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)];
}
Related
I have an old iOS app that uses UIKit and Objective C which I am currecntly porting to SwiftUI and Swift. Everything was going great and I am loving Swift and SwiftUI. The app is pretty much done but the app relies on the user being able to print and/or save the main view as a PDF. I just can't figure out how to access a view in swiftui in order to convert it to a PDF. Here is my existing/working objective-c code.
- (IBAction)actionPrint:(id)sender {
// CREATE CLEAR BACKGROUND
[legMain setBackgroundColor:[UIColor clearColor]];
// SCROLL TO BASE POSITION
[legMain scrollRectToVisible:CGRectMake(1, 1, 1, 1) animated:NO];
// RESET ZOOM
SnapPanel *myObject = [self fGetObject];
myObject.zoom = [NSNumber numberWithDouble:1.0];
[self fSave];
// RECORD FRAME SIZE AND SET TO CONTENT SIZE
double dWidth = legMain.frame.size.width;
double dHeight = legMain.frame.size.height;
[legMain setFrame:CGRectMake(legMain.frame.origin.x, legMain.frame.origin.y, legMain.contentSize.width, legMain.contentSize.height)];
// GET VIEW AS NSDATA FOR PDF
NSMutableData *pdfData = [NSMutableData data];
CGRect pageSize = CGRectMake(0.0, 0.0, 8.5 * 72.0, 11.0 * 72.0);
UIGraphicsBeginPDFContextToData(pdfData, pageSize, nil);
CGContextRef pdfContext = UIGraphicsGetCurrentContext();
// CREATE A SINGLE PAGE PDF
UIGraphicsBeginPDFPage();
[legMain.layer renderInContext:pdfContext];
UIGraphicsEndPDFContext();
// CREATE PRINT CONTROLLER
UIPrintInteractionController *pc = [UIPrintInteractionController sharedPrintController];
void (^completionHandler)(UIPrintInteractionController *, BOOL, NSError *) =
^(UIPrintInteractionController *pic, BOOL completed, NSError *error) {
if (!completed && error){
NSLog(#"Print error: %#", error);
}
};
// SETUP PRINT CONTROLLER
[pc setShowsNumberOfCopies:YES];
[pc setShowsPageRange:YES];
[pc setShowsPaperSelectionForLoadedPapers:YES];
pc.printingItem = pdfData;
// DISPLAY CONTROLLER DIALOG
if (UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPad) {
[pc presentFromRect:texName.frame inView:viewMain.superview
animated:YES completionHandler:completionHandler];
} else {
[pc presentAnimated:YES completionHandler:completionHandler];
}
// RESET BACKGROUND COLOUR AND FRAME SIZE
[legMain setBackgroundColor:[UIColor colorWithRed:.95 green:.95 blue:.95 alpha:1.0]];
[legMain setFrame:CGRectMake(legMain.frame.origin.x, legMain.frame.origin.y, dWidth, dHeight)];
}
legMain is the view that I am adjusting and eventually converting to a PDF. I have managed to port most of this code untill I reach line 26 where I need to render the view. I don't even know where to begin to get an instance of my view.
Having access to hosting window as described in How to access own window within SwiftUI view? you can get main UIView from any of your SwiftUI view as
let mainView = hostingWindow?.rootViewController.view
but for printing I would probably use dedicated view as below (to avoid affecting UI view)
if let hostingController = hostingWindow?.rootController as UIHostingController {
let printingView = UIHostingController(rootView: hostingController.rootView).view
// ... do anything with printingView here, because it will have
// a copy of SwiftUI rootView
}
Update: to the details in comment (hosting window is not needed in this case)
VStack {
PrintableView(arg: value) // << need to be made undependable, so all
// parameters should be passed via arguments
}
then on Print action it could be like
Button("Print") {
let printingView = UIHostingController(rootView: PrintableView(arg: value)).view
// do anything printing related with `printingView` here
}
I am asking this question regarding my questions Display photolibrary images in an effectual way iPhone and Highly efficient UITableView "cellForRowIndexPath" method to bind the PhotoLibrary images.
So I would like to request that answers are not duplicated to this one without reading the below details :)
Let's come to the issue,
I have researched detailed about my above mentioned issue, and I have found the document about operation queues from here.
So I have created one sample application to display seven photo-library images using operation queues through ALAsset blocks.
Here are the sample application details.
Step 1:
In the NSOperationalQueueViewController viewDidLoad method, I have retrieved all the photo-gallery ALAsset URLs in to an array named urlArray.
Step 2:
After all the URLs are added to the urlArray, the if(group != nil) condition will be false in assetGroupEnumerator, so I have created a NSOperationQueue, and then created seven UIImageView's through a for loop and created my NSOperation subclass object with the corresponding image-view and URL for each one and added them in to the NSOperationQueue.
See my NSOperation subclass here.
See my implementation (VierwController) class here.
Let's come to the issue.
It not displaying all the seven images consistently. Some of the images are missing. The missing order is changing multiple times (one time it doesn't display the sixth and seventh, and another time it doesn't display only the second and third). The console log displays Could not find photo pic number. However, the URLs are logged properly.
You can see the log details here.
Are there any mistakes in my classes?
Also, when I go through the above mentioned operational queue documentation, I have read about NSBlockOperation. Do I need to implement NSBlockOperation instead of NSOperation while dealing with ALAsset blocks?
The NSBlockOperation description says
A class you use as-is to execute one or more block objects
concurrently. Because it can execute more than one block, a block
operation object operates using a group semantic; only when all of the
associated blocks have finished executing is the operation itself
considered finished.
How can I implement the NSBlockOperation with ALAsset block regarding my sample application?
I have gone through Stack Overflow question Learning NSBlockOperation. However, I didn't get any idea to implement the NSBlockOperation with ALAsset block!!
This is the tutorial about "How to access all images from iPhonePhoto Library using ALAsset Library and show them on UIScrollView like iPhoneSimulator" .
First of all add AssetsLibrary.framework to your project.
Then in your viewController.h file import #import <AssetsLibrary/AssetsLibrary.h> header file.
This is your viewController.h file
#import <UIKit/UIKit.h>
#import <AssetsLibrary/AssetsLibrary.h>
#import "AppDelegate.h"
#interface ViewController : UIViewController <UIScrollViewDelegate>
{
ALAssetsLibrary *assetsLibrary;
NSMutableArray *groups;
ALAssetsGroup *assetsGroup;
// I will show all images on `UIScrollView`
UIScrollView *myScrollView;
UIActivityIndicatorView *activityIndicator;
NSMutableArray *assetsArray;
// Will handle thumbnail of images
NSMutableArray *imageThumbnailArray;
// Will handle original images
NSMutableArray *imageOriginalArray;
UIButton *buttonImage;
}
-(void)displayImages;
-(void)loadScrollView;
#end
And this is your viewController.m file -
viewWillAppear:
#import "ViewController.h"
#import <QuartzCore/QuartzCore.h>
#implementation ViewController
- (void)viewWillAppear:(BOOL)animated
{
[super viewWillAppear:animated];
assetsArray = [[NSMutableArray alloc]init];
imageThumbnailArray = [[NSMutableArray alloc]init];
imageOriginalArray = [[NSMutableArray alloc]init];
myScrollView = [[UIScrollView alloc]initWithFrame:CGRectMake(0.0, 0.0, 320.0, 416.0)];
myScrollView.delegate = self;
myScrollView.contentSize = CGSizeMake(320.0, 416.0);
myScrollView.backgroundColor = [UIColor whiteColor];
activityIndicator = [[UIActivityIndicatorView alloc]initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleGray];
activityIndicator.center = myScrollView.center;
[myScrollView addSubview:activityIndicator];
[self.view addSubview:myScrollView];
[activityIndicator startAnimating];
}
viewDidAppear:
-(void)viewDidAppear:(BOOL)animated
{
if (!assetsLibrary) {
assetsLibrary = [[ALAssetsLibrary alloc] init];
}
if (!groups) {
groups = [[NSMutableArray alloc] init];
}
else {
[groups removeAllObjects];
}
ALAssetsLibraryGroupsEnumerationResultsBlock listGroupBlock = ^(ALAssetsGroup *group, BOOL *stop) {
//NSLog(#"group %#",group);
if (group) {
[groups addObject:group];
//NSLog(#"groups %#",groups);
} else {
//Call display Images method here.
[self displayImages];
}
};
ALAssetsLibraryAccessFailureBlock failureBlock = ^(NSError *error) {
NSString *errorMessage = nil;
switch ([error code]) {
case ALAssetsLibraryAccessUserDeniedError:
case ALAssetsLibraryAccessGloballyDeniedError:
errorMessage = #"The user has declined access to it.";
break;
default:
errorMessage = #"Reason unknown.";
break;
}
};
[assetsLibrary enumerateGroupsWithTypes:ALAssetsGroupSavedPhotos usingBlock:listGroupBlock failureBlock:failureBlock];
}
And this is displayImages: method body
-(void)displayImages
{
// NSLog(#"groups %d",[groups count]);
for (int i = 0 ; i< [groups count]; i++) {
assetsGroup = [groups objectAtIndex:i];
if (!assetsArray) {
assetsArray = [[NSMutableArray alloc] init];
}
else {
[assetsArray removeAllObjects];
}
ALAssetsGroupEnumerationResultsBlock assetsEnumerationBlock = ^(ALAsset *result, NSUInteger index, BOOL *stop) {
if (result) {
[assetsArray addObject:result];
}
};
ALAssetsFilter *onlyPhotosFilter = [ALAssetsFilter allPhotos];
[assetsGroup setAssetsFilter:onlyPhotosFilter];
[assetsGroup enumerateAssetsUsingBlock:assetsEnumerationBlock];
}
//Seprate the thumbnail and original images
for(int i=0;i<[assetsArray count]; i++)
{
ALAsset *asset = [assetsArray objectAtIndex:i];
CGImageRef thumbnailImageRef = [asset thumbnail];
UIImage *thumbnail = [UIImage imageWithCGImage:thumbnailImageRef];
[imageThumbnailArray addObject:thumbnail];
ALAssetRepresentation *representation = [asset defaultRepresentation];
CGImageRef originalImage = [representation fullResolutionImage];
UIImage *original = [UIImage imageWithCGImage:originalImage];
[imageOriginalArray addObject:original];
}
[self loadScrollView];
}
Now you have two array one is imageThumbnailArray and another is imageOriginalArray.
Use imageThumbnailArray for showing on UIScrollView for which your scrolling will not be slow.... And use imageOriginalArray for an enlarged preview of image.
'loadScrollView:' method, This is how to images on UIScrollView like iPhoneSimulator
#pragma mark - LoadImages on UIScrollView
-(void)loadScrollView
{
float horizontal = 8.0;
float vertical = 8.0;
for(int i=0; i<[imageThumbnailArray count]; i++)
{
if((i%4) == 0 && i!=0)
{
horizontal = 8.0;
vertical = vertical + 70.0 + 8.0;
}
buttonImage = [UIButton buttonWithType:UIButtonTypeCustom];
[buttonImage setFrame:CGRectMake(horizontal, vertical, 70.0, 70.0)];
[buttonImage setTag:i];
[ buttonImage setImage:[imageThumbnailArray objectAtIndex:i] forState:UIControlStateNormal];
[buttonImage addTarget:self action:#selector(buttonImagePressed:) forControlEvents:UIControlEventTouchUpInside];
[myScrollView addSubview:buttonImage];
horizontal = horizontal + 70.0 + 8.0;
}
[myScrollView setContentSize:CGSizeMake(320.0, vertical + 78.0)];
[activityIndicator stopAnimating];
[activityIndicator removeFromSuperview];
}
And here you can find which image button has been clicked -
#pragma mark - Button Pressed method
-(void)buttonImagePressed:(id)sender
{
NSLog(#"you have pressed : %d button",[sender tag]);
}
Hope this tutorial will help you and many users who search for the same.. Thank you!
You have a line in your DisplayImages NSOperation subclass where you update the UI (DisplayImages.m line 54):
self.imageView.image = topicImage;
This operation queue is running on a background thread, and we know that you should only update the state of the UI on the main thread. Since updating the view of an image view is definitely updating the UI, this can be simply fixed by wrapping the call with:
dispatch_async(dispatch_get_main_queue(), ^{
self.imageView.image = topicImage;
});
This puts an asynchronous call on the main queue to update the UIImageView with the image. It's asynchronous so your other tasks can be scheduled in the background, and it's safe as it is running on the main queue - which is the main thread.
I'm kinda puzzeled about image storage in iOS devices for an app i'm making.
My requirement is to load an Image onto a tableViewCell, lets say in the default Image space of a UITableViewCell and hence isnt a background image.
Now The user can either add an Image either via the PhotoDirectory or take an entirely new image.
If a new image is taken, where should that image be stored preferebly? In the default photo directory ? or in the documents folder of the app sandbox?
Because these are image files, I'm afraid that store images within the app bundle can make it pretty big, I'm afraid I dont wana cross the size limit.
Performance wise though... what would be a better option?
I have an app that also does some of the things you describe. My solutions was to create a singleton that I call my imageStore. You can find information about a singleton here
In this imageStore, I store all my "full size" images; however, like you I am concerned about the size of these images, so instead of using them directly, I use thumbnails. What I do is this. For each object that I want to represent in the table, I make sure the object has a UIImage defined that is about thumnail size (64x64 or any size you desire). Then an object is created, I create a thumbnail that I store along with the object. I use this thumbnail instead of the larger images where I can get a way with it, like on a table cell.
I'm not behind my Mac at the moment, but if you want I can post some code later to demonstrate both the singleton and the creation and usage of the thumbnail.
Here is my header file for the ImageStore
#import <Foundation/Foundation.h>
#interface BPImageStore : NSObject {
NSMutableDictionary *dictionary;
}
+ (BPImageStore *)defaultImageStore;
- (void)setImage:(UIImage *)i forKey:(NSString *)s;
- (UIImage *)imageForKey:(NSString *)s;
- (void)deleteImageForKey:(NSString *)s;
#end
Here is the ImageStore.m file - my Singleton
#import "BPImageStore.h"
static BPImageStore *defaultImageStore = nil;
#implementation BPImageStore
+ (id)allocWithZone:(NSZone *)zone {
return [[self defaultImageStore] retain];
}
+ (BPImageStore *)defaultImageStore {
if(!defaultImageStore) {
defaultImageStore = [[super allocWithZone:NULL] init];
}
return defaultImageStore;
}
- (id)init
{
if(defaultImageStore) {
return defaultImageStore;
}
self = [super init];
if (self) {
dictionary = [[NSMutableDictionary alloc] init];
NSNotificationCenter *nc = [NSNotificationCenter defaultCenter];
[nc addObserver:self selector:#selector(clearCach:) name:UIApplicationDidReceiveMemoryWarningNotification object:nil];
}
return self;
}
- (void) clearCache:(NSNotification *)note {
[dictionary removeAllObjects];
}
- (oneway void) release {
// no op
}
- (id)retain {
return self;
}
- (NSUInteger)retainCount {
return NSUIntegerMax;
}
- (void)setImage:(UIImage *)i forKey:(NSString *)s {
[dictionary setObject:i forKey:s];
// Create full path for image
NSString *imagePath = pathInDocumentDirectory(s);
// Turn image into JPEG data
NSData *d = UIImageJPEGRepresentation(i, 0.5);
// Write it to full path
[d writeToFile:imagePath atomically:YES];
}
- (UIImage *)imageForKey:(NSString *)s {
// if possible, get it from the dictionary
UIImage *result = [dictionary objectForKey:s];
if(!result) {
// Create UIImage object from file
result = [UIImage imageWithContentsOfFile:pathInDocumentDirectory(s)];
if (result)
[dictionary setObject:result forKey:s];
}
return result;
}
- (void)deleteImageForKey:(NSString *)s {
if(!s) {
return;
}
[dictionary removeObjectForKey:s];
NSString *path = pathInDocumentDirectory(s);
[[NSFileManager defaultManager] removeItemAtPath:path error:NULL];
}
#end
Here is where I use the image store. In my Object "player", I have a UIImage to store the thumbnail and I have an NSString to house a key that I create. Each original image I put into the store has a key. I store the key with my Player. If I ever need the original image, I get by the unique key. It is also worth noting here that I don't even store the original image at full size, I cut it down a bit already. After all in my case, it is a picture of a player and nobody has too look so good as to have a full resolution picture :)
- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info
{
NSString *oldKey = [player imageKey];
// did the player already have an image?
if(oldKey) {
// delete the old image
[[BPImageStore defaultImageStore] deleteImageForKey:oldKey];
}
UIImage *image = [info objectForKey:UIImagePickerControllerOriginalImage];
// Create a CFUUID object it knows how to create unique identifier
CFUUIDRef newUniqueID = CFUUIDCreate(kCFAllocatorDefault);
// Create a string from unique identifier
CFStringRef newUniqueIDString = CFUUIDCreateString(kCFAllocatorDefault, newUniqueID);
// Use that unique ID to set our player imageKey
[player setImageKey:(NSString *)newUniqueIDString];
// we used Create in the functions to make objects, we need to release them
CFRelease(newUniqueIDString);
CFRelease(newUniqueID);
//Scale the images down a bit
UIImage *smallImage = [self scaleImage:image toSize:CGSizeMake(160.0,240.0)];
// Store image in the imageStore with this key
[[BPImageStore defaultImageStore] setImage:smallImage
forKey:[player imageKey]];
// Put that image onto the screen in our image view
[playerView setImage:smallImage];
[player setThumbnailDataFromImage:smallImage];
}
Here is an example of going back to get the original image from the imageStore:
// Go get image
NSString *imageKey = [player imageKey];
if (imageKey) {
// Get image for image key from image store
UIImage *imageToDisplay = [[BPImageStore defaultImageStore] imageForKey:imageKey];
[playerView setImage:imageToDisplay];
} else {
[playerView setImage:nil];
}
Finally, here is how I create a thumbnail from the original image:
- (void)setThumbnailDataFromImage:(UIImage *)image {
CGSize origImageSize = [image size];
CGRect newRect;
newRect.origin = CGPointZero;
newRect.size = [[self class] thumbnailSize]; // just give a size you want here instead
// How do we scale the image
float ratio = MAX(newRect.size.width/origImageSize.width, newRect.size.height/origImageSize.height);
// Create a bitmap image context
UIGraphicsBeginImageContext(newRect.size);
// Round the corners
UIBezierPath *path = [UIBezierPath bezierPathWithRoundedRect:newRect cornerRadius:5.0];
[path addClip];
// Into what rectangle shall I composite the image
CGRect projectRect;
projectRect.size.width = ratio * origImageSize.width;
projectRect.size.height = ratio *origImageSize.height;
projectRect.origin.x = (newRect.size.width - projectRect.size.width) / 2.0;
projectRect.origin.y = (newRect.size.height - projectRect.size.height) / 2.0;
// Draw the image on it
[image drawInRect:projectRect];
// Get the image from the image context, retain it as our thumbnail
UIImage *small = UIGraphicsGetImageFromCurrentImageContext();
[self setThumbnail:small];
// Get the image as a PNG data
NSData *data = UIImagePNGRepresentation(small);
[self setThumbnailData:data];
// Cleanup image context resources
UIGraphicsEndImageContext();
}
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
I am writing an app which would tile the images 256 * 256 and write those tile files back in the directory. I am updating my URL each time if there are any updates and tile those images back and store in the iphone folder. I am worried about two main things :
1) Memory consumption -- will the memory consumption for 5 images of size 200 KB a lot ?
2) How fast I can process my app if I have to tile 5 different URL with images at the same time ?
I have written a code to tile and save in the directory for one URL and would like to do the same for 5 URLs. Is it recommended to go with this approach or if anyone has a different approach?
- (void)viewDidLoad
{
[super viewDidLoad];
NSString *URLString = #"http://www.abc.com/abc.html?event=123";
NSURL *url = [[NSURL alloc] initWithString:URLString];
NSData * dataImage = [NSData dataWithContentsOfURL:url];
NSString *directoryPath = [[NSBundle mainBundle] bundlePath];
UIImage *big = [UIImage imageWithData:dataImage];
[self saveTilesOfSize:(CGSize){256,256} forImage:big toDirectory:directoryPath usingPrefix:#"image_124_"];
TileView *tv = [[TileView alloc] initWithFrame:(CGRect){{0,0}, (CGSize){5000,5000}}];
[tv setTileTag:#"image_110_"];
[tv setTileDirectory:directoryPath];
[scrollView addSubview:tv];
[scrollView setContentSize:(CGSize){5000,5000}];
}
- (void)saveTilesOfSize:(CGSize)size
forImage:(UIImage*)image
toDirectory:(NSString*)directoryPath
usingPrefix:(NSString*)prefix
{
CGFloat cols = [image size].width / size.width;
CGFloat rows = [image size].height / size.height;
int fullColumns = floorf(cols);
int fullRows = floorf(rows);
CGFloat remainderWidth = [image size].width -
(fullColumns * size.width);
CGFloat remainderHeight = [image size].height -
(fullRows * size.height);
if (cols > fullColumns) fullColumns++;
if (rows > fullRows) fullRows++;
CGImageRef fullImage = [image CGImage];
for (int y = 0; y < fullRows; ++y) {
for (int x = 0; x < fullColumns; ++x) {
CGSize tileSize = size;
if (x + 1 == fullColumns && remainderWidth > 0) {
// Last column
tileSize.width = remainderWidth;
}
if (y + 1 == fullRows && remainderHeight > 0) {
// Last row
tileSize.height = remainderHeight;
}
CGImageRef tileImage = CGImageCreateWithImageInRect(fullImage,
(CGRect){{x*size.width, y*size.height},
tileSize});
NSData *imageData = UIImagePNGRepresentation([UIImage imageWithCGImage:tileImage]);
NSString *path = [NSString stringWithFormat:#"%#/%d.png",
directoryPath, prefix];
[imageData writeToFile:path atomically:NO];
}
}
}
I have implemented solution for the similar problem(the difference is, I was not saving them in directory, those were for display purpose only.), with different approach.
In my problem, I have 84 images of 250x250 dimension with size 8KB each( I added them on scrollView and on scrolling I load them, a bit similar to google maps, but more smooth). At first I was using the same approach as yours, but performance was problem. So, I used asynchornous loading concept. I wrote an UIImageView subclass with connectiond delegates, so the UIImageView subclass was responsible for loading it's image. And as loading is asynchronous so performance is far better.
As you asked
1) Memory consumption -- will the memory consumption for 5 images of size 200 KB a lot?
Ans : 5x200KB = 1MB ~ 1.2MB or so(so you will need that much memory for displaying, if you have that much amount of memory then you should not worry.).. in my case 84x8KB = 672 ~ 900KB(as I was using some additional things like activity indicator for each imageview).
2) How fast I can process my app if I have to tile 5 different URL with images at the same time ?
Ans : As you are loading it in viewDidLoad ... or in main thread then performance will be an issue(blocking may happen, as I am not completely sure whether you are using threads or not).
Quick suggestion:
1. write an UIImageView subclass which has connection delegate methods.
2. have some method that you can call from outside to message this imageView to start loading.(give the url)
3. do proper deallocation of resources like responseData and connection object, once the downloading is complete.
4. when you move from this view to other view do proper deallocation and removal of all these imageviews.
5. use intruments to look for the allocations by this.
CODE :
TileImageView.h
#interface TileImageView : UIImageView
{
NSURLConnection *serverConnection;
BOOL isImageRequested;
NSMutableData *responseData;
}
-(void) startImageDownloading:(NSString *)pRequestURL
-(void) deallocateResources;
-(BOOL) isImageRequested;
-(void)cancelConnectionRequest;
-(void) addActivityIndicator;
-(void) removeActivityIndicator;
#end
TileImageView.m
#implementation TileImageView
- (id)initWithFrame:(CGRect)frame {
self = [super initWithFrame:frame];
if (self)
{
// Initialization code.
isImageRequested = NO;
}
return self;
}
-(BOOL) isImageRequested
{
return isImageRequested;
}
-(void) startImageDownloading:(NSString *)pRequestURL
{
if (!isImageRequested)
{
NSURL *pServerURL = [[NSURL alloc] initWithString:pRequestURL];
if (pServerURL != nil)
{
isImageRequested = YES;
[self addActivityIndicator];
[self setBackgroundColor:[UIColor lightGrayColor]];
NSURLRequest *pServerRequest = [[NSURLRequest alloc]initWithURL:pServerURL];
serverConnection = [[NSURLConnection alloc] initWithRequest:pServerRequest delegate:self];
if(serverConnection)
{
responseData = [[NSMutableData alloc] init];
}
[pServerURL release];
[pServerRequest release];
}
}
}
-(void) addActivityIndicator
{
UIActivityIndicatorView *tempActivityIndicator = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleWhite];
CGFloat size = self.frame.size.width*0.12;
[tempActivityIndicator setFrame:CGRectMake(0, 0, size, size)];
[tempActivityIndicator setCenter:CGPointMake(self.frame.size.width/2, self.frame.size.height/2)];
[tempActivityIndicator setTag:1000];
[tempActivityIndicator setHidesWhenStopped:YES];
[tempActivityIndicator startAnimating];
[self addSubview:tempActivityIndicator];
[tempActivityIndicator release];
}
-(void) removeActivityIndicator
{
UIActivityIndicatorView *tempActivityIndicator = (UIActivityIndicatorView *)[self viewWithTag:1000];
if (tempActivityIndicator != nil)
{
[tempActivityIndicator stopAnimating];
[tempActivityIndicator removeFromSuperview];
}
}
-(void)cancelConnectionRequest
{
if (isImageRequested && serverConnection != nil)
{
[serverConnection cancel];
[self removeActivityIndicator];
[self deallocateResources];
isImageRequested = NO;
}
}
// Name : connection: didReceiveAuthenticationChallenge:
// Description : NSURLConnectionDelegate method. Method that gets called when server sends an authentication challenge.
- (void)connection:(NSURLConnection *)connection didReceiveAuthenticationChallenge:(NSURLAuthenticationChallenge *)challenge
{
if ([challenge.protectionSpace.authenticationMethod isEqualToString:NSURLAuthenticationMethodServerTrust])
{
[challenge.sender useCredential:[NSURLCredential credentialForTrust:challenge.protectionSpace.serverTrust] forAuthenticationChallenge:challenge];
}
[challenge.sender continueWithoutCredentialForAuthenticationChallenge:challenge];
}
// Name : connection: didReceiveResponse:
// Description : NSURLConnectionDelegate method. Method that gets called when response for the launched URL is received..
-(void) connection:(NSURLConnection *) connection didReceiveResponse:(NSURLResponse *) response
{
[responseData setLength:0];
}
// Name : connection: didReceiveData:
// Description : NSURLConnectionDelegate method. Method that gets called when data for the launched URL is received..
-(void) connection:(NSURLConnection *) connection didReceiveData:(NSData *) data
{
[responseData appendData:data];
}
// Name : connection: didFailWithError:
// Description : NSURLConnectionDelegate method. Method that gets called when an error for the launched URL is received..
-(void) connection:(NSURLConnection *) connection didFailWithError:(NSError *) error
{
NSLog(#"Error occured while loading image : %#",error);
[self removeActivityIndicator];
[self deallocateResources];
UILabel *tempLabel = [[UILabel alloc] initWithFrame:CGRectMake(0, 0, 150, 30)];
[tempLabel setBackgroundColor:[UIColor clearColor]];
[tempLabel setFont:[UIFont systemFontOfSize:11.0f]];
[tempLabel setCenter:CGPointMake(self.frame.size.width/2, self.frame.size.height/2)];
[tempLabel setText:#"Image not available."];
[self addSubview:tempLabel];
[tempLabel release];
}
// Name : connectionDidFinishLoading
// Description : NSURLConnectionDelegate method. Method that gets called when connection loading gets finished.
-(void) connectionDidFinishLoading:(NSURLConnection *) connection
{
[self removeActivityIndicator];
UIImage *tempImage = [[UIImage alloc] initWithData:responseData];
self.image = tempImage;
[tempImage release];
[self deallocateResources];
}
-(void) deallocateResources
{
if (serverConnection != nil)
{
[serverConnection release];
serverConnection = nil;
}
if (responseData != nil)
{
[responseData release];
responseData = nil;
}
}
- (void)dealloc {
[super dealloc];
}
#end
So, If you use above code then only thing you have to do is to add the object of TileImageView and just call method -(void) startImageDownloading:(NSString *)pRequestURL.
Please use instruments to track allocations.
Update :
**How do I add TileImageView on scrollView ? :**
//like this I add 84 images in a 2D shape( 12 x 7) grid ... and once Images are added I set scrollView's contentSize as per complete grid size.
TileImageView *tileImageView = [[TileImageView alloc]initWithFrame:<myFrameAsPerMyNeeds>];
[tileImageView setTag:<this is the identifier I use for recognizing the image>];
[myImageScrollView addSubView:tileImageView];
[tileImageView release];
..later in code when user scroll's and other imageviews come in visibility.I use following code...
TileImageView *loadableImageView = (TileImageView *)[myImageScrollView viewWithTag:];
[loadableImageView startImageDownloading:];
I do not need to do anything in drawRect: , as I have no need to do custome drawing.
For Image names you can use tag property from imageView, but if you need some different name that are more like string then you can put another property in imageView for image name and set it while adding the image view. for saving data you can call your method once the image is downloaded in didFinishLoading method of TileImageView, where you can use that name.
SECODN UPDATE
How I add TileImageView on ScrollView
gridCount = 0;
rows = 7;
columns = 12;
totalGrids = rows*columns;
//*above : all are NSInteger type variable declared at class level
chunkWidth = 250;
chunkHeight = 250;
contentWidth = 0.0;
contentHeight = 0.0;
//*above : all are CGFloat type variable declared at class level
for (int i=0; i<rows; i++)
{
contentWidth = 0.0;
for (int j=0 ; j<columns; j++)
{
gridCount++;
CGRect frame = CGRectMake(contentWidth, contentHeight, chunkWidth, chunkHeight);
[self addNewImageViewWithTag:gridCount frame:frame];
contentWidth += chunkWidth;
}
contentHeight += chunkHeight;
}
[imageScrollView setContentSize:CGSizeMake(contentWidth, contentHeight)];
[imageScrollView setContentOffset:CGPointMake(0, 0)];
[imageScrollView setUserInteractionEnabled:YES];
And in ScrollViewDelegate method.
- (void) scrollViewDidScroll:(UIScrollView *)scrollView
{
if (isZoomed)
{
xOffset = scrollView.contentOffset.x;
yOffset = scrollView.contentOffset.y;
//*above : both are CGFloat type variable declared at class level
visibleColumn = xOffset/chunkWidth+1;
visibleRow = yOffset/chunkHeight+1;
gridNumber = (visibleRow-1)*columns+visibleColumn;
adjGrid1 = gridNumber+1;
adjGrid2 = gridNumber+columns;
adjGrid3 = adjGrid2+1;
//*above : all are NSInteger type variable declared at class level
if (gridNumber ==1)
{
[self createAndSendScrollRequest:gridNumber];
}
if (adjGrid1 > 0 && adjGrid1 <= totalGrids)
{
[self createAndSendScrollRequest:adjGrid1];
}
if (adjGrid2 > 0 && adjGrid2 <= totalGrids)
{
[self createAndSendScrollRequest:adjGrid2];
}
if (adjGrid3 > 0 && adjGrid3 <= totalGrids)
{
[self createAndSendScrollRequest:adjGrid3];
}
}
}
And this is how createAndSendScrollRequest is implemented.
- (void) createAndSendScrollRequest:(NSInteger)chunkId
{
TileImageView *loadingImageView = (TileImageView *)[imageScrollView viewWithTag:chunkId];
if ([loadingImageView image]==nil)
{
[loadingImageView startImageDownloading:<and here I pass url my url is based on tag so In reality I dont pass anything I just use it from the imageview's tag property>];
}
}
Thanks,