In my Android app I have an activity with a listview that displays about 4000 items that are stored
locally in a SQLite Database. If I make an edit to an item, how can I get only this change in the listview,
without having to refresh all the item list (which means a new query for 4000 results)? This query slows down the performance.
I would like something like NSFetchedResultsController of ios.
Strategy should be -
As you are editing the contact, if the update is successful you just fetch the latest info from db for this specific contact only.
Update the edited contact object in your adapter's source List/Array's specific position.
Invoke your adapter.notifyDataSetChanged().
you must have an id for each contact in your SQL lite database.
when you edit a contact update that specific record in your database on basis of the id.
if update is successfull means the information you sent to database is stored successfully .
now you can use the same informtion to update your ArrayList/HashMap whatever you are using to populate your listview.
Ex:- suppose you edited 3rd index contact in your listview on successfull update you add like yourarraylist.add(3,contact);
and the fire notifydatasetChanged.
Try these steps if possible:
Try to fetch the data from db, but do it in different thread which won't effect the main UIThread.
Then you can call the adapter.notifyDataSetChanged() on adapter object. It will do the job i hope :).
Related
I'm having trouble building a twitter style load more button in the middle of my recyclerview. I'm currently working with a syncAdapter to fetch new data before inserting them into a db. I also have a ContentProvider and i'm using a Loader which is a CursorLoader to update the recycler_view's adapter.
When the syncAdapter fetches newer data than what exists in the app and there is more data available between the last of the new items fetched and the previous top item I want to show a LoadMore button in between.
My would-be logic for activating the loadMore button in my adapter is if the last row id of the newly fetched data set doesn't exist in the db. But the problem is I don't know where to perform this logic.
I can't make it in onLoadFinished because it is called after the new data is inserted, so I can't check the incoming data against the old data there, because by then the id of the last row in the incoming data set has already been written to the db.
I've thought of making the check while unparsing the incoming json before inserting to the db. I can check if the last id received exists in the db there, and know if a load more button is warranted, but letting the adapter know from there seems non-trivial. Since data is fetched on another thread(syncadapter or a service I've got), i'd have to write the fact that loadmore exists between two rows in SharedPreferences or send a broadcast. Is there a more elegant way of doing this, maybe i've missed something.
I'm open to suggestions.
I already have a SQLite Database setup which I am using as cache for the Android application. The application does a HTTP Request and gets back a List of objects which I can insert into the db. After the first request, if I do anymore requests, how do all of the following in a better way:
1) insert all new objects from the list
2) update all objects that were already in the db
3) delete all rows that were not there in the latest list of objects.
I know that options 1 and 2 can be done using the "INSERT OR UPDATE" query. How can I manage the 3rd option efficiently?
Right now my approach is to delete all from table and then insert all. But that isn't very efficient. Any ideas how to improve it?
For that you can use the ids of the rows. For doing that first retrieve all the rows which you want to delete using SELECT query and add it a temporary arraylist, then use for loop over the arraylist to delete all those rows by using DELETE query.
You should do your operations using the applyBatch() method of the ContentProvider (http://developer.android.com/reference/android/content/ContentProvider.html#applyBatch(java.util.ArrayList)).
You can perform this method in a separate thread asynchronously so that you do not block anything else. You will have to create a list of ContentProviderOperations. In fact, you only need to specify the ones you need to insert or update within the ArrayList and implement the applyBatch() method such that it will automatically delete the rest of the entries in the database.
To answer your question about how to delete the entries not in the table, the logical assumption would be to search through your data sequentially and then delete the ones that do not need to exist.
I guess the intention is to refresh the Http request result set saved in the database. So I think the most efficient way is do a transaction or batch operation to delete all rows from the table first and then insert the new rows. A transaction might be better so that the result rows are either all new or all old, but not mixed.
The question posted in this thread asks how to update a ListView when the data has changed. It assumes, however, that the data that is modified in a ListView is stored in a database. Therefore, the ListView UI can be updated by simply calling requery() after the changes have been committed to the database.
What should one do when modified data of a ListView is not stored in a database?
For example, if each item in a ListView is showing the distance to a particular landmark based on the user's current GPS coordinates, what is the correct way to update the view with the updated distances as the user moves about? Should the distances simply be stored in the database as a matter of convenience, so that requery() will update the UI? This does not seem like the correct approach if it is not necessary to persist (frequently changing) GPS data.
Edit: To clarify, I'd specifically like to address the situation where some of the data is stored in a database (the coordinates of the landmarks, for example), however, the frequently changing data is computed on the fly (e.g., the distances).
ArrayAdapter can be used instead of CursorAdapter.
The notifyDataSetChanged() method can be used to tell the ListView to refresh itself by requerying the ArrayAdapter assigned to it.
I suggest using ArrayAdapter instead of CursorAdapter (which is used to populate a ListView based on cursor > database query)
ArrayAdapter
You should update the array data storing your coordinate data. When it changes call adapter.notifyDataSetChanged() to have your list updated with the latest array data
Hope that helps
I have an app that stores items in a local database, displayed to the user using a ListView, also in the layout is an EditText that can be used to filter the list. All of this works fine, my issue is I would also like to include items returned by a web service (JSON) in this list also. I'm not having an issue parsing the JSON, my issue is simply how do I insert/add the results from the web service to the ListView?
The data for the ListView comes from a cursor handled by a SimpleCursorAdapter, I just can not figure out how to add the items from the JSON results to the Cursor (I don't actually think you can write to a Cursor outside of performing a Query).
If you don't want to insert the JSON results into the local DB, then one approach would be to use an ArrayAdapter to back the ListView. You can then populate the array by inserting results from the cursor and the JSON query.
Hope this helps,
Phil Lello
I have a ListView which uses cursor adapter to show the records from database. When a new records is inserted in database ,it works great and shows that entry on top of ListView on requery.
Now I am facing problem when User scroll down the List, background thread call web service and brings old data. In this case when it does requery, old data is also getting appended on top of list which should append old data at the end of list.
What should i need to do differently, to add old data at the end of List rather than top ? do i need to change method of insertion when I am getting this old data ?
I think you need to store a date field in your bd table and make an ORDER BY in the query....