I'm using two threads in an iPhone app for the first time and I've run into a problem. In this prototype, I have a view controller that loads a local web page. I want an activity indicator to show until the page has finished loading. With the code below, the activity indicator starts, the page loads properly, but the activity indicator does not stop or hide. It doesn't look like the "loading" function ever gets called.
What am I doing wrong?
- (void)viewDidLoad {
[self.view addSubview:activityIndicator];
[activityIndicator startAnimating];
[NSThread detachNewThreadSelector:#selector(getData) toTarget:self withObject:nil];
[super viewDidLoad];
}
- (void)getData {
NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
[detailWebView loadRequest:[NSURLRequest requestWithURL:[NSURL fileURLWithPath:[[NSBundle mainBundle] pathForResource:#"page1" ofType:#"html"]isDirectory:NO]]];
[NSTimer scheduledTimerWithTimeInterval: (1.0/2.0) target:self selector:#selector(loading) userInfo:nil repeats:YES];
[pool release];
}
- (void)loading {
if(!detailWebView.loading){
[activityIndicator stopAnimating];
[activityIndicator removeFromSuperview];
}
There's an easier way to do this without creating your own thread.
- (void)viewDidLoad {
[self.view addSubview:activityIndicator];
[activityIndicator startAnimating];
[detailWebView setDelegate:self];
[detailWebView loadRequest:[NSURLRequest requestWithURL:[NSURL fileURLWithPath:[[NSBundle mainBundle] pathForResource:#"page1" ofType:#"html"]isDirectory:NO]]];
[super viewDidLoad];
}
- (void)webViewDidFinishLoad:(UIWebView *)webView {
[activityIndicator stopAnimating];
}
You 'd betetr stop the activity indicator in the webview delegate method :
-(void)webViewDidFinishLoad:(UIWebView*)webView
Have you added debug output to loading to whether it gets called ? The code sure looks like that, it should get called after 0.5 seconds and I'd guess that detailWebView is still loading then.
Also, GUI stuff should be run on the main thread, so you may need to do:
- (void)loading {
if(!detailWebView.loading){
[activityIndicator performSelectorOnMainThread:#selector(stopAnimating) withObject:nil waitUntilDone:YES];
[activityIndicator performSelectorOnMainThread:#selector(removeFromSuperView) withObject:nil waitUntilDone:YES];
}
}
You're using a webview, which already provides a mechanism to know when a load has finished, and already loads data asynchronously - the use of a custom thread really isn't needed.
Register your object as the UIWebView's delegate. Call loadRequest on the UIWebView and start animating the progress indicator. Stop animating the progress indicator in:
-(void)webViewDidFinishLoad:(UIWebView*)webView
This method is defined by the UIWebViewDelegate protocol - make sure your object implements this protocol. You implement this method:
- (void)webViewDidFinishLoad:(UIWebView *)webView {
[activityIndicator stopAnimating];
}
http://developer.apple.com/iphone/library/documentation/uikit/reference/UIWebViewDelegate_Protocol/Reference/Reference.html
Related
First time working with a HUD and I'm confused.
I setup the HUD like this in my viewDidLoad:
[MBProgressHUD showHUDAddedTo:self.view animated:YES];
dispatch_async(dispatch_get_global_queue( DISPATCH_QUEUE_PRIORITY_LOW, 0), ^{
[[[WSXmppUserManager shared] xmppStreamManager] connect];
dispatch_async(dispatch_get_main_queue(), ^{
[MBProgressHUD hideHUDForView:self.view animated:YES];
});
});
The HUD doesn't show. I think the reason is as follows. The xmpp connect method fires off a connection request to the xmpp server and then it's done. So there is no activity to wait for as is.
However, the connection isn't established until the server responds and the following delegate method is fired:
- (void)xmppStreamDidAuthenticate:(XMPPStream *)sender
I want to wait for this and only then dismiss the HUD, but I'm at a loss as to how to do that. I'm missing something very simple.
You need to move this code
dispatch_async(dispatch_get_main_queue(), ^{
[MBProgressHUD hideHUDForView:self.view animated:YES];
});
After your long running method has finished... that is, if this code is indeed returning immediately
[[WSXmppUserManager shared] xmppStreamManager] connect];
The hud is likely never going to display... as it gets told to display and then told to hide on the same run loop or perhaps one run loop right afterwards...
Why not put it at the end of this method if this indicates that a response has been received and the operation is completed?
- (void)xmppStreamDidAuthenticate:(XMPPStream *)sender
HUD =[[MBProgressHUD alloc] initWithWindow:self.view];
[HUD setDelegate:self];
[self.view addSubview:HUD];
[HUD showWhileExecuting:#selector(connectToServer)
onTarget:self
withObject:nil
animated:YES];
In the connectToServer
-(void)connectToServer
{
[[[WSXmppUserManager shared] xmppStreamManager] connect];
}
As soon as the connectToServer method comepletes it task in the background , a delegate of MBProgressHUD called hudWasHidden: is automatically called
-(void)hudWasHidden:(MBProgressHUD *)hud
{
//Further work after the background task completed
}
I have this problem where I am adding an UIActivityIndicatorView to a UIScrollView; Everything is working fine, except it does not start spinning unless the UIScrollView is scrolled.
Can anyone help me with this issue?
Thank you.
here is some code:
UIActivityIndicatorView *loaderActivity = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleGray];
loaderActivity.center = CGPointMake(87/2,y+56/2);
loaderActivity.tag=tag;
[mainScrollView addSubview:loaderActivity];
[loaderActivity startAnimating];
[loaderActivity release];
You need to call startAnimating on the activity indicator to have it animate. Alternatively in interface builder you can tick the "animating" tickbox.
The fact that it's not animating until you scroll in the scroll view is a symptom that your call to startAnimating is happening in a background thread. UIKit calls should be made in the main thread.
You can verify that it's happening in a background thread by adding code like this:
if ([NSThread isMainThread]) {
NSLog(#"Running on main thread.");
} else {
NSLog(#"Running on background thread.");
}
You'll want to make sure all of the code you showed in your question is running on the main thread. To do this, you can change your code to look something like this:
// this code would be wherever your existing code was
[self performSelectorOnMainThread:#selector(addActivityIndicatorToView:) withObject:mainScrollView waitUntilDone:YES];
// this would be a new method in the same class that your existing code is in
- (void) addActivityIndicatorToView:(UIView*) view {
UIActivityIndicatorView *loaderActivity = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleGray];
loaderActivity.center = CGPointMake(87/2,y+56/2);
loaderActivity.tag=tag;
[view addSubview:loaderActivity];
[loaderActivity startAnimating];
[loaderActivity release];
}
activityIndicator = [[UIActivityIndicatorView alloc]
initWithFrame:CGRectMake(87/2,y+56/2);
[activityIndicator setActivityIndicatorViewStyle:UIActivityIndicatorViewStyleWhite];
activityIndicator.tag=tag;
[mainScrollView addSubview:loaderActivity];
[activityIndicator startAnimating];
[activityIndicator release];
Had an issue where I made the startAnimating call in the viewDidLoad and didn't work. I moved the call in the viewWillAppear and it worked!
Try running the animator in a different thread.
NSThread *thread = [[NSThread alloc]initWithTarget:self selector:#selector(showProgress) object:nil];
[thread start];
//do whatever your want here
//call this when you want it stop animating
[activityIndicator stopAnimating];
[thread release];
- (void)showProgress{
[activityIndicator startAnimating];
}
I want to display the view first and then load the data in a background thread. When I navigate from root controller to the view controller, I want to display the view first. As of now, it stays on the root controller until the view controller is loaded. Here's my code for the root controller.
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
ProductDetailViewController *tempProductDetail = [[ProductDetailViewController alloc] init];
[self.navigationController pushViewController:tempProductDetail animated:YES];
[tempProductDetail release];
}
ProductDetailViewController, here I want to display the view first and then load the data...
- (void)viewWillAppear:(BOOL)animated{
[super viewWillAppear:YES];
[self performSelectorOnMainThread:#selector(workerThread) withObject:nil waitUntilDone:NO];
}
-(void) workerThread{
NSAutoreleasePool *arPool = [[NSAutoreleasePool alloc] init];
[arPool release];
}
Don't know what I'm doing wrong. Please, help.
Use [self performSelectorInBackground:#selector(workerThread) withObject:nil]; instead of
[self performSelectorOnMainThread:#selector(workerThread) withObject:nil waitUntilDone:NO];
found the answer for this issue,
- (void)viewWillAppear:(BOOL)animated{
[super viewWillAppear:YES];
[self performSelectorInBackground:#selector(workerThread) withObject:nil];
}
- (void) workerThread
{
// Set up a pool for the background task.
NSAutoreleasePool* pool = [[NSAutoreleasePool alloc] init];
// only do data fetching here, in my case from a webservice.
//...
// Always update the components back on the main UI thread.
[self performSelectorOnMainThread:#selector(displayView) withObject:nil waitUntilDone:YES];
[pool release];
}
// Called once the background thread task has finished.
- (void) displayView
{
//here in this method load all the UI components
}
Consider using the following pattern instead for threading, in my opinion it's much cleaner:
- (void)viewWillAppear:(BOOL)animated
{
NSInvocationOperation *operation = [[NSInvocationOperation alloc]
initWithTarget:self
selector:#selector(someFunction)
object:nil];
[[NSOperationQueue currentQueue] addObject:operation]; // this will actually start the thread
[operation release];
}
- (void)someFunction
{
// don't need to initialize and release an autorelease pool here,
// you can just write a function as usual ...
[self updateUI];
}
- (void)updateUI
{
if (![NSThread isMainThread]) // if we need a UI update, force it on main thread
{
[self performSelectorOnMainThread:#selector(updateUI) withObject:nil waitUntilDone:YES];
return;
}
// do UI updates here
}
By writing code in this way, you can more dynamically decide which function you want to thread, since there is no autorelease pool requirement. If you need to do UI updates, the updateUI function will make sure for itself that it's running on the main thread, so the caller doesn't need to take this into account.
I want to load a PDF file in a modal view controller.
Since the moment that I don't know the size of the file, I want to load it on a separate thread, so:
- (void)viewDidLoad {
[super viewDidLoad];
[[UISharedApplication sharedApplication] setNetworkActivityIndicatorVisibile:YES];
[NSThread detachNewThreadSelector:#selector(loadPDF) toTarget:self withObject:nil];
}
- (void)loadPDF {
NSAutoreleasePool *threadPool = [[NSAutoreleasePool alloc] init];
[self.webView loadRequest:[NSURLRequest requestWithURL:url]];
[threadPool release];
[self performSelectorOnMainThread:#selector(showPDF) withObject:nil waitUntilDone:NO];
}
- (void)showPDF {
[self.webView setHidden:NO];
[self.spinner stopAnimating];
[[UIApplication sharedApplication] setNetworkActivityIndicatorVisible:NO];
}
The method works pretty good in other files (at least I guess) where I parse some XML data, but here doesn't. Commenting:
[self performSelectorOnMainThread:#selector(showPDF) withObject:nil waitUntilDone:NO];
lets me to see the spinner and the activity indicator on the top. So I think that:
[self.webView loadRequest:[NSURLRequest requestWithURL:url]];
doesn't wait until finish and gives the control back to the caller. How can I fix it?
You can't/shouldn't (have got it to work once) update the UI on a separate thread, you should to it all on the main. As I believe webView is a UIWebView this is probably the reason.
Although you are changing the webview from hidden to visible on the main thread, all the updating and creating of the actual UIWebView is not.
Best thing to do is create the data from the URL then performSelectorOnMainThread and pass the data to a method on the main thread that updates the UIWebview with the data.
Implement the method webViewDidFinishLoad: of UIWebViewDelegate and call your showPDF there.
When I call startAnimating on a UIActivityIndicatorView, it doesn't start. Why is this?
[This is a blog-style self-answered question. The solution below works for me, but, maybe there are others that are better?]
If you write code like this:
- (void) doStuff
{
[activityIndicator startAnimating];
...lots of computation...
[activityIndicator stopAnimating];
}
You aren't giving the UI time to actually start and stop the activity indicator, because all of your computation is on the main thread. One solution is to call startAnimating in a separate thread:
- (void) threadStartAnimating:(id)data {
[activityIndicator startAnimating];
}
- (void)doStuff
{
[NSThread detachNewThreadSelector:#selector(threadStartAnimating:) toTarget:self withObject:nil];
...lots of computation...
[activityIndicator stopAnimating];
}
Or, you could put your computation on a separate thread, and wait for it to finish before calling stopAnimation.
I usually do:
[activityIndicator startAnimating];
[self performSelector:#selector(lotsOfComputation) withObject:nil afterDelay:0.01];
...
- (void)lotsOfComputation {
...
[activityIndicator stopAnimating];
}
This question is quite useful. But one thing that is missing in the answer post is , every thing that takes long time need to be perform in separate thread not the UIActivityIndicatorView. This way it won't stop responding to UI interface.
- (void) doLotsOFWork:(id)data {
// do the work here.
}
-(void)doStuff{
[activityIndicator startAnimating];
[NSThread detachNewThreadSelector:#selector(doLotsOFWork:) toTarget:self withObject:nil];
[activityIndicator stopAnimating];
}
All UI elements require to be on main thread
[self performSelectorOnMainThread:#selector(startIndicator) withObject:nil waitUntilDone:NO];
then:
-(void)startIndicator{
[activityIndicator startAnimating];
}
If needed, swift 3 version:
func doSomething() {
activityIndicator.startAnimating()
DispatchQueue.global(qos: .background).async {
//do some processing intensive stuff
DispatchQueue.main.async {
self.activityIndicator.stopAnimating()
}
}
}
Ok, sorry seems like I went through my code being blind.
I've ended the Indicator like this:
[activityIndicator removeFromSuperview];
activityIndicator = nil;
So after one run, the activityIndicator has been removed completely.