Android 使用http协议下载文件

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1. 创建HttpURLConnection对象

HttpDownloader downloader = new HttpDownloader();

2.获得一个InputStream对象

3.访问网络，在Manifest.xml声明：androi.permission.INTERNET

<?xml version="1.0" encoding="utf-8"?><manifest xmlns:android="http://schemas.android.com/apk/res/android"      package="mars.download"      android:versionCode="1"      android:versionName="1.0">    <application android:icon="@drawable/icon" android:label="@string/app_name">        <activity android:name=".Download"                  android:label="@string/app_name">            <intent-filter>                <action android:name="android.intent.action.MAIN" />                <category android:name="android.intent.category.LAUNCHER" />            </intent-filter>        </activity>    </application>    <uses-sdk android:minSdkVersion="4" />    <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</manifest>

4.正文

Environment.getExternalStorageDirectory()// 获得SD卡的路径

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 HttpDownloader{ private URL url=null;  /**  * 根据URL下载文本文件  */ 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;   }}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; }  }

二、代码编写

1.AndroidMainfest.xml中配置

主要是解决网络权限和写SDCard的权限

Java代码

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="linys.download" android:versionCode="1" android:versionName="1.0">
<uses-sdk android:minSdkVersion="8" />
<application android:icon="@drawable/icon" android:label="@string/app_name">
<activity android:name=".Download" android:label="@string/app_name">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
</manifest>

[java] view plaincopyprint?

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="linys.download" android:versionCode="1" android:versionName="1.0">
<uses-sdk android:minSdkVersion="8" />
<application android:icon="@drawable/icon" android:label="@string/app_name">
<activity android:name=".Download" android:label="@string/app_name">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
</manifest>

<?xml version="1.0" encoding="utf-8"?><manifest xmlns:android="http://schemas.android.com/apk/res/android"package="linys.download" android:versionCode="1" android:versionName="1.0"><uses-sdk android:minSdkVersion="8" /><application android:icon="@drawable/icon" android:label="@string/app_name"><activity android:name=".Download" android:label="@string/app_name"><intent-filter><action android:name="android.intent.action.MAIN" /><category android:name="android.intent.category.LAUNCHER" /></intent-filter></activity></application><!-- 访问网络和操作SD卡 加入的两个权限配置 --><uses-permission android:name="android.permission.INTERNET" /><uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" /></manifest>

2.Activity编写

利用Http协议下载文件并存储到SDCard
    1.创建一个URL对象
    2.通过URL对象,创建一个HttpURLConnection对象
    3.得到InputStream
    4.从InputStream当中读取数据
    存到SDCard
    1.取得SDCard路径
    2.利用读取大文件的IO读法，读取文件

Java代码

package linys.download;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import android.app.Activity;
import android.os.Bundle;
import android.os.Environment;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
/**
*
* @Project: Android_MyDownload
* @Desciption: 利用Http协议下载文件并存储到SDCard
1.创建一个URL对象
2.通过URL对象,创建一个HttpURLConnection对象
3.得到InputStream
4.从InputStream当中读取数据
存到SDCard
1.取得SDCard路径
2.利用读取大文件的IO读法，读取文件
*
* @Author: LinYiSong
* @Date: 2011-3-25~2011-3-25
*/
public class MyDownload extends Activity {
private Button downFileBtn;
private Button downMP3Btn;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
downFileBtn=(Button)this.findViewById(R.id.downFile);
downMP3Btn=(Button)this.findViewById(R.id.downMP3);
downFileBtn.setOnClickListener(new DownFileClickListener());
downMP3Btn.setOnClickListener(new DownMP3ClickListener());
}
/**
*
* @Project: Android_MyDownload
* @Desciption: 只能读取文本文件，读取mp3文件会出现内存溢出现象
* @Author: LinYiSong
* @Date: 2011-3-25~2011-3-25
*/
class DownFileClickListener implements OnClickListener{
@Override
public void onClick(View v) {
String urlStr="http://172.17.54.91:8080/download/down.txt";
try {
/*
* 通过URL取得HttpURLConnection
* 要网络连接成功，需在AndroidMainfest.xml中进行权限配置
* <uses-permission android:name="android.permission.INTERNET" />
*/
URL url=new URL(urlStr);
HttpURLConnection conn=(HttpURLConnection)url.openConnection();
//取得inputStream，并进行读取
InputStream input=conn.getInputStream();
BufferedReader in=new BufferedReader(new InputStreamReader(input));
String line=null;
StringBuffer sb=new StringBuffer();
while((line=in.readLine())!=null){
sb.append(line);
}
System.out.println(sb.toString());
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
}
/**
*
* @Project: Android_MyDownload
* @Desciption: 读取任意文件，并将文件保存到手机SDCard
* @Author: LinYiSong
* @Date: 2011-3-25~2011-3-25
*/
class DownMP3ClickListener implements OnClickListener{
@Override
public void onClick(View v) {
String urlStr="http://172.17.54.91:8080/download/1.mp3";
String path="file";
String fileName="2.mp3";
OutputStream output=null;
try {
/*
* 通过URL取得HttpURLConnection
* 要网络连接成功，需在AndroidMainfest.xml中进行权限配置
* <uses-permission android:name="android.permission.INTERNET" />
*/
URL url=new URL(urlStr);
HttpURLConnection conn=(HttpURLConnection)url.openConnection();
//取得inputStream，并将流中的信息写入SDCard
/*
* 写前准备
* 1.在AndroidMainfest.xml中进行权限配置
* <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
* 取得写入SDCard的权限
* 2.取得SDCard的路径： Environment.getExternalStorageDirectory()
* 3.检查要保存的文件上是否已经存在
* 4.不存在，新建文件夹，新建文件
* 5.将input流中的信息写入SDCard
* 6.关闭流
*/
String SDCard=Environment.getExternalStorageDirectory()+"";
String pathName=SDCard+"/"+path+"/"+fileName;//文件存储路径
File file=new File(pathName);
InputStream input=conn.getInputStream();
if(file.exists()){
System.out.println("exits");
return;
}else{
String dir=SDCard+"/"+path;
new File(dir).mkdir();//新建文件夹
file.createNewFile();//新建文件
output=new FileOutputStream(file);
//读取大文件
byte[] buffer=new byte[4*1024];
while(input.read(buffer)!=-1){
output.write(buffer);
}
output.flush();
}
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}finally{
try {
output.close();
System.out.println("success");
} catch (IOException e) {
System.out.println("fail");
e.printStackTrace();
}
}
}
}
}