In mu UITable view,I am displaying images from server..For that I am using lazy loading.
I can load the images when the rows are on screen.How to increase the number of images loaded.
like- for the first time 3 table cells are visible,and the images on those cells get loaded with 2seconds delay.How can I load the images on next 3 rows at same time ?
I am using below function to load images
- (void)loadImagesForOnscreenRows
{
if ([imageArray count] > 0)
{
NSArray *visiblePaths = [tableView indexPathsForVisibleRows];
for (NSIndexPath *indexPath in visiblePaths)
{
AppRecord *appRecord = [dataArray objectAtIndex:indexPath.row];
if (!appRecord.appIcon) // avoiding the imagen download if already has an image
{
[self startIconDownload:appRecord forIndexPath:indexPath];
}
}
}
}
Your way to do things
You can do that by downloading images on background and when they do finish, you can post a NSNotification to a method to reload tableView. But while the images are being downloaded, you have to show a loading view or something to the user to tell him that images are being downloaded.
Suggestion
I don't recommend that to you, the best way is to download each of them in background independently with SDWebImage and also make a faster response of your tableView. While the image is being downloaded you show a default image (placeholder), after the image is being downloaded this function sets it where it needs to be:
SDWebImage
You just need to #import <SDWebImage/UIImageView+WebCache.h> to your project, and you can define also the placeholder when image is being downloaded with just this code:
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *CellIdentifier;
CustomCell *cell = [tableview dequeueReusableCellWithIdentifier:CellIdentifier forIndexPath:indexPath];
MyObject *object = (MyObject *)[self.list.array objectAtIndex:indexPath.row];
//Here is where you set your image URL and it's placeholder
[cell.imageView setImageWithURL:[NSURL URLWithString:#"http://www.domain.com/path/to/image.jpg"]
placeholderImage:[UIImage imageNamed:#"placeholder.png"]];
return cell;
}
It also cache downloaded images and gives you great performance.
Why are you using this code you can just change below key value and it is just work perfectly with un limited images.
kIDStr = #"id";
kNameStr = #"im:name";
kImageStr = #"im:image";
kArtistStr = #"im:artist";
kEntryStr = #"entry";
Related
I have to add image in tableview in each. I have 2 list one is for twitter and second is for facebook. I want to show each list with their image icon. here is my code to attach value in table of twitter.
for (NSDictionary *wallText in sortedarray) {
NSString *wallNameValue = [wallText objectForKey:#"message"];
if(![[NSNull null] isEqual:wallNameValue] && [wallNameValue length])
{
[tableList addObject:wallNameValue];
}
}
I want to show twitter image in left of row. How will i add image.
Thanks in advance
Just try using in this Way:
cell.imageView.image = [UIImage imagedNamed:[wallText objectForKey:#"message"]];
& plus there is no need to run any loop for this.This is optimize your code.
Just access the array via indexpath.row
NSDictionary *wallText = (NSDictionary *)[[sortedarray objectAtIndex:indexPath.row]valueForKey:message];
Hope you are going to do all these things in - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath .
In your table view's delegate, in the method that sets up your UITableViewCell's, do something like this:
cell.imageView.image = myImage;
// myImage is a UIImage *.
Every UITableViewCell comes with a UIImageView built in that displays an image for you on the left side of the cell.
Reference:
http://developer.apple.com/library/ios/#DOCUMENTATION/UIKit/Reference/UITableViewCell_Class/Reference/Reference.html
In cellForRowAtIndexPath just do
cell.imageView.image = [UIImage imageWithData:[yourImageDataArray objectAtIndex:indexPath.row]];
In my application I parsed the data through NSXMLParser and made separate class to store that data from which i usually display the data. Everything works fine in simulator except the the title which is display in table cell with image. Images appears properly but the title not appear properly.
This is my code:-
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *CellIdentifier = #"Cell";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil) {
[[NSBundle mainBundle] loadNibNamed:#"TableCell3" owner:self options:NULL];
cell = nibLoadedCell;
}
NewsInfo *aNewsInfo = [appDelegate.newsArray objectAtIndex:indexPath.row];
titleLabel.text = aNewsInfo.title;
imageLabel.image = aNewsInfo.smallImageData;
return cell;
}
and in this way i configured my TableCell3.xib
Now i want my title data in 2 rows in label of the TableCell3.
I already used both the way through xib attributes settings or through code.
Code which i used instead of this xib attributes settings are:-
titleLabel.lineBreakMode = UILineBreakModeWordWrap;
titleLabel.numberOfLines = 2;
titleLabel.text = aNewsInfo.title;
Now Can any one help me to figure out this prob i want to display my title in two rows of the table view cell.
Thanks in Advance.
Just increase the height of your label and give a try. If the height is too less to hold 2 lines, the label will truncate the contents to 1 line and end with the ellipsis.
Shouldn't you be accessing them by
cell.titleLabel.text = sometest;
cell.imageLabel.image = someImage;
and also ensure that the titleLabel and imageLabel are connected properly to the outlets. And pls check your naming for the variables. imageLabel is not a good choice if you want that to be an imageview.
I wonder if anyone can speculate or better yet provide a piece of code as for the implementation of the lengthy friends list in the Facebook iPhone app.
when you open the app and go strait to the friends list, you get the list almost in an instant, at least for me with ~500 friends.
when I try it in my own app it takes lots of precious seconds to populate the table view with the same data, so how does Facebook accomplished such a quick response time ?
upon looking at the tableview in the facebook app you notice there is no scroll bar usually found in such tableview, could that be one sign of the neat trick facebook is utilizing to achieve this rapid rows insert ? could it be they implemented some sort of a virtual tableview with only holds a few dozen rows but rotates them ?
any thoughts ?
the UITableView will let you do this. There are a number of examples on the internet with UITableView and Custom Cell's
Essentially, you load your images in the background, and you reuse the Cells that are in the tableview
EDIT Added example code to demonstrate how this is accomplished.
IMPORTANT NOTE
This code was not tested and may or may not actually function as is.
It was pasted with some editing for length. I did a lot more then this in my app, but in the interest of keeping with the example requested I omitted a lot.
On with the example:
Here is where I get the cell, load it with the items that are readily available. And send it to the background thread to load the rest.
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *CellIdentifier = #"OfferCell";
static NSString *CellNib = #"OfferItem";
OfferCell* cell = (OfferCell*)[tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil)
{
NSArray *nib = [[NSBundle mainBundle] loadNibNamed:CellNib owner:self options:nil];
cell = (OfferCell*)[nib objectAtIndex:0];
}
NSDictionary* couponPackage = [self.jsonOfferData valueForKey:#"result"];
NSArray *couponList = [couponPackage valueForKey:#"offers"];
if ([couponList count] >= indexPath.row )
{
NSDictionary* couponData = [couponList objectAtIndex:indexPath.row];
Coupon *coupon = [[Coupon alloc] initWithDictionary:couponData];
NSDictionary *params = [NSDictionary dictionaryWithObjectsAndKeys:cell,#"cell",coupon,#"coupon", nil];
//Right here you would try to load any cached imaged from disk.
//Then send a Thread to the background to load the image.
[self performSelectorInBackground:#selector(loadTableViewCellData:) withObject:params];
//Load up the rest of the custom info into the custom cell.
[cell.captionLabel setText:coupon.name];
[cell.subTextLabel setText:coupon.subText];
[cell setAccessoryType:UITableViewCellAccessoryDetailDisclosureButton];
[cell setCommand:coupon.command];
[cell setParameter:coupon.commandArgs];
[cell setImageURL:coupon.imageURL];
[cell setImageAltURL:coupon.imageAltURL];
[cell setRegistrationCode:coupon.registrationCode];
[coupon release];
}
return cell;
}
as you can see, i call a background thread before i even load the custom content in the cell.
- (void) loadTableViewCellData:(NSDictionary*) objectData
{
OfferCell *cell = [objectData objectForKey:#"cell"];
Coupon *coupon = [objectData objectForKey:#"coupon"];
UIImage *image = [UIImage imageWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:[coupon iconURL]]]];
[objectData setValue:image forKey:#"image"];
self performSelectorOnMainThread:#selector(setImageOnMainThread:) withObject:objectData
}
after downloading the image, i send a Main thread request to update the Image that is in the cell object.
- (void) setImageOnMainThread:(NSDictionary*) objectData
{
OfferCell *cell = [objectData objectForKey:#"cell"];
Coupon *coupon = [objectData objectForKey:#"coupon"];
UIImage *image = [objectData objectForKey:#"image"];
cell.icon.image = image;
}
##AGAIN This May not Actually Function. ##
I did not copy all of my code for this. this is a hammer out so you can get the idea.
play with the code and test it. but the fundamentals are.
Dequeue the cell that will fit your needs (Reuse Identifier)
Use the cell if it can be dequeue'd or create a new one with a reuse identifier (my example uses a xib file named OfferItem.xib)
Send a thread to the background that will load the image data from disk or url (a combination of both is recommended)
Send a thread back to the UI when you are ready to load the image into the View (Updating the UI must be done on the main thread)
if you can do that, then your friends list (or in this case offers) will be loaded up as fast as possible. and the Images will pop on the screen as soon as they download.
Also if you use a Caching technique it will be faster for subsequent loads because in the the first method {tableView:cellForRowAtIndexPath:} you would load up the cached image immediately.
Aside from that, this should load your cell's pretty fast.
They obviously load the data from a local resource (plist, ManagedObject, ...)
Have a look at some sample code to draw a TableView:
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *kCellIdentifier = #"MyCellIdentifier";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:kCellIdentifier];
if (cell == nil) {
cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleValue1 reuseIdentifier:kCellIdentifier] autorelease];
}
return cell;
}
The dequeueReusableCellWithIdentifier: thing is one reason why TableViews in iOS can draw quickly. It works somehow like this:
1)You provide an identifier for a cell you're creating.
2)Cells that are visible at first get alloced (with identifier)
3)When a Cell is moved off the screen it gets put on a pile MyCellIdentifier
4)Whenever the system needs to draw a cell of identifier:MyCellIdentifier it first looks whether there are any cells currently unused on the MyCellIdentifier pile. If that's the case it picks one off the pile and thus doesn't have to alloc a new one. That way expensive allocing can be kept at a minimum.
I hope this answers your question :)
I am creating an application which uses a web service.And retrieves a list of users and there details like images, user id and there names.I displayed all the information related to users in table view, Thus each of the cell in the table view has an image with the for tables in it. I am using a Custom cell class to create the individual cells. selecting any row in table presents a detail view (using navigation) which show a larger image and all the details related to the particular user i selected.
in customcell and detail view class i am using web view to display image.
But when i run the app the images gets a bit of delay to display and same happens with the detail view.
Is there any alternative so that i can improve the performance of the table view so that i can have smooth scrolling of table view with out any delay in image loading and detail view??
here is the code...
- (UITableViewCell *)tableView:(UITableView *)tableView
cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
static NSString *CustomCellIdentifier = #"CustomCellIdentifier ";
CustomCell *cell = (CustomCell *)[tableView
dequeueReusableCellWithIdentifier: CustomCellIdentifier];
if (cell == nil)
{
NSArray *nib = [[NSBundle mainBundle] loadNibNamed:#"CustomCell" owner:self options:nil ];
//cell = [[CustomCell alloc] initwi ];
for (id oneObject in nib)
if ([oneObject isKindOfClass:[CustomCell class]])
cell = (CustomCell *)oneObject;
}
NSUInteger row = [indexPath row];
NSString *imageName = [imgArray objectAtIndex:row];
NSString *completeImageUrl = [[NSString alloc] initWithFormat:#"http://122.160.153.166:201/%#", imageName];
NSURL *url = [NSURL URLWithString:completeImageUrl];
//NSURLRequest *requestObj = [NSURLRequest requestWithURL:url];
NSData *imageData = [[NSData alloc] initWithContentsOfURL:url];
UIImage *image = [UIImage imageWithData:imageData]; /// check to see if we are getting all the arrays such as image array and userId array and name array of same size..
if(image == nil)
{
}
cell.imgView.image = image; /// other wise an execption of out out array range will be shown
[image release];
[imageName release];
//[cell.webView initWithFrame:CGRectZero];
//[cell.webView loadRequest:requestObj];
//cell.webView.frame = CGRectMake(20, 0, 80.0, 64);
cell.userIdLabel.text = (NSString *)[userId objectAtIndex:row];
cell.nameLabel.text = (NSString *)[userName objectAtIndex:row];
cell.accessoryType = UITableViewCellAccessoryDisclosureIndicator;
return cell;
}`
i think problem can be in imgArray array as i am setting it from other class. Where i request the web service and fetched all the data about users .
Any help is greatly appreciated . Thanks in advance
I got the same problem. For that I used EGOImageCache and some thing.
Find this Url for EGOImage
Download files those names starts with "EGO", and add those to your project.
and write the following code where ever you want to put the image:
EGOImageView *imgView = [[EGOImageView alloc] initWithFrame:CGRectMake(50,50,220,360)];
NSString *imageName = [imgArray objectAtIndex:row];
NSString *completeImageUrl = [[NSString alloc] initWithFormat:#"http://122.160.153.166:201/%#", imageName];
NSURL *url = [NSURL URLWithString:completeImageUrl];
imgView.imageUrl = url;
[self.view addSubView:imgView];
Thats it. Use the similar code, where ever you want the image.
At the first time while loading it will take some time to download the image. But later it will cache the image and use it the next time.
Is there any alternative so that i can improve the performance of the table view so that i can have smooth scrolling of table view with out any delay in image loading
For this the answer is Lazy Loading of images in cells
You can implement lazy loading on webviewDidLoad which shows that webview has loaded completely
Using a UIWebView to display a single image is overkill. You should be using NSURLConnection (or one of many alternative HTTP wrappers/libraries) to load the image data and UIImageView to display it in each of your table cells. In my experience, there is no way (or at least no straightforward way) to eliminate the rendering delay when using UIWebView.
Why are you using the webview for displaying the images. Imageview should be used instead. If you are getting the images from the server then you should get those in separate thread and after you receive the images you should reload that particular row.
Some code snippet is like this:
- (UITableViewCell *)cellForRowAtIndexPath:(NSIndexPath *)indexPath
...
...
UIImage *img = (UIImage *)[imagesArray objectAtIndex:indexPath.row];
if(img == nil){
[imgView setImage:temporaryImage];
[NSThread detachNewThreadSelector:#selector(getTheThumnbails:) toTarget:self withObject:indexPath];
}
else
[imgView setImage:img];
for further assistance look at this
Hope this helps.
Thanks,
Madhup
okay finally i removed the uiweb view from my app and used Imaged view and succeed.
i used the link that was given by the developer of the tweetie . here it is link text
i used the ABTableViewCell class and created the whole cell using the code.
The scrolling was very jerky when i executed the app. after applying almost 4 hours and with the help of lazy loading i was able to run my app smoothly. I stored the data which is retrieved from url into an array then applied the concept in tableView:cellForRowAtIndexPath:
method..
Thanks you guys for helping me ...
Three20 has a rich-text table view cell class (TTStyledTextTableCell I think) - should render significantly faster than an embedded UIWebView. You could also roll your own, though that would take a lot longer.
I use datamodel to store 2 objects : Video, Images.
Video contain just string attributes and Images have 2 "Binary data" attributes.
At the start the 2 binary data attributes was in the video object.
But all videos are loading during initialization of UITableView.
For 400 videos binary data represent 20 Mo, so imagine with 4000 videos...
Now with 2 objects the UITableView loading work well.
I load binary data when it's necessary in the method : tableView:cellForRowAtIndexPath
But now more I scroll into the list, more the memory grow up :(
look at my method :
- (UITableViewCell *)tableView:(UITableView *)myTableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
static NSString *CellIdentifier = #"videoCell";
Video *theVideo = (Video *)[[self fetchedResultsController] objectAtIndexPath:indexPath];
VideoCellViewController *cell = (VideoCellViewController *)[myTableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil) {
[[NSBundle mainBundle] loadNibNamed:#"VideoCellView" owner:self options:nil];
cell = editingTableViewCell;
self.editingTableViewCell = nil;
}
cell.video = theVideo;
return cell;
}
And the method setvideo in VideoCellViewController
- (void)setVideo:(Video *)newVideo {
if (newVideo != video) {
[video release];
video = [newVideo retain];
}
NSData *imageData = [video.allImages valueForKey:#"thumbnailImage"];
UIImage *uiImage = [[UIImage alloc] initWithData:imageData];
smallImage.image = uiImage;
nameLabel.text = video.displayName;
[uiImage release];
}
Even without set the smallImage, I have memory trouble.
If I load the image object, it's never release.
I try a lot of solution to release memory without succes...( didTurnIntoFault, release, CFRelease...)
In performance tool, I can see my binary data as CFData.
I use a lot iPhoneCoreDataRecipes and PhotoLocations sample.
I need help to clean my memory ;)
Thanks
Samuel
Clearly there is something going on with your table cell creation logic. Let's take a look at a typical cellForRow delegate handler first..
static NSString *MyIdentifier = #"MyIdentifier";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:MyIdentifier];
if (cell == nil) {
cell = [[[UITableViewCell alloc] initWithFrame:CGRectZero reuseIdentifier:MyIdentifier] autorelease];
}
// do stuff with cell
return cell;
Here we see we are
trying to get a reusable cell
if that fails (nil) create a new one and pass the reusable id to the ctor
then do stuff with the cell (new or existing) and return it
If you do not key the cell for reuse in the table view, you will always get a 'nil' cell returned from the dequeue, hence the need to create new cells every time. This will cause memory to continue to grow as you scroll around, but stay fairly flat when idle.
EDIT:
Assuming your cell is fine, then you need to narrow down if it's the video data or the image data that is leaking. What is smallImage? And are you sure you do not want to do everything only when the video is new?
- (void)setVideo:(Video *)newVideo {
if (newVideo != video) {
[video release];
video = [newVideo retain];
NSData *imageData = [video.allImages valueForKey:#"thumbnailImage"];
UIImage *uiImage = [[UIImage alloc] initWithData:imageData];
smallImage.image = uiImage;
nameLabel.text = video.displayName;
[uiImage release];
}
}