I'm developing a ios app. I use this code on a view, in order to made an activity indicator and a black background appear in place of the whole view while is loading.
// hiding all the uioutlet in the view
sfondo.hidden=TRUE;
dalText.hidden=TRUE;
alText.hidden=TRUE;
titoloText.hidden=TRUE;
// generating the activity indicator
CGRect screenBound = [[UIScreen mainScreen] bounds];
CGSize screenSize = screenBound.size;
CGFloat screenWidth = screenSize.width;
CGFloat screenHeight = screenSize.height;
imgCaricamento = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleWhiteLarge];
[imgCaricamento setCenter:CGPointMake(screenWidth/2.0, screenHeight/2.0)]; // I do this because I'm in landscape mode
[self.view addSubview:imgCaricamento]; // spinner is not visible until started
[imgCaricamento startAnimating]; // start!
Now the problem is that i launch this code before starting an update and do several things. What happen is that, at the moment this code is launched the view freezes for one-two seconds, only after this delay time, the activity appears. This time it's enough to convey to the user the impression that the app is acting bad... How can i make this code being executed before and immediately?
You are probably doing something that is blocking the main thread, maybe downloading an image, reading something from disk or parsing some data. The main thread is responsible for refreshing the UI and when it is blocked, the UI freezes. You can solve this by doing your processing in the background, on a different thread.
Apart from something maybe blocking the main thread therefore preventing the UI being updated I would prepare the UIActivityIndicatorView within viewWillAppear and execute [imgCaricamento startAnimating]; within viewDidAppear or where ever you start the updating process.
Related
I have my app setup to show this view when it is loading data:
self.loadingView = [UIView new];
self.loadingView.frame = CGRectMake(0, 0, self.tableView.frame.size.width, self.view.frame.size.height);
self.loadingView.backgroundColor = [UIColor groupTableViewBackgroundColor];
[self.view addSubview:self.loadingView];
[self.view bringSubviewToFront:self.loadingView];
self.activityIndicator = [UIActivityIndicatorView new];
self.activityIndicator.activityIndicatorViewStyle = UIActivityIndicatorViewStyleGray;
self.activityIndicator.center = CGPointMake(self.view.frame.size.width / 2.0, self.view.frame.size.height / 2.0);
[self.view addSubview:self.activityIndicator];
[self.view bringSubviewToFront:self.activityIndicator];
[self.activityIndicator startAnimating];
Then, I remove it from its superview. It works on iPhone. It works on iPad sometimes too, except for when I'm using the same code in a UISplitViewController. I've tried various adjustments to centering the views, etc., but can't figure it out. What's going wrong?
I've add trouble with activity indicators in the past as well. Make sure you are not calling the startAnimating or stopAnimating while any animations are taking place. I recommend calling the startAnimating selector in viewDidLayoutSubviews.
The line where you set the center of the indicator looks like the source of the problem. self.view.frame.size is probably equal to screen size at this point and so when you show that view controller over the whole screen it's ok, but inside a split view controller it's not because indicator is off-bounds. You can check that from Xcode's Debug -> View Debugging -> Capture View Hierarchy (while the app is running).
Try setting activity indicator's center using autolayout and it should work.
I am looking at adding AirPlay capabilities to one of my ViewControllers. The View Controller just shows a UIWebView. What I want to do is add a button that will mirror this content to an Apple TV. I know system-wide mirroring can be done, but it doesn't fill up the entire screen, has black bars all around. I have been searching online, but most everything I have found is way back from iOS 5 and out of date. Could someone point me in the direction of a tutorial or drop-in library that would help out? I just need it to mirror the content of just one view to be full-screen on Apple TV.
So far, here is what I have done, but I believe it only creates the second Window, without putting anything on it.
In the AppDelegate, I create a property for it:
#property (nonatomic, retain) UIWindow *secondWindow;
In didFinish method of AppDelegate I run:
NSNotificationCenter *center = [NSNotificationCenter defaultCenter];
[center addObserver:self selector:#selector(handleScreenDidConnectNotification:)
name:UIScreenDidConnectNotification object:nil];
[center addObserver:self selector:#selector(handleScreenDidDisconnectNotification:)
name:UIScreenDidDisconnectNotification object:nil];
Then in AppDelegate I have:
- (void)handleScreenDidConnectNotification:(NSNotification*)aNotification
{
UIScreen *newScreen = [aNotification object];
CGRect screenBounds = newScreen.bounds;
if (!self.secondWindow)
{
self.secondWindow = [[UIWindow alloc] initWithFrame:screenBounds];
self.secondWindow.screen = newScreen;
// Set the initial UI for the window.
}
}
- (void)handleScreenDidDisconnectNotification:(NSNotification*)aNotification
{
if (self.secondWindow)
{
// Hide and then delete the window.
self.secondWindow.hidden = YES;
self.secondWindow = nil;
}
}
In the viewController in which I would like to allow to mirror the WebView on Apple TV, I have:
- (void)checkForExistingScreenAndInitializeIfPresent
{
if ([[UIScreen screens] count] > 1)
{
// Get the screen object that represents the external display.
UIScreen *secondScreen = [[UIScreen screens] objectAtIndex:1];
// Get the screen's bounds so that you can create a window of the correct size.
CGRect screenBounds = secondScreen.bounds;
appDelegate.secondWindow = [[UIWindow alloc] initWithFrame:screenBounds];
appDelegate.secondWindow.screen = secondScreen;
// Set up initial content to display...
// Show the window.
appDelegate.secondWindow.hidden = NO;
NSLog(#"YES");
}
}
I got all this from here. However, that's all that it shows, so I'm not sure how to get the content onto that screen.
Depending on what’s going on in your web view, you’ll either have to make a second one pointed at the same page or move your existing one to the new window. Either way, you treat the second window pretty much the same as you do your app’s main window—add views to it and they should show up on the second display.
I assume you've seen it, but this is the only sample project I could find: https://github.com/quellish/AirplayDemo/
Here are some related questions that might be worth reading:
does anyone know how to get started with airplay?
Airplay Mirroring + External UIScreen = fullscreen UIWebView video playback?
iOS AirPlay: my app is only notified of an external display when mirroring is ON?
Good luck!
There are only two options to do Airplay 'mirroring' at the moment: the system-wide monitoring and completely custom mirroring. Since the system-wide mirroring is not a solution for you, you'll have to go down the way you already identified in your code fragments.
As Noah pointed out, this means providing the content for the second screen, the same way as providing it for the internal display. As I understand you, you want to show the same data/website as before on the internal display, but display it differently in the remote view/webview (e.g. different aspect ratio). One way can be having one webview follow the other in a master/slave setup. You'd have to monitor the changes (like user scolling) in the master and propagate them to the slave. A second way could be rendering the original webview contents to a buffer and drawing this buffer in part in a 'dumb' UIView. This would be a bit faster, as the website would not have to be loaded and rendered twice.
We're using version 1.2 (and trying beta 1.3.1) of the ZBarSDK for reading barcodes in our app. We have been using this code for some time with no problems in iOS 5 and 6, but iOS 7 appears to have some issues initializing the camera. When we call the start method in the ZBarReaderView it takes 30 to 60 seconds or even longer to initialize the camera. The user sees a black camera view that whole time and they are wondering if the app works.
Once the view is initialized we can close it and reopen it any number of times with no issues and it opens rapidly.
Here is the relevant part of our code:
- (void)showAnimated:(BOOL)animated
{
[self.controller overlayWillShow:self];
dispatch_async(dispatch_queue_create(0, 0), ^{[self.zBarReaderView start];});
CGRect frame = self.superview.frame;
frame.origin.y = -hiddenYOrigin;
[UIView animateWithDuration:0.4 animations:^{
self.superview.frame = frame;
} completion:^(BOOL finished){
if (((ScanController *)self.controller).scanMode == ScanModeManualEntry) {
[self.manualEntryTextField becomeFirstResponder];
}
self.showing = YES;
[self.controller overlayDidShow:self];
}];
}
All of that code executes rapidly, but the dispatch_queue_create call to ZBarReaderView start is where we are hung up for a long time.
Any ideas?
Your problem might be related to this (check the comments):
iOS7 : UIImageView Takes Forever to Appear
We don't know which commands [self.zBarReaderView start] actually executes, but the documentation for ZBarReaderView says :
This is a barcode reader encapsulted in a UIView.
If it's laying out subview in UIViews, supposedly it's not safe to call "start" in a background thread, and while in iOS6 this worked it doesn't in iOS7 anymore, since the internals have changed.
Try to init the camera in the main thread, and see if it works:
dispatch_async(dispatch_get_main_queue(), ^{[self.zBarReaderView start];});
I'm trying to increase the scrolling performance of my UIScrollView. I have a lot of UIButtons on it (they could be hundreds): every button has a png image set as background.
If I try to load the entire scroll when it appears, it takes too much time. Searching on the web, I've found a way to optimize it (loading and unloading pages while scrolling), but there's a little pause in scrolling everytime I have to load a new page.
Do you have any advice to make it scroll smoothly?
Below you can find my code.
- (void)scrollViewDidScroll:(UIScrollView *)tmpScrollView {
CGPoint offset = tmpScrollView.contentOffset;
//322 is the height of 2*2 buttons (a page for me)
int currentPage=(int)(offset.y / 322.0f);
if(lastContentOffset>offset.y){
pageToRemove = currentPage+3;
pageToAdd = currentPage-3;
}
else{
pageToRemove = currentPage-3;
pageToAdd = currentPage+3;
}
//remove the buttons outside the range of the visible pages
if(pageToRemove>=0 && pageToRemove<=numberOfPages && currentPage<=numberOfPages){
for (UIView *view in scrollView.subviews)
{
if ([view isKindOfClass:[UIButton class]]){
if(lastContentOffset<offset.y && view.frame.origin.y<pageToRemove*322){
[view removeFromSuperview];
}
else if(lastContentOffset>offset.y && view.frame.origin.y>pageToRemove*322){
[view removeFromSuperview];
}
}
}
}
if(((lastContentOffset<offset.y && lastPageToAdd+1==pageToAdd) || (lastContentOffset>offset.y && lastPageToAdd-1==pageToAdd)) && pageToAdd>=0 && pageToAdd<=numberOfPages){
int tmpPage=0;
if((lastContentOffset<offset.y && lastPageToAdd+1==pageToAdd)){
tmpPage=pageToAdd-1;
}
else{
tmpPage=pageToAdd;
}
//the images are inside the application folder
NSString *docDir = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0];
for(int i=0;i<4;i++){
UIButton* addButton=[[UIButton alloc] init];
addButton.layer.cornerRadius=10.0;
if(i + (tmpPage*4)<[imagesCatalogList count]){
UIImage* image=[UIImage imageWithContentsOfFile:[NSString stringWithFormat: #"%#/%#",docDir,[imagesCatalogList objectAtIndex:i + (tmpPage*4)]]];
if(image.size.width>image.size.height){
image=[image scaleToSize:CGSizeMake(image.size.width/(image.size.height/200), 200.0)];
CGImageRef ref = CGImageCreateWithImageInRect(image.CGImage, CGRectMake((image.size.width-159.5)/2,(image.size.height-159.5)/2, 159.5, 159.5));
image = [UIImage imageWithCGImage:ref];
}
else if(image.size.width<image.size.height){
image=[image scaleToSize:CGSizeMake(200.0, image.size.height/(image.size.width/200))];
CGImageRef ref = CGImageCreateWithImageInRect(image.CGImage, CGRectMake((image.size.width-159.5)/2, (image.size.height-159.5)/2, 159.5, 159.5));
image = [UIImage imageWithCGImage:ref];
}
else{
image=[image scaleToSize:CGSizeMake(159.5, 159.5)];
}
[addButton setBackgroundImage:image forState:UIControlStateNormal];
image=nil;
addButton.frame=CGRectMake(width, height, 159.5, 159.5);
NSLog(#"width %i height %i", width, height);
addButton.tag=i + (tmpPage*4);
[addButton addTarget:self action:#selector(modifyImage:) forControlEvents:UIControlEventTouchUpInside];
[tmpScrollView addSubview:addButton];
addButton=nil;
photos++;
}
}
}
lastPageToAdd=pageToAdd;
lastContentOffset=offset.y;
}
Here's a few recommendations:
1) First, understand that scrollViewDidScroll: will get called continuously, as the user scrolls. Not just once per page. So, I would make sure that you have logic that ensures that the real work involved in your loading is only triggered once per page.
Typically, I will keep a class ivar like int lastPage. Then, as scrollViewDidScroll: is called, I calculate the new current page. Only if it differs from the ivar do I trigger loading. Of course, then you need to save the dynamically calculated index (currentPage in your code) in your ivar.
2) The other thing is that I try not to do all the intensive work in the scrollViewDidScroll: method. I only trigger it there.
So, for example, if you take most of the code you posted and put it in a method called loadAndReleasePages, then you could do this in the scrollViewDidScroll: method, which defers the execution until after scrollViewDidScroll: finishes:
- (void)scrollViewDidScroll:(UIScrollView *)tmpScrollView {
CGPoint offset = tmpScrollView.contentOffset;
//322 is the height of 2*2 buttons (a page for me)
int currentPage = (int)(offset.y / 322.0f);
if (currentPage != lastPage) {
lastPage = currentPage;
// we've changed pages, so load and release new content ...
// defer execution to keep scrolling responsive
[self performSelector: #selector(loadAndReleasePages) withObject: nil afterDelay:0];
}
}
This is code that I've used since early iOS versions, so you can certainly replace the performSelector: call with an asynchronous GCD method call, too. The point is not to do it inside the scroll view delegate callback.
3) Finally, you might want to experiment with slightly different algorithms for calculating when the scroll view has actually scrolled far enough that you want to load and release content. You currently use:
int currentPage=(int)(offset.y / 322.0f);
which will yield integer page numbers based on the way the / operator, and the float to int cast works. That may be fine. However, you might find that you want a slightly different algorithm, to trigger the loading at a slightly different point. For example, you might want to trigger the content load as the page has scrolled exactly 50% from one page to the next. Or you might want to trigger it only when you're almost completely off the first page (maybe 90%).
I believe that one scrolling intensive app I wrote actually did require me to tune the precise moment in the page scroll when I did the heavy resource loading. So, I used a slightly different rounding function to determine when the current page has changed.
You might play around with that, too.
Edit: after looking at your code a little more, I also see that the work you're doing is loading and scaling images. This is actually also a candidate for a background thread. You can load the UIImage from the filesystem, and do your scaling, on the background thread, and use GCD to finally set the button's background image (to the loaded image) and change its frame back on the UI thread.
UIImage is safe to use in background threads since iOS 4.0.
Don't touch a line of code until you've profiled. Xcode includes excellent tools for exactly this purpose.
First, in Xcode, make sure you are building to a real device, not the simulator
In Xcode, choose Profile from the Product menu
Once Instruments opens, choose the Core Animation instrument
In your app, scroll around in the scroll view you're looking to profile
You'll see the real time FPS at the top, and in the bottom, you'll see a breakdown of all function and method calls based on total time ran. Start drilling down the highest times until you hit methods in your own code. Hit Command + E to see the panel on the right, which will show you full stack traces for each function and method call you click on.
Now all you have to do is eliminate or optimize the calls to the most "expensive" functions and methods and verify your higher FPS.
That way you don't waste time optimizing blind, and potentially making changes that have no real effect on the performance.
My answer is really a more general approach to improving scroll view and table view performance. To address some of your particular concerns, I highly recommend watching this WWDC video on advanced scroll view use: https://developer.apple.com/videos/wwdc/2011/includes/advanced-scrollview-techniques.html#advanced-scrollview-techniques
The line that is likely killing your performance is:
addButton.layer.cornerRadius=10.0;
Why? Turns out the performance for cornerRadius is AWFUL! Take it out... guaranteed huge speedup.
Edit: This answer sums up what you should do quite clearly.
https://stackoverflow.com/a/6254531/537213
My most common solution is to rasterize the Views:
_backgroundView.layer.shouldRasterize = YES;
_backgroundView.layer.rasterizationScale = [[UIScreen mainScreen] scale];
But it works not in every situation.. Just try it
The iPad app I'm working on is a book. To jump to a specific page, the user can press a button that overlays a view top of the current view, displaying images of thumbnails of each page in the book.
When the user goes through the book sequentially and displays this thumbnails menu, the scrolling animation is smooth and fine if the user showed the menu . The problem happens if the user calls showBookmarkMenu after having loaded about fifteen pages, the scrollview animation is very very slow, and the scrollview doesn't catch touches anymore.
I noticed that scrollViewDidEndDecelerating gets called when the scrolling animation is normal and smooth (shortly after loading the app), but it doesn't get called after the user has gone through several pages. So one hypothesis is that the CPU is struggling with the animation of the positioning of the scrollview's content. I ran the app using Instruments' Activity Monitor, but there are times when the app uses 97% and more of the CPU and the scrollview scrolls fine...
Any thoughts on this issue? I've posted my code below.
MainClass.m
//Called when user presses the open/close bookmark menu button
-(IBAction)toggleBookmarksMenu{
if([bookMarkMenu isHidden]){
[currentPage.view addSubview:bookMarkMenu];
[bookMarkMenu showBookmarkMenu];
}
else{
[bookMarkMenu hideBookmarksMenu];
}
}
ScrollViewClass.h
#interface BookmarkManager : UIView<UIScrollViewDelegate>{
UIScrollView *thumbnailScrollView;
}
#property (strong, nonatomic) UIScrollView *thumbnailScrollView;
#property (strong) id <BookmarkManagerDelegate> bookmarkManagerDelegate;
-(void)showBookmarkMenu;
-(void)hideBookmarksMenu;
#end
ScrollViewClass.m
-(void)showBookmarkMenu{
[self setHidden:NO];
[UIView animateWithDuration:0.5
animations:^{
self.center = CGPointMake(512, 384);
}
];
}
-(void)hideBookmarksMenu{
[UIView animateWithDuration:1
animations:^{
self.center = CGPointMake(512, -120);
}
completion:^(BOOL finished){
[self setHidden:YES];
[self removeFromSuperview];
}
];
}
-(id)init{
self = [super initWithFrame:CGRectMake(0, 0, 1024, 768)];
if(self){
[self setBackgroundColor:[UIColor clearColor]];
self.center = CGPointMake(512, 0);
thumbnailScrollView = [[UIScrollView alloc] initWithFrame:CGRectMake(0, 0, 1024, 120)];
[thumbnailScrollView setBackgroundColor:[UIColor clearColor]];
thumbnailScrollView.showsHorizontalScrollIndicator = NO;
//Add the UIButtons with images of the thumbnails
for(int i = 0; i < totalPages; i++){
UIButton *pageThumbnail = [UIButton buttonWithType:UIButtonTypeCustom];
pageThumbnail.frame = CGRectMake(0, 0, 125, 95);
[pageThumbnail setBackgroundImage:[UIImage imageWithContentsOfFile:[NSString stringWithFormat:#"%#/p%d_thumb.png", [[NSBundle mainBundle] resourcePath], i]] forState:UIControlStateNormal];
[thumbnailScrollView addSubview:pageThumbnail];
[pageThumbnail addTarget:self action:#selector(thumbnailTapped:) forControlEvents:UIControlEventTouchDown];
}
[self addSubview:thumbnailScrollView];
[thumbnailScrollView setContentSize:CGSizeMake(totalPages * 125 + (20*(totalPages+1)), 120)];
[thumbnailScrollView setDelegate:self];
[self setHidden:YES];
}
return self;
}
I have to go with possible low memory issue.
A possible alternative to using a slew of buttons is using UITableView. The way your code is currently working, it loads up ALL the buttons with images. For a large book this could be painful.
Using UITableView you only use as much memory as you see (about). And, since each image is loaded dynamically, your memory usage is only as much as is displayed. That would be how I would go about it (actually, I'm doing that now, just not with a book).
A shot in the dark, based on your observation that the scrolling becomes slow after loading 15 pages or so: possibly your device is busy handling a low memory condition. In such cases, as you possibly know, a system wide notification is sent to a considerable number of apps/objects for them to recover as much memory as possible.
Could you check if at more or less the same time when the scrolling becomes slow your app is executing didReceiveMemoryWarning?
If you confirm that the issue could be related to memory saturation/reclaiming, then I would suggest implementing a lazy loading scheme for your images:
you only load images when you are required to display them;
you only keep in memory 3-5 images total, to ensure a smooth scrolling.
The basic step requires id providing your delegate
- (void)scrollViewDidScroll:(UIScrollView *)scrollView;
implementation. Here you will preload images:
knowing your position, you know your current image (say, image number N);
unload images N-2, N+2;
load images N-1, N+1.
The images to load/unload I provided are fine if you just want one "buffer" image.
In any case, if you google "iso scroll view lazy loading" you will find plenty of info.
Turns out it wasn't a low memory issue, but an overly busy CPU issue.
It is the CPU that does the calculations required for the scrollview's scrolling animations, and when the scrolling becomes this slow I thought I'd try to figure out why I was using 97% of the CPU in the first place. Turns out that past page 15, I had CPU-intensive recursive functions (calculating UIBezierPaths for another part of the app) caught in an infinite loop. The app was calculating hundreds of UIBezierPaths a second, and there reached a point where the CPU just couldn't keep up with the calculations for the scrollview's animation.
Once I made sure the recursive functions stopped calling themselves when they were not needed, CPU usage remained under 20% throughout the app, and the scrollview performed perfectly well.