Making data obtained in one activity available to all the activities

Question

I store strings obtained from parsing XML in an ArrayList. There are many such arrayLists. How do I make these ArrayLists available to all the activities in the application so that I don't need to pass arrays to the activities using intents.

Answer 1

I don't think a static field is what you want here. You haven't mentioned where this xml is coming from, but I'm assuming you mean a string array specified in a xml file included in your app. In that case, you'll need to get a handle to the Resources object and for that you'll need a Context.

The Application object is always around and is accessible from all of your Activities. I would create and store these global ArrayLists there. Since it sounds like you have a bunch of them, could have a Map of ArrayLists and a function in your Application class that takes the name of the ArrayList you want and returns the appropriate ArrayList from the Map.

public class MyApp extends Application {

private Map<String, ArrayList<String>> mLists=new HashMap<String, ArrayList<String>>();


public void addList(String key, ArrayList<String> list) {
      mLists.put(key,list);

}

public ArrayList<String> getList(String key) {

   return mLists.get(key);

}

}

Answer 2

Extend Application and have it hold your data. Then in your intent you do

((MyApplication)getApplication()).getData();

Answer 3

Avoid making static variables. It's quick and painless, but it becomes messy real quick.

Check this earlier question

Answer 4

There's a good write-up of various ways of doing this in the Android Application Framework FAQ.

Answer 5

Having 'many' lists and making them static is not very efficient. You could use content providers that are more efficient I think.

Answer 6

You are best defining a handler to pass data between activities.

A good explanation of use is in this stackoverflow post

How to access original activity's views from spawned background service

and android dev write up is here

http://developer.android.com/reference/android/os/Handler.html

You would define a handler on your main thread with the ArrayLists you want to make available.