdirs()){    Log.e(TAG, "Failed to make directories:"+mOutput.getAbsolutePath());   }  }  if(context!=null){   mDialog = new ProgressDialog(context);  }  else{   mDialog = null;  }  mContext = context;  mReplaceAll = replaceAll; } @Override protected Long doInBackground(Void... params) {  // TODO Auto-generated method stub  return unzip(); } @Override protected void onPostExecute(Long result) {  // TODO Auto-generated method stub  //super.onPostExecute(result);  if(mDialog!=null&&mDialog.isShowing()){   mDialog.dismiss();  }  if(isCancelled())   return; } @Override protected void onPreExecute() {  // TODO Auto-generated method stub  //super.onPreExecute();  if(mDialog!=null){   mDialog.setTitle("Extracting");   mDialog.setMessage(mInput.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 void onProgressUpdate(Integer... values) {  // TODO Auto-generated method stub  //super.onProgressUpdate(values);  if(mDialog==null)   return;  if(values.length>1){   int max=values[1];   mDialog.setMax(max);  }  else   mDialog.setProgress(values[0].intValue()); } private long unzip(){  long extractedSize = 0L;  Enumeration<ZipEntry> entries;  ZipFile zip = null;  try {   zip = new ZipFile(mInput);   long uncompressedSize = getOriginalSize(zip);   publishProgress(0, (int) uncompressedSize);   entries = (Enumeration<ZipEntry>) zip.entries();   while(entries.hasMoreElements()){    ZipEntry entry = entries.nextElement();    if(entry.isDirectory()){     continue;    }    File destination = new File(mOutput, entry.getName());    if(!destination.getParentFile().exists()){     Log.e(TAG, "make="+destination.getParentFile().getAbsolutePath());     destination.getParentFile().mkdirs();    }    if(destination.exists()&&mContext!=null&&!mReplaceAll){    }    ProgressReportingOutputStream outStream = new ProgressReportingOutputStream(destination);    extractedSize+=copy(zip.getInputStream(entry),outStream);    outStream.close();   }  } catch (ZipException e) {   // TODO Auto-generated catch block   e.printStackTrace();  } catch (IOException e) {   // TODO Auto-generated catch block   e.printStackTrace();  }finally{   try {    zip.close();   } catch (IOException e) {    // TODO Auto-generated catch block    e.printStackTrace();   }  }  return extractedSize; } private long getOriginalSize(ZipFile file){  Enumeration<ZipEntry> entries = (Enumeration<ZipEntry>) file.entries();  long originalSize = 0l;  while(entries.hasMoreElements()){   ZipEntry entry = entries.nextElement();   if(entry.getSize()>=0){    originalSize+=entry.getSize();   }  }  return originalSize; } 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;   }   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 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.testzipanddownload;import android.os.Bundle;import android.os.Environment;import android.app.Activity;import android.app.AlertDialog;import android.content.DialogInterface;import android.content.DialogInterface.OnClickListener;import android.util.Log;import android.view.Menu;public class MainActivity extends Activity { private final String TAG="MainActivity"; @Override protected void onCreate(Bundle savedInstanceState) {  super.onCreate(savedInstanceState);  setContentView(R.layout.activity_main);  Log.d(TAG, "Environment.getExternalStorageDirectory()="+Environment.getExternalStorageDirectory());  Log.d(TAG, "getCacheDir().getAbsolutePath()="+getCacheDir().getAbsolutePath());  showDownLoadDialog();  //doZipExtractorWork();  //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 showDownLoadDialog(){  new AlertDialog.Builder(this).setTitle("确认")  .setMessage("是否下载？")  .setPositiveButton("是", new OnClickListener() {   @Override   public void onClick(DialogInterface dialog, int which) {    // TODO Auto-generated method stub    Log.d(TAG, "onClick 1 = "+which);    doDownLoadWork();   }  })  .setNegativeButton("否", new OnClickListener() {   @Override   public void onClick(DialogInterface dialog, int which) {    // TODO Auto-generated method stub    Log.d(TAG, "onClick 2 = "+which);   }  })  .show(); } public void showUnzipDialog(){  new AlertDialog.Builder(this).setTitle("确认")  .setMessage("是否解压？")  .setPositiveButton("是", new OnClickListener() {   @Override   public void onClick(DialogInterface dialog, int which) {    // TODO Auto-generated method stub    Log.d(TAG, "onClick 1 = "+which);    doZipExtractorWork();   }  })  .setNegativeButton("否", new OnClickListener() {   @Override   public void onClick(DialogInterface dialog, int which) {    // TODO Auto-generated method stub    Log.d(TAG, "onClick 2 = "+which);   }  })  .show(); } public void doZipExtractorWork(){  //ZipExtractorTask task = new ZipExtractorTask("/storage/usb3/system.zip", "/storage/emulated/legacy/", this, true);  ZipExtractorTask task = new ZipExtractorTask("/storage/emulated/legacy/testzip.zip", "/storage/emulated/legacy/", this, true);  task.execute(); } private void doDownLoadWork(){  DownLoaderTask task = new DownLoaderTask("http://192.168.9.155/johnny/testzip.zip", "/storage/emulated/legacy/", this);  //DownLoaderTask task = new DownLoaderTask("http://192.168.9.155/johnny/test.h264", getCacheDir().getAbsolutePath()+"/", this);  task.execute(); }}

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