IntentService提供了一种在后台线程中运行任务的方式，适合处理运行时间较长的后台任务。

长处：

（1）IntentService执行在单独的线程中，不会堵塞UI线程

（2）IntentService不受生命周期的影响

缺点：

（1）不能与UI直接进行交互，能够用Broadcast

（2）顺序运行请求，第二个请求仅仅有在第一个请求运行完以后才干运行

（3）请求不能被中断

使用IntentService的步骤：

（1）在Activity中通过startService启动service，并传递參数。

（2）Service中接收參数，做耗时的处理，处理完成，发送Broadcat。并把处理结果传递出来

（3）Activity中注冊BroadcastReceiver，监听广播。更新UI。

看一个样例：

public class MainActivity extends Activity {	@Override	protected void onCreate(Bundle savedInstanceState) {		super.onCreate(savedInstanceState);		setContentView(R.layout.activity_main);		Button btn = (Button) this.findViewById(R.id.btn);		btn.setOnClickListener(new View.OnClickListener() {			@Override			public void onClick(View v) {//通过startService启动service，并传递參数。				Intent mServiceIntent = new Intent(MainActivity.this,RSSPullService.class);				mServiceIntent.setData(Uri.parse("http://www.baidu.com/"));				MainActivity.this.startService(mServiceIntent);			}		});		//注冊BroadcastReceiver。监听广播		IntentFilter statusIntentFilter = new IntentFilter(Constants.BROADCAST_ACTION);        // Sets the filter's category to DEFAULT        statusIntentFilter.addCategory(Intent.CATEGORY_DEFAULT);		DownloadStateReceiver mDownloadStateReceiver = new DownloadStateReceiver();		// Registers the DownloadStateReceiver and its intent filters		LocalBroadcastManager.getInstance(this).registerReceiver(mDownloadStateReceiver, statusIntentFilter);	}	private class DownloadStateReceiver extends BroadcastReceiver {		@Override		public void onReceive(Context context, Intent intent) {			String data = intent.getStringExtra(Constants.EXTENDED_DATA);			Log.e("test", data);			Toast.makeText(context, data, Toast.LENGTH_SHORT).show();		}	}}

public class RSSPullService extends IntentService {	public RSSPullService() {		super("RSSPullService");	}		@Override	protected void onHandleIntent(Intent workIntent) {//接收參数。做耗时的处理，处理完成。发送Broadcat		String localUrlString = workIntent.getDataString();		String data = download(localUrlString);		Intent localIntent = new Intent(Constants.BROADCAST_ACTION);	    // Puts the status into the Intent		localIntent.putExtra(Constants.EXTENDED_DATA, data);	    // Broadcasts the Intent to receivers in this app.	    LocalBroadcastManager.getInstance(this).sendBroadcast(localIntent);	}		private String download(String localUrlString){		try{			URL url = new URL(localUrlString);			HttpURLConnection conn = (HttpURLConnection)url.openConnection();			InputStream in = conn.getInputStream();			ByteArrayOutputStream out = new ByteArrayOutputStream();			byte[] buff = new byte[1024];			int len = 0;			while((len = in.read(buff)) != -1){				out.write(buff,0,len);			}			in.close();			return new String(out.toByteArray());		}catch(Exception e){			e.printStackTrace();			return "";		}	}}

public class Constants {	// Defines a custom Intent action	public static final String BROADCAST_ACTION = "com.example.android.threadsample.BROADCAST";	// Defines the key for the status "extra" in an Intent	public static final String EXTENDED_DATA_STATUS = "com.example.android.threadsample.STATUS";		public static final String EXTENDED_DATA = "com.example.android.threadsample.DATA";}

AndroidManifest.xml:

參考：