intent不能跳转怎么办

10-26 03:03:59.504: WARN/ActivityManager(60): Unable to start service Intent { cmp=com.mp3player/com.service.DownLoadService (has extras) }: not found
10-26 03:04:03.164: WARN/ActivityManager(60): Unable to start service Intent { cmp=com.mp3player/com.service.DownLoadService (has extras) }: not found 毕业论文 

xml文件
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.mp3player"
    android:versionCode="1"
    android:versionName="1.0" >
  
    <application
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name" >
        <activity
            android:label="@string/app_name"
            android:name=".Mp3ListActivity" >
            <intent-filter >
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <service android:name=".DownLoadService"></service>
    </application>
    <uses-sdk android:minSdkVersion="8" />
    <uses-permission android:name="android.permission.INTERNET"/>
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>

</manifest>

程序段
protected void onListItemClick(ListView l,View v,int position,long id){
Mp3Info mp3info = mp3infos.get(position);
System.out.println("mp3info-------->" + mp3info);
Intent intent = new Intent();
intent.putExtra("mp3info", mp3info);
intent.setClass(this,DownLoadService.class);
startService(intent);
super.onListItemClick(l, v, position, id);
｝

<category android:name="android.intent.category.LAUNCHER" />
  </intent-filter>
  </activity>
  <service android:name="com.service.DownLoadService"></service>
  </application>

这样可以啦...