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();
 }
}