Android 文件的下载操作

 

经过几个小时的努力，终于完成了，现在跟大家一起分享下，本人还是新手有很多不成熟的地方，

还望大家包含，有什么不足之处还望不惜赐教

 

在string.xm中声明两个变量以便于使用

 

<?xml version="1.0" encoding="utf-8"?> <resources> <string name="hello">FileDownloadActivity!</string> <string name="app_name">FileDownload</string> <string name="FileDownload_txt">下载文本文件</string> <string name="FileDownload_void">下载视频文件</string> </resources>  

 

main.xml中声明两个Button按钮

 

main.xml文件 <?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="fill_parent" > <Button android:id="@+id/btnDownloadTxt" android:layout_width="fill_parent" android:layout_height="wrap_content" android:text="@string/FileDownload_txt"/> <Button android:id="@+id/btnDownloadVoid" android:layout_width="fill_parent" android:layout_height="wrap_content" android:text="@string/FileDownload_void"/> </LinearLayout> 

 

在AndroidManifest.xml中声明权限

<uses-permission android:name="com.studio.android.WRITE_EXTERNAL_STORAGE"/> 

 

在SRC中另外声明一个包,包名为con.demo.FileDownloadClass

包中有两个类FileUtils.java ,HttpDownloader.java

 

FileUtils.java类

package com.demo.FilesDownloadClass; 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; public String getSDPATH(){ return SDPATH; } public FileUtils(){ //得到当前外部存储设备的目录 SDPATH=Environment.getExternalStorageDirectory()+"/"; } //在SD卡上创建文件 public File createSDFile(String fileName) throws IOException{ File file=new File(SDPATH +fileName); return file; } //在SD卡上创建目录 public File createSDDir(String dirName){ File dir=new File(SDPATH + dirName); dir.mkdir(); return dir; } //判断SD卡上是否已经相同文件 public boolean isFileExist(String fileName){ File file=new File(SDPATH +fileName); return file.exists(); } //将一个InputStream里面的数据写到SD卡中 public File writeDataIntoSDCare(String path,String fileName,InputStream input){ File file =null; OutputStream output=null; try { createSDDir(path); File f=createSDFile(path + fileName); output = new FileOutputStream(f); byte buffer[] =new byte[4 * 1024]; while ((input.read(buffer))!=-1){ output.write(buffer); } System.out.println(path); file = new File(path); } catch (Exception e) { // TODO: handle exception e.printStackTrace(); } finally{ try { output.close(); } catch (Exception e) { // TODO: handle exception e.printStackTrace(); } } return file; } }  

 

HttpDownloader.java类

 

package com.demo.FilesDownloadClass; import java.io.BufferedReader; import java.io.File; import java.io.IOException; import java.io.InputStream; import java.io.InputStreamReader; import java.net.MalformedURLException; import java.net.URL; import javax.net.ssl.HttpsURLConnection; public class HttpDownloader { private URL url=null; /* * 文本文件的下载 *根据URL下载文件,前提是这个文件当中的内容上个文本,函数还回的内容就是文本文件的内容 *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 * */ public String download(String urlStr){ StringBuffer sb=new StringBuffer(); String line=null; BufferedReader buffer=null; try { //创建一个URL对象 url=new URL(urlStr); //创建一个Http连接 HttpsURLConnection urlConn=(HttpsURLConnection)url.openConnection(); //使用IO流读取数据 buffer=new BufferedReader(new InputStreamReader(urlConn.getInputStream())); while((line=buffer.readLine())!= null){ sb.append(line); } } catch (Exception e) { // TODO: handle exception e.printStackTrace(); } finally{ try { buffer.close(); } catch (Exception e) { // TODO: handle exception e.printStackTrace(); } } return sb.toString(); } /* * 视频文件的下载 * 该函数还回值为整型, -1:代表下载文件出错,0：表示下载文件成功,1：表示下载文件已经存在 */ 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 res = fileUtils.writeDataIntoSDCare(path, fileName, inputStream); if(res == null){ return -1; } } } catch (Exception e) { // TODO: handle exception e.printStackTrace(); return -1; } finally{ try { inputStream.close(); } catch (Exception e) { // TODO: handle exception e.printStackTrace(); } } return 0; } //根据URL得到输入流 private InputStream getInputStreamFromUrl(String urlStr) throws MalformedURLException ,IOException{ // TODO Auto-generated method stub url = new URL(urlStr); HttpsURLConnection urlConn = (HttpsURLConnection) url.openConnection(); InputStream inputStream = urlConn.getInputStream(); return inputStream; } }  

 

RCS中的Activity

package com.demo.FilesDownload; //引入自定义包 import com.demo.FilesDownloadClass.*; import android.app.Activity; import android.os.Bundle; import android.view.View; import android.view.View.OnClickListener; import android.widget.Button; /* * 文件下载的主要步骤： * 1.创建一个HttpURLConnection对象 HttpURLConnection urlConn=(HttpURLConnection)url.openConnection(); * 2.获取一个InputStream对象 urlConn.getInputStream(); * 3.访问网络的权限android.permission.INTERNET * 注意必须在AndroidManifest.xml文件中配置权限<uses-permission android:name="com.studio.android.WRITE_EXTERNAL_STORAGE"/> * 此例子的结果只能在longCat中看到 * */ public class FileDownloadActivity extends Activity { private Button btnOne,btnTwo; /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); btnOne=(Button)findViewById(R.id.btnDownloadTxt); btnOne.setOnClickListener(new DownloadTxtOnClickListener()); btnTwo=(Button)findViewById(R.id.btnDownloadVoid); btnTwo.setOnClickListener(new DownloadVoidOnClickListener()); } //下载文本文件的监听器 class DownloadTxtOnClickListener implements OnClickListener { @Override public void onClick(View v) { // TODO Auto-generated method stub HttpDownloader httpDownloader=new HttpDownloader(); String path="http://www.rrting.com/search/download.asp?filename=/English/vocabulary/30201/30201.txt"; String lrc= httpDownloader.download(path);//lrc为String型 System.out.println(lrc); } } //下载视频文件的监听器 class DownloadVoidOnClickListener implements OnClickListener { @Override public void onClick(View v) { // TODO Auto-generated method stub HttpDownloader httpDownloader=new HttpDownloader(); String path="http://220.168.248.30/bf5ae554b43e5f29a21cbc8bb69a625e/English/yyjc/yych/ytbdc2000/cd13.mp3"; //path：目录,voa/ ：子目录 ,cd13.mp3 ：文件名（可以取自己喜欢的名称,不一定要与path中的名字相同） int res= httpDownloader.downFile(path,"voa/","cd13.mp3");//res为int型 System.out.println(res); } } } 

        以上代码还有很多不足之处，望有更好的可以一起探讨。呵呵