I have an array whose contents are updated and new entries are added on every seconds. How can i show the contents of an array in a table view so that i can see the newly inserted rows and updation of the added row.Can anyone help me.
Thanks in advance!!!
The answer suggested; [theTableView reload] definitely works fine. If you update the table every view seconds, however, your users will hate you.
Try to capture the reloading data in a notification handler. In that handler, check if the updated data belongs somewhere between the currently visible cells, if so, update the currently visible view. If not, ignore the updated data (but do add it to your underlying model). If the user scrolls further, after your update, cellForIndexPath: is called and the updated data will be drawn automatically.
reload is quite heavy to do every view seconds, certainly with a lot of data. drawing might get screwed up or worse..
You need to do a reload every time your datasource is updated. So if you table view is theTableView you would execute this instruction after your array is updated:
[theTableView reload]
Related
I have read several articles about UITableView, including the official doc and some on SO. But my situation seems to be different.
I want to update the Table each time the view loaded. And I must fetch the data using HTTP request.
What I got now is:
When enter the table view, I should use a non-synchronous HTTP request to update the data. Because I don't want the main thread to wait. One place to do that, is in the tableView:cellForRowAtIndexPath: method. So I return 0 for no data exist at the beginning.
When I get the HTTP respond, I update rows on main thread using beginUpdates endUpdates insertRowsAtIndexPaths:withRowAnimation:
And I must update the "Data Source" at the same time, but how to do that?
Or should I make a daemon thread and update my data every once in a while? So that the data will be ready when TableView is loaded.
You would do it like this:
Have a boolean or some variable where you can reliably detect whether you have all the data.
In viewWillAppear, reset everything. Start loading your data.
If you don't have the data yet, you only display one section with one cell (a placeholder cell that reads "Loading..." and shows a spinner, for instance).
Once the data is completely loaded, you set the bool or whatever.
Call [self.tableView reloadData];
In all of your UITableViewDataSource methods you would need to check whether you've got the data already or not. If not, you return the placeholder data.
[yourtablename reloadData]; will help you relaod the data in the tableview, You can call this once you get the response from your server
I'm not sure there's a "best method" for what you're trying to accomplish here. I would suggest trying the method you have, and seeing if it provides an adequate user experience (whatever that means to you) and if it doesn't, try something else. I would definitely suggest having some sort of "loading" indicator while the table is empty and waiting for http response.
In terms of your question about the "data source", the data source of a UITableView is simply an object that implements the UITableViewDataSource protocol which you can read about here. Often times, you will have XCode set up a UITableViewController object which will act as both delegate and data source to your table view. How you actually store your data is up to you. The data source protocol simply provides the methods by which a table view will "ask" for the data it needs to load.
I need your help, maybe its something silly but I can't find the error.
I have a table view and an add button, when its clicked I show a modal view with a little form, when save button is pressed I send the data to the TableView controller to show it, also I'm using NSUserDefaults to save this data in an array.
My problem comes when, for example, I add 2 new rows and delete 1 of them, then when I add another, it shows the last row I delete instead of showing the one I just add.
I'm doing the saving and reading this way:
in viewDidAppear I read the NSUserDefaults and get the data if exist.
in the method that catches the data from the ModalView I save to userdefaults.
in commitEditing method I read userdefaults and then delete the row from the array and from the table and then save this change in userdefaults.
I don't know what I doing wrong, Can anybody help me with this?
Use [self.tableView reloadData]; in the viewWillAppear of that class. You can also reference that class in another view controller, create an object for it and call [classObject.tableView reloadData];
Always remember to reload the tableView after an add operation or a delete operation.
Don’t use NSUserDefaults to act as the direct datasource of a table. Store it in an intermediate model. It’ll be a LOT easier to debug that way.
If you’re having trouble keeping your model synced with the user defaults, call [[NSUserDefaults standardUserDefaults] synchronize] whenever you alter them.
Also, make sure you’re not making some mistakes in your table cell reuse. You might be seeing old data if you have a customer UITableViewCell class and you’re not correctly implementing -prepareForReuse.
I am updating my table data resource and then I am calling
[self.tableView reloadData]
to load the table view with this new data. This is all happening in a thread. Now, it works fine with lets say I add 4-5 objects but at some point it stops calling the cellForRowAtIndexPath to reload the table with new data.
Data source is getting updated all the time to contain latest data. So, data source has 10 objects but I can see only 5 on the screen. And it keeps on adding the data but do not show it. Breakpoint shows the call to reloadData is not invoking cellForRowAtIndexPath after that.
What could be the reason.
hunch: make sure you message UIKit objects from the main thread (exclusively).
I am processing several large RSS feeds and displaying results in a TableView. The processing starts after the user clicks on the relevant tab. All works well, but as it takes a couple of seconds to process, the NIB and Table don't load until the processing finishes and it looks like the iPhone has seized up. I have added an Activity indicator to the NIB, but because it doesn't load until the table is ready to display, it appears too late to be of any use.
Does anyone have any ideas how to display a message to a user while the table builds/loads? I have tried loading a UIView first and adding the Table as a subview but, again, both seem to load only after the table is ready.
Guidance appreciated.
It's kind of hard to guess what's going on from your description but it looks like your calls aren't asynchronous. Here's what you should be doing in your code:
Make all calls asynchronous. You said your phone is seizing up. Makes it sound like your requests and responses are happening on the main thread. There are many libraries you could use to handle asynchronous calls. ASIHTTPRequest for one example....
Don't wait for the data to come in before displaying the tableView. It's a design principle that you load as much of the UI as possible so that the user has something to look at while your data loads up in the background. What you should be doing is initializing an NSMutableArray to hold the data. Initially this array will contain no objects. This is the array that you use in your data source methods: Use array size for numberOfRowsInSection and use the array objects in cellForRowAtIndexPath. Once your RSS feed XML comes in and is parsed, store that in your arrays and call [tableView reloadData]. This way you don't leave your users looking at a blank screen. (Another good practice is when the array size is zero, show one cell in your tableview that says "data is loading" or something).
When you first initialize and load up your table and then fire off those RSS feed requests, that's where you show an activity indicator view on the tableView. Stop animating the indicator when the RSS data comes in and your tableView reloads.
These are the standard steps you should follow while showing non local data in a tableview. Makes for a smooth user experience.
Like I said before, it seems from your question that your calls are not asynchronous. If I'm wrong, correct me and let's take it from there...
In my UIView I've got a UITableView (UITV) which is controlled by an NSFetchedResultsController (NSFRC). The UIView is inside a UINavigationController.
When the view is about to be loaded/displayed I start some background activities which fetch data from a remote server (JSON) and parse into Core Data.
The NSFRC is being called when the parsing is done and the threaded NSManagedObjectContext have been merged into the main context.
The problem is that sometimes many rows are being inserted to Core Data at once, a lot of table cells are being added and there is quite a delay from that the actual fetching and parsing is done, until the rows are being displayed.
Now I wonder if anyone knows of any solution to, for example:
hook up a spinner to some "fetched results controller inserted all its rows for this time" (or something) notification/delegate call to at least tell the user that "something is going to show up soon"?
Or might the best solution simply be to not initialize the NSFRC until the background fetching and processing is completed?
Thanks!
If I understand your question correctly, you may want to look into the NSFetchedResultsControllerDelegate methods, with documentation available here: http://developer.apple.com/library/ios/#documentation/CoreData/Reference/NSFetchedResultsControllerDelegate_Protocol/Reference/Reference.html
There are delegate methods available for pre changes with controllerWillChangeContent:, post changes with controllerDidChangeContent and during changes with didChangeSection: and didChangeObject.
I hope it helps!
Rog