In my applicayion i am using a uiimageview ,and it will load diffrent images on a button click. But there is memory leak when i load images, is that needed to release uiimageview.image property before i load another image to it. Any help please...........
code for loading images to uiimageview
-(void)setOverlayImage:(UIImage *)img
{
overlayView.image=nil;
overlayView.image=img;
}
Before i do overlayView.image=img; i hope the memory allocated for the previous image will be replaced with the new image.
Or is that needed to do [overlayView.image release] and then overlayView.image=img;???????
But when i tried to release, the app crashed.
-(void)setOverlayImage:(UIImage *)img
{
overlayView.image=img;
}
This should be sufficient but you can also go for this.
-(void)setOverlayImage:(UIImage *)img
{
if(overlayView)
{
[overlayView release];
overlayView = nil;
}
overlayView = [[UIImageView alloc] initWithImage:img];
overlayView.frame = yourFrame;
// Add this to your parent view
[self.view addSubview:overlayView];
}
Hope this helps
Related
hey i am running into a problem.
i maade an image object that gets added every 2 seconds by an nstimer.
and an update timer updates it so the image goes forward.
but it only goes forward until a new one gets added and i can't solve why.
this is the method for adding it.
-(void)addTarget {
UIImage *image1=[UIImage imageNamed:#"enemy.png"];
image=[[UIImageView alloc]initWithImage:image1];
image.frame=CGRectMake(0,0,50,50);
[self.view addSubview:image];
image.center = CGPointMake(150, 150);
image.tag = 1;
[_targets addObject:image];
[image release];
}
self explaining.
-(void) update {
image.center = CGPointMake(image.center.x+2, image.center.y);
}
and this spawns them.
-(void) spawn {
[self addTarget];
}
Its because you are constantly reallocating the image. You need to be creating a new image1 variable every time and then adding it to an NSMutableArray.
Then in the update method use a for loop to move each image in the array's centre to whatever point.
- (void)update {
for (UIImage *image in _targets) {
image.center = CGPointMake(image.center.x+2, image.center.y);
}
}
I'm using some sample code I got from a tutorial to create basically a snapshot using AVCamRecorder. It doesn't save a picture, it just displays it in a little rect under the live camera view whenever I click a button. It seemed to be allocating more and more memory each time I clicked the button to update the image, so I put an if (image) {[image release]} and then continued with the rest of the code to capture the image. The problem I ran into there is that eventually I hit an EXC_BAD_ACCESS if I click the button fast enough repeatedly. I tried inserting an if (image) immediately before assigning it to my view, but I still get EXC_BAD_ACCESS. I tried adding an [NSThread sleepForTimeInterval:1] at the end, but that didn't help either. I still get the EXC_BAD_ACCESS after clicking the button several times. Is there a proper way to reuse this view? Thanks
if (image) {
[image release];
exifAttachments = nil;
}
[[self stillImageOutput] captureStillImageAsynchronouslyFromConnection:stillImageConnection completionHandler:^(CMSampleBufferRef imageDataSampleBuffer, NSError *error) {
exifAttachments = CMGetAttachment(imageDataSamplebuffer, kCGImagePropertyExifDictionary, NULL);
if (exifAttachments) {
// NSLog
} else {
// NSLog
}
NSData *imagedata = [AVCaptureStillImageOutput jpegStillImageNSDataRepresentation:imageDataSampleBuffer];
image = [[UIImage alloc] initWithData:imageData];
if (image) {
self.capturedPicView.image = image;
}
}];`
Is the image variable declared as __block? If not, you may get all sorts of weird things because you can't modify it within a block.
You probably don't need a separate image variable - just do:
self.capturedPicView.image = [[[UIImage alloc] initWithData:imageData] autorelease];
in your block.
P.S. And it looks like your original memory leak was due to not releasing the new image - you could have added autorelease to UIImage creation or just release it right after assigning (UIImageView.image retains it anyway):
image = [[UIImage alloc] initWithData:imageData];
if (image) {
self.capturedPicView.image = image;
[image release];
}
In my view controller, how can I know when a certain UIImageView has finished loading (large jpeg from documents directory)? I need to know so that I can then swap a placeholder low-res imageview with this hi-res imageview. Do I need to create a custom callback to know this? Any way is fine.
By the way, here is a snippet of code where I load the image:
NSString *fileName = [NSString stringWithFormat:#"hires_%i.jpg", currentPage];
NSString *filePath = [NSString stringWithFormat:#"%#/BookImage/%#", [self documentsDirectory], fileName];
hiResImageView.image = [[[UIImage alloc] initWithContentsOfFile:filePath] autorelease];
UIImageView isn't doing any loading at all. All the loading is being done by [[UIImage alloc] initWithContentsOfFile:filePath], and your thread is blocked while the file is loaded (so the load is already complete by the time that call finally returns).
What you want to do is something like this:
- (void)loadImage:(NSString *)filePath {
[self performSelectorInBackground:#selector(loadImageInBackground:) withObject:filePath];
}
- (void)loadImageInBackground:(NSString *)filePath {
NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
UIImage *image = [[UIImage alloc] initWithContentsOfFile:filePath];
[self performSelectorOnMainThread:#selector(didLoadImageInBackground:) withObject:image waitUntilDone:YES];
[image release];
[pool release];
}
- (void)didLoadImageInBackground:(UIImage *)image {
self.imageView.image = image;
}
You would set up self.imageView to display the low-res image and then call loadImage: to load the high-res version.
Note that if you call this repeatedly before didLoadImageInBackground: gets called from earlier calls, you may cause the device to run out of memory. Or you might have the image from the first call take so much longer to load than image from the second call that didLoadImageInBackground: gets called for the second image before it gets called for the first. Fixing those issues is left as an exercise for the reader (or for another question).
I have a view that generates an image based on a series of layers. I have images for the background, for the thumbnail, and finally for an overlay. Together, it makes one cohesive display.
It seems to work a dream, except for when it doesn't. For seemingly no reason, I get an EXC_BAD_ACCESS on the specified line below after it's generated somewhere between 8 and 20 images. I've run it through the memory leak tool and allocation tool, and it's not eating up tons of memory and it's not leaking. I'm totally stumped.
Here's the relevant code:
- (UIImage *)addLayer:(UIImage *)layer toImage:(UIImage *)background atPoint:(CGPoint)point {
CGSize size = CGSizeMake(240, 240);
UIGraphicsBeginImageContext(size);
[background drawAtPoint:CGPointMake(0, 0)]; // <--- error here
[layer drawAtPoint:point];
UIImage* result = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return result;
}
// Build the layered image -- thingPage onto thingBackground,
// then the screenshot on that, then the thingTop on top of it all.
// thingBackground, thingPage and thingTop are all preloaded UIImages.
-(UIImage *)getImageForThing:(Thing *)t {
[self loadImageCacheIfNecessary];
if (!t.screenshot) {
return [UIImage imageNamed:#"NoPreview.png"];
} else {
UIImage *screenshot = t.screenshot;
UIImage *currentImage = [self addLayer:thingPage toImage:thingBackground atPoint:CGPointMake(0, 0)];
currentImage = [self addLayer:screenshot toImage:currentImage atPoint:CGPointMake(39, 59)];
currentImage = [self addLayer:thingTop toImage:currentImage atPoint:CGPointMake(0, 1)];
return currentImage;
}
}
I can't find anywhere that this is going wrong, and I've been tearing my hair out for a couple of hours on this. It's the final known bug in the system, so you can imagine how antsy I am to fix it! :-)
Thanks in advance for any help.
As to me, I always use -(void)drawInRect: instead of -(void)drawAtPoint:
CGRect rtDraw;
rtDraw.origin = CGPointZero;
rtDraw.size = size;
[background drawInRect:rtDraw];
[layer drawInRect:rtDraw];
And ....
The paint method with UIGraphicsBeginImageContext(size) and UIGraphicsEndImageContext() is not thread-safe.
Those functions will push or pop a context with stack struct, which is managed by system.
EXC_BAD_ACCESS is almost always due to accessing an object that has already been released. In your code this seems to be t.screenshot. Check creation (and retaining if it is an instance variable) of the object returned by Thing's screenshot property.
As it turns out, the error wasn't in the code I posted, it was in my caching of the thingBackground, thingPage and thingTop images. I wasn't retaining them. Here's the missing code, fixed:
-(void)loadImageCacheIfNecessary {
if (!folderBackground) {
thingBackground = [[UIImage imageNamed:#"ThingBack.png"] retain];
}
if (!folderPage) {
thingPage = [[UIImage imageNamed:#"ThingPage.png"] retain];
}
if (!folderTop) {
thingTop = [[UIImage imageNamed:#"ThingTop.png"] retain];
}
}
I will admit I'm still not comfortable with the whole retain/release/autorelease stuff in Objective C. Hopefully it'll sink in one day soon. :-)
I am having trouble with my UITableView in the NavigationController.
When I add data to the table I use another class to download images to display in that table, while all that works great but if in the middle of images being download I swtich back to the previous view in the navigationcontroller app crashed.
Here is my code to explain further
- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{
// Set appIcon and clear temporary data/image
UIImage *image = [[UIImage alloc] initWithData:self.activeDownload];
UIImage *appIcon;
if (image.size.width != kAppIconHeight && image.size.height != kAppIconHeight)
{
CGSize itemSize = CGSizeMake(125, 85);
UIGraphicsBeginImageContext(itemSize);
CGRect imageRect = CGRectMake(0.0, 0.0, itemSize.width, itemSize.height);
[image drawInRect:imageRect];
appIcon = UIGraphicsGetImageFromCurrentImageContext();
///UIGraphicsEndImageContext();
}
else
{
appIcon = image;
//self.appRecord.appIcon = image;
}
self.activeDownload = nil;
// Release the connection now that it's finished
self.imageConnection = nil;
// call our delegate and tell it that our icon is ready for display
if(delegate != nil)
[delegate appImageDidLoad:self.indexPathInTableView imaged:appIcon ];
[image release];
}
The appImageDidLoad is a method that exists in my UITableView view.
Is there a way I can check to see if the UITableView is valid in my imagedownload class so I know not to send the image.
Thanks in advance.
The crash is due to delegate getting release by the time the image was ready!
Try this in ViewWillDisappear
// terminate all pending download connections
NSArray *allDownloads = [self.imageDownloadsInProgress allValues];
[allDownloads performSelector:#selector(cancelDownload)];
This is the solution for this crash.
-(void)viewDidDisappear:(BOOL)animated
{
[super viewDidDisappear:animated];
// terminate all pending download connections
NSArray *allDownloads = [self.imageDownloadsInProgress1 allValues];
[allDownloads makeObjectsPerformSelector:#selector(cancelDownload)];
}