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Background: I'm trying to implement a messenging system in my app, and I'm writing a custom CursorAdapter to display the messages in a ListView in the chat window. I want to use a different row layout for incoming and outgoing messages (information that is saved in the SQLite row in the cursor). Each row has the same elements in it with the same IDs, but they are arranged differently.

The Problem: Currently, I have overridden newView() and bindView(). When the ListView is first populated, it creates all of the Views perfectly, checking each row to see if it's either incoming or outgoing, and inflating the proper XML file. However, when I scroll or a new message is added to the window, the adapter recycles Views for the wrong rows. I would override getView(), but it is not passed the Cursor as a parameter, so I have no way of knowing whether the row should be incoming or outgoing.

I'm not looking for code, but rather, some suggestion for an elegant implementation. Thanks in advance!

Glendon Trullinger
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2 Answers2

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Here are two possible solutions:

(1) Use a single layout for all items, which you can adjust when binding to show as desired. The most straight-forward way would just to have the root view be a FrameLayout which contains N children for each of the different states, and you make one of them visible and all others gone when binding. Of course you want to take care to not let this cause your items to explode in the number of views they contain.

(2) Implement Adapter.getItemViewType() http://developer.android.com/reference/android/widget/Adapter.html#getItemViewType(int) to tell the list view about the different types of items you have so it will recycle the correct one.

hackbod
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  • While the second answer is a bit of an extension of Bob's suggestion, I really like your first suggestion. I think I'm going to go that route. Thanks! – Glendon Trullinger Jun 04 '11 at 05:37
  • For posterity, I accomplished what I wanted by creating a very simple, two-level layout with 3 children in a `RelativeLayout`. I then apply different `RelativeLayout.LayoutParams` to the layout in `bindView()`. – Glendon Trullinger Jul 02 '11 at 21:44
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Just a few thoughts, I personnaly find the whole ListView and CursorAdapter combination to be a little... err... is bloated the right word? Would it just be simpler to have a ScrollView/ LinearLayout combination that will just add the appropriate TextView as requested?

But as for your solution, since the user seems to be unable to change the order of the messages as they are added, you could add a ArrayList<String> field to your custom CursorAdapter that will keep track of whether the messages are incoming or outgoing. Something like:

private ArrayList<String> cursorMonitor; //"incoming" and "outgoing" as your options.

...and then inside wherever the ListView gets populated just use

cursorMonitor.add(my_cursor.getString("outgoing_or_incoming"));

And then in the getView() you can override it and use the cursorMonitor to determine which layout you need to inflate.

Bob
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