I have a subview where there is an uitableview that gets data from an online server (title, subtitle and image). When I click the button that shows the subview it takes a little time to get there using WiFi connection, but under 3G network it takes longer, so that you really feel the gap between loading the view and having pressed the button
what I'd like to do, is to display an uiactivityindicatorview when you press the button and after loading the view, and when it has loaded stop the activity indicator
how can I check that the uitableview has finished loading ?
do you have other suggestions ?
Thanks in advance
Use asynchronious requests or threading (take a look at NSOperation)
Look into doing network operations asynchronously, rather than blocking the main UI's thread. ASIHTTPRequest is a really good library for this: http://allseeing-i.com/ASIHTTPRequest/
As the others said, if you are not using an asynchronous approach to this, I strongly suggest you to do so, because otherwise you will block your application for as long as the data is being downloaded.
With that said, you could show the activity indicator while the data is being loaded, and that is until the delegate method
- (void)connectionDidFinishLoading:(NSURLConnection *)connection
is called. Then, your table should be populated with the data and the indicator would dissapear.
I hope this helped you a bit
Related
I have a MBProgressHUD that shows when data is being pulled on the background asynchronously. Sometimes when the network is slow this will take forever. So as of now I am just hiding it after 30 seconds if it hasn't been dismissed. What is a good way to dismiss this HUD for a slow network connection?
I would say that the best solution is probably to keep the HUD up the whole time the data is loading so that the user knows that something is happening, and perhaps give them an option to cancel it if that is appropriate for your app. Alternatively, if it is possible for you to load and display the data piecemeal (i.e. before you have the entire set of data), then you should just display the HUD until you have enough data that you can start displaying something in the UI that the user can interact with.
Basically, what you want to avoid is a situation where it could appear to the user that nothing is happening and the UI is essentially blank with nothing for them to do.
Implement MBProgressHUD delegate
it will be called every time whether if it is fast or slow network connection,In case of slow network connection there will be a time out and this delegate will be fired,remove the hud from the superview in this delegate
-(void)hudWasHidden
{
[HUD removeFromSuperview];
}
I am loading data of NSArray into UITableView . Its going ok. I really confuse to show UIActivityindicator at time of loading uitableview.
So please, give guideline, sample code.
Thanks.
No matter how much data you have (how many elements your NSArray model contains), only the visible cells will be needed for the table view, that is small. So if you already have you model data loaded then you don't need an activity monitor.
If you are talking about acquiring the data prior to refreshing the table view (filling your array based data model), or downloading data from a remote URL then you will need to do this in a background thread so that the main thread is free to update your UI (specifically your activity indicator). Once your data is ready you reload your table view on the main thread.
NSObject has a number of convenience methods to achieve this including
- (void)performSelectorInBackground:(SEL)aSelector withObject:(id)arg
- (void)performSelectorOnMainThread:(SEL)aSelector withObject:(id)arg waitUntilDone:(BOOL)wait
Except if you have a LOT of data in your array, or if some data come from the internet, the loading of your UITableView (well, the cells that are displayed) should take less than a frame, so it is useless to try to display a UIActivityIndicator in this case.
I have a UITableView which loads its data from the web. It takes a while to load this data and therefore I would like an acitivity indicator to animate while the data is loading. I am doing the following in my attempt to make this work:
1) In viewDidLoad I add an observer to listen to when the data loading is done and after that I call loadDataFromWeb
2) loadDataFromWeb creates the activity indicator, adds it as a subview to self.view and then it loads the data. At last it posts a notification (the one that viewDidLoad observes) to indicate that the loading process is done.
3) Finally, when the observer catches the post from loadDataFromWeb, it calls removeLoadingScreen to remove the indicator.
Pretty obvious I am not seeing my indicator view. If I comment out the line that removes the indicator, it stays on the screen when everything is loaded. I am aware that I'm probably messing around with which methods are called when in the process, and this is where I need help.
I should mention that the whole purpose is that instead of the user's looking at a screen on which nothing is happening (while the data loads), I want a activity indicator to show up to indicate that there's something going on here.
Thanks
#Muncken have a look at this MBProgresHUD project, this will help you a lot to do a downloading progress in background (secondary thread not main thread) and shows a activity indicator over you view -
https://github.com/matej/MBProgressHUD
I've made a custom activity indicator (actually just an imageView)
When user clicks something and I expect it will take a bit long to process(alloc a UIViewController and push on to navigation stack),
I alloc the indicator and add it as subview of current view just before the lengthy process starts.
Strange thing is, indicator doesn't show up until the push (left-right) animation starts.
Is it because the lengthy job takes the system, and ui drawing for activity indicator is delayed?
Am I doing something wrong here?
Thank you
Edit
Looks like I can do the "push" in background.. i'm trying it now
IPhone SDK - Leaking Memory with performSelectorInBackground
Is your job synchrone or asynchrone ?
If it's the first case, then it can be the problem.
Check all the method like :
[ self performSelector:<#(SEL)aSelector#> ];
You can thread this to avoid your [potential] problem.
Good luck.
You should process your lengthy tasks in the background. The UI won't update if you block the main thread.
So you have to refactor your app, the alloc and push of the viewController should happen within the blink of an eye, because you can't do this in the background.
But you can do the processing (downloading data I guess) in the background.
There is plenty information available about background processing. The way to go varies heavily on what you want to do exactly.
I have a UITableView subclass and a UITableViewCell subclass that I'm using for cells. I'm bulding all my cells in advance and store them in an array from where I use them in cellForRowAtIndexPath. Aside from this I have a thread that loads some images in each cell, in the background. The problem is that the cells don't get refreshed as fast as the images are loaded. For example, if I don't scroll my table view, the first cells only get refreshed when all cells have been modified and the thread has exited.
Any ideas on how I can effectively refresh my tableview/cell?
Have you tried calling [cell setNeedsDisplay] but on the main thread?
setNeedsDisplay when called on a background thread does pretty much nothing,
try this:
[cell performSelectorOnMainThread:#selector(setNeedsDisplay) withObject:nil waitUntilDone:NO];
Are you using a callback to notify the controller of your tableview that the images have been loaded? If not, that would be an ideal method.
When the image loads, fire off a callback to the table view controller that sets the image on the cell, and then calls reloadData on the tableView.
This way whenever a new image loads, the table will update to display it.
Not sure exactly what you are trying to achieve with the images - but can I guess they are coming from a server and that is why you want to download them in another thread?
I would not try to load up the cells before you display the table - you should use lazy loading as much as possible to make sure you are making the most of the memory on a device.
My suggestion would be to look at using a subclass of NSOperation to manage the loading of images. Firstly NSOperation will handle all the complexity of threading for you and allow you to queue up the operations. You will then be able to prioritise the operations that you want completed for the cells at the top.
As each operation completes you can make a call back to the cell or tableViewController (perhaps create a delegate protocol to make this really easy).
If you have an operation per image/cell combination then you should be able to refresh each cell as the operation completes. Doing this along with prioritising the operations will give you an optimal solution.
If the NSOperations sound complex or you are put off by this - please do try it - it is a lot simpler than I might have made it sound.
Have you tried calling [cell setNeedsDisplay]?