A weird problem.
I wanna load an image from web, so i use NSURLConnection to do it.
Everything is ok when i do testing my code on ios4.3.
But when i'm launch my app on ios5.0, i found the connection:didreceiveData haven't been called whatever what i did.
otherelse functions is called normally, just like connectionDidFinishLoading in ios4.3 and connectionDidFinishDownloading in ios5.0.
so u guys, who can help me, thanks advanced!
-(void)load
{
if(isDownloading){
return;
}
if(conn != nil){
[conn release];
}
if(data != nil){
[data release];
data = nil;
}
[self isDownloading:YES];
ImageDownloadData* imageDownloadData = [imageList objectAtIndex:count];
NSURL* url = [imageDownloadData url];
NSURLRequest* request = [NSURLRequest requestWithURL:url cachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:60.0];
conn = [[NSURLConnection alloc] initWithRequest:request delegate:self];
if(conn){
[conn start];
}
}
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)rd
{
NSLog(#"data");
if(!data){
data = [[NSMutableData alloc] initWithData:rd];
return;
}
[data appendData:rd];
}
I can't be sure if this is the same problem you're having, but I had a similar issue, and resolved it by taking out the in methods and references to NSURLConnectionDownloadDelegate. Apparently delegates of NSURLConnection can only implement one of the two protocols that are derived from NSURLConnectionDelegate at a time.
There's been some odd API changes between 4.3 and 5.0. Apple changed the NSURLConnectionDelegate from an informal protocol to a formal one, and branched out some of the methods into two additional subprotocols: NSURLConnectionDataDelegate and NSURLConnectionDownloadDelegate. (Oddly though, they depreciated the identical methods in NSURLConnectionDelegate but didn't document where they moved to.)
I've been noticing when compiling my code against the 6.0 API that I've been having trouble getting Cocoa Touch to call connection: didReceiveData: if I Implement methods from both NSURLConnectionDataDelegate and NSURLConnectionDownloadDelegate. All the other methods I implemented were called as expected.
Related
Here is my actual issue, as some suggested I want to write a class for handling the multiple download progress in a UITableView. I have no idea how to write a class for this, can somebody help with some tips or ideas?
The group to look at is NSURLRequest and NSURLConnection. The former let's you specify the request (URL, http method, params, etc) and the latter runs it.
Since you want to update status as it goes (I answered a sketch of this in your other question, I think), you'll need to implement the NSURLConnectionDelegate protocol that hands over chunks of data as it arrives from the connection. If you know how much data to expect, you can use the amount received to calculate a downloadProgress float as I suggested earlier:
float downloadProgress = [responseData length] / bytesExpected;
Here's some nice looking example code in SO. You can extend for multiple connections like this...
MyLoader.m
#interface MyLoader ()
#property (strong, nonatomic) NSMutableDictionary *connections;
#end
#implementation MyLoader
#synthesize connections=_connections; // add a lazy initializer for this, not shown
// make it a singleton
+ (MyLoader *)sharedInstance {
#synchronized(self) {
if (!_sharedInstance) {
_sharedInstance = [[MyLoader alloc] init];
}
}
return _sharedInstance;
}
// you can add a friendlier one that builds the request given a URL, etc.
- (void)startConnectionWithRequest:(NSURLRequest *)request {
NSURLConnection *connection = [[NSURLConnection alloc] initWithRequest:request delegate:self];
NSMutableData *responseData = [[NSMutableData alloc] init];
[self.connections setObject:responseData forKey:connection];
}
// now all the delegate methods can be of this form. just like the typical, except they begin with a lookup of the connection and it's associated state
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data {
NSMutableData *responseData = [self.connections objectForKey:connection];
[responseData appendData:data];
// to help you with the UI question you asked earlier, this is where
// you can announce that download progress is being made
NSNumber *bytesSoFar = [NSNumber numberWithInt:[responseData length]];
NSDictionary *userInfo = [NSDictionary dictionaryWithObjectsAndKeys:
[connection URL], #"url", bytesSoFar, #"bytesSoFar", nil];
[[NSNotificationCenter defaultCenter] postNotificationName:#"MyDownloaderDidRecieveData"
object:self userInfo:userInfo];
// the url should let you match this connection to the database object in
// your view controller. if not, you could pass that db object in when you
// start the connection, hang onto it (in the connections dictionary) and
// provide it in userInfo when you post progress
}
I wrote this library to do exactly that. You can checkout the implementation in the github repo.
First of all the questions are failry simiple.. if you just want to see what they are skip to the bottom of this post and you will see them in bold.. for more detail then you can read the rest of this post...
I am just trying to iron out my NSURLConnection so that its working smoothly and I understand this properly. There is a profound lack of example/tutorials for Asynchronous connections on the internet or not any that I can find that explaine what is going on with any level of depth other than getting the connection up and running which after working on it seems pretty simple. Hopefully this question can full the void that I feel is out there for other users.
So, in my .h file i have imported the foundations headers and declared the methods required for the received or lack of received data (errors etc).
.h
#import <UIKit/UIKit.h>
#import <Foundation/Foundation.h> //add foundations
//.. other headers can be imported here
#interface MyViewController: UITableViewController {
//Im not setting any delegates to access the methods because Is all happening in the same
//place so I just use the key word 'self' when accessing the methods declared below
//I'm not sure if this is the best thing to do but I wasn't able to get my head around declaring the delegate or how it would help me with the way I have set up my request etc.
}
- (IBAction)setRequestString:(NSString *)string; //this method sets the request and connection methods
//these methods receive the response from my async nsurlconnection
- (void)receivedData:(NSData *)data;
- (void)emptyReply;
- (void)timedOut;
- (void)downloadError:(NSError *)error;
So thats my header file.. pretty simple not much explaining needed.
.m
//call setRequestString from some other method attached to a button click or something
[self setRequestString:#"rss.xml"];
//..
- (IBAction)setRequestString:(NSString *)string
{
//Set database address
NSMutableString *databaseURL = [[NSMutableString alloc] initWithString:#"http:www.comicbookresources/feeds/"]; // address not real jsut example
//append the string coming in to the end of the databaseURL
[databaseURL appendString:string];
//prepare NSURL with newly created string
NSURL *url = [NSURL URLWithString:databaseURL];
//AsynchronousRequest to grab the data
NSURLRequest *request = [NSURLRequest requestWithURL:url];
NSOperationQueue *queue = [[NSOperationQueue alloc] init];
[NSURLConnection sendAsynchronousRequest:request queue:queue completionHandler:^(NSURLResponse *response, NSData *data, NSError *error)
{
if ([data length] > 0 && error == nil){
[self receivedData:data];
}else if ([data length] == 0 && error == nil){
[self emptyReply];
}else if (error != nil && error.code == NSURLErrorTimedOut){ //used this NSURLErrorTimedOut from foundation error responses
[self timedOut];
}else if (error != nil){
[self downloadError:error];
}
}];
}
now set up the methods that were initialized in the .h file and called in the if statement above
- (void)receivedData:(NSData *)data
{
NSString* newStr = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
NSLog(#"%#", newStr); //logs recived data
//now you can see what data is coming in on your log
//do what you want with your data here (i.e. start parsing methods
}
- (void)emptyReply
{
//not sure what to do here yet?
}
- (void)timedOut
{
//also not sure what to do here yet?
}
- (void)downloadError:(NSError *)error
{
NSLog(#"%#", error);
UIAlertView *errorAlert = [[UIAlertView alloc] initWithTitle:#"Error!" message:#"A connection failure occurred." delegate:self cancelButtonTitle:#"OK" otherButtonTitles:nil, nil];
[errorAlert show];
}
Cool so that pretty much the basics of what I have done right there.. now the questions I have are as follows.
Question one:
Where I call NSURLConnection like so
[NSURLConnection sendAsynchronousRequest:request queue:queue completionHandler:^(NSURLResponse *response, NSData *data, NSError *error)
{
What is happening here what is the ^ for is that executing that whole block (including the if statements) on a different thread or something? because it looks alot like grand central dispatch formatting but slightly different.
Question two:
what should I be doing inside emptyReply & timedOut methods?
Question three:
How would I incorporate caching into this? I would like to cache the responses I get back from different requests. i.e. with my setRequestString you will see there is a string input parameter, so i can request different rss feeds with the same method.. I need to figure out how to cache these responses into individual caches.. but im not sure where to start with it.
Finally
If you have made it this far, thank you very much for reading my question. Hopefully with your responses we can get a pretty nice solution going here.. that other people can use for themselves and pick and choose the bits and peices they need that works for there own solution..
Anyway thank you very much for reading and I look forward to your replies.. even if they are just refrences to tutorials or examples you think might help me.. anything is good I just want to fully understand whats going on and whats a good solution.
Read about blocks in Apple documentation. Its new. Or you can read here
You can show errors such as request timed out etc. You don't really have to handle them separately than the error one unless you have special logic.
Try this for caching
NSURLRequest *urlRequest = [NSURLRequest requestWithURL:url cachePolicy:NSURLRequestReloadIgnoringLocalAndRemoteCacheData timeoutInterval:TIMEOUT_INTERVAL];
I have searched and tried a lot but in my application (which is using iOS 5 sdk) the NSURLConnection delegate methods gets called only when I initialise and start the connection in viewDidLoad method or on click event of any button.
But I want to call it after parsing my JSON file. And create a new connection for every record in JSON.
Can anyone tell me what is happening? Is something changed in ios sdk 5.
Here is my code:
-(void)getData:(NSString*)URL{
NSURLRequest *urlRequest = [[NSURLRequest alloc] initWithURL:[NSURL URLWithString:URL]];
shortURL = [NSString stringWithString:URL];
connection = [[NSURLConnection alloc] initWithRequest:urlRequest delegate:self];
//NSAssert(connection!=nil, #"no connection", nil);
[connection start];
}
- (NSURLRequest *)connection:(NSURLConnection *)connection willSendRequest:(NSURLRequest *)request redirectResponse:(NSURLResponse *)response
{
// application specific stuff
}
The getData function is written in a class inherited from NSObject. And it is called from
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
method of UITableView.
Please help me with this.
Assuming that the JSON parsing code is happening in a background thread, you have to create an NSRunLoop for that thread.
The NSURLConnection class is simply adding itself to the runloop, if none exists, no processing or delegate methods will get invoked.
connection = [[NSURLConnection alloc] initWithRequest:urlRequest delegate:self];
[[NSRunLoop currentRunLoop] run];
Note: The run method will block
This might be a dumb question. Sorry if it is.
But Im working on a project that consumes web services. I can connect to the web service and get the data I need fine.
I would like to have a method that returns this data obtained from the web service to the caller. The only problem is that the data is only obtained inside the ConnectionDidFinishLoading method, and I can't access this data from my method.
here is my code, that works fine:
- (NSData *) dataForMethod:(NSString *)webMethod withPostString:(NSString *)postString
{
NSURL *url = [NSURL URLWithString:[SigameWebServiceAddress stringByAppendingFormat:#"%#%#", #"/", webMethod]];
NSMutableURLRequest *req = [NSMutableURLRequest requestWithURL:url];
NSString *msgLength = [NSString stringWithFormat:#"%d", [postString length]];
[req addValue:#"application/x-www-form-urlencoded" forHTTPHeaderField:#"Content-Type"];
[req addValue:msgLength forHTTPHeaderField:#"Content-Length"];
[req setHTTPMethod:#"POST"];
[req setHTTPBody: [postString dataUsingEncoding:NSUTF8StringEncoding]];
conn = [[NSURLConnection alloc] initWithRequest:req delegate:self];
if (conn)
{
webData = [NSMutableData data];
}
// I WOULD LIKE TO RETURN WEBDATA TO THE CALLER HERE, BUT WEBDATA IS EMPTY NOW, THE
//connectionDidFinishLoading ONLY GETS CALLED WITH THE DATA I WANT AFTER THE COMPILER
//IS DONE EXECUTING MY METHOD.
}
-(void) connection:(NSURLConnection *) connection didReceiveResponse:(NSURLResponse *) response
{
[webData setLength: 0];
}
-(void) connection:(NSURLConnection *) connection didReceiveData:(NSData *) data
{
[webData appendData:data];
}
-(void) connection:(NSURLConnection *) connection didFailWithError:(NSError *) error
{
NSLog(#"FATAL ERROR");
}
-(void) connectionDidFinishLoading:(NSURLConnection *) connection
{
NSLog(#"DONE. Received Bytes: %d", [webData length]);
NSString *theXML = [[NSString alloc] initWithBytes: [webData mutableBytes] length:[webData length] encoding:NSUTF8StringEncoding];
//---shows the XML---
NSLog(#"%#", theXML); //NOW, THIS IS THE DATA I WANT. BUT HOW CAN I RETURN THIS TO
//THE CALLER. I MEAN, THE CALLER THAT CALLED MY METHOD
//+ (NSData *) dataForMethod: withPostString:
}
Any help here is appreciated!
Thanks
There are really two ways to go about this.
Create a delegate interface
Use Blocks
I would strongly advise against using the synchronous methods - unless you are/have created your own asynchronous framework around them (i.e. you are manually starting another thread and executing your synchronous request on that thread). In the long run you will realize you need the requests to be async, and you'll have to re-work everything such that they are.
To give a quick overview of the two options I gave:
1. Create a delegate interface
The idea here is to create a class which performs the request, and create a protocol the caller must implement. When the request is complete, you will invoke a specified method on the delegate with the data:
The protocol might look something like this:
#protocol RequestClassDelegate <NSObject>
- (void)requestCompleted:(ResponseClass *)data;
- (void)requestError:(NSError *)error;
#end
The class which makes the request might look something like this:
#interface RequestClass : NSObject
- (void)makeRequest:(id<RequestClassDelegate>)delegate;
#end
And the request class implementation might contain some of the following, in addition to your connection logic:
#implementation RequestClass
{
__weak id<RequestClassDelegate> _delegate;
}
// Connection Logic, etc.
- (void)makeRequest:(id<RequestClassDelegate>)delegate
{
_delegate = delegate;
// Initiate the request...
}
-(void) connectionDidFinishLoading:(NSURLConnection *) connection
{
NSString *theXML = [[NSString alloc] initWithBytes: [webData mutableBytes] length:[webData length] encoding:NSUTF8StringEncoding];
// Processing, etc.
// Here we'll call the delegate with the result:
[_delegate requestCompleted:theResult];
}
#end
2. Use Blocks
This solution is much the same as the first solution - but, a bit more elegant in my opinion. Here, we'll change the RequestClass to use blocks instead of a delegate:
typedef void (^requestCompletedBlock)(id);
typedef void (^requestErrorBlock)(NSError *);
#interface RequestClass : NSObject
#property (nonatomic, copy) requestCompletedBlock completed;
#property (nonatomic, copy) requestErrorBlock errored;
- (void)makeRequest:(requestCompletedBlock)completed error:(requestErrorBlock)error;
#end
And the implementation of that might look something like this:
#implementation RequestClass
#synthesize completed = _completed;
#synthesize errored = _errored;
// Connection Logic, etc.
- (void)makeRequest:(requestCompletedBlock)completed error:(requestErrorBlock)error
{
self.completed = completed;
self.errored = error;
// Initiate the request...
}
-(void) connectionDidFinishLoading:(NSURLConnection *) connection
{
NSString *theXML = [[NSString alloc] initWithBytes: [webData mutableBytes] length:[webData length] encoding:NSUTF8StringEncoding];
// Processing, etc.
// Here we'll call the delegate with the result:
self.completed(theResult);
}
#end
It sounds like you are trying to use return the data synchronously from your method, but you are using an asynchronous method (using an NSURLConnection and presumably calling its start method) to begin retrieving data. If you really want your method to return its result synchronously, read on. As #Steve says in another answer, however, you may also reconsider your interface design and instead implement it using an asynchronous approach and use his recommendations for either a delegate or block-based interface.
If you want to return the data synchronously from your method, use a synchronous request. So change this part of your code:
conn = [[NSURLConnection alloc] initWithRequest:req delegate:self];
[conn start]; // I presume you have this somewhere
if (conn)
{
webData = [NSMutableData data];
}
with something more like this:
NSURLResponse *response = nil;
NSError *error = nil;
webdata = [NSURLConnection sendSynchronousRequest:req returningResponse:&response error:&error];
if (webdata) {
return webdata;
}
else {
// Handle error by looking at response and/or error values
return nil;
}
You will no longer need any of your delegate code if you use this approach. You will be limited in some ways though. For example, if your web service requires authentication via something other than URL parameters you can't use this approach.
Steve's answer is great and I can only suggest the way using blocks. Actually, as I am new into Objective-C I implemented the approach steve outlined. It works perfectly.
The Post for more details and my own point of view you can find here:
http://kerkermeister.net/how-to-build-an-cocos2d-ios-app-communicating-with-a-restful-api-the-sequence/
The Post contains all the tiny steps you need to follow to get Steve's solution approach with blocks working. That includes:
- an updateable view that will render information as soon as retrieved from Web API asynchronously
- a controller invoking the HTTP request to the Web API
- the actual HttpRequest class that uses iOS standard NSURLConnections
- a model class that uses blocks as callbacks to update its data
Your going to have to either implement a separate method in which you use the data once the data has been returned by the connectionDidFinishLoading method or make the request synchronously. The reason I believe the above does not work is because the request is happening on a separate thread, so the main thread continues, but does not actually have the data.
This is a good way to do that if synchronous is what you want:
Does all NSURLConnections connect asynchronously? iOs
In order to download data from webserivce - use NSURLSession -
A URL session task that returns downloaded data directly to the app in memory.
// 1. create NSURL link to your webservice
NSString *dataUrl = #"DATA_LINK_TO_WEBSERVICE";
NSURL *url = [NSURL URLWithString:dataUrl];
// 2. create a NSURLSessionDataTask
NSURLSessionDataTask *downloadTask = [[NSURLSession sharedSession]
dataTaskWithURL:url completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {
//Handle response here
}];
// 3.resume the task
[downloadTask resume];
Refernces:
apple documentation refrence:
https://developer.apple.com/documentation/foundation/nsurlsessiondatatask?language=objc
Raywanderlich great cookbook:
https://www.raywenderlich.com/2392-cookbook-using-nsurlsession
Your going to need to parse the XML that comes back. There are some good Objective C XML parsers out there. One in particular is made for ease of use....
http://nfarina.com/post/2843708636/a-lightweight-xml-parser-for-ios
It's a very light weight parser for extracting the values you want from XML. I've used many times with great success and little hassle. Here is how I query a web address and turn it into data.
NSString *query = [NSString stringWithFormat:#"http://WEB_ADDRESS_FOR_XML];
NSURL *URL = [NSURL URLWithString:query];
NSData *data = [NSData dataWithContentsOfURL:URL];
Or with NSURLConnection, in the did receive data:
-(void) connection:(NSURLConnection *) connection didReceiveData:(NSData *) data
{
//USE THE DATA RETURNED HERE....
}
Then use the Parser from my link to get the contents:
SMXMLDocument *document = [SMXMLDocument documentWithData:data error:NULL];
NSLog("\nXML Returned:%#",document);
Why doesn't this code work? It shows the Google screen but it doesn't change the text box value. I confirmed that the JS does work by running it in Safari, and this code seems to work otherwise since running alert('hi') does work.
NSURL *web_url = [NSURL URLWithString:#"http://www.google.com"];
NSURLRequest *web_request = [NSURLRequest requestWithURL:web_url];
[web_screen loadRequest:web_request];
NSString *js_result = [web_screen stringByEvaluatingJavaScriptFromString:#"document.getElementsByTagName('input')[1].value='test';"];
Just expanding on the previous answer. You need to conform to the UIWebViewDelegate protocol by setting the delegate property of the UIWebView like this:
web_screen.delegate = self;
Then you can implement one of the delegate methods to know when a request has finished loading and is therefore ready to have scripts run like so:
- (void)webViewDidFinishLoad:(UIWebView *)webView {
NSString *js_result = [webView stringByEvaluatingJavaScriptFromString:#"document.getElementsByTagName('input')[1].value='test';"];
}
For more information on the UIWebViewDelegate protocol visit the Apple site http://developer.apple.com/library/ios/#documentation/uikit/reference/UIWebViewDelegate_Protocol/Reference/Reference.html
The Load URL action takes place asynchronously. It does not even start until your method has ended. So your javascript is being pushed into an empty UIWebView, then your method ends, then the load happens.
You need to let your method end before the js is pushed in. The standard approach for this is to use a Delegate object, which will have a method called on it when the load completes. Only then does it make sense to push in the javascript.
Does it work if you wait for the page to finish loading first?
Consider looking at NSURLConnection and its delegate methods. You can use these to check on the status of a download.
#interface
...
NSURLConnection *connectionInProgress;
NSData *googleRequestResponseData;
NSURL *googleURL;
...
#implementation
...
- (void) setUpRequest {
googleURL = [[NSURL URLWithString:#"http://www.google.com/"] retain];
googleRequestResponseData = [[NSMutableData data] retain];
NSURLRequest *request = [NSURLRequest requestWithURL:url cachePolicy:NSURLRequestReturnCacheDataElseLoad timeoutInterval:30.0];
connectionInProgress = [[NSURLConnection alloc] initWithRequest:request delegate:self startImmediately:YES];
}
#pragma mark NSURLConnection delegate methods
- (void) connection:(NSURLConnection *)connection didReceiveData:(NSData *)data {
[googleRequestResponseData appendData:data];
}
- (void) connectionDidFinishLoading:(NSURLConnection *)connection {
[web_screen loadData:googleRequestResponseData MIMEType:#"application/octet-stream" textEncodingName:#"utf-8" baseURL:googleURL];
NSString *js_result = [web_screen stringByEvaluatingJavaScriptFromString:#"document.getElementsByTagName('input')[1].value='test';"];
NSLog (js_result);
[googleURL release];
[googleRequestResponseData release];
[connectionInProgress release];
connectionInProgress = nil;
}
- (void) connection:(NSURLConnection *)connection didFailWithError:(NSError *)error {
NSLog (#"Connection failed to load data from Google!");
[googleURL release];
[googleRequestResponseData release];
[connectionInProgress release];
connectionInProgress = nil;
}
Alternatively, check out Ben Copsey's ASIHTTPRequest wrapper, which includes a simplified approach to asynchronous downloads (see ASINetworkQueue, specifically).
You can use ASINetworkQueue to run a method of your choice (to run the Javascript code, for example), once the request download is complete.
add '.innerHTML' after what you are searching for
In your case do the following
- (void)webViewDidFinishLoad:(UIWebView *)webView {
NSString *js_result = [webView stringByEvaluatingJavaScriptFromString:#"document.getElementsByTagName('input')[1].value='test'.innerHTML"];
}
This worked for me .
check this for more info here