Question

I want to ask a general question about the proper way to handle a list with a hierarchy. The way I am doing it now is by calling the same activity with a bundle to handle the next query so I can drill down into the list. I am wondering if there is a better way to deal with lists like mine. Should I use multiple activities? (don’t know the depth of the list) or just requery my data when a user selects a list item. The problem with this solution is remembering the list item that was selected and the back button on the phone. I am sure I am missing something obvious but I’m new to Android. Any help or suggestions would be greatly appreciated. So here is what I do now:

1. Query the data and display the list in MainActivity with with the root items.
2. User clicks on one of the items, get the index of that item and call MainActivity with a bundle that contains the index of the item selected.
3. Query the data with the new item and display the new list in MainActivity.
4. rinse and repeat…

Also my list is more then two levels deep so I thing the ExpandableListView is out.

Answer 1

One of the reasons why ExpandableListView supports only two levels of in depth, is because its very hard to make n-level tree to be user-friendly. Just imagine the mass on user’s screen if he or she goes to 5th level.

But, nevertheless, here is the approach I would take. I haven’t implemented it yet, but this should be doable.

1. Introduce “Navigation Bar” at the top (like Windows Explorer has, or some sites have):

   Root > item 1 > subitem 2 > …

2. Use `Expandable list to show current level and the next level.

3. If user clicks on the item you will invalidate data and re-fill ExpandbleListView with next levels.

Her is an example:

> Root 
---------------
Item 1
   Subitem 1
   Subitem 2
   Subitem 3
Item 2 
   Subitem 4
   Subitem 5
Item 3
   Subitem 6

User clicks on Subitem 4 and sees:

> Root > Item 2
---------------
Subitem 4
   SubSubItem 1
   SubSubItem 2
   SubSubItem 3
Subitem 5
   SubSubItem 4
   SubSubItem 5

This is not trivial to implement, but shouldn’t be too hard. This gives navigation inside one Activity and uses highly optimized ExpandableListView control. You only need to implement custom adapter.