I currently have a really weird bug.
A method gets called, that is supposed to hide an UIActivityIndicatorView by stopping it (automatic hiding when stopped is enabled) and an UIImageView called badIndicator.
As a replacement it is supposed to show another UIImageView called goodIndicator.
[goodIndicator setHidden:NO];
[badIndicator setHidden:YES];
[refreshIndicator stopAnimating];
NSLog(#"statussetting good should be completed");
The console prints the following right away, but it takes about three seconds for the changes to happen on the screen.
2013-05-31 20:24:57.835 app name[5948:1603] statussetting good should be completed
I have tried calling the setNeedsDisplay method on the objects and on the parent view and also replace hidden with alpha.
Still get the same problem.
It sounds like you are calling this from a background thread. All interaction with UIKit needs to happen from the main thread. Try using:
dispatch_async(dispatch_get_main_queue(), ^{
[goodIndicator setHidden:NO];
[badIndicator setHidden:YES];
[refreshIndicator stopAnimating];
NSLog(#"statussetting good should be completed");
});
you need to call this method in main thread.Try using:
-(void)hideControls {
[goodIndicator setHidden:NO];
[badIndicator setHidden:YES];
[refreshIndicator stopAnimating];
NSLog(#"statussetting good should be completed");
}
Related
When a UIButton is triggered, a UIActivityIndicator is started, and then stopped when implementLogin finishes:
-(IBAction)loginButton {
NSLog(#"loginButton triggered");
// Checks the Fields are not empty
if ([sessionIdField.text length] != 0 && [usernameField.text length] != 0 ) {
NSLog(#"Beginning Spinner");
// Displays spinner
[activitySpinner startAnimating];
[self implementLogin];
// Displays spinner
[activitySpinner stopAnimating];
}
}
However at runtime, the spinner doesn't appear! I have set the spinner to 'hide when stopped'.
When I set the activity indicator to animate before the view loads, it appears as it should, so I'm guessing it has a problem with the UIButton... (Also, I'm using 'Touch Up Inside' for the button.)
It's a simple problem... Can anyone help?
Thanks
Whatever implementLogin is doing (making a network request, perhaps?), it's doing it on the main thread, which is likely blocking UI updates like spinner animation.
You could recode something like this:
[activitySpinner startAnimating];
dispatch_async(dispatch_get_global_queue(DISPATCH_PRIORITY_DEFAULT, 0), ^{
[self implementLogin];
dispatch_async(dispatch_get_main_queue(), ^{
// Stops spinner
[activitySpinner stopAnimating];
}
}
[Code is untested, but you get the idea.]
What is happening here is that you are dispatching the login task to the background, and the last thing that block will do is stop the spinner on the main thread (as a separate task).
Without more code, one can only guess the reason why it doesn't work.
I assume 'Beginning Spinner' output correctly(?)
If so, you probably didn't properly initialize the UIActivityIndicatorView.
Does it look like this?
activitySpinner = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleGray];
activitySpinner.hidesWhenStopped = YES;
[view addSubview:activitySpinner];
I'd like to display an activity indicator BEFORE the work undertaken by willAnimateRotationToInterfaceOrientation:duration: begins. Most of the time in my app, this work is quickly completed and there would be no need for an activity indicator, but occasionally (first rotation, i.e. before I have cached data, when working with a large file) there can be a noticeable delay. Rather than re-architect my app to cope with this uncommon case, I'd rather just show the UIActivityIndicatorView while the app generates a cache and updates the display.
The problem is (or seems to be) that the display is not updated between the willRotateToInterfaceOrientation:duration and the willAnimateRotationToInterfaceOrientation:duration: method. So asking iOS to show UIActivityIndicator view in willRotate method doesn't actually affect the display until after the willAnimateRotation method.
The following code illustrates the issue. When run, the activity indicator appears only very briefly and AFTER the simulateHardWorkNeededToGetDisplayInShapeBeforeRotation method has completed.
Am I missing something obvious? And if not, any smart ideas as to how I could work around this issue?
Update: While suggestions about farming the heavy lifting off to another thread etc. are generally helpful, in my particular case I kind of do want to block the main thread to do my lifting. In the app, I have a tableView all of whose heights need to be recalculated. When - which is not a very common use case or I wouldn't even be considering this approach - there are very many rows, all the new heights are calculated (and then cached) during a [tableView reloadData]. If I farm the lifting off and let the rotate proceed, then after the rotate and before the lifting, my tableView hasn't been re-loaded. In the portrait to landscape case, for example, it doesn't occupy the full width. Of course, there are other workarounds, e.g. building a tableView with just a few rows prior to the rotate and then reloading the real one over that etc.
Example code to illustrate the issue:
#implementation ActivityIndicatorViewController
#synthesize activityIndicatorView = _pgActivityIndicatorView;
#synthesize label = _pgLabel;
- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{
return (interfaceOrientation != UIInterfaceOrientationPortraitUpsideDown);
}
- (void) willRotateToInterfaceOrientation:(UIInterfaceOrientation)toInterfaceOrientation duration:(NSTimeInterval)duration;
{
NSLog(#"willRotate");
[self showActivityIndicatorView];
}
- (void) willAnimateRotationToInterfaceOrientation:(UIInterfaceOrientation)toInterfaceOrientation duration:(NSTimeInterval)duration;
{
NSLog(#"willAnimateRotation");
[self simulateHardWorkNeededToGetDisplayInShapeBeforeRotation];
}
- (void) didRotateFromInterfaceOrientation:(UIInterfaceOrientation)fromInterfaceOrientation;
{
NSLog(#"didRotate");
[self hideActivityIndicatorView];
}
- (void) simulateHardWorkNeededToGetDisplayInShapeBeforeRotation;
{
NSLog(#"Starting simulated work");
NSDate* date = [NSDate date];
while (fabs([date timeIntervalSinceNow]) < 2.0)
{
//
}
NSLog(#"Finished simulated work");
}
- (void) showActivityIndicatorView;
{
NSLog(#"showActivity");
if (![self activityIndicatorView])
{
UIActivityIndicatorView* activityIndicatorView = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleGray];
[self setActivityIndicatorView:activityIndicatorView];
[[self activityIndicatorView] setCenter:[[self view] center]];
[[self activityIndicatorView] startAnimating];
[[self view] addSubview: [self activityIndicatorView]];
}
// in shipping code, an animation with delay would be used to ensure no indicator would show in the good cases
[[self activityIndicatorView] setHidden:NO];
}
- (void) hideActivityIndicatorView;
{
NSLog(#"hideActivity");
[[self activityIndicatorView] setHidden:YES];
}
- (void) dealloc;
{
[_pgActivityIndicatorView release];
[super dealloc];
}
- (void) viewDidLoad;
{
UILabel* label = [[UILabel alloc] initWithFrame:CGRectMake(50.0, 50.0, 0.0, 0.0)];
[label setText:#"Activity Indicator and Rotate"];
[label setTextAlignment: UITextAlignmentCenter];
[label sizeToFit];
[[self view] addSubview:label];
[self setLabel:label];
[label release];
}
#end
The app doesn't update the screen to show the UIActivityIndicatorView until the main run loop regains control. When a rotation event happens, the willRotate... and willAnimateRotation... methods are called in one pass through the main run loop. So you block on the hard work method before displaying the activity indicator.
To make this work, you need to push the hard work over to another thread. I would put the call to the hard work method in the willRotate... method. That method would call back to this view controller when the work is completed so the view can be updated. I would put show the activity indicator in the willAnimateRotation... method. I wouldn't bother with a didRotateFrom... method. I recommend reading the Threaded Programming Guide.
Edit in response to a comment: You can effectively block user interaction by having the willAnimateRotation... method put a non functioning interface on screen such as a view displaying a dark overlay over and the UIActivityIndicatorView. Then when the heavy lifting is done, this overlay is removed, and the interface becomes active again. Then the drawing code will have the opportunity to properly add and animate the activity indicator.
More digging (first in Matt Neuberg's Programming iPhone 4) and then this helpful question on forcing Core Animation to run its thread from stackoverflow and I have a solution that seems to be working well. Both Neuberg and Apple issue strong caution about this approach because of the potential for unwelcome side effects. In testing so far, it seems to be OK for my particular case.
Changing the code above as follows implements the change. The key addition is [CATransaction flush], forcing the UIActivityIndicatorView to start displaying even though the run loop won't be ended until after the willAnimateRotationToInterfaceOrientation:duration method completes.
- (void) willRotateToInterfaceOrientation:(UIInterfaceOrientation)toInterfaceOrientation duration:(NSTimeInterval)duration;
{
NSLog(#"willRotate");
[self showActivityIndicatorView];
[CATransaction flush]; // this starts the animation right away, w/o waiting for end of the run loop
}
- (void) willAnimateRotationToInterfaceOrientation:(UIInterfaceOrientation)toInterfaceOrientation duration:(NSTimeInterval)duration;
{
NSLog(#"willAnimateRotation");
[self simulateHardWorkNeededToGetDisplayInShapeBeforeRotation];
[self hideActivityIndicatorView];
}
- (void) didRotateFromInterfaceOrientation:(UIInterfaceOrientation)fromInterfaceOrientation;
{
NSLog(#"didRotate");
}
Try performing you work on a second thread after showing the activity view.
[self showActivityIndicatorView];
[self performSelector:#selector(simulateHardWorkNeededToGetDisplayInShapeBeforeRotation) withObject:nil afterDelay:0.01];
Either execute the heavy lifting in a background thread and post the results in the foreground thread to update the UI (UIKit is only thread safe since iOS 4.0):
[self performSelectorInBackground:#selector(simulateHardWorkNeededToGetDisplayInShapeBeforeRotation) withObject:nil]
Or you can schedule the heavy lifting method to be executed after the rotation took place:
[self performSelector:#selector(simulateHardWorkNeededToGetDisplayInShapeBeforeRotation) withObject:nil afterDelay:0.4]
But these are only hacks and the real solution is to have proper background processing if your UI needs heavy processing to get updated, may it be in portrait or landscape. NSOperation and NSOperationQueue is a good place to start.
When my main viewController is first clicked, it starts showing a demo (on repeat) as follows:
showingDemo = YES;
[self startDemo];
- (void)startDemo {
if (showingDemo) {
[self performSelector:#selector(stepone) withObject:nil afterDelay:1.5f];
[self performSelector:#selector(steptwo) withObject:nil afterDelay:2.0f];
[self performSelector:#selector(stepthree) withObject:nil afterDelay:3.8f];
[self performSelector:#selector(stepfour) withObject:nil afterDelay:4.3f];
[self performSelector:#selector(startDemo) withObject:nil afterDelay:5.6f];
}
}
When it is clicked a second time, I bring a new ViewController to the screen
showingDemo = NO;
[self.view addSubview:newView];
I thought this would stop the endless loop.
When the user returns back to my main viewController:
[newView.view removeFromSuperview];
And clicks on the screen again:
showingDemo = YES;
[self startDemo];
In testing my app, if I click back quickly (before the loop has had time to end, the program seems to be running through the loop twice - the one that was previously going and the new one - and therefore it looks all weird, with the 'stepthree' function happening before 'stepone' and so forth.
Anybody know a better way to STOP the loop I've programmed for good so that when I go to start it again later, it doesn't run multiple loops thinking that the previous one hasn't been finished?
Thanks so much!
When you set showingDemo to NO, call NSObject's cancelPreviousPerformRequestsWithTarget: to cancel any pending perform requests:
showingDemo = NO;
[NSObject cancelPreviousPerformRequestsWithTarget:self];
[self.view addSubview:newView];
In my iPhone app, I want to add activity indicator on top of a searchbar.
When it is searching it should display activity indicator.
I have added the activity indicator in XIB and created its outlet.
I am making it hide when the searching finishes, but Activity Indicator does not display.
Problem
I figured out that search function(say A)(where I animate the activity indicator) in turn calls another function(say B) so the main thread is being used in executing the function B. But for activity indicator to animate we require the main thread.
So I tried calling function B using performSelectorInBackGround:withObject method. Now when I click search the activity indicator is shown but the functionality of function B does not execute.
What can be a work-around for this?
There is not quite enough in your question to go on, but to start debugging, I would do the following.
Verify that the activity variably is really wired to the UIActivityIndicator you are creating in IB. (I would set a breakpoint on the setHidden: lines and make sure the variable is not null. Or throw an NSAssert(activity,#"Whoops! actity is null"); in there.)
If the variable is indeed set, I would start checking that it is in the right place in the view hierarchy. (I'd try doing a [self.view addSubview:activity] and see that it appears. You might have to replace it somewhere else.)
You might also want to try having it on by default in IB, until you have everything figured out.
Good Luck. Hope this helps.
Save yourself the hassle of creating a custom activity indicator and use the standard one that's available for you already - in the top bar. Also, IMO users tend to expect that one to spin when something is happening.
UIApplication* app = [UIApplication sharedApplication];
app.networkActivityIndicatorVisible = YES;
Obviously, set it to NO when your activity is over.
First of all, make sure you have #synthesize activity at the top of your .m file. Then in the viewDidLoad method, type activity.hidesWhenStopped = TRUE;. Next, in the method that is called when the search starts, type [activity startAnimating]; and [activity stopAnimating]; in the method when the searching stops.
try this:
set hidesWhenStopped = NO, so that is displayed all the time and then hide and show it manually. But the View should be set in IB to hidden first.
- (void)startActivityView {
NSAutoreleasePool *pool = [[NSAutoreleasePool alloc]init];
activity_view.hidden = NO;
[pool drain];
}
- (void)stopActivityView {
NSAutoreleasePool *pool = [[NSAutoreleasePool alloc]init];
activity_view.hidden = YES;
[pool drain];
}
- (void)doSomething {
[self performSelectorInBackground:#selector(startActivityView) withObject:nil];
// do some time consuming work
[self performSelectorInBackground:#selector(stopActivityView) withObject:nil];
}
Perhaps you have a view in front of your activity indicator? What if you always bring it to the front....
loadView = [[UIActivityIndicatorView alloc]
initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleWhiteLarge];
loadView.frame = CGRectMake(0.0, 0.0, 40.0, 40.0);
loadView.center = window.center;
loadView.opaque = NO;
[window addSubview: loadView];
[window bringSubviewToFront:loadView];
[loadView startAnimating];
I suggest that you use DSActivityView for showing your activity indicator. The source code can be found at Dejal blog.
Showing, and hiding, the activity view is a simple line of code.
[DSActivityView activityViewForView:self.view];
start animating the activity indicator and with a delay of 0.1 or 0.2 just call the other method u want.... i tried and it is working for me....
I have got the solution and it is as follows.
I just wrote the below line in Search button click event.
[NSThread detachNewThreadSelector:#selector(threadStartAnimating:) toTarget:self withObject:nil];
And defined the function threadStartAnimating: as follows:
-(void)threadStartAnimating:(id)data
{
[activityIndicator setHidden:NO];
[activityIndicator startAnimating];
}
I'm trying to do something like this:
- (void)sectionChanged:(id)sender {
[self.view addSubview:loadingView];
// Something slow
[loadingView removeFromSuperview];
}
where loadingView is a semi-transparent view with a UIActivityIndicatorView. However, it seems like added subview changes don't take effect until the end of this method, so the view is removed before it becomes visible. If I remove the removeFromSuperview statement, the view shows up properly after the slow processing is done and is never removed. Is there any way to get around this?
Run your slow process in a background thread:
- (void)startBackgroundTask {
[self.view addSubview:loadingView];
[NSThread detachNewThreadSelector:#selector(backgroundTask) toTarget:self withObject:nil];
}
- (void)backgroundTask {
NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];
// do the background task
[self performSelectorOnMainThread:#selector(backgroundTaskDone) withObject:nil waitUntilDone:NO];
[pool release];
}
- (void)backgroundTaskDone {
[loadingView removeFromSuperview];
}
Two potential problems spring to mind, both centred around how you've implemented the 'do something slow here' code.
First off, if it's locking up the main thread then it's possible the application's UI isn't being redrawn in time to display the view, i.e. Add Subview, tight loop/intensive processing tying up the main thread, then immediately after the view is removed.
Secondly if the 'something slow' is being done asynchronously, then the view is being removed while the slow processing is running.
One things for sure, your requirements are as follows:
Add a subview to display some kind of 'loading' view
Invoke a slow running piece of functionality
Once the slow running functionality completes, remove the 'loading' subview.
- (void)beginProcessing {
[self.view addSubview:loadingView];
[NSThread detachNewThreadSelector:#selector(process) toTarget:self withObject:nil];
}
- (void)process {
// Do all your processing here.
[self performSelectorOnMainThread:#selector(processingComplete) withObject:nil waitUntilDone:NO];
}
- (void)processingComplete {
[loadingView removeFromSuperview];
}
You could also achieve something similar with NSOperations.