Where should I globally keep/cache data needed for all application lifecycle?

I'm fairly new in Androi开发者_如何转开发d/Java programming, so some of the basic stuff is still quite confusing. So, lets say my application gets all data (articles) it requires from external XML files, it parses them to data models (Article class) and those articles will be used (displaying in lists or single article) all over the application for all it's lifecycle.

Where should I keep them? Can I create singleton class with an array containing all the articles I've parsed? Or should I save them to database and then query it on demand? (that sounds like too much work, I don't need to cache them for now) What's the best practice here?

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Keep them in Application. This is a base class of any android application and it's alive during the whole lifetime of the application, whereas Activities are killed when not shown or orientation is changed.

You have to declare android:name in your AndroidManifest.xml:

<application android:name=".YourApplication"/>

Edited:

This is also relevant: How do I pass data between Activities/Services within a single application?

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that depends what is your programming style lol.

you can as you said create a singleton that will read your xml and store everything.

you can create a static hash in your class. this way when you create a new object you will have access to the static information from that class.

you can pass the information from class to class as parameters.

if you want us to tell you which one would be the best it will be difficult without knowing the architecture of your program.

for example you could have a view controller that handle any changes and then it is simple to store the data at that level to pass it on when you switch views.

you could have static views in wich you could directly set all the values as you open them.

you could have losely linked views that call each other without any controller to handle the switching and in that case you would may prefer having a way to collect the info you need from a singleton or a static method...

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As long as you make sure that you don't have any threads acting on the shared data you can just create a static class with static members. each activity will be able to access it. If using async download for your data then in the onPostExecute of your handler you can touch the GlobeVars because that runs on the UI thread.

public class GlobalVars {
  public static String userId = "?";
  //public static String serverUrl = "10.0.2.2"; //localhost when developing
  public static String serverUrl = "192.168.1.4"; //on device to laptop
  //public static String serverUrl = "102.192.293.10"; //production
  public static Book currentBook = null;
  public static Chapter currentChapter = null;
  public static int lastclickedChapter = -1;
  public static Voice currentVoice = null;
  public static String catalogJson = "";
  public static ArrayList<Book> catalogItems = null;
}

onCreate of MainActivity I can set the catalog to my downloaded list of xml coverted to objects

GlobeVars.catalogItems = downloaded xml to object list

in my SubActivity which is a list of chapters in onclicklistener I can set:

GlobeVars.currentChapter = items[clickeditem];

when you return to the main activity the values will still be set.