< xml version="1.0" encoding="utf-8" >
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
>
android:id="@+id/downloadTxt"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="下载文本文件"
/>

android:id="@+id/downloadMp3"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="下载MP3文件"
/>

Androidmanifest.xml

< xml version="1.0" encoding="utf-8" >
package="com.learning.example"
android:versionCode="1"
android:versionName="1.0">

android:label="@string/app_name">

下载助手类httpdownloader 代码

package com.learning.example.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下载文件,前提是这个文件当中的内容是文本,函数的返回值就是文本当中的内容
* 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
* @param urlStr
* @return
*/
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 (IOException e) {
e.printStackTrace();
}
}
return sb.toString();
}

/**
*
* @param urlStr
* @param path
* @param fileName
* @return
* -1:文件下载出错
* 0:文件下载成功
* 1:文件已经存在
*/
public int downFile(String urlStr, String path, String fileName){
InputStream inputStream = null;
try {
FileUtils fileUtils = new FileUtils();

if(fileUtils.isFileExist(path + fileName)){
return 1;
} else {
inputStream = getInputStreamFromURL(urlStr);
File resultFile = fileUtils.write2SDFromInput(path, fileName, inputStream);
if(resultFile == null){
return -1;
}
}
}
catch (Exception e) {
e.printStackTrace();
return -1;
}
finally{
try {
inputStream.close();
} catch (IOException e) {
e.printStackTrace();
}
}
return 0;
}

/**
* 根据URL得到输入流
* @param urlStr
* @return
*/
public InputStream getInputStreamFromURL(String urlStr) {
HttpURLConnection urlConn = null;
InputStream inputStream = null;
try {
url = new URL(urlStr);
urlConn = (HttpURLConnection)url.openConnection();
inputStream = urlConn.getInputStream();

} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}

return inputStream;
}
}

文件操作类fileutils 代码

package com.learning.example.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 FileUtils {
private String SDPATH;

private int FILESIZE = 4 * 1024;

public String getSDPATH(){
return SDPATH;
}

public FileUtils(){
//得到当前外部存储设备的目录( /SDCARD )
SDPATH = Environment.getExternalStorageDirectory() + "/";
}

/**
* 在SD卡上创建文件
* @param fileName
* @r