Android: launch different activities in a stack, using the same class

I have a similar issue with this one: Android: Multiple activity instances launched by same intent. Bring one uniquely to foreground?

I need to create a stack of activities, all created by using the same class: it is a class defining a news list, only there needs to be multiple children activities that are also news lists, but from different categories. (I do need to have these activities in a stack)

The trouble is I need to change data on each of these activities after they are shown, but I can't find a way to access each one of these activities separately, since they are all using the same class, so if I used static methods, I would change the data on all these activities at the same time. Ideally, there could be a way to use references of each activity, so that I can access methods on each one separately, but I don't think there is a way of doing this.

I might as well pass parameter IDs when starting each activity, and instantiate objects at the same time, for each activity, and using these IDs later access the respective objects' methods...

Edit to clarify: Let me use an example to what I am trying to achieve. I have an A class and I am using this same class to instantiate multiple activities, in a stack. After the creation of these activities, I need to alter da开发者_如何学JAVAta, say, on one of these activities statically, so by calling A.alterData(); , but not when the activities are created, so there is no way of doing this by starting the activities with different data.. Since there are multiple instances of this class, if I do so, this will result on altering the data on all these activities, that are using the A class. Would I be able to somehow use objects and methods to these objects to alter data on different activities that are using the same class?

any other ideas?

You could use an ActivityGroup. It basically holds a list of activities and you need to control the navigation around them. It sounds like it suits your situation. There are many examples of them that can be found through google.

How I would approach changing the data on the other screens is by using shared preferences. You can store whatever data you need in there, and then (through your activity group) when you change screen, the data is refreshed. This is faster and a little more efficient than restarting the intent every time.

Another way is to change the data in the background without the user noticing. This can be done because an Activity group loads all of the Activity it holds and they are always there in the background, running, unless the developer states otherwise.

You could grab a a hold of the appropriate instance of the class you want to change the data on and then just change it.

Does any of this make sense?

I can elaborate more if needed.

I would supply the parameters to each activity, such as:

intent.putExtra("category", categoryId);

That way you aren't managing too much global state.

About changing the data - if you are talking about refreshing the data from its original source, then you should probably be doing this in the onResume() method of the Activity. Check out the Activity Lifecycle.

This has a few benefits:

• you will have access to all of the context of that Activity
• you won't have to do something nasty like access another Activity's data
• you won't waste time refreshing data the user isn't looking at

Even if you have to make updates to the data, there are ways to make sure each Activity "minds its own business".