从子活动调用父活动中的函数-Android

Question

How can I call function (with parameters) in parent activity from child activity in Android. I iOS is simple with delegate and protocols, but in Android I found that can be a problem if the screen is rotated.

I also do not want to use startActivityForResult because I do not want to close the child Activity.

ADDED: I am creating a library so other developers can attach it to their project. In developers activity they put button that shows my(by my I mean from library) Activity and when something is done in my activity I instantly need to inform the main project(activity) that something happened (via function or something), but I do not want to close my activity yet. I also should not change their code a lot and it should be easy to include to their code.

Answer 1

The point is that once you started a child activity, Android might decide to close your parent activity at any time, if system requires more memory. This means you cannot rely on the fact your parent activity still runs. That is why you cannot use static variable approach either, because parent activity might not be there already.

If you want your app to run reliable in any situation you have to use startActivityForResult and close child activity.

If this is not acceptable for you because of some reasons, you might share more details and we will try to find an appropriate solution for you in terms of Android concepts.

ADDED: I am creating a library...

As already mentioned, you cannot control whether your parent activity gets closed or not as long you started a new child activity. Android can kill your parent activity at any time and you need to be prepared to handle this situation properly.

To solve your problem you need a place, which is shared between parent and child activities. A sequence will be like this. Parent activity starts a child activity and goes into background. User changes something in child activity and it stores changes (as data) into the shared place. At this step it doesn't matter whether parent activity still running or now. Once parent activity is visible again, if must read data stored by child activity, and update itself accordingly. You can use onStart() method for this.

Now about that shared place. I would discourage you from using a static variables. Instead you could use Application object (it's a singleton) or shared preferences (they are also shared).