ANDROID_MARS学习笔记_S01原始版_021_MP3PLAYER001_下载mp3文件

一、简介

1.在onListItemClick()中new Intent,Intent以存储序列化后的mp2Info对象作为参数，启动serivce

2.DownloadService在onStartCommand()中通过intent 获取mp3info,开启新线程，利用HttpDownloader下载文件到sdcard

二、代码
1.xml
(1)AndroidManifest.xml

增加

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

2.java
(1)Mp3ListActivity.java

     @Override
     protected void onListItemClick(ListView l, View v, int position, long id) {
         //根据用户点击列表当中的位置来得到响应的Mp3Info对象
         Mp3Info info = infos.get(position);
         //生成Intent对象
         Intent intent = new Intent();
         //将Mp3Info对象存入到Intent对象当中
         intent.putExtra("mp3Info", info);
         intent.setClass(this, DownloadService.class);
         //启动Service
         startService(intent);
         super.onListItemClick(l, v, position, id);
     }

(2)DownloadService.java

 package tony.mp3player.service;

 import tony.download.HttpDownloader;
 import tony.model.Mp3Info;
 import android.app.Service;
 import android.content.Intent;
 import android.os.IBinder;

 public class DownloadService extends Service{

     @Override
     public IBinder onBind(Intent intent) {
         return null;
     }

     //每次用户点击ListActivity当中的一个条目时，就会调用该方法
     @Override
     public int onStartCommand(Intent intent, int flags, int startId) {
         //从Intent对象当中将Mp3Info对象取出
         Mp3Info info = (Mp3Info) intent.getSerializableExtra("mp3Info");
         //生成一个下载线程，并将Mp3Info对象作为参数传递到线程对象当中
         DownloadThread thread = new DownloadThread(info);
         //启动新线程
         new Thread(thread).start();
         return super.onStartCommand(intent, flags, startId);
     }

     class DownloadThread implements Runnable {
         private Mp3Info info;

         public DownloadThread(Mp3Info info) {
             super();
             this.info = info;
         }

         @Override
         public void run() {
             //根据MP3文件的名字，生成下载地址
             String urlStr = "http://192.168.1.104:8080/mp3/" + info.getMp3Name();
             HttpDownloader downloader = new HttpDownloader();
             int result = downloader.downFile(urlStr, "mp3", info.getMp3Name());
             String msg = null;
             switch (result) {
             // -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
             case -1:
                 msg = "下载失败";break;
             case 0:
                 msg = "文件下载成功";break;
             case 1:
                 msg = "文件已经存在，不需要重复下载";break;
             }
             //使用Notification提示客户下载结果
         }

     }
 }