UIAlertView Rendering Error - iphone

Question

I have been working on an app for a couple of months now, but have finally run into an issue that I can't solve myself, and can't find anything on the internet to help.
I am using several normal UIAlertViews, in my app. Some have 2 buttons, some have 3 buttons, and a couple have 2 buttons and a text field. However all have the same issue. When you call [someAlertView show]; the alert view appears as normal, but then suddenly its graphics context seems to get corrupted as you can see from the screenshot.
This happens on both iPhone and iPad simulators (both 5.0 and 5.1), and happens on an iPad and iPhone4S device as well.
The image showing through is whatever happens to be behind the alertView.
The Alert still works, I can click the buttons, type in the text field, then when it dismisses the delegate methods are called correctly and everything goes back to normal. When the alertView appears again, the same thing happens.
The view behind the alert is a custom UIScrollView subclass with a content size of approximately 4000 pixels by 1000 with a UIImage as the background. The png file is mostly transparent, so is only about 80kB in memory size, and the phone is having no issues rendering it - the scroll view is still fully responsive and not slow.
It also has a CADisplayLink timer attached to it as part of the subclass. I have tried disabling this just before the alertView is shown, but it makes no difference so I am doubtful that is the issue.
This app is a partial rewrite of one I made for a university project, and that one could display UIAlertViews over the top of a scrollView of the same size and subclass without issue. The difference between this app and that one is that in my old app, I had subclassed UIAlertView to add extra things such as a pickerView, however I decided that I didn't like the way it looked so moved everything out of the alert and am just sticking with a standard UIAlertView.
This is how the alertView in the screenshot is called:
- (IBAction)loadSimulation:(id)sender {
importAlert = [[UIAlertView alloc] initWithTitle:#"Load Simulation" message:#"Enter Filename:" delegate:self cancelButtonTitle:#"Cancel" otherButtonTitles:#"Load", nil];
[importAlert setAlertViewStyle:UIAlertViewStylePlainTextInput];
[importAlert showPausingSimulation:self.simulationView]; //Calling [importAlert show]; makes no difference.
if ([[UIDevice currentDevice] userInterfaceIdiom] == UIUserInterfaceIdiomPhone) {
[self hideOrganiser]; //Not an issue as the problem occurs on iPad as well.
}
}
With this being the categorised AlertView to add the ability to stop the scrollViews CADisplay link.
#interface UIAlertView(pauseDisplayLink)
- (void)showPausingSimulation:(UILogicSimulatorView*)simulationView;
#end
#implementation UIAlertView(pauseDisplayLink)
- (void)showPausingSimulation:(UILogicSimulatorView *)simulationView {
[simulationView stopRunning];
[simulationView removeDisplayLink]; //displayLink needs to be removed from the run loop, otherwise it will keep going in the background and get corrupted.
[self show];
}
I get no memory warnings when this happens, so I am doubtful it is due to lack of resources.
Has anyone come across an issue like this before? If you need further information I can try to provide it, but I am limited in what code I can post. Any help would be appreciated, I've been trying to solve this for two weeks and can't figure it out.
Edit:
It appears that it is not the AlertView at all (or rather it is not just the alertView), as the problem goes away when I remove the scroll view behind it, so there must be some issue between the two. This is the code for my UIScrollView subclass:
.h file:
#import
#import
#class ECSimulatorController;
#interface UILogicSimulatorView : UIScrollView {
CADisplayLink *displayLink;
NSInteger _updateRate;
ECSimulatorController* _hostName;
}
#property (nonatomic) NSInteger updateRate;
#property (nonatomic, strong) ECSimulatorController* hostName;
- (void) removeDisplayLink;
- (void) reAddDisplayLink;
- (void) displayUpdated:(CADisplayLink*)timer;
- (void) startRunning;
- (void) stopRunning;
- (void) refreshRate:(NSInteger)rate;
- (void) setHost:(id)host;
- (void)setMinimumNumberOfTouches:(NSInteger)touches;
- (void)setMaximumNumberOfTouches:(NSInteger)touches;
#end
.m file:
#import "UILogicSimulatorView.h"
#import "ECSimulatorController.h"
#import <QuartzCore/QuartzCore.h>
#implementation UILogicSimulatorView
#synthesize updateRate = _updateRate;
#synthesize hostName = _hostName;
- (void)reAddDisplayLink {
[displayLink addToRunLoop:[NSRunLoop mainRunLoop] forMode:NSDefaultRunLoopMode]; //allows the display link to be re-added to the run loop after having been removed.
}
- (void)removeDisplayLink {
[displayLink removeFromRunLoop:[NSRunLoop mainRunLoop] forMode:NSDefaultRunLoopMode]; //allows the display link to be removed from the Run loop without deleting it. Removing it is essential to prevent corruption between the games and the simulator as both use CADisplay link, and only one can be in the run loop at a given moment.
}
- (void)startRunning {
[self refreshRate:self.updateRate];
[displayLink setPaused:NO];
}
- (void)refreshRate:(NSInteger)rate {
if (rate > 59) {
rate = 59; //prevent the rate from being set too an undefined value.
}
NSInteger frameInterval = 60 - rate; //rate is the number of frames to skip. There are 60FPS, so this converts to frame interval.
[displayLink setFrameInterval:frameInterval];
}
- (void)stopRunning {
[displayLink setPaused:YES];
}
- (void)displayUpdated:(CADisplayLink*)timer {
//call the function that the snakeController host needs to update
[self.hostName updateStates];
}
- (void)setHost:(ECSimulatorController*)host;
{
self.hostName = host; //Host allows the CADisplay link to call a selector in the object which created this one.
}
- (id)initWithFrame:(CGRect)frame
{
//Locates the UIScrollView's gesture recogniser
if(self = [super initWithFrame:frame])
{
[self setMinimumNumberOfTouches:2];
displayLink = [CADisplayLink displayLinkWithTarget:self selector:#selector(displayUpdated:)]; //CADisplayLink will update the logic gate states.
self.updateRate = 1;
[displayLink setPaused:YES];
}
return self;
}
- (void)setMinimumNumberOfTouches:(NSInteger)touches{
for (UIGestureRecognizer *gestureRecognizer in [self gestureRecognizers])
{
if([gestureRecognizer isKindOfClass:[UIPanGestureRecognizer class]])
{
//Changes the minimum number of touches to 'touches'. This allows the UIPanGestureRecogniser in the object which created this one to work with one finger.
[(UIPanGestureRecognizer*)gestureRecognizer setMinimumNumberOfTouches:touches];
}
}
}
- (void)setMaximumNumberOfTouches:(NSInteger)touches{
for (UIGestureRecognizer *gestureRecognizer in [self gestureRecognizers])
{
if([gestureRecognizer isKindOfClass:[UIPanGestureRecognizer class]])
{
//Changes the maximum number of touches to 'touches'. This allows the UIPanGestureRecogniser in the object which created this one to work with one finger.
[(UIPanGestureRecognizer*)gestureRecognizer setMaximumNumberOfTouches:touches];
}
}
}
#end

Answer 1

Well, I have managed to come up a solution to this. Really it is probably just masking the issue rather than finding the route cause, but at this point I will take it.
First some code:
#interface UIView (ViewCapture)
- (UIImage*)captureView;
- (UIImage*)captureViewInRect:(CGRect)rect;
#end
#implementation UIView (ViewCapture)
- (UIImage*)captureView {
return [self captureViewInRect:self.frame];
}
- (UIImage*)captureViewInRect:(CGRect)rect
{
UIGraphicsBeginImageContext(rect.size);
CGContextRef context = UIGraphicsGetCurrentContext();
[self.layer renderInContext:context];
UIImage *screenShot = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return screenShot;
}
#end
- (void)showPausingSimulation:(UILogicSimulatorView *)simulationView {
[simulationView stopRunning];
UIView* superView = simulationView.superview;
CGPoint oldOffset = simulationView.contentOffset;
for (UIView* subview in simulationView.subviews) {
//offset subviews so they appear when content offset is (0,0)
CGRect frame = subview.frame;
frame.origin.x -= oldOffset.x;
frame.origin.y -= oldOffset.y;
subview.frame = frame;
}
simulationView.contentOffset = CGPointZero; //set the offset to (0,0)
UIImage* image = [simulationView captureView]; //Capture the frame of the scrollview
simulationView.contentOffset = oldOffset; //restore the old offset
for (UIView* subview in simulationView.subviews) {
//Restore the original positions of the subviews
CGRect frame = subview.frame;
frame.origin.x += oldOffset.x;
frame.origin.y += oldOffset.y;
subview.frame = frame;
}
[simulationView setHidden:YES];
UIImageView* imageView = [[UIImageView alloc] initWithFrame:simulationView.frame];
[imageView setImage:image];
[imageView setTag:999];
[superView addSubview:imageView];
[imageView setHidden:NO];
superView = nil;
imageView = nil;
image = nil;
[self show];
}
- (void)dismissUnpausingSimulation:(UILogicSimulatorView *)simulationView {
UIView* superView = simulationView.superview;
UIImageView* imageView = (UIImageView*)[superView viewWithTag:999];
[imageView removeFromSuperview];
imageView = nil;
superView = nil;
[simulationView setHidden:NO];
[simulationView startRunning];
}
Then modifying the dismiss delegate method in my class to have this line:
- (void)alertView:(UIAlertView *)alertView didDismissWithButtonIndex:(NSInteger)buttonIndex {
[alertView dismissUnpausingSimulation:self.simulationView];
...
When the alert view is called, but before it is shown, I need to hide the simulator to prevent it corrupting the alert. However just hiding it is ugly as then all is visible behind is a empty view.
To fix this, I first make a UIImage from the simulator views graphics context. I then create a UIImageView with the same frame as the simulator and set the UIImage as its image.
I then hide the simulator view (curing the alert issue), and add my new UIImageView to the simulators superview. I also set the tag of the image view so I can find it later.
When the alert dismisses, the image view is then recovered based on its tag, and removed from its superview. The simulator is then unhidden.
The result is that the rendering issue is gone.

Answer 2

I know its too late for an answer to this question. Lately I had experianced this very same issue.
My Case:
Added couple of custom UIViews with background images and some controlls to the scroll view with shadow effect. I had also set the shadowOffset.
The Solution:
After some step by step analysis, I found out that setting the setShadowOpacity caused The rendering problem for me. When i commented that line of code, it cured the UIAlertView back to normal appearance.
More:
To make sure, I created a new project mimicing the original ui with shadowOpacity. But it didnt caused the rendering problem as i expected. So I am not sure about the root cause. For me it was setShadowOpacity.