I have the following methods in my class:
-(IBAction)loginToAccount:(id)sender {
// Display the network activity status indicator
[UIApplication sharedApplication].networkActivityIndicatorVisible = YES;
// Show the load indicator
[self.loadIndicator startAnimating];
self.loadIndicator.hidden = NO;
self.loadLabel.hidden = NO;
[usernameTextField resignFirstResponder];
[passwordTextField resignFirstResponder];
[self CheckLoginCredentials];
}
-(void)CheckLoginCredentials {
NSString *APIURL = [[NSString alloc] initWithFormat:#"http://mysite.com/xml.xml"];
NSURL *url = [[NSURL alloc] initWithString:APIURL];
NSXMLParser *xmlParser = [[NSXMLParser alloc] initWithContentsOfURL:url];
[APIURL release];
[url release];
[xmlParser setDelegate:self];
[xmlParser parse];
}
When I comment [self CheckLoginCredentials], the loadIndicator gets animated and shown but when I uncomment [self CheckLoginCredentials], the loadIndicator does not get shown and also usernameTextField/passwordTextField resignFirstResponder do no work.
What am I doing wrong? Thanks!
I believe that -initWithContentsOfURL: is a synchronous url connection, and therefore blocks the thread it's run on until it completes.
Because of this, the progress indicator won't get shown because it requires that the thread it's running on has an active run loop. Using the synchronous url connection on the main thread will block the UI on that thread, so you won't see your progress indicator.
The correct way to do this would be to use NSURLConnection's
+ (NSURLConnection *)connectionWithRequest:(NSURLRequest *)request delegate:(id)delegate
Simply create an NSURLRequest object that encapsulates your API request, and then pass it off to that method on NSURLConnection.
Then implement the delegate call backs to get your data back.
The advantage of this method is that all of this is done on a separate thread and handled for you, and therefore won't block your UI.
Related
I'm using a UISearchBar in my application and the problem is when I call a few json methods searchBarSearchButtonClicked seems to not resign the keyboard until the other methods are done loading the data. I've tried alternatively using UIAlertView and UIButtons to replace the searchBarSearchButtonClicked function but they appear to literally freeze and stay in a "pressed down" state too. I was also wondering if this would be a reason why [UIApplication sharedApplication].networkActivityIndicatorVisible = YES; wouldn't show an activity indicator in the device's status bar.
- (void)searchBarSearchButtonClicked:(UISearchBar *)searchBar{
self.args = searchBar.text;
[self grabData];
[self fillVars];
[searchBar resignFirstResponder];
[self.tableView reloadData];
}
[self grabData] is where I grab the JSON data and [self fillVars] just fills a few things that are later used.
-(void)grabData{
self.args = [self.args stringByAddingPercentEscapesUsingEncoding:NSASCIIStringEncoding];
urlString = [NSString stringWithFormat:#"%#%#?key=%#&q=%#",baseUrl,func,apiKey,args];
url = [NSURL URLWithString:urlString];
NSData *jsonData = [NSData dataWithContentsOfURL:url];
NSError *error;
NSDictionary *json = [NSJSONSerialization JSONObjectWithData:jsonData options:kNilOptions error:&error];
self.matches = [json objectForKey:#"matches"];
[UIApplication sharedApplication].networkActivityIndicatorVisible=YES;
}
You will have to use threading. All manipulation with your interface happens on the main thread, so when you perform a lengthy task on the main thread, the interface won't be able to update itself before the task has completed.
In a UIViewController you can do [self performSelectorInBackground:#selector(grabData) withObject:self], which is a convenience method for dispatching a new queue (thread) using grand central dispact.
You could also do that manually, using the GCD API. You would do something along the lines of this:
dispatch_queue_t jsonQueue = dispatch_queue_create("JSON Queue", NULL);
dispatch_async(jsonQueue, ^{
// fetch JSON data ...
dispatch_async(dispatch_get_main_queue(), ^{
// perhaps do something back on the main queue once you're done!
});
});
I am developing an iphone app in which I am extracting RSS feeds and then parsing them.My code is as bellow:
- (void)viewDidAppear:(BOOL)animated
{
[super viewDidAppear:animated];
NSLog(#"in view did appear");
if ([stories count] == 0) {
NSString * path = #"http://www.shire.com/shireplc/rss.jsp";
//[self parseXMLFileAtURL:path];
//[self performSelectorInBackground:#selector(parseXMLFileAtURL:) withObject:path];
NSLog(#"internet is %d",[self checkInternet]);
if([self checkInternet]==1)
[NSThread detachNewThreadSelector:#selector(parseXMLFileAtURL:)
toTarget:self withObject:path];
}
}
- (void)parseXMLFileAtURL:(NSString *)URL
{
NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
stories = [[NSMutableArray alloc] init];
//you must then convert the path to a proper NSURL or it won't work
NSURL *xmlURL = [NSURL URLWithString:URL];
// here, for some reason you have to use NSClassFromString when trying to alloc NSXMLParser, otherwise you will get an object not found error
// this may be necessary only for the toolchain
rssParser = [[NSXMLParser alloc] initWithContentsOfURL:xmlURL];
// Set self as the delegate of the parser so that it will receive the parser delegate methods callbacks.
[rssParser setDelegate:self];
// Depending on the XML document you're parsing, you may want to enable these features of NSXMLParser.
[rssParser setShouldProcessNamespaces:NO];
[rssParser setShouldReportNamespacePrefixes:NO];
[rssParser setShouldResolveExternalEntities:NO];
[rssParser parse];
[pool release];
}
Can anyone tell me where I am going wrong?
My log is as bellow:
log: [Switching to thread 12803]
[Switching to thread 12035]
2011-05-10 11:31:30.932 Annual Report[454:490b] found file and started parsing
[Switching to thread 14339]
2011-05-10 11:32:04.742 Annual Report[454:640b] found file and started parsing
[Switching to thread 13827]
[Switching to thread 13827]
Program received signal: “EXC_BAD_ACCESS”.
gdb stack trace at 'putpkt: write failed':
0 gdb-arm-apple-darwin 0x0019026b remote_backtrace_self + 54
I am not sure but i guess the parameter for the method gets released at some point. Can you make sure that the URL is present in the method parseXMLFileAtURL
Finally,I used a flag to check if the view is appeared or not(by making flag true in viewdidAppear) and if the view is not appearing,don't run the thread function.That solved the problem!!!
// you can use the method, which is safer if your have not to update the UserInterface
[self performSelectorInBackground:#selector(parseXMLFileAtURL:) withObject:path];
if UserInterface needs also to be updated you can first parse data in background and the update the ui with method.
[self performSelectorOnMainThread:#selector(myUpdateUI) withObject:nil waitUntilDone:YES];
Kinda stuck on this problem and I'm not sure, where I've gone wrong. Heres what I'm doing:
Class calls:
- (void)updateApplicationDataInBackground {
updateView = [[UpdatingView alloc] init];
[self.view addSubview:updateView.view];
DataSynchronizer *dataSynchronizer = [[DataSynchronizer alloc] init];
[NSThread detachNewThreadSelector:#selector(initWithDataRequest:) toTarget:dataSynchronizer withObject:self];
[dataSynchronizer release];
This creates a thread to retrieve data from the server and parse it. In DataSynchronizer this is the method being called:
- (void)initWithDataRequest:(id)parent {
NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
controller = parent;
NSLog(#"DataSynchronizer initWithDataRequest called");
NSURL *url = [NSURL URLWithString: ApiUrl];
ASIFormDataRequest *request = [ASIFormDataRequest requestWithURL:url];
[request setPostValue:ApiKey forKey:#"key"];
[request setPostValue:ApiPass forKey:#"password"];
[request setPostValue:#"somevalue" forKey:#"framework"];
[request setPostValue:#"somevalue" forKey:#"method"];
[request setDidFinishSelector:#selector(parseResult:)];
[request setDidFailSelector:#selector(requestError:)];
[request setTimeOutSeconds:60];
[request setDelegate:self];
[request startAsynchronous];
[pool release];
After my data is received I parse the contents and do my data synch. This is all working as expected. I've decided to throw in a UIProgressView so the user can see what is going on with this request, this progress view lives in updateView which is created in the updateApplicationDataInBackground.
I'm not trying to show progress for the web service call but simply when milestones are reached in the data processing. In the DidFinishSelector its calling parseResult
There are five method its calls with the response data:
[self parseData:[data objectForKey:#"types"] forObject:[Types class] andParent:nil];
[controller performSelectorOnMainThread:#selector(updateProgress:) withObject:[NSNumber numberWithFloat:.4] waitUntilDone:YES];
After each process I'm trying to update the UIProgressView, it will never update. Now if I simply call performSelectorOnMainThread from outside the ASIHTTPRequest it works as expected, but not within the DidFinishSelector. I've tried many variations on this where it calls a local method which updates the mainThread, where I simply use performSelector. Nothing works, how do I update the the UIProgessView?
Is the problem a thread spawning a thread?
Thanks
EDIT:
Looks like the DidFinishSelector is being called on the main thread already. I've updated my code to simply call:
[controller updateProgress:[NSNumber numberWithFloat:.8]]
Still no luck....
Realized it might be helpful to see the UIProgessView update method.
- (void)updateProgress:(NSNumber *)progress {
float newProgess = [progress floatValue];
[updateView.myProgress setProgress: newProgess];
Ok so it looks like I found my own answer after changing somethings around. Because ASIHttpRequest performs SetDidFinish selector on the main thread my calls performSelectorOnMainThread weren't doing anything. I changed my initial call for the DataSynchronizer to the main thread and added changed the DidFinish method to:
- (void)parseDataInBackground:(ASIHTTPRequest *)request {
[NSThread detachNewThreadSelector:#selector(parseResult:) toTarget:self withObject:request];
Which then makes the parse method run on separate thread (since its the bulk of the processing and now performOnMainThread works without issue.
I'm writing test cases for a wrapper class written around ASIHTTPRequest. For reasons I can't determine, my test cases complete with failure before the ASIHTTPRequest finishes.
Here's how the program flow works.
Start in my test case.
Init my http engine object, instruct it to create a new list
Create the new ASIHTTPRequest object and set it up.
Add the request to an operation queue.
Wait until that queue is empty
Check to see if my delegate methods were called and fail the test if they weren't.
Now, most of the time everything works fine and the test passes, but some of the time it fails because my delegate methods were called AFTER the operation queue returned control to my wait method.
Test Case
// Set my flags to 'NO'
- (void)setUp {
requestDidFinish = NO;
requestDidFail = NO;
}
- (void)testCreateList {
NSString *testList = #"{\"title\": \"This is a list\"}";
JKEngine *engine = [[JKEngine alloc] initWithDelegate:self];
NSString *requestIdentifier = [engine createList:jsonString];
[self waitUntilEngineDone:engine];
NSString *responseString = responseString_;
[engine release];
GHAssertNotNil(requestIdentifier, nil);
GHAssertTrue(requestDidFinish, nil);
GHAssertTrue([responseString hasPrefix:#"{\"CreateOrEditListResult\""], nil);
}
// Puts the test into a holding pattern until the http request is done
- (void)waitUntilEngineDone:(JKEngine *)engine {
[engine waitUntilFinishedRunning];
}
// The delegate method called on successful completion
- (void)requestFinished:(NSString *)requestIdentifier withResponse:(NSString *)response {
NSLog(#"request did finish");
requestDidFinish = YES;
responseIdentifier_ = [requestIdentifier retain];
responseString_ = [response retain];
}
Engine Code
- (NSString *)createList:(NSString *)list {
ASIHTTPRequest *request = [[ASIHTTPRequest alloc] initWithURL:[NSURL URLWithString:url]];
[request addRequestHeader:#"Content-Type" value:kContentType];
[request setRequestMethod:kPOST];
request.delegate = self;
[request appendPostData:[list dataUsingEncoding:NSUTF8StringEncoding]];
NSString *requestIdentifier = [NSString stringWithNewUUID];
[operationQueue_ addOperation:request];
[operationDictionary_ setObject:request forKey:requestIdentifier];
return requestIdentifier;
}
// This is the ASIHTTPRequest delegate method that's called on success
// but it sometimes isn't called until AFTER the operationQueue finishes running
- (void)requestFinished:(ASIHTTPRequest *)request {
DLog([request responseString]);
BOOL canNotifiyDelegate = [self.delegate respondsToSelector:#selector(requestFinished:withResponse:)];
if (canNotifiyDelegate) {
NSArray *keyArray = [operationDictionary_ allKeysForObject:request];
NSString *requestIdentifier = [keyArray objectAtIndex:0];
[operationDictionary_ removeObjectForKey:requestIdentifier];
if ([keyArray count] != 1) {
ALog(#"It looks like a request was added to the operation dictionary multiple times. There's a bug somewhere.", nil);
}
[self.delegate requestFinished:requestIdentifier withResponse:[request responseString]];
}
}
- (void)waitUntilFinishedRunning {
[operationQueue_ waitUntilAllOperationsAreFinished];
}
This is the way ASIHTTPRequest works. Delegate methods are called on the main thread, and calls to delegates do not block the request thread, so it's perfectly possible your delegates will be called after the queue finishes.
ASIHTTPRequest calls delegate methods on the main thread, by default GH-Unit runs its tests on a background thread. I'm still a little hazy on exactly what was going on, but forcing my network tests to run on the main thread fixed the problem.
I implemented the following method in my network test class.
- (BOOL)shouldRunOnMainThread {
return YES;
}
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