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• setNeedsDisplayInRect: paints a white rectangle only

  - by Ion Tichy

  Hi, I'm still a little fresh to CoreGraphics programming, so please bear with me. I'm trying to write an application, which allows the user to rub stuff off an image with the finger. I have the basic functionality nailed down, but the result is sluggish since the screen is redrawn completely every time a touch is rendered. I did some research and found out that I can refresh only a portion of the screen using UIView's setNeedsDisplayInRect: method. This does call drawRect: as expected, however everything I draw in the drawRect: following the setNeedsDisplayInRect: is ignored. Instead, the area in the rect parameter is simply filled with white. No matter what I draw inside, all I end up with is a white rectangle. In essence, this is what I do: 1) when user touches screen, this touch is rendered into a mask 2) when the drawRect: is called, the image is masked with that mask There must be something simple I'm overlooking, surely?

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• How do I stop setNeedsDisplayInRect / drawRect coalescence?

  - by No One in Particular

  When programming my app, I get to the point where I have to update two rectangles on the screen. So I call [self setNeedsDisplayInRect:rect1] and then [self setNeedsDisplayInRect:rect2]. When my drawRect method is called, the rectangle parameter is the smallest rectangle which contains both rect1 and rect2. I can handle this with no problem, but when the two rectangles are far apart, then I am updating a lot of real estate with no gain. In this case, I would just like to repaint my two small rectangles. So my question is how can I prevent the underlying system from coalescing my two calls into one?

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• Update a portion UIView

  - by Brett

  Hi; I'm using -setNeedsDisplayinRect to update only a part of my UIView. However, all of my drawing done previously to calling this method is erased. Here is my code in the UIView subclass: -(void)drawRect:(CGRect)rect{ CGContextRef context = UIGraphicsGetCurrentContext(); CGContextSetRGBFillColor(context, r, g, b, 1); CGContextSetRGBStrokeColor(context, r, g, b, 1); CGRect arect = CGRectMake(x,y,1,1); CGContextFillRect(context, arect); NSLog(@"drawing"); } and in the view controller: -(void)drawView{ drawingView = [[DrawingView alloc]init]; x=10; y=10; r=0; g=0; b=0; [drawingView setNeedsDisplayInRect:CGRectMake(x, y, 1, 1)]; x=20; y=20; r=0; g=0; b=0; [drawingView setNeedsDisplayInRect:CGRectMake(x, y, 1, 1)]; } I end up with a screen where there is only one pixel at 20,20. Any help with this is so much appreciated. I am a beginner with XCode and am trying to complete a class project asap.

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• How do you update a secondary view?

  - by Troy Sartain

  Perhaps there's a better way to set this up so I'm open to suggestions. But here's what I'm doing. I have a main UIView. On top of that I have a UIImageView and another UIView. When the UIImageView changes, I want to change the second UIView. So I have a class for it and the IB object's type is set to the class. In the .m of that class is a drawRect method that draws some rectangles. Also in the .m is a NSMutableArray property that is synthesized. I created an instance of that class in the controller of the main view. The problem: despite the fact that the drawRect works fine when the app starts (as traced in the debugger,) when the UIImageView changes I call a "setNeedsDisplay" on the instance variable of the second view after updating the @synthesize'd array but the drawRect does not get called. I think it has to do with instances. I wouldn't think threading would be an issue here. I just want to draw in a separate area of the screen based on an image also displayed.

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• About updating a View using in iPhone using Objective C.

  - by Tattat

  I have a scene, called testScene, it works like this: @interface testScene : myScene { IBOutlet UIView *subview; IBOutlet UIView *drawingCanvasView; IBOutlet UIButton *update; } - (void)updateDrawingCanvas: (id) sender; and when the user click the button, update, it will run the updateDrawingCanvas method. So, I have a drawingCanvasView, which gave a drawingCanvas.h, and .m, it like this: #import <UIKit/UIKit.h> @interface DrawingCanvasView : UIView { CGImageRef image; } -(void)setNeedsDisplayInRect:(CGContextRef)context; @end In the DrawingCanvasView, I have a drawRect method like this: CGContextRef context = UIGraphicsGetCurrentContext(); CGContextSetLineWidth(context, 2.0); CGContextSetStrokeColorWithColor(context, [UIColor redColor].CGColor); CGContextMoveToPoint(context, 0.0f, 0.0f); CGContextAddLineToPoint(context, 100.0f, 100.0f); CGContextStrokePath(context); And I want the user click the button, and execute this, so I added a new method called setNeedsDisplayInRect: CGContextRef context = UIGraphicsGetCurrentContext(); CGContextSetLineWidth(context, 2.0); CGContextSetStrokeColorWithColor(context, [UIColor yellowColor].CGColor); CGContextMoveToPoint(context, 0.0f, 0.0f); CGContextAddLineToPoint(context, 200.0f, 200.0f); CGContextStrokePath(context); But I can't called that in my updateDrawingCanvas method, it work like this: - (void)updateDrawingCanvas: (id) sender{ NSLog(@"loaded"); [DrawingCanvasView setNeedsDisplayInRect:UIGraphicsGetCurrentContext()]; } It my logic / concept right? or something I did wrong, thx.

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• Is this crash in libdispatch caused by Reachability?

  - by esilver

  Can anyone tell me if this crashing stack appears to be caused by Reachability? I am running apple's latest implementation of Reachability, downloadable at https://developer.apple.com/library/ios/samplecode/reachability/Introduction/Intro.html I have an app where ARC is not enabled by default (it is a legacy app) but I enable it on a per-file basis. I have enabled -fobjc-arc for Reachability.m When I look at these threads, my code is nowhere to be found. I see some activity happening because of a WebHTMLView (probably the ad network view code currently on screen; it's not mine). On Thread 10, I see a SCNetworkReachabilityDeallocate, then a dispatch_semaphore_wait_slow, and the crash happens on Thread 14 in libdispatch. Do you think this crash is being caused by that Reachability code, and have I erred in using -fobjc-arc with Reachability.m? Exception Type: EXC_BAD_ACCESS (SIGSEGV) Exception Subtype: KERN_INVALID_ADDRESS at 0x2000000c Triggered by Thread: 14 Thread 0: 0 libsystem_kernel.dylib 0x39cafa84 mach_msg_trap + 20 1 libsystem_kernel.dylib 0x39caf87c mach_msg + 36 2 CoreFoundation 0x2f3e255c __CFRunLoopServiceMachPort + 152 3 CoreFoundation 0x2f3e0cc2 __CFRunLoopRun + 858 4 CoreFoundation 0x2f34b53c CFRunLoopRunSpecific + 520 5 CoreFoundation 0x2f34b31e CFRunLoopRunInMode + 102 6 GraphicsServices 0x340822e6 GSEventRunModal + 134 7 UIKit 0x31c021e0 UIApplicationMain + 1132 8 MyApp 0x00053ad4 main (main.m:33) 9 libdyld.dylib 0x39c0bab4 start + 0 Thread 1: 0 libsystem_kernel.dylib 0x39caf838 kevent64 + 24 1 libdispatch.dylib 0x39bfe0d0 _dispatch_mgr_invoke + 228 2 libdispatch.dylib 0x39bf863e _dispatch_mgr_thread + 34 Thread 2 name: com.apple.NSURLConnectionLoader Thread 2: 0 libsystem_kernel.dylib 0x39cb0910 close + 8 1 CoreFoundation 0x2f370ef6 CFSocketInvalidate + 434 2 CFNetwork 0x2f0122a2 Schedulables::_SchedulablesInvalidateApplierFunction(void const*, void*) + 14 3 CoreFoundation 0x2f34af6e CFArrayApplyFunction + 34 4 CFNetwork 0x2f011a94 SocketStream::close(void const*) + 280 5 CFNetwork 0x2f01194e CoreStreamBase::_streamInterface_Close() + 46 6 CFNetwork 0x2f030286 HTTPReadFilter::_streamImpl_Close() + 66 7 CFNetwork 0x2f01194e CoreStreamBase::_streamInterface_Close() + 46 8 CFNetwork 0x2f0301c6 NetConnection::shutdownConnectionStreams() + 98 9 CFNetwork 0x2f0309c8 NetConnection::closeStreamsIfPossibleOrSignalThatThatNeedsToBeDonePrettyPlease() + 56 10 CFNetwork 0x2f030d12 HTTPConnectionCacheEntry::removeUnauthConnection(NetConnection*) + 182 11 CoreFoundation 0x2f34af6e CFArrayApplyFunction + 34 12 CFNetwork 0x2f075678 HTTPConnectionCacheEntry::purgeIdleConnections(double, double) + 256 13 CFNetwork 0x2f030ad4 HTTPConnectionCache::performIdleSweep() + 156 14 CFNetwork 0x2f073b42 HTTPConnectionCache::timeoutIdleCellConnections() + 18 15 CFNetwork 0x2f0b3394 ___ZNK17CoreSchedulingSet13_performAsyncEPKcU13block_pointerFvvE_block_invoke + 16 16 CoreFoundation 0x2f34af6e CFArrayApplyFunction + 34 17 CFNetwork 0x2f019f10 RunloopBlockContext::perform() + 160 18 CFNetwork 0x2f019de2 MultiplexerSource::perform() + 218 19 CFNetwork 0x2f019c70 MultiplexerSource::_perform(void*) + 44 20 CoreFoundation 0x2f3e2f24 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 12 21 CoreFoundation 0x2f3e23ea __CFRunLoopDoSources0 + 202 22 CoreFoundation 0x2f3e0bda __CFRunLoopRun + 626 23 CoreFoundation 0x2f34b53c CFRunLoopRunSpecific + 520 24 CoreFoundation 0x2f34b31e CFRunLoopRunInMode + 102 25 Foundation 0x2fd8664c +[NSURLConnection(Loader) _resourceLoadLoop:] + 316 26 Foundation 0x2fdfbdc2 __NSThread__main__ + 1058 27 libsystem_pthread.dylib 0x39d28c5a _pthread_body + 138 28 libsystem_pthread.dylib 0x39d28bca _pthread_start + 98 29 libsystem_pthread.dylib 0x39d26ccc thread_start + 4 Thread 3 name: WebThread Thread 3: 0 CoreGraphics 0x2f49163c CGRectIsEmpty + 0 1 WebCore 0x37291700 -[WAKView setNeedsDisplayInRect:] + 76 2 WebKit 0x37cad22a -[WebHTMLView setNeedsDisplayInRect:] + 214 3 WebCore 0x372915cc WebCore::ScrollView::platformRepaintContentRectangle(WebCore::IntRect const&, bool) + 148 4 WebCore 0x37291412 WebCore::ScrollView::repaintContentRectangle(WebCore::IntRect const&, bool) + 98 5 WebCore 0x37291272 WebCore::FrameView::doDeferredRepaints() + 90 6 WebCore 0x372dc96c WebCore::FrameView::layout(bool) + 1748 7 WebCore 0x3721fb94 WebCore::ThreadTimers::sharedTimerFiredInternal() + 132 8 WebCore 0x3721fae6 WebCore::timerFired(__CFRunLoopTimer*, void*) + 22 9 CoreFoundation 0x2f3e2e84 __CFRUNLOOP_IS_CALLING_OUT_TO_A_TIMER_CALLBACK_FUNCTION__ + 12 10 CoreFoundation 0x2f3e2a9e __CFRunLoopDoTimer + 790 11 CoreFoundation 0x2f3e0e26 __CFRunLoopRun + 1214 12 CoreFoundation 0x2f34b53c CFRunLoopRunSpecific + 520 13 CoreFoundation 0x2f34b31e CFRunLoopRunInMode + 102 14 WebCore 0x372ae7d8 RunWebThread(void*) + 416 15 libsystem_pthread.dylib 0x39d28c5a _pthread_body + 138 16 libsystem_pthread.dylib 0x39d28bca _pthread_start + 98 17 libsystem_pthread.dylib 0x39d26ccc thread_start + 4 Thread 4: 0 libsystem_kernel.dylib 0x39cafa84 mach_msg_trap + 20 1 libsystem_kernel.dylib 0x39caf87c mach_msg + 36 2 CoreFoundation 0x2f3e255c __CFRunLoopServiceMachPort + 152 3 CoreFoundation 0x2f3e0c7c __CFRunLoopRun + 788 4 CoreFoundation 0x2f34b53c CFRunLoopRunSpecific + 520 5 CoreFoundation 0x2f34b31e CFRunLoopRunInMode + 102 6 libAVFAudio.dylib 0x2e3295ae GenericRunLoopThread::Entry(void*) + 126 7 libAVFAudio.dylib 0x2e31dbf4 CAPThread::Entry(CAPThread*) + 176 8 libsystem_pthread.dylib 0x39d28c5a _pthread_body + 138 9 libsystem_pthread.dylib 0x39d28bca _pthread_start + 98 10 libsystem_pthread.dylib 0x39d26ccc thread_start + 4 Thread 5 name: JavaScriptCore::BlockFree Thread 5: 0 libsystem_kernel.dylib 0x39cc1f38 __psynch_cvwait + 24 1 libsystem_pthread.dylib 0x39d28262 _pthread_cond_wait + 538 2 libsystem_pthread.dylib 0x39d2903c pthread_cond_wait + 36 3 JavaScriptCore 0x3036f408 JSC::BlockAllocator::blockFreeingThreadMain() + 204 4 JavaScriptCore 0x3036ca70 WTF::wtfThreadEntryPoint(void*) + 12 5 libsystem_pthread.dylib 0x39d28c5a _pthread_body + 138 6 libsystem_pthread.dylib 0x39d28bca _pthread_start + 98 7 libsystem_pthread.dylib 0x39d26ccc thread_start + 4 Thread 6 name: JavaScriptCore::Marking Thread 6: 0 libsystem_kernel.dylib 0x39cc1f38 __psynch_cvwait + 24 1 libsystem_pthread.dylib 0x39d28262 _pthread_cond_wait + 538 2 libsystem_pthread.dylib 0x39d2903c pthread_cond_wait + 36 3 JavaScriptCore 0x3050daf2 JSC::GCThread::waitForNextPhase() + 74 4 JavaScriptCore 0x3050db4c JSC::GCThread::gcThreadMain() + 48 5 JavaScriptCore 0x3036ca70 WTF::wtfThreadEntryPoint(void*) + 12 6 libsystem_pthread.dylib 0x39d28c5a _pthread_body + 138 7 libsystem_pthread.dylib 0x39d28bca _pthread_start + 98 8 libsystem_pthread.dylib 0x39d26ccc thread_start + 4 Thread 7 name: com.apple.CFSocket.private Thread 7: 0 libsystem_kernel.dylib 0x39cc2440 select$DARWIN_EXTSN + 20 1 CoreFoundation 0x2f3e645e __CFSocketManager + 482 2 libsystem_pthread.dylib 0x39d28c5a _pthread_body + 138 3 libsystem_pthread.dylib 0x39d28bca _pthread_start + 98 4 libsystem_pthread.dylib 0x39d26ccc thread_start + 4 Thread 8 name: AFNetworking Thread 8: 0 libsystem_kernel.dylib 0x39cafa84 mach_msg_trap + 20 1 libsystem_kernel.dylib 0x39caf87c mach_msg + 36 2 CoreFoundation 0x2f3e255c __CFRunLoopServiceMachPort + 152 3 CoreFoundation 0x2f3e0c7c __CFRunLoopRun + 788 4 CoreFoundation 0x2f34b53c CFRunLoopRunSpecific + 520 5 CoreFoundation 0x2f34b31e CFRunLoopRunInMode + 102 6 Foundation 0x2fd39822 -[NSRunLoop(NSRunLoop) runMode:beforeDate:] + 250 7 Foundation 0x2fd8a664 -[NSRunLoop(NSRunLoop) run] + 76 8 MyApp 0x002c33d0 +[AFURLConnectionOperation networkRequestThreadEntryPoint:] (AFURLConnectionOperation.m:184) 9 Foundation 0x2fdfbdc2 __NSThread__main__ + 1058 10 libsystem_pthread.dylib 0x39d28c5a _pthread_body + 138 11 libsystem_pthread.dylib 0x39d28bca _pthread_start + 98 12 libsystem_pthread.dylib 0x39d26ccc thread_start + 4 Thread 9 name: WebCore: CFNetwork Loader Thread 9: 0 libsystem_kernel.dylib 0x39cafa84 mach_msg_trap + 20 1 libsystem_kernel.dylib 0x39caf87c mach_msg + 36 2 CoreFoundation 0x2f3e255c __CFRunLoopServiceMachPort + 152 3 CoreFoundation 0x2f3e0c7c __CFRunLoopRun + 788 4 CoreFoundation 0x2f34b53c CFRunLoopRunSpecific + 520 5 CoreFoundation 0x2f34b31e CFRunLoopRunInMode + 102 6 WebCore 0x372f7872 WebCore::runLoaderThread(void*) + 250 7 JavaScriptCore 0x3036ca70 WTF::wtfThreadEntryPoint(void*) + 12 8 libsystem_pthread.dylib 0x39d28c5a _pthread_body + 138 9 libsystem_pthread.dylib 0x39d28bca _pthread_start + 98 10 libsystem_pthread.dylib 0x39d26ccc thread_start + 4 Thread 10: 0 libsystem_kernel.dylib 0x39cafad4 semaphore_wait_trap + 8 1 libdispatch.dylib 0x39bfcdec _dispatch_semaphore_wait_slow + 172 2 libxpc.dylib 0x39d370d6 xpc_connection_send_message_with_reply_sync + 150 3 SystemConfiguration 0x31b77362 _reach_server_target_remove + 90 4 SystemConfiguration 0x31b772d2 __SCNetworkReachabilityServer_targetRemove + 38 5 SystemConfiguration 0x31b5e318 __SCNetworkReachabilityDeallocate + 92 6 CoreFoundation 0x2f347efc CFRelease + 464 7 libdispatch.dylib 0x39bfc7e0 _dispatch_root_queue_drain + 220 8 libdispatch.dylib 0x39bfc9cc _dispatch_worker_thread2 + 52 9 libsystem_pthread.dylib 0x39d26dfc _pthread_wqthread + 296 10 libsystem_pthread.dylib 0x39d26cc0 start_wqthread + 4 Thread 11: 0 libsystem_kernel.dylib 0x39cc2c7c __workq_kernreturn + 8 1 libsystem_pthread.dylib 0x39d26e06 _pthread_wqthread + 306 2 libsystem_pthread.dylib 0x39d26cc0 start_wqthread + 4 Thread 12: 0 libsystem_kernel.dylib 0x39cc2c7c __workq_kernreturn + 8 1 libsystem_pthread.dylib 0x39d26e06 _pthread_wqthread + 306 2 libsystem_pthread.dylib 0x39d26cc0 start_wqthread + 4 Thread 13: 0 libsystem_kernel.dylib 0x39cafa84 mach_msg_trap + 20 1 libsystem_kernel.dylib 0x39caf87c mach_msg + 36 2 CoreFoundation 0x2f3e255c __CFRunLoopServiceMachPort + 152 3 CoreFoundation 0x2f3e0c7c __CFRunLoopRun + 788 4 CoreFoundation 0x2f34b53c CFRunLoopRunSpecific + 520 5 CoreFoundation 0x2f38f1a6 CFRunLoopRun + 94 6 CoreMotion 0x2fa03394 ___lldb_unnamed_function1407$$CoreMotion + 724 7 libsystem_pthread.dylib 0x39d28c5a _pthread_body + 138 8 libsystem_pthread.dylib 0x39d28bca _pthread_start + 98 9 libsystem_pthread.dylib 0x39d26ccc thread_start + 4 Thread 14 Crashed: 0 libobjc.A.dylib 0x3970db66 objc_msgSend + 6 1 CoreFoundation 0x2f347f58 CFRelease + 556 2 libdispatch.dylib 0x39bf7100 _dispatch_call_block_and_release + 8 3 libdispatch.dylib 0x39bfbe72 _dispatch_queue_drain + 370 4 libdispatch.dylib 0x39bf8f96 _dispatch_queue_invoke + 38 5 libdispatch.dylib 0x39bfc74e _dispatch_root_queue_drain + 74 6 libdispatch.dylib 0x39bfc9cc _dispatch_worker_thread2 + 52 7 libsystem_pthread.dylib 0x39d26dfc _pthread_wqthread + 296 8 libsystem_pthread.dylib 0x39d26cc0 start_wqthread + 4

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• What is faster? Drawing or Compositing?

  - by mystify

  I make extensive use of -drawRect: to do some nice animations. A timer tries to fire 30 times per second with -setNeedsDisplay, but it feels like just 20 times. Also I can't use -setNeedsDisplayInRect: because the animation covers the entire thing. Would it help to take some of those drawing operations out of -drawRect: and move them to a subview? -drawRect has to do less then, but instead the OS will have more work with compositing views. Is there a rule of thumb which one is more worse? I remember from an apple text that they claimed Core Animation doesn't redraw during animation. So is that their secret of speed? Using subviews in animations?

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• Copy/Paste functionality in UITableViewController.

  - by Simon

  Hi.. I have a UITableViewController. I want to pop the copy/paste menu up when the user touches a cell. How to implement this functionality. Can someone help me. I tried this code, UIMenuController *theMenu = [UIMenuController sharedMenuController]; [theMenu setTargetRect:CGRectMake(10, 200, 100, 40) inView:[self tableView]]; [theMenu setMenuVisible:YES animated:YES]; But it doesn't work. My question is, What CGRect I have to pass as the setTargetRect parameter? Do I need to call SetNeedsDisplayInRect in my TableViewController? What else to do to make this work?

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• Creating a button on a View from a second View

  - by BigJoke

  Hi, I have this app I'm working on, which on a second view asks (textfield) the name for a button to be created on first view. After specifying the name and pressing OK button, the first view pops up (as demanded) but there's no new button, although created indeed. Can I use the following code in a second view method, to "refresh" the first view before presenting itself. What's wrong with this code? Any other approach? Thank you. -(void)initWithView:(View1Controller *)aSuperview { theSuperview = aSuperview; } - (IBAction)itemNameButton { ... CGRect rectang; rectang = CGRectMake(0, 0, 320, 460);// just in case [theSuperview.view setNeedsDisplayInRect:rectang]; ... }

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• Optimizing drawing on UITableViewCell

  - by Brian

  I am drawing content to a UITableViewCell and it is working well, but I'm trying to understand if there is a better way of doing this. Each cell has the following components: Thumbnail on the left side - could come from server so it is loaded async Title String - variable length so each cell could be different height Timestamp String Gradient background - the gradient goes from the top of the cell to the bottom and is semi-transparent so that background colors shine through with a gloss It currently works well. The drawing occurs as follows: UITableViewController inits/reuses a cell, sets needed data, and calls [cell setNeedsDisplay] The cell has a CALayer for the thumbnail - thumbnailLayer In the cell's drawRect it draws the gradient background and the two strings The cell's drawRect it then calls setIcon - which gets the thumbnail and sets the image as the contents of the thumbnailLayer. If the image is not found locally, it sets a loading image as the contents of the thumbnailLayer and asynchronously gets the thumbnail. Once the thumbnail is received, it is reset by calling setIcon again & resets the thumbnailLayer.contents This all currently works, but using Instruments I see that the thumbnail is compositing with the gradient. I have tried the following to fix this: setting the cell's backgroundView to a view whose drawRect would draw the gradient so that the cell's drawRect could draw the thumbnail and using setNeedsDisplayInRect would allow me to only redraw the thumbnail after it loaded --- but this resulted in the backgroundView's drawing (gradient) covering the cell's drawing (text). I would just draw the thumbnail in the cell's drawRect, but when setNeedsDisplay is called, drawRect will just overlap another image and the loading image may show through. I would clear the rect, but then I would have to redraw the gradient. I would try to draw the gradient in a CAGradientLayer and store a reference to it, so I can quickly redraw it, but I figured I'd have to redraw the gradient if the cell's height changes. Any ideas? I'm sure I'm missing something so any help would be great.

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• [iPhone Obj-C] How to move a label with the wave of the iPhone?

  - by Didi

  The code below is from the book Beginning iPhone 3 Development, chapter 15, using the accelerometer to control a ball. I want to use a label instead of the ball, and only move in the x direction. However, I donno how to revise the code to achieve this goal. Can anyone please help me? THX so much!!!! (id)initWithCoder:(NSCoder *)coder { if (self = [super initWithCoder:coder]) { self.image = [UIImage imageNamed:@"ball.png"]; self.currentPoint = CGPointMake((self.bounds.size.width / 2.0f) + (image.size.width / 2.0f), (self.bounds.size.height / 2.0f) + (image.size.height / 2.0f)); ballXVelocity = 0.0f; ballYVelocity = 0.0f; } return self; } (id)initWithFrame:(CGRect)frame { if (self = [super initWithFrame:frame]) { // Initialization code } return self; } (void)drawRect:(CGRect)rect { // Drawing code [image drawAtPoint:currentPoint]; } (void)dealloc { [image release]; [acceleration release]; [super dealloc]; } //#pragma mark - - (CGPoint)currentPoint { return currentPoint; } - (void)setCurrentPoint:(CGPoint)newPoint { previousPoint = currentPoint; currentPoint = newPoint; if (currentPoint.x < 0) { currentPoint.x = 0; //ballXVelocity = 0; ballXVelocity = - (ballXVelocity / 2.0); } if (currentPoint.y < 0){ currentPoint.y = 0; //ballYVelocity = 0; ballYVelocity = - (ballYVelocity / 2.0); } if (currentPoint.x > self.bounds.size.width - image.size.width) { currentPoint.x = self.bounds.size.width - image.size.width; //ballXVelocity = 0; ballXVelocity = - (ballXVelocity / 2.0); } if (currentPoint.y > self.bounds.size.height - image.size.height) { currentPoint.y = self.bounds.size.height - image.size.height; //ballYVelocity = 0; ballYVelocity = - (ballYVelocity / 2.0); } CGRect currentImageRect = CGRectMake(currentPoint.x, currentPoint.y, currentPoint.x + image.size.width, currentPoint.y + image.size.height); CGRect previousImageRect = CGRectMake(previousPoint.x, previousPoint.y, previousPoint.x + image.size.width, currentPoint.y + image.size.width); [self setNeedsDisplayInRect:CGRectUnion(currentImageRect, previousImageRect)]; } (void)draw { static NSDate *lastDrawTime; if (lastDrawTime != nil) { NSTimeInterval secondsSinceLastDraw = -([lastDrawTime timeIntervalSinceNow]); ballYVelocity = ballYVelocity + -(acceleration.y * secondsSinceLastDraw); ballXVelocity = ballXVelocity + acceleration.x * secondsSinceLastDraw; CGFloat xAcceleration = secondsSinceLastDraw * ballXVelocity * 500; CGFloat yAcceleration = secondsSinceLastDraw * ballYVelocity * 500; self.currentPoint = CGPointMake(self.currentPoint.x + xAcceleration, self.currentPoint.y +yAcceleration); } // Update last time with current time [lastDrawTime release]; lastDrawTime = [[NSDate alloc] init]; }

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