202184.Eclipseframework之servicetracker

本文以eclipse 4.20为参考.

serviceTracker相较于serviceListener更方便使用, 从功能上说, 它实际上是 serviceListener &＃43; filter.

指定要跟踪的serviceReference

serviceTracker的构造有3种形式, 可以根据需要选择.

1. 关注特定serviceReference的serviceEvent.
2. 关注特定class的一类serviceReferences的serviceEvent.
3. 直接指定filter, 关注匹配该filter的serviceReferences的serviceEvent.

关于tracked object

tracked object是接口ServiceTrackerCutomizer引入的概念.

public interface ServiceTrackerCustomizer {public T addingService(ServiceReference reference);public void modifiedService(ServiceReference reference, T service);public void removedService(ServiceReference reference, T service);
}

ServiceTrackerCutomizer对应了ServiceEvent的几个事件类型. 而addingService()的返回值就是tracked object, 它会回传给modifiedService()和removedService()中. ServiceTracker.Tracked负责保存service object与tracked object的对应关系.