Kindly look the below code..i found from web
- (void) loadData {
NSOperationQueue *queue = [NSOperationQueue new];
NSInvocationOperation *operation = [[NSInvocationOperation alloc] initWithTarget:self
selector:#selector(loadDataWithOperation) object:nil];
[queue addOperation:operation];
[operation release];
}
- (void) loadDataWithOperation {
NSURL *dataURL = [NSURL URLWithString:#"http://icodeblog.com/samples/nsoperation/data.plist"];
NSArray *tmp_array = [NSArray arrayWithContentsOfURL:dataURL];
for(NSString *str in tmp_array) {
[self.array addObject:str];
}
[self.tableView performSelectorOnMainThread:#selector(reloadData) withObject:nil waitUntilDone:YES];
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
static NSString *CellIdentifier = #"Cell";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (cell == nil) {
cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier] autorelease];
}
[cell.textLabel setText:[self.array objectAtIndex:indexPath.row]];
return cell;
}
I have found the above code which loads the text from the web without any problem.( i mean gui is not hanging ).like wise i want to load images into the table view.for that i have wriiten the below code.
- (void) loadDataWithOperation {
NSString *Img_id, *Img_name, *DynamicImgUrl;
Img_id = xmltag.equip_id;
Img_name = xmltag.image;
DynamicImgUrl = [NSString stringWithFormat:#"http://test.com/pics/equipment/%#/%#",Img_id, Img_name];
NSURL *ImageUrl = [NSURL URLWithString:DynamicImgUrl];
//UIImage *image = [UIImage imageWithData: [NSData dataWithContentsOfURL:ImageUrl]];
NSArray *tmp_array = [NSArray arrayWithContentsOfURL:ImageUrl];
for(NSString *str in tmp_array) {
[self.array addObject:str];
}
[self.tableView performSelectorOnMainThread:#selector(reloadData) withObject:nil waitUntilDone:YES];
}
Am i correct here? how can i go with adding into the table view...
Kindly help me out...
U are seeking to display images on Tableview from URL, when u download image from url we need to consider some issues, it will freeze ur table view if u goahead with ordinary loading image.
i suggest u look at LazyLoading image
u see this link http://developer.apple.com/library/ios/#samplecode/LazyTableImages/Introduction/Intro.html
Download this sample and get to know the things
Related
I am loading 4 cities string in the table view which is working but when I select one of the cell and navigate to the other table it navigate too slow. I am using the same code below in the the other table with different link. Could you please tell me why it takes long time (~4 - 6 Sec) to get to the other view?
- (void)viewDidLoad
{
[super viewDidLoad];
NSURL * url = [NSURL URLWithString:#"http://kalkatawi.com/jsonTest.php"];
NSData * data = [NSData dataWithContentsOfURL:url];
NSError *e = nil;
jsonArray = [NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingMutableContainers error:&e];
jsonArray1 = [[NSMutableArray alloc] init];
for(int i=0;i<[jsonArray count];i++)
{
NSString * city = [[jsonArray objectAtIndex:i] objectForKey:#"city"];
[jsonArray1 addObject:city];
}
-
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
NSString *tempString = [jsonArray1 objectAtIndex:indexPath.row];
cell.textLabel.text = tempString;
return cell;
}
-
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
SeconfViewController *second = [[SeconfViewController alloc] initWithNibName:#"SeconfViewController" bundle:nil];
UITableViewCell *selectedCell = [tableView cellForRowAtIndexPath:indexPath];
NSString *cellText = selectedCell.textLabel.text;
NSString *edit = [NSString stringWithFormat:#"http://kalkatawi.com/jsonTest.php?d=1&il=%#", cellText];
second.str2 = edit;
[self.navigationController pushViewController:second animated:YES];
}
It takes more time to navigate on the other screen because you are synchronously loading the data from the server. In iOS all the UI is done on the main thread, and by making your data call on the main thread you are blocking it. The best way I know to handle this is to use GCD (Grand Central Dispatch). It's an API in iOS that will spawn threads for you without a hassle. You just need to tell that you want to make the call to load data from the server on a background thread. When you do that, view should navigate instantaneously. You can use an Activity indicator while the data comes.
dispatch_async(dataQueue, ^{
// Load all your data here
dispatch_async(dispatch_get_main_queue(), ^{
// Update the UI
});
});
Maybe because you are downloading synchronous and you are blocking the main thread maybe that is the reason that your app freeze for 4-6 sec, try to download your json asynchronous
- (void)viewDidLoad
{
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
NSData *response = [[NSData alloc] initWithContentsOfURL:[NSURL URLWithString:#"http://kalkatawi.com/jsonTest.php"]];
NSError *parseError = nil;
jsonArray = [NSJSONSerialization JSONObjectWithData:response options:NSJSONReadingAllowFragments error:&parseError];
jsonArray1 = [[NSMutableArray alloc] init]
for(int i=0;i<[jsonArray count];i++)
{
NSString * city = [[jsonArray objectAtIndex:i] objectForKey:#"city"];
[jsonArray1 addObject:city];
}
}
dispatch_sync(dispatch_get_main_queue(), ^{
[self.myTableView reloadData];
});
});
}
I have a segment and a table view, I have to reload the data in the table view its working but when i switch the segment buttons fast then application crashes.
On segment i have three buttons and on their action I am triggering a request to a url and fetching the json from that url (3 different urls resp. and returns 10, 17 and 8 results in json).
I have a custom table cell which have the images in it and i am trying to lazily load theose images.
In JSON result each object of json have various keys in it like name, id, imageurl etc.
the id is unique throughout the application and I am trying to load the images and save the images in local memory based on that unique id, so that i can show the cashed images and no need to redownload the images on segment change because some enteries on all three segments are same.
Here is my complete code
- (IBAction)segmentedControlIndexChanged {
NSString *offerRequestUrl = nil;
switch (self.mySegment.selectedSegmentIndex) {
case 0:
offerRequestUrl = #"url_one";
self.feedRequestUrl = [NSURL URLWithString:offerRequestUrl];
break;
case 1:
offerRequestUrl = #"url_two";;
self.feedRequestUrl = [NSURL URLWithString:offerRequestUrl];
break;
case 2:
offerRequestUrl = #"url_three";;
self.feedRequestUrl = [NSURL URLWithString:offerRequestUrl];
break;
default:
break;
}
[self parseJSONWithURL:self.feedRequestUrl];
}
- (void) parseJSONWithURL:(NSURL *) jsonURL
{
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
NSData* data = [NSData dataWithContentsOfURL: jsonURL];
[self performSelectorOnMainThread:#selector(fetchedData:) withObject:data waitUntilDone:YES];
});
}
- (void)fetchedData:(NSData *)responseData {
//parse out the json data
NSError* error;
NSDictionary* json = [NSJSONSerialization JSONObjectWithData:responseData
options:kNilOptions
error:&error];
self.feedsArray = [json objectForKey:#"result"];
[self.myTableView reloadData];
}
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
int count = self.feedsArray.count;
// if there's no data yet, return enough rows to fill the screen
if (count == 0)
{
return 1;
}
return count;
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
// customize the appearance of table view cells
//
static NSString *CellIdentifier = #"MyTableCell";
static NSString *PlaceholderCellIdentifier = #"PlaceholderCell";
// add a placeholder cell while waiting on table data
int nodeCount = [self.feedsArray count];
if (nodeCount == 0 && indexPath.row == 0)
{
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:PlaceholderCellIdentifier];
if (cell == nil)
{
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle
reuseIdentifier:PlaceholderCellIdentifier];
cell.detailTextLabel.textAlignment = UITextAlignmentCenter;
cell.selectionStyle = UITableViewCellSelectionStyleNone;
}
cell.detailTextLabel.text = #"Loading . . .";
[self performSelector:#selector(checkAndDisplayAlert) withObject:self afterDelay:10.0];
return cell;
}
CustomCell *cell = (CustomCell*)[tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (nodeCount > 0)
{
// Configure the cell...
cell.carImageView.image = [UIImage imageNamed:#"Placeholder"]; //acts as default image
if([self.imageDict valueForKey:[NSString stringWithFormat:#"%#", self.feedsArray[indexPath.row][#"id_str"]]]==nil)
{
[NSThread detachNewThreadSelector:#selector(displayingSmallImage:) toTarget:self withObject:indexPath];
} else {
cell.carImageView.image = [self.imageDict valueForKey:[NSString stringWithFormat:#"%#", self.feedsArray[indexPath.row][#"id_str"]]];
}
cell.imageView.clipsToBounds = YES;
cell.titleLabel.text = self.feedsArray[indexPath.row][#"title_key"];
}
return cell;
}
- (void) displayingSmallImage:(NSIndexPath *)indexPath
{
NSString *imageUrl = self.feedsArray[indexPath.row][#"icon_url"];
NSURL *url = [NSURL URLWithString:imageUrl];
UIImage *image = [UIImage imageWithData:[NSData dataWithContentsOfURL:url]];
if(image == nil)
{
image = [UIImage imageWithContentsOfFile:[[[NSBundle mainBundle] resourcePath] stringByAppendingPathComponent:#"Placeholder"]];
}
[self.imageDict setObject:image forKey:[NSString stringWithFormat:#"%#", self.feedsArray[indexPath.row][#"id_str"]]];
[self performSelectorOnMainThread:#selector(imageReceived:) withObject:indexPath waitUntilDone:NO];
}
- (void) imageReceived:(NSIndexPath *)indexPath
{
UIImage *image = (UIImage *)[self.imageDict objectForKey: [NSString stringWithFormat:#"%#", self.feedsArray[indexPath.row][#"id_str"]]];
UIImageView *imgs = (UIImageView *)[[self.myTableView cellForRowAtIndexPath:indexPath] viewWithTag:IMG_TAG];
[imgs setImage:image];
[self.myTableView reloadRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationNone];
}
- (void) checkAndDisplayAlert
{
if (!self.feedsArray && self.isAlertPresent == NO) {
UIAlertView *nilAlert = [[UIAlertView alloc] initWithTitle:#"Sorry!"
message:#"No result returned from server."
delegate:self
cancelButtonTitle:#"OK"
otherButtonTitles:nil];
[nilAlert setTag:kNilAlertTag];
self.isAlertPresent = YES;
[nilAlert show];
}
}
The main things I have to do is
lazily download the images
cache the images in local memory based on unique ID
Check the cashed images dictionary for already downloaded image and display it
If possible save these downloaded images in the local memory (nsuserdefaults etc) so that if user restart the app then also images are there and can be displayed based on their unique ID and no need to download again.
Any help would be appreciated.
Please post the error log, if it is array out of bounds exception I suspect these two methods
- (void)fetchedData:(NSData *)responseData & your tableViewDatasource
To find which line of code causes this crash do this. Go to break points tab on the left side and click + in the bottom.
Then you would get something like this:
Just hit done, run your code again and tell us which line caused the exception.
I understood your problem, why do you want to take the URL from the array in this function
- (void) displayingSmallImage:(NSIndexPath *)indexPath
you could pass the Url to load to that function, from cellForRowAtIndex like this:
NSArray *argsToPass=[NSArray arrayWithObjects:indexPath,self.feedsArray[indexPath.row][#"icon_url"]];
[NSThread detachNewThreadSelector:#selector(displayingSmallImage:) toTarget:self withObject:argsToPass];
and your function is modified as:
- (void) displayingSmallImage:(NSArray *)args
{
if([args count] == 0)
{
NSString *imageUrl = [args objectAtIndex:1];
NSIndexPath *indexPath=[args objectAtIndex:0];
NSURL *url = [NSURL URLWithString:imageUrl];
UIImage *image = [UIImage imageWithData:[NSData dataWithContentsOfURL:url]];
if(image == nil)
{
image = [UIImage imageWithContentsOfFile:[[[NSBundle mainBundle] resourcePath] stringByAppendingPathComponent:#"Placeholder"]];
}
[self.imageDict setObject:image forKey:[NSString stringWithFormat:#"%#", self.feedsArray[indexPath.row][#"id_str"]]];
[self performSelectorOnMainThread:#selector(imageReceived:) withObject:indexPath waitUntilDone:NO];
}
}
you can set self.view.userInteractionEnabled=NO when you are sending request to server.
and when u get the data just enable the user interaction .so that multiple requests are avoided.
I am using [NSOperationQueue mainQueue] and NSInvocationOperation in table view cellforRowAtIndexPath method to load images from web in background.But it is not stopping after download image. Here is my code
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
UITableViewCell *cell=[mytable dequeueReusableCellWithIdentifier:#"cell"];
if (cell == nil)
{
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:#"cell"];
}
imageLabel=(UIImageView *)[cell viewWithTag:5];
UIImage *image=[dict objectForKey:[appSmallLogos objectAtIndex:indexPath.row]];
if (image) {
imageLabel.image=image;
} else {
NSURL *on=[appSmallLogos objectAtIndex:indexPath.row];
NSString *on1=[appNames objectAtIndex:indexPath.row];
NSMutableArray *array=[[NSMutableArray alloc] initWithObjects:on,on1,indexPath, nil];
operation = [[NSInvocationOperation alloc] initWithTarget:self selector:#selector(didGetAlbums:) object:arr];
q =[NSOperationQueue mainQueue];
[q addOperation:operation];
imageLabel.image=[dict objectForKey:on1];
}
return cell;
}
//didgetalbums method
- (void )didGetAlbums: (NSMutableArray* )url
{
dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0ul);
dispatch_async(queue, ^{
NSData *data=[NSData dataWithContentsOfURL:[url objectAtIndex:0]];
UIImage *image1 = [UIImage imageWithData:data];
dispatch_sync(dispatch_get_main_queue(), ^{
[dict setObject:image1 forKey:[url objectAtIndex:1]];
});
});
//reload the requested cell after download image
[self. mytable beginUpdates];
[self. mytable reloadRowsAtIndexPaths:[NSArray arrayWithObjects:[url objectAtIndex:2], nil] withRowAnimation:UITableViewRowAnimationNone];
[self. mytable endUpdates]; // imageLabel.image=[dict objectForKey:[appSmallLogos objectAtIndex:indexPath.row]];
}
I use:
self performSelector:#selector(loadData) withObject:nil...
it look like working with some command only in "loadData" but the rest are not.
Here is my viewdidload:
- (void)viewDidLoad
{
[super viewDidLoad];
[mActivity startAnimating];
[self performSelector:#selector(loadData) withObject:nil afterDelay:2];
//[mActivity stopAnimating];
}
and here is loadData:
-(void)loadData
{
[mActivity startAnimating];
NSLog(#"Start LoadData");
AppDelegate *delegate=(AppDelegate *)[[UIApplication sharedApplication] delegate];
NSString *selectData=[NSString stringWithFormat:#"select * from k_proverb ORDER BY RANDOM()"];
qlite3_stmt *statement;
if(sqlite3_prepare_v2(delegate.db,[selectData UTF8String], -1,&statement,nil)==SQLITE_OK){
NSMutableArray *Alldes_str = [[NSMutableArray alloc] init];
NSMutableArray *Alldes_strAnswer = [[NSMutableArray alloc] init];
while(sqlite3_step(statement)==SQLITE_ROW)
{
NSString *des_strChk= [NSString stringWithUTF8String:(char *)sqlite3_column_text(statement,3)];
if ([des_strChk isEqualToString:#"1"]){
NSString *des_str= [NSString stringWithUTF8String:(char *)sqlite3_column_text(statement,4)];
[Alldes_str addObject:des_str];
}
}
Alldes_array = Alldes_str;
Alldes_arrayAnswer = Alldes_strAnswer;
}else{
NSLog(#"ERROR '%s'",sqlite3_errmsg(delegate.db));
}
listOfItems = [[NSMutableArray alloc] init];
NSDictionary *desc = [NSDictionary dictionaryWithObject:
Alldes_array forKey:#"description"];
[listOfItems addObject:desc];
//[mActivity stopAnimating];
NSLog(#"Finish loaData");}
it give me only printing 2 line, but did not load my Data to the table, but if I copy all the code from inside "loadData" and past in "viewDidLoad", it load the data to the table.
Any advice or help please.
A few things: If you see any NSLog output at all, then the performSelector is succeeding. You should change the title of your question.
If you are trying to load data into a table, the method should end with telling the UITableView to reloadData (or a more elaborate load using begin/end updates).
If the listOfItems is the data supporting the table, get this working first by hard-coding something like this:
-(void)loadData {
listOfItems = [NSArray arrayWithObjects:#"test1", #"test2", nil];
[self.tableView reloadData];
return;
// keep all of the code you wrote here. it won't run until you remove the return
}
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
static NSString *CellIdentifier = #"Cell";
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
if (!cell) {
cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier];
}
NSString *string = [listOfItems objectAtIndex:indexPath.row];
cell.textLabel.text = string;
return cell;
// keep all of the code you probably wrote for this method here.
// as above, get this simple thing running first, then move forward
}
Good luck!
I am using a navigation base application. When I go to next view or back to the previous view, the thread does not stop. Can someone give me a solution for stopping the thread when switching between views? When I switch to next or previous, the application crashes. I use thread like this for downloading the image
- (void)viewWillAppear:(BOOL)animated {
AppDeleget= [[UIApplication sharedApplication] delegate];
ProcessView *Process=[[ProcessView alloc] init];
[Process SearchProperty:AppDeleget.PropertyURL page:AppDeleget.Page];
[Process release];
for(NSDictionary *status in AppDeleget.statuses)
{
NSMutableString *pic_string = [[NSMutableString alloc] initWithFormat:#"%#",[status objectForKey:#"picture"]];
if([pic_string isEqualToString:#""])
{
[ListPhotos addObject:#"NA"];
}
else
{
NSString *str= [[[status objectForKey:#"picture"] valueForKey:#"url"] objectAtIndex:0];
[ListPhotos addObject:str];
}
}
[NSThread detachNewThreadSelector:#selector(LoadImage) toTarget:self withObject:nil];
[AppDeleget.MyProgressView stopAnimating];
[AppDeleget.Progress removeFromSuperview];
[super viewWillAppear:animated];
}
-(void)LoadImage
{
for(int x=0;x<[ListPhotos count];x++)
{
NSData *imageData =[ListPhotos objectAtIndex:x];
id path = imageData;
NSURL *url = [NSURL URLWithString:path];
NSLog(#"%#",url);
NSData *data = [NSData dataWithContentsOfURL:url];
UIImage *img = [[UIImage alloc] initWithData:data];
[self performSelectorOnMainThread:#selector(downloadDone:) withObject:img waitUntilDone:NO];
}
}
-(void)downloadDone:(UIImage*)img {
NSIndexPath *indexPath = [NSIndexPath indexPathForRow:count inSection:0];
if(img == nil)
{
TableCell *cell = (TableCell *)[TableView cellForRowAtIndexPath:indexPath];
cell.myImageView.image=[UIImage imageNamed:#"No_image.png"];
++count;
[TableView reloadData];
}
else
{
TableCell *cell = (TableCell *)[TableView cellForRowAtIndexPath:indexPath];
cell.myImageView.image=img;
++count;
[TableView reloadData];
}
}
You can cancel a thread which is being executed using the instance method cancel
[yourThread cancel];
Or you can use exit
[yourThread exit];
which will terminate the thread
You have started the thread in viewWillAppear, hence it will get called when you switch between your view controllers. If you want to execute your thread only once, then try putting it in viewDidLoad.