types of push notifications in android

16) JAVA Implementation callback (implementation of various listener types in Android and Swing) and androidlistener Developers familiar with the MS-Windows and X Windows event-driven design modes usually pass a method pointer to the event source, this method (also called "Callback") is called when an event occurs "). Java's object-oriented model currently does not support method pointers, and it seems th

.singleTask: this instance will be generated in a new task, which will be used for each invocation, and will not produce a new instance.4.singleInstance: Is the only activity on its stack, which is reused every time.Launchmode plays an important role in the process of multiple activity jumps, it can decide whether to generate new activity instances, whether to reuse existing activity instances, and whether to share a task with other activity instances. Here is a brief introduction to the concept