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  • UIScrollView - with paging enabled, can I "change" the page width?

    - by Mike McMaster
    What's the simplest way to have a scroll view (with pagingEnabled set to YES) have a page width set to something other than the scroll view's bounds? Let me give an example. Suppose I have a scroll view with 10 items, each 150 pixels wide, and my scroll view is 300 pixels wide. If I start with views 1 and 2 visible and scroll horizontally to the right, I want the next "page" to show items 2 and 3. If I scroll one more page to the right, I would see items 3 and 4. Has anyone done this? If not, what strategy would you use?

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  • Using Core Data Concurrently and Reliably

    - by John Topley
    I'm building my first iOS app, which in theory should be pretty straightforward but I'm having difficulty making it sufficiently bulletproof for me to feel confident submitting it to the App Store. Briefly, the main screen has a table view, upon selecting a row it segues to another table view that displays information relevant for the selected row in a master-detail fashion. The underlying data is retrieved as JSON data from a web service once a day and then cached in a Core Data store. The data previous to that day is deleted to stop the SQLite database file from growing indefinitely. All data persistence operations are performed using Core Data, with an NSFetchedResultsController underpinning the detail table view. The problem I am seeing is that if you switch quickly between the master and detail screens several times whilst fresh data is being retrieved, parsed and saved, the app freezes or crashes completely. There seems to be some sort of race condition, maybe due to Core Data importing data in the background whilst the main thread is trying to perform a fetch, but I'm speculating. I've had trouble capturing any meaningful crash information, usually it's a SIGSEGV deep in the Core Data stack. The table below shows the actual order of events that happen when the detail table view controller is loaded: Main Thread Background Thread viewDidLoad Get JSON data (using AFNetworking) Create child NSManagedObjectContext (MOC) Parse JSON data Insert managed objects in child MOC Save child MOC Post import completion notification Receive import completion notification Save parent MOC Perform fetch and reload table view Delete old managed objects in child MOC Save child MOC Post deletion completion notification Receive deletion completion notification Save parent MOC Once the AFNetworking completion block is triggered when the JSON data has arrived, a nested NSManagedObjectContext is created and passed to an "importer" object that parses the JSON data and saves the objects to the Core Data store. The importer executes using the new performBlock method introduced in iOS 5: NSManagedObjectContext *child = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSPrivateQueueConcurrencyType]; [child setParentContext:self.managedObjectContext]; [child performBlock:^{ // Create importer instance, passing it the child MOC... }]; The importer object observes its own MOC's NSManagedObjectContextDidSaveNotification and then posts its own notification which is observed by the detail table view controller. When this notification is posted the table view controller performs a save on its own (parent) MOC. I use the same basic pattern with a "deleter" object for deleting the old data after the new data for the day has been imported. This occurs asynchronously after the new data has been fetched by the fetched results controller and the detail table view has been reloaded. One thing I am not doing is observing any merge notifications or locking any of the managed object contexts or the persistent store coordinator. Is this something I should be doing? I'm a bit unsure how to architect this all correctly so would appreciate any advice.

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  • Memory Allocation increases in didSelectRowAtIndexPath

    - by mongeta
    Hello, I'm testing my App and in a very simple view, each time a tap on a UITableView row, my allocation overall bytes get higher and higher and never go downs. I don't have any special code there, so I created a new project from scratch with a very simple view, force one section and just three rows. In the didSelectRowAtIndexPath code do nothing, and fire it with instruments and memory allocation and, the memory goes up with every cell selection ... Is this normal behaviour ? thanks, regards, m.

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  • UITextfield and webservice

    - by milanjansari
    Hello everyone, I have one query regarding the (UITextfield and Webservice) for example When i start writing text in UITextfield. Make sure, the app does not query the server(Webservice) for each letter typed. It should wait till I make a pause and then send the request. Is this possible to when using of UITextField? Thanks in advance

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  • Displaying modal view in Objective-C

    - by kpower
    I'm trying to display Modal View in my app. I have subclass of UIViewController that has only the "Done" button (UIButton created with IB and linked with XCode). .h @interface myModalVC : UIViewController { UIButton *bDone; } @property (nonatomic, retain) IBOutlet UIButton *bDone; - (IBAction)bDoneTouchDown:(id)sender; @end .m #import "myModalVC.h" @implementation myModalVC @synthesize bDone; - (void)dealloc { [bDone release]; [super dealloc]; } - (void)viewDidLoad { [super viewDidLoad]; } - (void)viewDidUnload { } - (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation { return (UIInterfaceOrientationLandscapeLeft == interfaceOrientation || UIInterfaceOrientationLandscapeRight == interfaceOrientation); } - (void)didReceiveMemoryWarning { [super didReceiveMemoryWarning]; } - (IBAction)bDoneTouchDown:(id)sender { [self.parentViewController dismissModalViewControllerAnimated:YES]; } @end I'm trying to display modal view with this code (from my main view): myModalVC *temp = [[[myModalVC alloc] initWithNibName:@"myModalVC" bundle:[NSBundle mainBundle]] autorelease]; [self presentModalViewController:temp animated:YES]; If this code is placed in some method, that responds to button touches - everything is fine. But when I place it to some other method (called during some processes in my app) - modal view is displayed without problems, but when I press (touch) "Done" button, application crashes with "Program received signal: “EXC_BAD_ACCESS”." What am I doing wrong?

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  • Proper two-level iPad UITableView

    - by Knodel
    I have an iPad app with split view. In the root view I need to make a two-level UITableView, so the UIWebView in the DetailView shows corresponding content. What I need is to make a two-level UITableView without editing, moving etc, so it can send the name of the selected row in the second level of the table to the DetailViewController. What is the best way to do it? Thanks in advance!

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  • Cocos2d - smooth sprite movement in tile map RPG

    - by Lendo92
    I've been working on a 2-D Gameboy style RPG for a while now, and the game logic is mostly all done so I'm starting to try to make things look good. One thing I've noticed is that the walking movement / screen movement is a little bit choppy. Technically, it should work fine, but either it seems to be having some quirks, either due to taking up a lot of processing power or just timing inconsistencies between moving the screen and moving the sprite. To move the sprite, once I know where I want to move it, I call: tempPos.y += 3*theHKMap.tileSize.width/5; id actionMove = [CCMoveTo actionWithDuration:0.1 position:tempPos]; id actionMoveDone = [CCCallFuncN actionWithTarget:self selector:@selector(orientOneMove)]; [guy runAction:[CCSequence actions:actionMove, actionMoveDone, nil]]; [self setCenterOfScreen:position]; Then, in orientOneMove, I call: [self.guy setTexture:[[CCTextureCache sharedTextureCache] addImage:@"guysprite07.png"]]; //the walking picture-I change texture back at the end of the movement id actionMove = [CCMoveTo actionWithDuration:0.15 position:self.tempLocation2]; id actionMoveDone = [CCCallFuncN actionWithTarget:self selector:@selector(toggleTouchEnabled)]; [guy runAction:[CCSequence actions:actionMove, actionMoveDone, nil]]; The code for the concurrently running setCenterOfScreen:position method is: id actionMove = [CCMoveTo actionWithDuration:0.25 position:difference]; [self runAction: [CCSequence actions:actionMove, nil, nil]]; So the setCenterOfScreen moves the camera in one clean move while the guy moving is chopped into two actions to animate it (which I believe might be inefficient.) It's hard to tell what is making the movement not perfectly clean from looking at it, but essentially the guy isn't always perfectly in the center of the screen -- during movement, he's often times a pixel or two off for an instant. Any ideas/ solutions?

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  • How to track the touch vector?

    - by mystify
    I need to calculate the direction of dragging a touch, to determine if the user is dragging up the screen, or down the screen. Actually pretty simple, right? But: 1) Finger goes down, you get -touchesBegan:withEvent: called 2) Must wait until finger moves, and -touchesMoved:withEvent: gets called 3) Problem: At this point it's dangerous to tell if the user did drag up or down. My thoughts: Check the time and accumulate calculates vectors until it's secure to tell the direction of touch. Easy? No. Think about it: What if the user holds the finger down for 5 minutes on the same spot, but THEN decides to move up or down? BANG! Your code would fail, because it tried to determine the direction of touch when the finger didn't move really. Problem 2: When the finger goes down and stays at the same spot for a few seconds because the user is a bit in the wind and thinks about what to do now, you'll get a lot of -touchesMoved:withEvent: calls very likely, but with very minor changes in touch location. So my next thought: Do the accumulation in -touchesMoved:withEvent:, but only if a certain threshold of movement has been exceeded. I bet you have some better concepts in place?

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  • remove image from tableViewCell created programatically

    - by Ruthy
    Hello, I would like to move an imageView contained on a cell and it works but creating a new image at new position keeping old image (then two are shown). How could I remove old one?? used code: UIImage *cellImage = [UIImage imageNamed:(@"%@", showIconName)]; UIImageView *imageViewToPutInCell = [[UIImageView alloc] initWithImage:cellImage]; imageViewToPutInCell.frame = CGRectMake(iconPos, 7, cellImage.size.width, cellImage.size.height); [cell.contentView addSubview:imageViewToPutInCell]; every time that I reload tableView, it creates a new overlapped image. [cell.contentView removeFromSuperview]; used before, removes it but then new image is not created. Please help!! Thanx

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  • Fatsest way to edit alpha of CGImage (or UIImage) with touch and then display?

    - by Pankaj
    I have two image views, one on top of the another, with two different images. As the user touches the image and moves his/her finger, the top image should become transparent along the touch points with a fixed radius. (Like the PhotoChop app). Currently I am doing it this way... For each touch. Get a copy of the image buffer from CGImage of the top image. Edit the alpha channel of the buffer to create a transparent circle centered at the touch point. Create new CGImage from the buffer. Create UIImage from the CGImage and use the new UIImage as the top image view's image. This works but as you can see too many copy, creates are involved and it is slow. Can somebody please suggest me a faster way of doing the same thing?

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  • how to display specific dates in KCalander

    - by yakub_moriss
    hi ,All i want to use KCalander (which is Open Source on www.code.google.com) in my project but i want to allow select only one date from awailable dates (means every monday of limited time period/dates awailable for reservations) what am i want to display only that dates/day in KCalander. is that possible with the use of UIDatePicker controller. which one is easy sollution ? waiting for your reply... Thanks in advance... Yakub Moriss

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  • Calling delegate methods and calling selectors

    - by Crystal
    I'm new to the concept of delegates and selectors when used with notifications. So my first question is, 1) Let's say you have a button that has a delegate that implements some doWork method. If you want the same functionality that's in the method, is it 'ok' to just call that method? I didn't know if that was considered good coding practices and/or if you should do that, or do something different in getting that type of functionality. Like if that is ok architecture? 2) Similarly, with NSNotificationCenter, I see some code that posts a notification. Then there's a HandleSegmentedControl:(NSNotification *)notification method. If I want to manually have that functionality, but without pressing the segment control, is it 'ok' to just take that functionality out of that method and put it in a new method so it would look like this: Original: - (void)HandleSegmentedControl:(NSNotification *)notification { NSDictionary *dict = [userInfo notification]; // do stuff with the dictionary } New: - (void)HandleSegmentedControl:(NSNotification *)notification { NSDictionary *dict = [userInfo notification]; [self newMethod:dict]; } - (void)newMethod:(NSDictionary *)dict { // do stuff with the dictionary } - (void)myOtherMethodThatNeedsTheSameFunctionality { NSDictionary *dict = // create some dictionary [self newMethod:dict]; } Sorry if these are basic questions. I'm not sure what the best practices are for things like this and wanted to start the right way. Thanks.

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  • UI design for screen which has number of data entry textFields.

    - by shilpa
    Hi all, my app is an e-commerce application. During the checkout process, I have "recipient" and "credit card" screens. In the recipient screen, there are number of fields for address entry, which makes it very clumsy. Same in the case of the credit card screen, where the user is asked to enter their credit card info and billing address. Can anyone suggest how to design these two pages?

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  • Not receiving touchesEnded/Moved/Cancelled after adding subView

    - by Sam
    Title more or less says it all. In response to a touchesBegan event, my UIViewController recolours itself and adds some subviews. It never receives the touchesEnded. I guess because the added subviews are somehow intercepting the event. I tried calling resignFirstResponder on the subviews to no avail. The code works fine when I don't add the child views and the touch events are called as normal. Any ideas? Thanks

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  • How to fix: unrecognized selector sent to instance

    - by Matt
    I am having a problem that may be simple to fix, but not simple for me to debug. I simple have a button inside a view in IB; the file's owner is set to the view controller class I am using and when making the connections, everything seems fine, ie. the connector is finding the method I am trying to call etc. however, I am receiving this error: Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '*** -[UIApplication getStarted:]: unrecognized selector sent to instance 0x3d19130' My code is as follows: RootViewController.h @interface RootViewController : UIViewController { IBOutlet UIButton* getStartedButton; } @property (nonatomic, retain) UIButton* getStartedButton; - (IBAction) getStarted: (id)sender; @end RootViewController.m #import "RootViewController.h" #import "SimpleDrillDownAppDelegate.h" @implementation RootViewController @synthesize getStartedButton; - (void)viewDidLoad { [super viewDidLoad]; } - (IBAction) getStarted: (id)sender { NSLog(@"Button Tapped!"); //[self.view removeFromSuperview]; } - (void)dealloc { [getStartedButton release]; [super dealloc]; } @end Seems simple enough...any thoughs?

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  • Reason for getting error in Reverse Geocoder Delegate method in the morning times.

    - by Srilakshmi
    - (void)reverseGeocoder:(MKReverseGeocoder *)geocoder didFailWithError:(NSError *)error { NSLog(@"reverseGeocoder:%@ didFailWithError:%@", geocoder, error); } This method is getting called in morning times and it is not showing the placemark while running the application in simulator. From Afternoon it is showing the placemark as "Cupertino". Will you give me the reason for not getting the placeMark at morning times?

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  • Init array with bool values

    - by iFloh
    my attempt to init an array with a number of bool values using: [myArray initWithObjects:[NSNumber numberWithBool:YES], [NSNumber numberWithBool:YES], [NSNumber numberWithBool:YES], nil]; seems to fail since the debugger shows an empty array after this statement is carried out ... Any clues?

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