what method within a ViewController's class can I call to check when it has been brought to the foreground?
For example Im looking at a page on my application and I decide to close the application and go back to it later. When I go back to it the same view as I was looking at was on the screen. However... As soon as I open the application I want to segue over to another view.
How can I do this?
Currently trying this:
- (void) applicationDidBecomeActive:(NSNotification*) notification
{
[self checkActivity];
// Do your stuff here
}
- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
if (self) {
// Custom initialization
[[NSNotificationCenter defaultCenter] addObserver:self
selector:#selector(applicationWillEnterForeground:)
name:UIApplicationWillEnterForegroundNotification
object:nil];
[[NSNotificationCenter defaultCenter] addObserver:self
selector:#selector(applicationDidBecomeActive:)
name:UIApplicationDidBecomeActiveNotification
object:nil];
}
return self;
}
- (void)checkActivity{
NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
NSLog(#"Checking if re-authentication required...");
if([[defaults objectForKey:#"shouldgotologin"] isEqualToString:#"yes"]){
NSLog(#"View Should go to login...performing segue");
[defaults setObject:#"no" forKey:#"shouldgotologin"];
[defaults synchronize];
[self performSegueWithIdentifier:#"backtologin" sender:self];
} else {
NSLog(#"Should go to login is not true.");
}
}
Register your view controller to observe UIApplicationWillEnterForegroundNotification:
1) Inside view controller's init method:
[[NSNotificationCenter defaultCenter] addObserver:self
selector:#selector(applicationWillEnterForeground:)
name:UIApplicationWillEnterForegroundNotification
object:nil];
2) Inside view controller's dealloc method:
[[NSNotificationCenter defaultCenter] removeObserver:self];
3) Also, have your view controller implement this method:
- (void) applicationWillEnterForeground:(NSNotification*) notification
{
// This method will be called just before entering the foreground;
// Do your stuff here
}
If the timing of UIApplicationWillEnterForegroundNotification doesn't suit you, check all the available notifications for UIApplication here:
http://developer.apple.com/library/ios/#DOCUMENTATION/UIKit/Reference/UIApplication_Class/Reference/Reference.html
Jump To ApplicationDelegate File, you will find following methods.
- (void)applicationWillResignActive:(UIApplication *)application
{
}
- (void)applicationDidEnterBackground:(UIApplication *)application
{
}
- (void)applicationWillEnterForeground:(UIApplication *)application
{
}
- (void)applicationDidBecomeActive:(UIApplication *)application
{
}
Remember, It is not the viewController who receives the notifications related to the Application states like willResignActive,didEnterBackground,willEnterForeground. ApplicationDelegate object is going to handle those notifications. So, Try putting your logic in above methods.
Hope that helps. If not, add your queries using comments below my answer.
Related
I have the following snippet of code in viewDidLoad which I post a notification to be received by a different ViewController, and prior to iOS 7 (and XCode 5) this has worked:
if ([PFUser currentUser] && [PFFacebookUtils isLinkedWithUser:[PFUser currentUser]]) {
NSLog(#"Current user exists and is logged in"); //current works, so I know that this if-statement is satisfied
[self performSegueWithIdentifier:#"GoToRatingsView" sender:self];
[[NSNotificationCenter defaultCenter] postNotificationName:#"testSetup" object:nil]; //part in question
}
And in the segued ViewController, I have the following:
(void)viewDidLoad
{
[super viewDidLoad];
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(testSetupFunction) name:#"testSetup" object:nil];
}
(void)testSetupFunction
{
NSLog(#"This function executed");
}
Currently, testSetupFunction does not executed, which means the notification is not received. I am unsure whether its because I have segued to a different view and then posted the notification, or that this is something new with iOS 7, but currently the notification is no longer received.
Thanks for your help!
Post the notification once the viewcontroller has time to load.
- (void)postNotificaiton
{
[[NSNotificationCenter defaultCenter] postNotificationName:#"testSetup" object:nil];
}
if ([PFUser currentUser] && [PFFacebookUtils isLinkedWithUser:[PFUser currentUser]]) {
[self performSegueWithIdentifier:#"GoToRatingsView" sender:self];
[self performSelector:#selector(postNotification) withObject:nil afterDelay:0.0];
}
You could also post a notification from your segued View Controller saying that it was loaded, and in response to that notification, post your testSetup notification.
did you try adding the observer in the init method
- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
if (self) {
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(testSetupFunction) name:#"testSetup" object:nil];
// Custom initialization
}
return self;
}
OR You can also try to put a log in viewDidLoad to check actually the view is loaded at that time, sometimes it takes time to load the view, view is only loaded only when it is needed.
i want to reload table when app comes to foreground from background, in my app delegate.m i did like this, but its not working
- (void)applicationWillEnterForeground:(UIApplication *)application
{
NSLog(#"applicationWillEnterForeground");
[[NSNotificationCenter defaultCenter] postNotificationName:#"EnteredForeground"
object:nil];
}
and in my viewController i am working like
- (void)viewDidLoad
{
[super viewDidLoad];
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(whenAppEnteredIntoForeground:) name:#"EnteredForeground" object:nil];
}
- (void)whenAppEnteredIntoForeground:(id)object {
NSLog(#"log msg");
[tblSearch reloadData];
}
what should i do? what mistake i am doing? any help please
Firstly, you don't need to rebroadcast a notification when the app comes to the foreground, you can register for the notification from your view controller.
In your case, it's likely to be that the view is not loaded until after your secondary notification is sent, which is why your view controller cannot respond to it. Using breakpoints will confirm if this is the case.
Use this instead:
- (void)viewDidLoad {
[super viewDidLoad];
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(whenAppEnteredIntoForeground:) name:UIApplicationWillEnterForegroundNotification object:nil];
}
And you don't need to rebroadcast a notification from your appdelegate.
- (void)viewDidLoad {
[super viewDidLoad];
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(appEnteredIntoForeground:) name:UIApplicationWillEnterForegroundNotification object:nil];
}
- (void)appEnteredIntoForeground:(id)object {
[tableView reloadData];
}
Make sure that your Reload Data must call from main Thread Otherwise it will not be reloaded.
I am posting a notification locally in the app when ever I receive a remote notification.
- (void)application:(UIApplication *)application didReceiveRemoteNotification:(NSDictionary *)userInfo
{
NSLog(#"Received notification: %#", userInfo);
[[NSNotificationCenter defaultCenter] postNotificationName:#"NEWMESSAGE" object:nil userInfo:userInfo]; }
I have added an observer to the view in the function viewWillAppear() and remove the observer in viewWillDisappear().
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(newMessageReceived:) name:#"NEWMESSAGE" object:nil];
and
[[NSNotificationCenter defaultCenter] removeObserver:self];
My question is I want to override every viewWillAppear and viewWillDisappear functions in all *.m files that use these functions in my app.
or how can I dynamically add an observer (like above) to the present view and remove the observer when that view disappears. it should be like a global action whenever view changes observer to be added and removed when it changes again.
Is this possible? if so please guide me.
thanks in advance.
Some thoughts:
You can subclass UIViewController and implement these method in the subclass-ed view controller class. Then you need to create all your views as the subclass of this UIViewController.
Example:
//Creating a custom subclass of UIViewController
#interface CustomViewController : UIViewController
#end
#implementation CustomViewController
- (void)viewWillAppear:(BOOL)animated
{
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(newMessageReceived:) name:#"NEWMESSAGE" object:nil];
}
- (void)viewWillDisappear:(BOOL)animated
{
[[NSNotificationCenter defaultCenter] removeObserver:self];
}
#end
And create all your view controller as the subclass of CustomViewController.
I want to integrate shake feature throughout the app. So I am doing everything in appDelegate. I need to push a viewController, I am able to push in motionBegan, but i wanted to do it motionEnded. yes motion ended does work in a view controller, but in app delegate it is not being called.
Doing as
- (void)applicationDidBecomeActive:(UIApplication *)application {
[self becomeFirstResponder];
}
- (BOOL)canBecomeFirstResponder{
return YES;
}
motionEnded not called
-(void) motionEnded:(UIEventSubtype)motion withEvent:(UIEvent *)event {
if(event.subtype==UIEventSubtypeMotionShake){
NSLog(#"motionEnded called");
}
}
motionBegan called
-(void) motionBegan:(UIEventSubtype)motion withEvent:(UIEvent *)event {
if(event.subtype==UIEventSubtypeMotionShake){
NSLog(#"motionBegan called");
}
}
you could basically register your viewController for applicationDidBecomeActiveNotification or any depending on your needs
for example in your viewController's viewDidLoad method you could register it for notification
[[NSNotificationCenter defaultCenter] addObserver:self
selector:#selector(myMethod)
name:UIApplicationDidBecomeActiveNotification object:nil];
and implement this method in your class, your myMethod will call everytime your application will become active
-(void) myMethod(){
// do your stuff
}
finally un-register viewController from the notification in dealloc method
-(void)dealloc{
[[NSNotificationCenter defaultCenter] removeObserver:self];
}
I'm trying to present a Modal View Controller when the app enters in foreground.. These are my files:
AppDelegate.m :
#import "AppDelegate.h"
#import "MainViewController.h"
- (void)applicationWillEnterForeground:(UIApplication *)application
{
[self.window makeKeyAndVisible];
MainViewController * vc = [[MainViewController alloc]init];
[vc myMethodHere];
}
MainViewController.h :
//[..]
-(void) myMethodHere;
MainViewController.m :
-(void)myMethodHere{
NSLog(#"myMethodHere Activated.");
TWTweetComposeViewController *tweetViewController = [[TWTweetComposeViewController alloc] init];
[self presentModalViewController:tweetViewController animated:YES];
}
NSLog(#"myMethodHere Activated.") works.. so I can't understand why "presentModalViewController" doesn't! What should I edit/add? Maybe a delay? Thanks for your help..
p.s. I know my english sucks.. Forgive me :)
I wouldn't rely on the methods in your app delegate for this (even though it seems like the obvious solution) because it creates unnecessary coupling between your application delegate and the view controller. Instead, you can have MainViewController listen for the UIApplicationDidBecomeActive notification, and present the tweet composer view controller in response to this notification.
First, register for the notification in -viewDidLoad.
- (void)viewDidLoad
{
[super viewDidLoad];
[[NSNotificationCenter defaultCenter] addObserver:self selector:#selector(myMethodHere) name:UIApplicationDidBecomeActiveNotification object:nil];
}
Now, when this notification is received when your app returns from the background, myMethodHere will be invoked.
Lastly, remember to remove yourself as an observer when the view unloads.
- (void)viewDidUnload
{
[super viewDidUnload];
[[NSNotificationCenter defaultCenter] removeObserver:self name:UIApplicationDidBecomeActiveNotification object:nil];
}