IntentService实现原理及内部代码
?? ?很多网友可能发现Android中除了Service还有一个IntentService，他们之间到底有哪些区别呢? 在继承关系上而言IntentService是Service的子类，内部实现的代码中涉及到一些Android入门开发者不了解的Looper，Android123在早期的文章中已经说明他们的用法，这里不再赘述，有关原理大家可以看源码实现如下:
public abstract class IntentService extends Service {
??? private volatile Looper mServiceLooper;?
??? private volatile ServiceHandler mServiceHandler; //一个Handler封装了Looper对象
??? private String mName;
??? private boolean mRedelivery;
??? private final class ServiceHandler extends Handler {
??????? public ServiceHandler(Looper looper) {
??????????? super(looper);
??????? }
??????? @Override
??????? public void handleMessage(Message msg) {
??????????? onHandleIntent((Intent)msg.obj);
??????????? stopSelf(msg.arg1);
??????? }
??? }
??? public IntentService(String name) { //构造方法，需要提供一个name作为标识
??????? super();
??????? mName = name;
??? }
? 对于下面的setIntentRedelivery的参数，如果为真时
onStartCommand(Intent, int, int)} will return
Service#START_REDELIVER_INTENT}, so if this process dies before
onHandleIntent(Intent)} returns, the process will be restarted
如果为假时
onStartCommand(Intent, int, int)} will return
Service#START_NOT_STICKY}, and if the process dies
???? public void setIntentRedelivery(boolean enabled) {
??????? mRedelivery = enabled;
??? }
??? @Override
??? public void onCreate() { //这里重写父类Service的创建，主要是构造一个线程
??????? super.onCreate();
??????? HandlerThread thread = new HandlerThread("IntentService[" + mName + "]");
??????? thread.start();
??????? mServiceLooper = thread.getLooper();
??????? mServiceHandler = new ServiceHandler(mServiceLooper);
??? }
??? @Override
??? public void onStart(Intent intent, int startId) {? //Android 2.0以前的Service启动参数控制
??????? Message msg = mServiceHandler.obtainMessage();
??????? msg.arg1 = startId;
??????? msg.obj = intent;
??????? mServiceHandler.sendMessage(msg);
??? }
??? @Override?
??? public int onStartCommand(Intent intent, int flags, int startId) { //Android 2.0以后的服务启动参数
??????? onStart(intent, startId);
??????? return mRedelivery ? START_REDELIVER_INTENT : START_NOT_STICKY;
??? }
??? @Override
??? public void onDestroy() { //服务摧毁的时候Looper一定要释放掉，这点很重要。
??????? mServiceLooper.quit();
??? }
??? @Override
??? public IBinder onBind(Intent intent) {
??????? return null;
??? }
??? protected abstract void onHandleIntent(Intent intent);
}
?从上面的代码相信大家可以看出IntentService和Service的不同了，通过Looper和Thread来解决标准Service中处理逻辑的阻塞问题，毕竟Android的Service也是会阻塞的。
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摘自：http://www.189works.com/article-16485-1.html
