Unable to refresh list without orientation change - Android / Java

Question

I have some code which should allow a user to delete a folder (which it does) then it should be removed from the ‘recent folders’ list - however it is not. The folder remains on the ‘recent folders’ list even after the user has deleted it - which is undesired.

/**
* Add recent folders to the list in order as acquired by the {@link RecentFolderList}.
*
* @param destination List of drawer items to populate
*/
private void addRecentsToList(List<DrawerItem> destination) {
    // If there are recent folders, add them.
    final List<Folder> recentFolderList = getRecentFolders(mRecentFolders);
    // Remove any excluded folder types
    if (mExcludedFolderTypes != null) {
        final Iterator<Folder> iterator = recentFolderList.iterator();
        while (iterator.hasNext()) {
            if (isFolderTypeExcluded(iterator.next())) {
                iterator.remove();
            }
        }
    }
    if (recentFolderList.size() > 0) {
        destination.add(DrawerItem.ofHeader(mActivity, R.string.recent_folders_heading,
        mBidiFormatter));
        // Recent folders are not queried for position.
        for (Folder f : recentFolderList) {
            destination.add(DrawerItem.ofFolder(mActivity, f, DrawerItem.FOLDER_RECENT,
            mBidiFormatter));
        }
    }
}

The strange part is if I perform an orientation change - the folders are removed from the 'recent folders list' as desired - and I’m unsure as to why this might be happening.

I have a feeling the list may simply need to be refreshed (after the folder has been deleted) however I am unsure.

Any suggestions, clues or pointers are greatly appreciated.

Full Source:

http://pastebin.com/fiX4S9fB

P.S.

Calling notifyDataSetChanged() on the adapter (as suggested by one of the answers below - and whomever flagged this as a duplicate - does not seem to have any effect)

Answer 1

Call invalidate method on ListView to cause the refresh or notifyDatasetChanged on the adapter.

Answer 2

If you perform an orientation change your activity gets destroyed and rebuild. Then your member variable mRecentFolders might be empty. To prevent this add the last line in the following code in your AndroidManifest.xml to your activity:

<activity
android:name="name"
android:label="label"
android:configChanges="orientation|keyboardHidden|screenSize"> /*add this line*/

Answer 3

I looked at your code and it seems like you have a lot of different copies of the list you're working with. My guess is that you're deleting the folder from one of the lists, but not from the others.

The way ListAdapters in Android work is: you create them with a reference to a data source (say a list or array) and then when you change that data source, you have to notify them using notifyDataSetChanged() and it's their responsibility to refresh the view. If this is not happening in your case, that means the data source with which you created your list adapter is not getting updated... and that's just a matter of your internal app logic and has nothing to do with Android.

Also, I noticed that your code has multiple adapters and some of them override notifyDataSetChanged() and don't call the super-implementation. Make sure you're not breaking the chain by doing this.

Oh, and the reason why it gets refreshed when you rotate the screen is that the entire Activity gets recreated at that point and all your data gets re-loaded from the ultimate source as if you're opening that screen for the first time (or from passed data from the old instance of the Activity, if you've set it up that way).