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
        }
        
    }
}