I have an NSOperation subclass that does some heavy calculations. It has a delegate as well.
If the user does not provide correct input, I validate it in the main method and through performSelectorOnMainThreadI create and show an alert (from my NSOperation subclass) and then I call the delegate method as such:
-(void) main{
[self performSelectorOnMainThread:#selector(showAnAlert)
withObject:nil
waitUntilDone:YES];
[self cancel]; //I need to cancel the operation
return; //don't want to finish main running.
}
- (void) showAnAlert{
//Create an alert here
[alert show];
}
And in my VC I have this:
- (void) aDelegateMethodFromMyOperation{
[self.textField setEndEditing:YES];
}
Now the problem is, once I dismiss the alert, I can't input any text in my textField.... It will show the keyboard on tap... but it won't accept my input... why is that?
Perhaps try:
[textField becomeFirstResponder];
Because you're switching through multiple UI elements in the NSOperation, it is possible that full control is not being regained by the text field.
Related
I have two UITableViewControllers A and B, and this is what I'm trying to do when I click on a table view cell in A:
Prepare to segue from A to B by setting some of B's variables from A.
Perform segue from A to B.
B appears.
Display a "Loading" activity indicator with [MBProgressHUD][1].
In a background task, retrieve data from a URL.
If an error occurs in the URL request (either no data received or non-200 status code), (a) hide activity indicator, then (b) display UIAlertView with an error message
Else, (a) Reload B's tableView with the retrieved data, then (b) Hide activity indicator
However, this is what's happening, and I don't know how to fix it:
After clicking a cell in A, B slides in from the right with an empty plain UITableView. The MBProgressHUD DOES NOT SHOW.
After a while, the tableView reloads with the retrieved data, with the MBProgressHUD appearing very briefly.
The MBProgressHUD immediately disappears.
There doesn't seem to be an error with the way the background task is performed. My problem is, how do I display the MBProgressHUD activity indicator as soon as my B view controller appears? (And actually, how come it's not showing?) Code is below.
A's prepareForSegue
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {
B *b = (B *)[segue destinationViewController];
// Set some of B's variables here...
}
Relevant methods in B
- (void)viewDidAppear:(BOOL)animated {
[self startOver];
}
- (void)startOver {
[self displayLoadingAndDisableTableViewInteractions];
[self retrieveListings];
[self.tableView reloadData];
[self hideLoadingAndEnableTableViewInteractions];
}
- (void)displayLoadingAndDisableTableViewInteractions {
MBProgressHUD *hud = [MBProgressHUD showHUDAddedTo:self.view animated:YES];
hud.labelText = #"Loading";
[UIApplication sharedApplication].networkActivityIndicatorVisible = YES;
self.tableView.userInteractionEnabled = NO;
}
- (void)hideLoadingAndEnableTableViewInteractions {
[MBProgressHUD hideHUDForView:self.view animated:YES];
[UIApplication sharedApplication].networkActivityIndicatorVisible = NO;
self.tableView.userInteractionEnabled = YES;
}
- (void)retrieveListings {
__block NSArray *newSearchResults;
// Perform synchronous URL request in another thread.
dispatch_sync(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
newSearchResults = [self fetchNewSearchResults];
});
// If nil was returned, there must have been some error--display a UIAlertView.
if (newSearchResults == nil) {
[[[UIAlertView alloc] initWithTitle:#"Oops!" message:#"An unknown error occurred. Try again later?" delegate:self cancelButtonTitle:#"OK" otherButtonTitles:nil] show];
} else {
// Add the retrieved data to this UITableView's model. Then,
[self.tableView reloadData];
}
}
- (NSArray *)fetchNewSearchResults {
// Assemble NSMutableArray called newSearchResults from NSURLConnection data.
// Return nil if an error or a non-200 response code occurred.
return newSearchResults;
}
I think you have to call [self hideLoadingAndEnableTableViewInteractions]; after newSearchResults = [self fetchNewSearchResults]; You are retrieving data in another thread which means -startOver will continue executing after calling [self retrieveListings]; and will hide the HUD right away. Also because you are updating the display you have to make sure you are doing that on the main thread. See example
dispatch_async(dispatch_get_main_queue(), ^{
//update UI here
});
When B appears, it displays a plain and empty UITableView, but does not display the MBProgressHUD even if the task does begin in the background (and yet, the MBProgressHUD is called to show before that). Hence, my solution is to show the MBProgressHUD in viewDidLoad, which precedes viewWillAppear.
- (void)viewDidLoad {
// ...
[self displayLoadingAndDisableUI];
}
I set up two additional boolean properties to B--one in .h, called shouldStartOverUponAppearing, and one in a class extension in .m, called isLoadingAndDisabledUI. In startOver, I added the following lines:
- (void)startOver {
if (!self.isLoadingAndDisabledUI) {
[self displayLoadingAndDisabledUI];
}
}
The check is done so that startOver doesn't display another MBProgressHUD when it has already been displayed from viewDidLoad. That is because I have a third view controller, called C, that may call on B's startOver, but doesn't need to call viewDidLoad just to display the MBProgressHUD.
Also, this is how I defined viewDidAppear:
- (void)viewDidAppear:(BOOL)animated {
if (self.shouldStartOverUponAppearing) {
[self startOver];
self.shouldStartOverUponAppearing = NO;
}
}
This way, startOver will only be invoked IF B appeared from A. If B appears by pressing "Back" in C, it will do nothing and only display the old data that was there.
I think that this solution is FAR from elegant, but it works. I guess I'll just ask for a better approach in a separate SO question.
I have used a common method for MBProgressHUD.
#import "MBProgressHUD.h" in AppDelegate.h also following methods.
- (MBProgressHUD *)showGlobalProgressHUDWithTitle:(NSString *)title;
- (void)dismissGlobalHUD;
In AppDelegate.m add following methods.
- (MBProgressHUD *)showGlobalProgressHUDWithTitle:(NSString *)title {
[MBProgressHUD hideAllHUDsForView:self.window animated:YES];
MBProgressHUD *hud = [MBProgressHUD showHUDAddedTo:self.window animated:YES];
hud.labelText = title;
return hud;
}
- (void)dismissGlobalHUD {
[MBProgressHUD hideHUDForView:self.window animated:YES];
}
How to use?
AppDelegate *appDel = (AppDelegate *)[[UIApplication sharedApplication]delegate];
//Show Indicator
[appDel showGlobalProgressHUDWithTitle:#"Loading..."];
//Hide Indicator
[appDel dismissGlobalHUD];
Hope this helps.
I have a ViewController called GetInfoViewController. Basically it takes the users input and then sends the input to a NSObject class, ServerConnection. ServerConnection makes a nsurlconnection request and when it is done I want the MBProgressHUD to hide.
GetInfoViewController
- (IBAction)go:(id)sender{
ServerConnection *serverConnection = [[ServerConnection alloc]init];
MBProgressHUD *HUD = [MBProgressHUD showHUDAddedTo:self.view animated:YES];
HUD.labelText = #"Searching...";
// here the progressHUD shows normally, and the yelpConnectionMethod is successful in retrieving the result.
[serverConnection yelpConnectionMethod];
}
-(void)endProgressHUD{
NSLog(#"end called");
[MBProgressHUD hideHUDForView:self.view animated:YES];
}
ServerConnection.h
I am not going to put all the nsurlconnection code because I don't think it really applies.. but if you want it I can post it
The only line that matters is:
(this is called after all the connections are done.)
GetInfoViewController *getinfoVC = [[GetInfoViewController alloc]init];
[getinfoVC endProgressHUD];
I call the endProgressHUD method of the getInfoViewController successfully, as it logs "end called". however, the progress hud stays spinning and does not hide.
Any input would be helpful.
Try this method when showing the HUD.
- (void)showWhileExecuting:(SEL)method onTarget:(id)target withObject:(id)object animated:(BOOL)animated;
It is a method of MBProgressHUD - selector should be the yelpConnectionMethod and target the serverConnection, object = nil and animated depends on you :)
I am using the [performSelector:#selector(reloadData) withObject:nil afterDelay:0.01] inside IBAction of a UIButton, the reloadData method draw some subviews on the main view in a particular way, the issue is when I tap the button quickly and repeatedly the selector "ReloadData" executed multiple times, event though I am canceling the all previous requests to that selector, and this results in duplication for the subviews in the main view
-(IBAction) myButtonIsTapped
{
[NSObject cancelPreviousPerformRequestsWithTarget:self selector:#selector(reloadData) object:nil];
[self performSelector:#selector(reloadData) withObject:nil afterDelay:0.01];
}
and reload data method like the following:
-(void) reloadData
{
#synchronized(self){
// clear all subviews from the main view
// draw new subviews
}
}
What about this:
-(IBAction) myButtonIsTapped
{
[self.myButton setUserInteractionEnabled:NO];
[self performSelector:#selector(reloadData) withObject:nil afterDelay:0.01];
}
-(void) reloadData
{
// Long task...
// Enable the button again:
[self.myButton setUserInteractionEnabled:YES];
}
Sometimes is just easier to control what the user is doing (UI), than logically dealing with what he has done.
Do one Thing create one BOOL variable and set in viewdidload yes and check in function if it is yes then method call and also make it no in buttonmake method.
I am trying to implement the SVProgressHUD progress activity indicator. I copied the class from the [demo].1
My app loads up but the activity indicator doesn't show up. This is my first time trying to use one of these, so any help would be appreciated.
Here is the code:
#import "SVProgressHUD.h"
#implementation QuotesAppDelegate
- (void)startLoading
{
//call this in your app delegate instead of setting window.rootViewController to your main view controller
//you can show a UIActivityIndiocatorView here or something if you like
[SVProgressHUD show];
[self performSelectorInBackground:#selector(loadInBackground) withObject:nil];
}
- (void)loadInBackground
{
//do your loading here
//this is in the background, so don't try to access any UI elements
[self populateFromDatabase];
[SVProgressHUD dismiss];
[self performSelectorOnMainThread:#selector(finishedLoading) withObject:nil waitUntilDone:NO];
}
- (void)finishedLoading
{
//back on the main thread now, it's safe to show your view controller
[window addSubview:[navigationController view]];
[window makeKeyAndVisible];
}
- (void)applicationDidFinishLaunching:(UIApplication *)application {
[self copyDatabaseIfNeeded];
[self startLoading];
}
For anyone else having a similar problem, this can also happen because you have a long loop or a piece of code that takes a long time to execute. If this happens, your progress bar wont be shown until after the loop, which kind of defeats the purpose.
To solve this issue you need to you this:
- (void)performSelectorInBackground:(SEL)aSelector withObject:(id)arg
Basically your code would look something like this:
- (IBAction)submitPost:(id)sender {
//now we show the loading bar and submit the comment
[SVProgressHUD showWithStatus:#"Submitting post" maskType:SVProgressHUDMaskTypeGradient];
SEL aSelector = #selector(submitDataOfPost);
[self performSelectorInBackground:aSelector withObject:sender];
}
This will basically load the progress bar, and in a background thread, the method you want to execute will be called. This makes sure that the UI is updated (shows the progress hud) at the same time that your code is executed.
First of all you were not adding your SVProgressHUD to the view.
If your class inherited from UIViewController then [self.view addSubview:]; or if your class is simple UIView then [self addSubView:];
I do not understand your requirement but as far as i can understand through your code that you are showing [SVProgressHUD show]; in your startLoading method and then you are calling loadInBackground method in that method where you are hiding your hud using [SVProgressHUD dismiss];
I will suggest you to trace it by using breakpoint and figure it out.
I had the same problem. When I changed a version of SVProgressHUD to the later one the problem disappeared. My current version supports ARC.
=>
(IBAction)fetchData:(id)sender
{
[SVProgressHUD showWithStatus:#"Loading..." maskType:SVProgressHUDMaskTypeGradient];
[self performSelectorOnMainThread:#selector(getDataFromSomeWhere) withObject:nil waitUntilDone:NO];
}
=>
(void)getDataFromSomeWhere
{
//Do your data populating here. and dismiss the ProgressHud.
[SVProgressHUD dismiss];
}
I have a tableView that loads an XML feed as follows:
- (void)viewDidAppear:(BOOL)animated {
[super viewDidAppear:animated];
if ([stories count] == 0) {
NSString *path = #"http://myurl.com/file.xml";
[self parseXMLFileAtURL:path];
}
}
I'd like to have the spinner to show on the top bar at the app launch and dissapear once the data is displayed on my tableView.
I thought that putting the beginning at viewDidAppear and the end at -(void)parserDidEndDocument:(NSXMLParser *)parser but it didn't work.
I'd appreciate a good explained solution on how to implement this solution.
Here's the problem: NSXMLParser is a synchronous API. That means that as soon as you call parse on your NSXMLParser, that thread is going to be totally stuck parsing xml, which means no UI updates.
Here's how I usually solve this:
- (void) startThingsUp {
//put the spinner onto the screen
//start the spinner animating
NSString *path = #"http://myurl.com/file.xml";
[self performSelectorInBackground:#selector(parseXMLFileAtURL:) withObject:path];
}
- (void) parseXMLFileAtURL:(NSString *)path {
//do stuff
[xmlParser parse];
[self performSelectorOnMainThread:#selector(doneParsing) withObject:nil waitUntilDone:NO];
}
- (void) doneParsing {
//stop the spinner
//remove it from the screen
}
I've used this method many times, and it works beautifully.
Starting a new thread can be overkilling and a source of complexity if you want to do things that are supposed to start on the main thread.
In my own code, I need to start a MailComposer by pushing a button but it can take some time to appear and I want to make sure the UIActivityIndicator is spinning meanwhile.
This is what I do :
-(void)submit_Clicked:(id)event
{
[self.spinner startAnimating];
[self performSelector:#selector(displayComposerSheet) withObject:nil afterDelay:0];
}
It will queue displayComposerSheet instead of executing it straight away. Enough for the spinner to start animating !
I typically implement an NSTimer that will call my spinner method, which I fire off right before I go into doing the heavy work (the work that will typically block the main thread).
The NSTimer fires and my spinner method is called. When the main work is finished, I disable the spinner.
Code for that is like:
IBOutlet UIActiviyIndicatorView *loginIndicator;
{
...
[loginIndicator startAnimating];
[NSTimer scheduledTimerWithTimeInterval:0.1 target:self selector:#selector(executeAuthenticationRequest)
userInfo:nil repeats:NO];
...
}
- (void) executeAuthenticationRequest
{
/* Simulate doing a network call. */
sleep(3);
[loginIndicator stopAnimating];
...
}
You can also do:
IBOutlet NSProgressIndicator *pIndicator;
Start:
[pIndicator startAnimation:self];
[pIndicator setHidden:NO];
And Stop:
[pIndicator stopAnimation:self];
[pIndicator setHidden:YES];
In Cocoa (and most other app frameworks) the user interface is updated by the main thread. When you manipulate views, they are typically not redrawn until control returns to the run loop and the screen is updated.
Because you are parsing the XML in the main thread, you are not allowing the screen to update, and that is why your activity indicator is not appearing.
You should be able to fix it by doing the following:
In viewDidAppear, show/animate the spinner and then call
[self performSelector:#selector(myXMLParsingMethod) withObject:nil afterDelay:0];
In myXMLParsingMethod, parse your XML, then hide/stop the spinner.
This way, control will return to the run loop before parsing begins, to allow the spinner to begin animating.