一、onStartCommand(Intent intent, int flags, int startId)
位置:/frameworks/base/core/java/android/app/Service.java
/** * Called by the system every time a client explicitly starts the service by calling * {@link android.content.Context#startService}, providing the arguments it supplied and a * unique integer token representing the start request. Do not call this method directly. * * <p>For backwards compatibility, the default implementation calls * {@link #onStart} and returns either {@link #START_STICKY} * or {@link #START_STICKY_COMPATIBILITY}. * * <p>If you need your application to run on platform versions prior to API * level 5, you can use the following model to handle the older {@link #onStart} * callback in that case. The <code>handleCommand</code> method is implemented by * you as appropriate: * * {@sample development/samples/ApiDemos/src/com/example/android/apis/app/ForegroundService.java * start_compatibility} * * <p class="caution">Note that the system calls this on your * service's main thread. A service's main thread is the same * thread where UI operations take place for Activities running in the * same process. You should always avoid stalling the main * thread's event loop. When doing long-running operations, * network calls, or heavy disk I/O, you should kick off a new * thread, or use {@link android.os.AsyncTask}.</p> * * @param intent The Intent supplied to {@link android.content.Context#startService}, * as given. This may be null if the service is being restarted after * its process has gone away, and it had previously returned anything * except {@link #START_STICKY_COMPATIBILITY}. * @param flags Additional data about this start request. Currently either * 0, {@link #START_FLAG_REDELIVERY}, or {@link #START_FLAG_RETRY}. * @param startId A unique integer representing this specific request to * start. Use with {@link #stopSelfResult(int)}. * * @return The return value indicates what semantics the system should * use for the service's current started state. It may be one of the * constants associated with the {@link #START_CONTINUATION_MASK} bits. * * @see #stopSelfResult(int) */ public int onStartCommand(Intent intent, int flags, int startId) { onStart(intent, startId); return mStartCompatibility ? START_STICKY_COMPATIBILITY : START_STICKY; }
【START_STICKY】:如果service进程被kill掉,保留service的状态为开始状态,但不保留递送的intent对象。随后系统会尝试重新创建service,由于服务状态为开始状态, 所以创建服务后一定会调用onStartCommand(Intent,int,int)方法。如果在此期间没有任何启动命令被传递到service,那么参数Intent将为null。 【START_NOT_STICKY】:“非粘性的”。使用这个返回值时,如果在执行完onStartCommand后,服务被异常kill掉,系统不会自动重启该服务。 【START_REDELIVER_INTENT】:重传Intent。使用这个返回值时,如果在执行完onStartCommand后,服务被异常kill掉,系统会自动重启该服务,并将Intent的值传入。 【START_STICKY_COMPATIBILITY】:START_STICKY的兼容版本,但不保证服务被kill后一定能重启。