I have a NSArray (actually is a mutable array) with a UIWebView object in each index. I use this array to populate cell in a UITableView. I use a for loop to initialize each object in the array as following:
for (int i = 0; i < [self.events count]; i++) {
[self.uiWebViewArray addObject:[[UIWebView alloc] init]];
[[self.uiWebViewArray objectAtIndex:i] setUserInteractionEnabled:NO];
[[self.uiWebViewArray objectAtIndex:i] loadHTMLString:HTMLContent baseURL:nil];
}
At this point I am not populating the UITableViewCells yet.
Although it works, I think that it a terrible approach. Performance goes down when I increase the number of cell. At some point, it is possible to the user note the latency.
I also tried to populate each cell directly with a UIWebView but it is basically the same thing.
Does anyone have a suggestion to solve the problem of populate UITableViewCell with UIWebView objects in a efficient way?
A really appreciate any help.
The problem is not the array, is the webview that is really slow and memory hugry.
If you want to display HTML text with basic CSS and you are deploying >= iOS7, you should use NSAttributeString and that method:
NSDictionary *importParams = #{ NSDocumentTypeDocumentAttribute: NSHTMLTextDocumentType,NSCharacterEncodingDocumentAttribute: #(NSUTF8StringEncoding) };
NSError *error = nil;
NSData *stringData = [HTML dataUsingEncoding:NSUTF8StringEncoding] ;
NSAttributedString *attributedString = [[NSAttributedString alloc] initWithData:stringData options:importParams documentAttributes:NULL error:&error];
Or you can use third party libraries DTCoreText is one of them.
I think using a custom cell with a Web View inside it will be the better. Although whole concept of Web View inside a table view is weird.
Inside cellForRowAtIndexPath you would need to do something like:
[cell.webView loadHTMLString:HTMLContent baseURL:nil];
The main advantage of Table View is that the number of actual UITableViewCell instances created in memory are far less than total number of logical cells/rows. Actually, in usual cases Table View only creates cells needed to fill the frame, plus few extra.
So using custom table view cell with Web View inside is way better approach memory wise, but as I said whole idea is a bit weird.
Related
I'm developing an Emoji keyboard. This is my approach:
I decided to use UICollectionView. I do everything in code and don't intend to use Xib files.
I create a subclass of UICollectionViewCell. This is going to contain a single label showing the Emoji. This is what I do inside its initWithFrame
- (instancetype)initWithFrame:(CGRect)frame {
self = [super initWithFrame:frame];
if (self) {
if (_label == nil) {
_label = [[UILabel alloc] initWithFrame:CGRectMake(0, 0, frame.size.width, frame.size.height)];
_label.autoresizingMask = (UIViewAutoresizingFlexibleWidth |
UIViewAutoresizingFlexibleHeight);
_label.textAlignment = NSTextAlignmentCenter;
[_label setNumberOfLines:1];
self.contentView.layer.cornerRadius = 6.0;
[self.contentView addSubview:_label];
}
}
return self;
}
In UICollectionView dataSource object, I read a plist file containing an NSDictionary with NSString as keys and NSArrays as values. Inside each NSArray, one can find the emojis I'm going to show. I then store the dictionary in a property. Here is the code:
#property (nonatomic, strong) NSDictionary *emojis;
- (NSDictionary *)emojis {
if (!_emojis) {
NSString *plistPath = [[NSBundle mainBundle] pathForResource:#"EmojisList"
ofType:#"plist"];
_emojis = [NSDictionary dictionaryWithContentsOfFile:plistPath];
}
return _emojis;
}
In the following method, I try to populate the cells:
- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath {
NSString *cellIdentifier = #"Cell";
EmojiCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:cellIdentifier forIndexPath:indexPath];
cell.label.font = [UIFont systemFontOfSize:self.isiPad ? 47 : 33];
NSArray *dataArray = [self.emojis objectForKey:self.categoryNames[indexPath.section]];
cell.label.text = dataArray[indexPath.row];
return cell;
}
The problem I have, is that the memory usage increases when I scroll. This leads to crash on real device.
Please help me. I tested many different ways to solve this but I had no success.
This is a screenshot of instruments. I really don't know what those are about.
Font size do the tricks.
"Apple Color Emoji" font replaces emoji characters to different size of PNG images based on font size. Bigger images soon use up 40MB memory limit.
In my case, I tried font size of 16 and use 1.5 scale transform to make it bigger enough. The result doesn't look good but at least it works...
I'm not sure how much memory is really allocated, but it really shouldn't crash because of the collection view. However, do realize that the keyboard, especially running on the iPhone 6+, is restricted to a rather small memory footprint. Having lots of cells shown with many subviews could therefore lead to memory issues like that.
However, I'm assuming that this is due to a retain cycle. Two classes are most likely capture each other strongly. This can happen in any kind of block or two strong properties referring to each other.
When you can't track down the point where this is happing it's probably the easiest way to just narrow down the code it can possibly be caused by.
Do so by for example not loading the emoji from the plist to check whether that code is affecting it.
I hope this helps, it's basically impossible to tell without looking through your whole project.
Are you reading the plist from disk every time you load a cell? If so you are probably reading the plist into memory every time a cell is loaded and it isn't getting released again. Try disabling the code which reads the plist (put some test strings in the array for now) and see if that helps. If so, that's the problem.
I have really same issue,
Well, still issue is remaining but....
What I found is that when I use transform rather then UIFont.size, it reduces the memory usage quite a bit.
You might want to offload the UIViewCells and contents out of the memory as you scroll and these cells are off the screen. UICollectionView should be doing that but I would double check.
try set the label's opaque YES
My app pulls HTML from an API, converts it into a NSAttributedString (in order to allow for tappable links) and writes it to a row in an AutoLayout table. Trouble is, any time I invoke this type of cell, the height is miscalculated and the content is cut off. I have tried different implementations of row height calculations, none of which work correctly.
How can I accurately, and dynamically, calculate the height of one of these rows, while still maintaining the ability to tap HTML links?
Example of undesired behavior
My code is below.
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
switch(indexPath.section) {
...
case kContent:
{
FlexibleTextViewTableViewCell* cell = (FlexibleTextViewTableViewCell*)[TableFactory getCellForIdentifier:#"content" cellClass:FlexibleTextViewTableViewCell.class forTable:tableView withStyle:UITableViewCellStyleDefault];
[self configureContentCellForIndexPath:cell atIndexPath:indexPath];
[cell.contentView setNeedsLayout];
[cell.contentView layoutIfNeeded];
cell.selectionStyle = UITableViewCellSelectionStyleNone;
cell.desc.font = [UIFont fontWithName:[StringFactory defaultFontType] size:14.0f];
return cell;
}
...
default:
return nil;
}
}
- (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath {
UIFont *contentFont = [UIFont fontWithName:[StringFactory defaultFontType] size:14.0f];
switch(indexPath.section) {
...
case kContent:
return [self textViewHeightForAttributedText:[self convertHTMLtoAttributedString:myHTMLString] andFont:contentFont andWidth:self.tappableCell.width];
break;
...
default:
return 0.0f;
}
}
-(NSAttributedString*) convertHTMLtoAttributedString: (NSString *) html {
return [[NSAttributedString alloc] initWithData:[html dataUsingEncoding:NSUTF8StringEncoding]
options:#{NSDocumentTypeDocumentAttribute: NSHTMLTextDocumentType,
NSCharacterEncodingDocumentAttribute: #(NSUTF8StringEncoding)}
documentAttributes:nil
error:nil];
}
- (CGFloat)textViewHeightForAttributedText:(NSAttributedString*)text andFont:(UIFont *)font andWidth:(CGFloat)width {
NSMutableAttributedString *mutableText = [[NSMutableAttributedString alloc] initWithAttributedString:text];
[mutableText addAttribute:NSFontAttributeName value:font range:NSMakeRange(0, text.length)];
UITextView *calculationView = [[UITextView alloc] init];
[calculationView setAttributedText:mutableText];
CGSize size = [self text:mutableText.string sizeWithFont:font constrainedToSize:CGSizeMake(width,FLT_MAX)];
CGSize sizeThatFits = [calculationView sizeThatFits:CGSizeMake(width, FLT_MAX)];
return sizeThatFits.height;
}
In the app I'm working on, the app pulls terrible HTML strings from a lousy API written by other people and converts HTML strings to NSAttributedString objects. I have no choice but to use this lousy API. Very sad. Anyone who has to parse terrible HTML string knows my pain. I use Text Kit. Here is how:
parse html string to get DOM object. I use libxml with a light wrapper, hpple. This combination is super fast and easy to use. Strongly recommended.
traverse the DOM object recursively to construct NSAttributedString object, use custom attribute to mark links, use NSTextAttachment to mark images. I call it rich text.
create or reuse primary Text Kit objects. i.e. NSLayoutManager, NSTextStorage, NSTextContainer. Hook them up after allocation.
layout process
Pass the rich text constructed in step 2 to the NSTextStorage object in step 3. with [NSTextStorage setAttributedString:]
use method [NSLayoutManager ensureLayoutForTextContainer:] to force layout to happen
calculate the frame needed to draw the rich text with method [NSLayoutManager usedRectForTextContainer:]. Add padding or margin if needed.
rendering process
return the height calculated in step 5 in [tableView: heightForRowAtIndexPath:]
draw the rich text in step 2 with [NSLayoutManager drawGlyphsForGlyphRange:atPoint:]. I use off-screen drawing technique here so the result is an UIImage object.
use an UIImageView to render the final result image. Or pass the result image object to the contents property of layer property of contentView property of UITableViewCell object in [tableView:cellForRowAtIndexPath:].
event handling
capture touch event. I use a tap gesture recognizer attached with the table view.
get the location of touch event. Use this location to check if user tapped a link or an image with [NSLayoutManager glyphIndexForPoint:inTextContainer:fractionOfDistanceThroughGlyph] and [NSAttributedString attribute:atIndex:effectiveRange:].
Event handling code snippet:
CGPoint location = [tap locationInView:self.tableView];
// tap is a tap gesture recognizer
NSIndexPath *indexPath = [self.tableView indexPathForRowAtPoint:location];
if (!indexPath) {
return;
}
CustomDataModel *post = [self getPostWithIndexPath:indexPath];
// CustomDataModel is a subclass of NSObject class.
UITableViewCell *cell = [self.tableView cellForRowAtIndexPath:indexPath];
location = [tap locationInView:cell.contentView];
// the rich text is drawn into a bitmap context and rendered with
// cell.contentView.layer.contents
// The `Text Kit` objects can be accessed with the model object.
NSUInteger index = [post.layoutManager
glyphIndexForPoint:location
inTextContainer:post.textContainer
fractionOfDistanceThroughGlyph:NULL];
CustomLinkAttribute *link = [post.content.richText
attribute:CustomLinkAttributeName
atIndex:index
effectiveRange:NULL];
// CustomLinkAttributeName is a string constant defined in other file
// CustomLinkAttribute is a subclass of NSObject class. The instance of
// this class contains information of a link
if (link) {
// handle tap on link
}
// same technique can be used to handle tap on image
This approach is much faster and more customizable than [NSAttributedString initWithData:options:documentAttributes:error:] when rendering same html string. Even without profiling I can tell the Text Kit approach is faster. It's very fast and satisfying even though I have to parse html and construct attributed string myself. The NSDocumentTypeDocumentAttribute approach is too slow thus is not acceptable. With Text Kit, I can also create complex layout like text block with variable indentation, border, any-depth nested text block, etc. But it does need to write more code to construct NSAttributedString and to control layout process. I don't know how to calculate the bounding rect of an attributed string created with NSDocumentTypeDocumentAttribute. I believe attributed strings created with NSDocumentTypeDocumentAttribute are handled by Web Kit instead of Text Kit. Thus is not meant for variable height table view cells.
EDIT:
If you must use NSDocumentTypeDocumentAttribute, I think you have to figure out how the layout process happens. Maybe you can set some breakpoints to see what object is responsible for layout process. Then maybe you can query that object or use another approach to simulate the layout process to get the layout information. Some people use an ad-hoc cell or a UITextView object to calculate height which I think is not a good solution. Because in this way, the app has to layout the same chunk of text at least twice. Whether you know or not, somewhere in your app, some object has to layout the text just so you can get information of layout like bounding rect. Since you mentioned NSAttributedString class, the best solution is Text Kit after iOS 7. Or Core Text if your app is targeted on earlier iOS version.
I strongly recommend Text Kit because in this way, for every html string pulled from API, the layout process only happens once and layout information like bounding rect and positions of every glyph are cached by NSLayoutManager object. As long as the Text Kit objects are kept, you can always reuse them. This is extremely efficient when using table view to render arbitrary length text because text are laid out only once and drawn every time a cell is needed to display. I also recommend use Text Kit without UITextView as the official apple docs suggested. Because one must cache every UITextView if he wants to reuse the Text Kit objects attached with that UITextView. Attach Text Kit objects to model objects like I do and only update NSTextStorage and force NSLayoutManager to layout when a new html string is pulled from API. If the number of rows of table view is fixed, one can also use a fixed list of placeholder model objects to avoid repeat allocation and configuration. And because drawRect: causes Core Animation to create useless backing bitmap which must be avoided, do not use UIView and drawRect:. Either use CALayer drawing technique or draw text into a bitmap context. I use the latter approach because that can be done in a background thread with GCD, thus the main thread is free to respond to user's operation. The result in my app is really satisfying, it's fast, the typesetting is nice, the scrolling of table view is very smooth (60 fps) since all the drawing process are done in background threads with GCD. Every app needs to draw some text with table view should use Text Kit.
You need to update intrinsic content size.
I assume that you set attributed text to label in this code [self configureContentCellForIndexPath:cell atIndexPath:indexPath];
So, it should look like this
cell.youLabel.attributedText = NSAttributedString(...)
cell.youLabel.invalidateIntrinsicContentSize()
cell.youLabel.layoutIfNeeded()
You height calculation code (CGFloat)textViewHeightForAttributedText:(NSAttributedString*)text andFont:(UIFont *)font andWidth:(CGFloat)width should be replaced with cell height calculation using prototyping cell.
I'm assuming you are using a UILabel to display the string?
If you are, I have had countless issues with multiline labels with autoLayout. I provided an answer here
Table View Cell AutoLayout in iOS8
which also references another answer of mine that has a breakdown of how i've solved all my issues. Similar issues have cropped up again in iOS 8 that require a similar fix in a different area.
All comes down to the idea of setting the UILabel's preferredMaxLayoutWidth every time is bounds change. What also helped is setting the cells width to be the width of the tableview before running:
CGSize size = [cell.contentView systemLayoutSizeFittingSize:UILayoutFittingCompressedSize];
I ran into a very similar issue on another project where fields using NSAttributedString weren't rendering with the correct height. Unfortunately, there are two bugs with it that made us completely drop using it in our project.
The first is a bug that you've noticed here, where some HTML will cause an incorrect size calculation. This is usually from the space between the p tags. Injecting CSS sort of solved the issue, but we had no control over the incoming format. This behaves differently between iOS7 and iOS8 where it's wrong on one and right on the other.
The second (and more serious) bug is that NSAttributedString is absurdly slow in iOS 8. I outlined it here: NSAttributedString performance is worse under iOS 8
Rather than making a bunch of hacks to have everything perform as we wanted, the suggestion of using https://github.com/Cocoanetics/DTCoreText worked out really well for the project.
If you can target iOS 8 using dynamic cell sizing is the ideal solution to your problem.
To use dynamic cell sizing, delete heightForRowAtIndexPath: and set self.tableView.rowHeight to UITableViewAutomaticDimension.
Here is a video with more details:
https://developer.apple.com/videos/wwdc/2014/?include=226#226
You can replace this method to calculate the height of attributed string:
- (CGFloat)textViewHeightForAttributedText:(NSAttributedString*)text andFont:(UIFont *)font andWidth:(CGFloat)width {
CGFloat result = font.pointSize + 4;
if (text)
result = (ceilf(CGRectGetHeight([text boundingRectWithSize:CGSizeMake(width, CGFLOAT_MAX) options:NSStringDrawingUsesLineFragmentOrigin | NSStringDrawingUsesFontLeading context:nil])) + 1);
return result;
}
Maybe the font you changed doesnt matches with the font of content on html pages. So, use this method to create attributed string with appropriate font:
// HTML -> NSAttributedString
-(NSAttributedString*) convertHTMLtoAttributedString: (NSString *) html {
NSError *error;
NSDictionary *options = #{NSDocumentTypeDocumentAttribute: NSHTMLTextDocumentType};
NSAttributedString *attrString = [[NSAttributedString alloc] initWithData:[html dataUsingEncoding:NSUTF8StringEncoding] options:options documentAttributes:nil error:&error];
if(!attrString) {
NSLog(#"creating attributed string from HTML failed: %#", error.debugDescription);
}
return attrString;
}
// force font thrugh & css
- (NSAttributedString *)attributedStringFromHTML:(NSString *)html withFont:(UIFont *)font {
return [self convertHTMLtoAttributedString:[NSString stringWithFormat:#"<span style=\"font-family: %#; font-size: %f\";>%#</span>", font.fontName, font.pointSize, html]];
}
and in your tableView:heightForRowAtIndexPath: replace it with this:
case kContent:
return [self textViewHeightForAttributedText:[self attributedStringFromHTML:myHTMLString withFont:contentFont] andFont:contentFont andWidth:self.tappableCell.width];
break;
You should be able to convert to an NSString to calculate the height like this.
-(CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath
{
UIFont * font = [UIFont systemFontOfSize:15.0f];
NSString *text = [getYourAttributedTextArray objectAtIndex:indexPath.row] string];
CGFloat height = [text boundingRectWithSize:CGSizeMake(self.tableView.frame.size.width, maxHeight) options:(NSStringDrawingUsesLineFragmentOrigin|NSStringDrawingUsesFontLeading) attributes:#{NSFontAttributeName: font} context:nil].size.height;
return height + additionalHeightBuffer;
}
[cell.descriptionLabel setPreferredMaxLayoutWidth:375.0];
I am trying to load a UITextView with content from instances of a NSManagedObject subclass (verses in a Bible reader app).
My UITextView is loaded by iterating through the verses in a selected chapter and appending each consecutive verse.
NSArray *selectedVerses = [[Store sharedStore] versesForBookName:selectedBook
ChapterNumber:selectedChapterNum];
displayString = #"";
for (Verse *v in selectedVerses) {
NSMutableString *addedString =
[NSMutableString stringWithFormat:#"%d %#", [v versenum], [v verse]];
displayString = [NSMutableString stringWithFormat:#"%# %#", addedString, displayString];
}
NSString *title = [NSString stringWithFormat:#"%# %#", selectedBook, selectedChapter];
[self setTitle:title];
[[self readerTextView] setNeedsDisplay];
[[self readerTextView] setText:displayString];
The above code generates the correct view, but only allows for one size of text for the entire UITextView.
I would like to have the verse number that precedes each verse to be a smaller size font than its verse, but have not found a way to make it work. I've been reading through the documentation, and it seems that this should be possible with TextKit and CoreText through the use of attributed strings, but I can't seem to get this to compile.
I do not want to load the view as a UIWebView.
Any suggestions for this are greatly appreciated.
You're looking for NSAttributedString and NSMutableAttributedString. You should read Introduction to Attributed String Programming Guide. They're generally like normal strings, but additionally contain attributes with ranges to which they apply. One more method that would be helpful to you is:
[self readerTextView].attributedText = yourAttributedString;
If you have some specific problems with attributed strings, please post your code.
I'm adding image in subviews of a scrollView, but only to a certain custom class AsyncImageView. This takes some time because there are a lot of subviews and the application has lost it's smooth scrolling.
NSArray *subviewsArray = [[NSArray alloc] initWithArray:[scrollView subviews]];
for (int j = 0; j < [subviewsArray count]; j++) {
for (AsyncImageView *checkView in [[subviewsArray objectAtIndex:j] subviews]) {
if ([checkView isKindOfClass:[AsyncImageView class]]) {
[[AsyncImageLoader sharedLoader] cancelLoadingImagesForTarget:checkView];
NSString* urlTextEscaped = [[imageInfo objectAtIndex:0] stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
NSURL *URL = [NSURL URLWithString:urlTextEscaped];
if (URL)
{
checkView.imageURL = URL;
}
else
{
NSURL *defaultURL = [NSURL URLWithString:#"http://www.domain.com/user_avatar_default.jpg"];
checkView.imageURL = defaultURL;
}
}
}
}
Is there a better way to access the view that I need and add image to it? Some other logic that I haven't think of.
This is the hierarchy of the scrollView
scrollView
|
|
MaseterView
|
|
AsyncImageView - TitleView - OtherImageView
You don't need to create a new array with the subviews of the scroll view before you iterate it. You have 2 general options:
A. Still looping, but not done by you. Only meaningful if you have a single image view or have multiple image views that you want to update individually.
Set the tag of the image view, then use [scrollView viewWithTag:...];
B. If you have multiple image views and you want to update all of them at the same time.
Hold a mutable array property and add the image views to it when you create them.
Other things to think about:
Do you need to update all the image views - are they all on display?
Can you observe the scrolling of the scroll view and only start loads for images when they're on display (and cancel incomplete loads when scrolled off display)?
You can use
UIView *v = [self.containerView viewWithTag:uniqueTagvalue];
set unique tag value for the views you need and fetch it
I have an iOS app I'm working on that grabs a bunch of photo URLs from a MySQL database with a JSON request. Once I have these photos and related information, I use it to populate the datasource for a UITableView. I want to create a grid of UIButtons, made out of photos, 4 per row. This current code works, however it is wildly slow and my phone / simulator freezes right up as I scroll through the table. Tables with only a couple rows work fine, but once I reach 10 or more rows it slows right down and near crashes. I'm new to iOS and objective-c, so I'm assuming it's an inefficiency in my code. Any suggestions? Thanks!!
- (UITableViewCell *)tableView:(UITableView *)tableView
cellForRowAtIndexPath:(NSIndexPath *)indexPath {
NSUInteger row = [indexPath row];
static NSString *CompViewCellIdentifier = #"CompViewCellIdentifier";
UITableViewCell *cell = [tableView
dequeueReusableCellWithIdentifier: CompViewCellIdentifier];
if (cell == nil) {
cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CompViewCellIdentifier] autorelease];
}
// The photo number in the photos array that we'll need to start off with.
NSUInteger photoNumber = (row * 4);
// Assemble the array of all 4 photos we'll need for this table row (for this cell).
NSMutableArray *rowPhotos = [[[NSMutableArray alloc] initWithObjects:[self.photos objectAtIndex:photoNumber], nil] retain];
NSInteger counter = 1;
while ([self.photos count] > photoNumber+counter && counter<4) {
[rowPhotos addObject:[self.photos objectAtIndex:photoNumber+counter]];
counter = counter+1;
}
NSLog(#"The rowPhotos array: %#", rowPhotos);
for (int i=0; i<[rowPhotos count]; i++) {
// Set which photo we're dealing with for this iteration by grabbing it from our rowPhotos array we assembled. Use i as the index.
NSDictionary *photoRow = [[NSDictionary alloc] initWithDictionary:[rowPhotos objectAtIndex:i]];
// Get the photo.
NSString *photoPath = [[NSString alloc] initWithFormat:#"http://localhost/photorious%#", [photoRow objectForKey:#"path"]];
NSURL *url = [NSURL URLWithString: photoPath];
[photoPath release];
UIImage *cellPhoto = [[UIImage alloc] initWithData:[NSData dataWithContentsOfURL:url]];
// Figure out the container size and placement.
int xCoordinate = ((i*70)+8*(i+1));
CGRect containerRect = CGRectMake(xCoordinate, 0, 70, 70);
// Create the Button
UIButton *cellPhotoButton = [UIButton buttonWithType:UIButtonTypeCustom];
[cellPhotoButton setFrame:containerRect];
[cellPhotoButton setBackgroundImage:cellPhoto forState:UIControlStateNormal];
[cellPhotoButton setTag:(NSInteger)[photoRow objectForKey:#"id"]];
// Add the button to the cell
[cell.contentView addSubview:cellPhotoButton];
// Add the action for the button.
[cellPhotoButton addTarget:self
action:#selector(viewPhoto:)
forControlEvents:UIControlEventTouchUpInside];
[cellPhoto release];
}
[rowPhotos release];
return cell;
}
This is slow because you do everything in tableView:cellForRowAtIndexPath:.
tableView:cellForRowAtIndexPath: Is called really ofter, especially each time a cell need to be displayed in your tableview, which includes when your are scrolling your tableView. Thus this method needs to be fast, and non-blocking (especially don't do synchronous downloads!)
Moreover your don't use the reusability of your tableview cells correctly. This drastically decrease performance as you recreate the content (subviews) for each cell each time.
When your cell is reused from a previous one (see it as being "recycled"), you must NOT redo everything, especially you must not re-add every subviews as there already are in the cell itself, as it has been reused and is not a clean new one!
Instead, when dequeueReusableCellWithIdentifier: returns a cell (= an old cell previously created but not used anymore so you can "recycle"/reuse it), you should only change what differs from cell to cell. In your example, typically you will only change the 4 images displayed, but don't recreate the UIImageView, neither add them to as a subview (as these subviews already exists) nor reaffect the target/action.
You only need to create the UIImageView, add them a target/action, set their frame and add them as a subview when your are creating a brand new cell, with alloc/initWithReuseIdentifier:/autorelease.
Moreover, you are fetching your images from the network directly in your tableView:cellForRowAtIndexPath:, and synchronously in addition (which means it blocks your application until it finished downloading the image from the net!!).
Do an asynchronous download instead, way before your tableView:cellForRowAtIndexPath: (when your app is loaded for example) and store them locally (in an NSArray, or sthg similar for example), and only fetch the local, already downloaded image in your tableView:cellForRowAtIndexPath:.
The thing you are trying to do is not the greatest idea to begin with if you are new to iOS programming. What you wanna do may seem easy, but it implies concepts like asynchronous downloads, MVC design of your app and prefetching the images from the net in your model before displaying them in your view, provide a way to update the tableview when the download is done, and the basic concepts of cell reuse in tableviews.
DO read the TableView Programming Guide before going further. It explains it in details and it really worth reading.
Also consult Apple's LazyTableImages sample code which explains how to load images in a tableview lazyly (meaning loading images asynchronously when they are needed), and the URL Loading Programming Guide which explains how to do asynchronous downloads of data.
These guides and samples are really worth reading if you want to do what you explain. There are also a lot of classes to do Grid Views on the net, one of them being my work (OHGridView), but you need to understand basics explained above and in the mentioned guides first before going further.