In my application i am uploading some images to the servelet, which takes some time to complete upload. I have implemented an uiactivityviewer using IB and connected it to an outlet named acticityIndicator. But when i call
[activityIndicator startsAnimating];
nothing is happening!!!
What might be the problem.
i've debugged the code,
the statement is executing, but nothing happens!!!
Are you performing your uploading on the main thread, or kicking off a background thread to do it?
If the former then you are blocking the UI thread so it doesn't have a chance to update the activity indicator.
Related
Currently I encounter an issue somehow, the application lost all those artistic UI animation for example, page flipping, alert view popup, action sheet slide up and etc. That means all those UI will show up immediately without any transition animation. It looked very weird.
Firstly, the app will run smoothly until something trigger the issue above, and after that only re-run the app or kill the app will stop the problem.
There is no error message or any clue that I can figure out what could be the reason. Have any one of you guy has encountered similar issue as above? Please share with me how am I able to solve the issue above. Thanks.
Animations may get disabled for the entire app whenever an attempt is made to animate views on a background thread, e.g. by calling one of UIView's animateWithDuration:animations: family of class methods from a background thread. Be sure to update your app's UI only from the main thread.
You can check if code is running on the main thread by testing [NSThread currentThread].isMainThread and you can ensure it runs on the main thread like so:
dispatch_async(dispatch_get_main_queue(), ^(void) {
// Your code
});
Alternatively, ensure that you're not calling [UIView setAnimationsEnabled:NO] anywhere, as that will also disable animations for the entire app.
I am trying to get my UIActivityIndicator start animating when the process of data consumption start downloading. My concern is: how do you get the activity indicator start animating at the same time? I have gone through some solutions here on Stack Overflow, yet I am trying to find some universal solution, since I am utilizing a subclass of UIActivityIndicator. I am not sure if a separate thread can resolve this issue?
I used:
[self performSelector:#selector(methodname) withObject:nil afterDelay:0];
However, this didn't solve my problem.
Just return from the method starting the activity indicator. The UI (including the activity indicator) updates after an app returns to the main run loop. Handle any long activities (such as your download) asynchronously with delegates or callbacks, so that the activity indicator can continue to run. So return from the method that starts your download as well. Finish later in another method.
Another option is to do the download, or other long process, in another thread. Operation queues and blocks can be used for this purpose. Use a performselector on the main thread to update the UI, as an app can't update the UI directly from within a background thread.
i wrote like:
[self performSelectorInBackground:#selector(backgroundImageLoading) withObject:nil];
to load image background but know i need to stop this when i refresh the view but i don't have any idea how to do
See NSOperation and NSOperationQueue.
Its also to do the process concurrently as like background thread. Here in NSOperation you have cancel method available to stop the operation.
The threads should not be forced to kill. look out the reasons here. It may help you to find the solution.
I use NSOperationQueue to create UIImages in the background,
upon image creation, main thread gets notified and set the image to a view.
While it works and all, main thread is not responding as I hoped while the NSOperationQueue is working.
The point of using thread here is to let UI be responsive to user interactions.
Am I missing something here?
check Invoking thread with a single parameter
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.