学步园

Android平台有3中网络接口：

1. java.net.*;//标准java接口
2. org.apache.*;//Apache接口，提供 Apache HttpClient ，比JDK更完善
3. android.net.*;//对Apache HttpClient封装

按钮1：从Internet下载一个纯文本文件，然后输出显示在System.in过滤器中

按钮2：下载MP3文件到模拟器的/sdcard/voa/MySoul.mp3

这个是主运行程序

package com.xxDroid.download;<br /> import com.zjut.utils.HttpDownloader;<br /> import android.app.Activity;<br /> import android.os.Bundle;<br /> import android.view.View;<br /> import android.view.View.OnClickListener;<br /> import android.widget.Button;<br /> public class Download extends Activity {<br /> /** Called when the activity is first created. */<br /> Button buttonTxt = null;<br /> Button buttonMp3 = null;<br /> @Override<br /> public void onCreate(Bundle savedInstanceState) {<br /> super.onCreate(savedInstanceState);<br /> setContentView(R.layout.main);<br /> buttonTxt = (Button)findViewById(R.id.buttonTxt);<br /> buttonTxt.setOnClickListener(new ButtonTxtListener());<br /> buttonMp3 = (Button)findViewById(R.id.buttonMp3);<br /> buttonMp3.setOnClickListener(new ButtonMp3Listener());</p> <p> }</p> <p> class ButtonTxtListener implements OnClickListener {<br /> @Override<br /> public void onClick(View v) {<br /> // TODO Auto-generated method stub<br /> HttpDownloader httpDownloader = new HttpDownloader();<br /> String lrc = httpDownloader.download("http://www.hazegray.org/danfs/csn/a.txt");<br /> System.out.println(lrc);<br /> }</p> <p> }</p> <p> class ButtonMp3Listener implements OnClickListener {<br /> @Override<br /> public void onClick(View arg0) {<br /> // TODO Auto-generated method stub<br /> HttpDownloader httpDownloader = new HttpDownloader();<br /> httpDownloader.downFile("http://127.0.0.1/android/test.mp3", "music/", "MySoul.mp3");<br /> System.out.println("Success download the Mp3");<br /> }</p> <p> }<br /> }

HttpDownloader.java

package com.xxDroid.utils;<br /> import java.io.BufferedReader;<br /> import java.io.File;<br /> import java.io.IOException;<br /> import java.io.InputStream;<br /> import java.io.InputStreamReader;<br /> import java.net.HttpURLConnection;<br /> import java.net.MalformedURLException;<br /> import java.net.URL;<br /> public class HttpDownloader {<br /> private URL url = null;<br /> /**<br /> * 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件当中的内容<br /> * 1.创建一个URL对象<br /> * 2.通过URL对象，创建一个HttpURLConnection对象<br /> * 3.得到InputStram<br /> * 4.从InputStream当中读取数据<br /> * @param urlStr<br /> * @return<br /> */<br /> public String download(String urlStr) {<br /> StringBuffer sb = new StringBuffer();<br /> String line = null;<br /> BufferedReader buffer = null;<br /> try {<br /> // 创建一个URL对象<br /> url = new URL(urlStr);<br /> // 创建一个Http连接<br /> HttpURLConnection urlConn = (HttpURLConnection) url<br /> .openConnection();<br /> // 使用IO流读取数据<br /> buffer = new BufferedReader(new InputStreamReader(urlConn<br /> .getInputStream()));<br /> while ((line = buffer.readLine()) != null) {<br /> sb.append(line);<br /> }<br /> } catch (Exception e) {<br /> e.printStackTrace();<br /> } finally {<br /> try {<br /> buffer.close();<br /> } catch (Exception e) {<br /> e.printStackTrace();<br /> }<br /> }<br /> return sb.toString();<br /> }<br /> /**<br /> * 该函数返回整形 -1：代表下载文件出错 0：代表下载文件成功 1：代表文件已经存在<br /> */<br /> public int downFile(String urlStr, String path, String fileName) {<br /> InputStream inputStream = null;<br /> try {<br /> FileUtils fileUtils = new FileUtils();</p> <p> if (fileUtils.isFileExist(path + fileName)) {<br /> return 1;<br /> } else {<br /> inputStream = getInputStreamFromUrl(urlStr);<br /> File resultFile = fileUtils.write2SDFromInput(path,fileName, inputStream);<br /> if (resultFile == null) {<br /> return -1;<br /> }<br /> }<br /> } catch (Exception e) {<br /> e.printStackTrace();<br /> return -1;<br /> } finally {<br /> try {<br /> inputStream.close();<br /> } catch (Exception e) {<br /> e.printStackTrace();<br /> }<br /> }<br /> return 0;<br /> }<br /> /**<br /> * 根据URL得到输入流<br /> *<br /> * @param urlStr<br /> * @return<br /> * @throws MalformedURLException<br /> * @throws IOException<br /> */<br /> public InputStream getInputStreamFromUrl(String urlStr)<br /> throws MalformedURLException, IOException {<br /> url = new URL(urlStr);<br /> HttpURLConnection urlConn = (HttpURLConnection) url.openConnection();<br /> InputStream inputStream = urlConn.getInputStream();<br /> return inputStream;<br /> }<br /> }<br />

FileUtils.java，为HttpDownloader.java提供的工具类

package com.zjut.utils;<br /> import java.io.File;<br /> import java.io.FileOutputStream;<br /> import java.io.IOException;<br /> import java.io.InputStream;<br /> import java.io.OutputStream;<br /> import android.os.Environment;<br /> public class FileUtils {<br /> private String SDPATH;<br /> public String getSDPATH() {<br /> return SDPATH;<br /> }<br /> public FileUtils() {<br /> //得到当前外部存储设备的目录<br /> // /SDCARD<br /> SDPATH = Environment.getExternalStorageDirectory() + "/";<br /> }<br /> /**<br /> * 在SD卡上创建文件<br /> *<br /> * @throws IOException<br /> */<br /> public File creatSDFile(String fileName) throws IOException {<br /> File file = new File(SDPATH + fileName);<br /> file.createNewFile();<br /> return file;<br /> }</p> <p> /**<br /> * 在SD卡上创建目录<br /> *<br /> * @param dirName<br /> */<br /> public File creatSDDir(String dirName) {<br /> File dir = new File(SDPATH + dirName);<br /> dir.mkdir();<br /> return dir;<br /> }<br /> /**<br /> * 判断SD卡上的文件夹是否存在<br /> */<br /> public boolean isFileExist(String fileName){<br /> File file = new File(SDPATH + fileName);<br /> return file.exists();<br /> }</p> <p> /**<br /> * 将一个InputStream里面的数据写入到SD卡中<br /> */<br /> public File write2SDFromInput(String path,String fileName,InputStream input){<br /> File file = null;<br /> OutputStream output = null;<br /> try{<br /> creatSDDir(path);<br /> file = creatSDFile(path + fileName);<br /> output = new FileOutputStream(file);<br /> byte buffer [] = new byte[4 * 1024];<br /> while((input.read(buffer)) != -1){<br /> output.write(buffer);<br /> }<br /> output.flush();<br /> }<br /> catch(Exception e){<br /> e.printStackTrace();<br /> }<br /> finally{<br /> try{<br /> output.close();<br /> }<br /> catch(Exception e){<br /> e.printStackTrace();<br /> }<br /> }<br /> return file;<br /> }<br /> }

AndroidManifest.xml应加入以下两行，使Application具有访问Internet和SD卡的权限

<uses-permission android:name="android.permission.INTERNET"/><br /> <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />