I need to change a data (a label) from the app's delegate method ApplicationDidEnterForeground without allocating a new view. The view is called "Reminder", so I imported it into the delegate and I can access its data only if I allocate it (Reminder *anything = [Reminder alloc...etc), but since I want to change the current view loaded I need to have direct access to the view that's already loaded.
How would I do to change the main view's label from the delegate as soon as my application enters foreground?
obs: I know I can do it on -(void)ViewDidLoad or -(void)ViewWillAppear but it won't solve my problem, since it won't change the label if, for example, the user opens the app through a notification box (slide icon when phone is locked). In that case, none of the above methods are called if the app was open in background.
I don't know if I was clear, hope I was. Thank you in advance.
IF you are using storyboards, you can do this to access the current view being seen
- (void)applicationDidEnterBackground:(UIApplication *)application
{
UINavigationController *a=_window.rootViewController;
Reminder *rem = a.topViewController;
rem.label.text=#"test";
}
IF not using story boards
When I create views that I need to access later, I define them as a property, like this
on AppDelegate.h
//#interface SIMCAppDelegate : UIResponder <..........>
//{
//Some variables here
//}
//Properties here
#property (strong, nonatomic) Reminder *reminder;
//Some method declaration here
//eg: -(void) showSomething;
on AppDelegate.m
//#implementation AppDelegate
#synthesize reminder;
so when I alloc/init the view like this
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
//codes before here
self.reminder = [[Reminder alloc] init];
self.reminder.label.text = #"OLD LABEL";
//codes after here
}
I will be able to access it again after allocation on other methods, like this
- (void)applicationWillEnterForeground:(UIApplication *)application
{
self.reminder.label.text = #"NEW LABEL";
}
just send a notification from your ApplicationDidEnterForeground: method and receive it on that class where you want to update the label... Like this..
//Your ApplicationDidEnterForeground:
[[NSNotificationCenter defaultCenter] postNotificationWithName:#"UpdateLabel" withObject:nill];
and add observer in it viewDidLoad: of that controller where you want to update label
[[NSNotificationCenter defaultCenter] addObserver:self
selector:#selector(updateLabel:)
name:#"UpdateLabel"
object:nil];
made your method in same class ...
- (void)updateLabel:(NSNotification *)notification{
update label
}
Might be you can try following code -
NSMutableArray *activeControllerArray = [self.navigationController.viewControllers mutableCopy];
for (int i = 0; i< [activeControllerArray count]; i++) {
if ([[activeControllerArray objectAtIndex:i] isKindOfClass:[Reminder Class]) {
Reminder *object = [activeControllerArray objectAtIndex:i];
//Perform all the task here which you want.
break; //Once found break the loop to do further processing.
}
}
Related
How to achieve this stuff below? Please give me some guidance for it. I describe my issue below.
When I tap home button and remove app from tray and while I am opening app I get the login screen. I know how to use NSUserDefaults well.
But my issue is that when I navigate 3rd or 4th viewController and I press Home Button and remove app from tray, Then whenever I open app than I want to open with last open viewController.
Also same when my app is Crashing and I am opening it again then I want to open app with last open viewController state.
So I just want to know that is that possible or not? If yes, then please guide me how to achieve this stuff.
Thank you
Yes, both cases are possible.
On crash, you can use UncaughtExceptionHandler to perform some code. In you app delegate, register you handler like this:
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
NSSetUncaughtExceptionHandler(&uncaughtExceptionHandler);
// Other didFinishLaunchingWithOptions code
And add your handler method to the same .m file
void uncaughtExceptionHandler(NSException *exception)
{
// App crashed, save last selected tabbar index to the to the NSUserDefaults
[[NSUserDefaults standardUserDefaults] setInteger:tabBarController.selectedIndex forKey:#"LastSelectedTabbarIndex"];
[[NSUserDefaults standardUserDefaults] synchronize];
}
While app runs, to keep track of last selected tab bar controller, use UITabBarControllerDelegate and save newly selected tabbar's index to NSUserDefaults. Short example:
- (void)tabBarController:(UITabBarController *)tabBarController didSelectViewController:(UIViewController *)viewController
{
NSUInteger tabIndex = [[tabBarController viewControllers] indexOfObject:viewController];
// I have newly selected index, now save it to the NSUserDefaults
}
This code will save last selected tabbar's index to the NSUserDefaults every time tabbar's selected index changes.
Finally, when you app starts (in your didFinishLaunchingWithOptions), read last saved tabbar index from NSUserDefaults and set tabbar's selected index accordingly
self.tabBarController.selectedIndex = lastSelectedIndexFromDefaults;
Edit:
If you also need to restore UINavigationControllers controllers stack, its pretty difficult task. I give you just a quick overview what comes to my mind.
There are 2 cases:
You have custom view controllers initializers and need to pass custom object to those controllers - In this case, its almost impossible (in some reasonable time) implement this
You use only -init or -initWithNibName...: to initialize view controllers in navigation stack. You could enumerate controllers from the root UINavigationController of the tab, get their classes names using NSStringFromClass and save them to NSUserDefaults. On apps start, you would reverse procedure (initialize controllers using their names strings read from NSUserDefaults using something like this: UIViewController *vc = [[NSClassFromString(#"aa") alloc] init];).
I understand you are ok with the code part so i will just give my suggestion
on viewDidLoad of every view controller set a nsuserdefault value of the top most object on navigation array.
if their are not too many branches then you can manage the push at root view controller easily
This is not the proper answer but you can use it for Navigating view after launching.
In AppDelegate file use below codes:---
#import "NewSAppDelegate.h"
#import "NewSViewController.h"
static NewSAppDelegate *globalSelf;
#implementation NewSAppDelegate
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
// Override point for customization after application launch.
self.viewController = [[NewSViewController alloc] initWithNibName:#"NewSViewController" bundle:nil];
self.navController=[[UINavigationController alloc] initWithRootViewController:self.viewController];
self.window.rootViewController = self.navController;
[self.window makeKeyAndVisible];
globalSelf=self;
NSSetUncaughtExceptionHandler(&uncaughtExceptionHandler);
return YES;
}
void uncaughtExceptionHandler(NSException *exception)
{
UIViewController *currentVC = globalSelf.navController.visibleViewController;
[[NSUserDefaults standardUserDefaults] setObject:NSStringFromClass(currentVC.class) forKey:#"lastVC"];
}
- (void)applicationDidEnterBackground:(UIApplication *)application
{
UIViewController *currentVC = self.navController.visibleViewController;
[[NSUserDefaults standardUserDefaults] setObject:NSStringFromClass(currentVC.class) forKey:#"lastVC"];
}
- (void)applicationDidBecomeActive:(UIApplication *)application
{
[[NSNotificationCenter defaultCenter] postNotificationName:#"appDidBecomeActive" object:nil];
// Restart any tasks that were paused (or not yet started) while the application was inactive. If the application was previously in the background, optionally refresh the user interface.
}
In your login viewController's init method add an observer for notification and in notification method , you can apply if conditions for viewController's name received.and push to that viewController on launching LoginView controller as:---
- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
if (self) {
[[NSNotificationCenter defaultCenter] addObserver:self
selector:#selector(openLastVC)
name:#"appDidBecomeActive"
object:nil];
// Custom initialization
}
return self;
}
-(void)openLastVC
{
NSLog(#"val ==%#",[[NSUserDefaults standardUserDefaults] valueForKey:#"lastVC"]);
if ([[[NSUserDefaults standardUserDefaults] valueForKey:#"lastVC"] isEqualToString:#"GhachakViewController"]) {
GhachakViewController *gvc=[[GhachakViewController alloc] initWithNibName:#"GhachakViewController" bundle:nil];
[self.navigationController pushViewController:gvc animated:NO];
}
}
May this help you....
I wrote a custom class, TagsScrollView, which displays tags inside a scroll view.
When the tags are pressed, TagsScrollView relies on its delegate to implement what to do. Almost all the time, this involves:
Changing the tab index to another index
Pushing TagsDetailVC to the current navigation controller.
Right now, this is how my app is structured:
Dotted line indicates a "has" relationship. MainVC has a FeedView, which has a few FeedCellViews, which in turn has a TagsScrollView each.
Solid line indicates a "push" relationship. ImageDetailVc is pushed onto the navController of MainVC.
How can I organize my code such that TagsScrollView's delegate can be pointed at MainVC elegantly?
right now I have defined the following:
TagsScrollView.h
#protocol TagPressedDelegate<NSObject>
#required
- (void)tagPressed:(id)sender forQuery:(NSString *)query;
#end
FeedCellView.m
self.tagsScrollView.tagPressedDelegate = self.tagPressedDelegate
FeedView.m
self.cells[0].tagPressedDelegate = self.tagPressedDelegate
MainViewVC.m
self.feed.tagPressedDelegate = self
....
- (void)tagPressed...
How can I avoid this pattern? What can I do better? Should I have TagsScrollViewDelegate extend ScrollViewDelegate instead?
You can definitely do better, remove the delegation pattern, use blocks.
Add a block based property to your TagsScrollView .h file
#property (copy, nonatomic) void (^tagPressedBlock)(id sender, NSString *query);
in the .m file add the related callbacks
- (void)tagPressed:(id)sender {
if (_tagPressedBlock) {
_tagPressedBlock(sender, self.query); // I'm assuming that the query is your iVar
}
}
assign the property like this
tagsScrollView.tagPressedBlock = ^(id sender, NSString *query) {
// do stuff with those parameters
}
That's for "doing it better"
As for how to pass a tag pressed event to your MainVC class, you should use NSNotificationCenter.
Define the notification name somewhere globally visible, for instance I'd suggest creating a Defines.h file and #including it in your Prefix.pch file.
Anyway, define the notification name:
static NSString *const TagPressedNotification = #"TagPressedNotification";
Next publish that notification when the -tagPressed: is executed and encapsulate the valuable information into the userInfo dictionary:
- (void)tagPressed:(id)sender {
[[NSNotificationCenter defaultCenter] postNotificationName:TagPressedNotification object:nil userInfo:#{#"sender" : sender, #"query" : self.query, #"scrollView" : self.tagScrollView}];
//.. code
}
Next add your MainVC as an observer to that notification:
MainVC.m
- (void)viewDidLoad {
[super viewDidLoad];
[[NSNotificationCenter defaultCenter] addObserver:self
selector:#selector(tagPressed:)
name:TagPressedNotification
object:nil];
}
And implement -tagPressed: method in your MainVC
- (void)tagPressed:(NSNotification *)notification {
id sender = notification.userInfo[#"sender"];
NSString *query = notification.userInfo[#"query"];
TagScrollView *scrollView = notification.userInfo[#"scrollView"];
if (scrollView == myScrollView) { // the one on your mainVC
// do stuff
}
}
Add don't forget to clean yourself out of NotificationCenter's register:
- (void)dealloc {
[[NSNotificationCenter defaultCenter] removeObserver:self];
}
easy
edit
I suppose you should also pass the scroll view, which is the sender, since your mainVC contains that scroll view as well. Edited the code
Another edit
Create an enumeration define in your Defines.h file
enum {
TagSenderTypeFeed = 1,
TagSenderTypeImageDetail
};
typedef NSInteger TagSenderType;
When creating a notification add appropriate enum value to your notification's userInfo dictionary #"senderType" : #(TagSenderTypeFeed)
I have a project i'm working on which involves 3 tabs in a UITabBarController (all done in a storyboard).
Each tab is running off a different view controller.
I have a button on tab 1 that performs a calculation and returns a result in a text box. I want it so that when I hit calculate, the result is also returned in a text box in tab 2.
I'm not really sure how to pass data between UIViewControllers so any help is appreciated.
as per vshall says you can do this stuff like bellow:-
yourAppdelegate.h
#interface yourAppdelegate : UIResponder <UIApplicationDelegate,UITabBarControllerDelegate>
{
NSString *myCalResult;
}
#property (nonatomic,retain) NSString *myCalResult;
yourAppdelegate.m
#implementation yourAppdelegate
#synthesize myCalResult,
yourCalclass.h
#import "yourAppdelegate.h"
#interface yourCalclass : UIViewController
{
yourAppdelegate *objAppdelegate;
}
yourCalclass.m
- (void)viewDidLoad
{
objAppdelegate = (yourAppdelegate *) [[UIApplication sharedApplication]delegate];
[super viewDidLoad];
}
-(IBAction)ActionTotal
{
objAppdelegate.myCalResult=result;
}
Now you result stored in objAppdelegate.myCalResult you can use this variable in your another tab with creating object of yourAppdelegat. Hope its helps you
You can define a variable in app delegate and store the result in that variable for class one. And once you switch the class you can fetch that value in your class two by creating an instance of your appDelegate and assign it to your textfield.
As Sanjit has suggested, NSUserDefaults is also a very convenient and clean way to achieve this.
Thanks.
If you don't really need to store the computed value but just notify the other controller in tab2 that the value changed, you can use NSNotificationCenter to post an NSNotification.
When you initialize the controller in tab2 you'll need to add it as an observer of the notification.
Something like that:
in tab1:
NSNumber *value = nil; // the computed value
[[NSNotificationCenter defaultCenter]
postNotificationName:#"com.company.app:ValueChangedNotification"
object:self
userInfo:#{#"value" : value}];
in tab2: register as an observer (in init or viewDidLoad methods)
[[NSNotificationCenter defaultCenter]
addObserver:self
selector:#selector(valueChanged:)
name:#"com.company.app:ValueChangedNotification"
object:nil];
the method that will be called when the notification is posted:
- (void)valueChanged:(NSNotification *)note
{
NSDictionary *userInfo = note.userInfo;
NSNumber *value = userInfo[#"value"];
// do something with value
}
Don't forget to remove the controller from the observers in viewDidUnload or sooner:
[[NSNotificationCenter defaultCenter] removeObserver:self];
I came across an interesting problem, i have main ViewController let's call him MainVC with navigationController and i am doing performSegueWithIdentifier from him to Mine second ViewController let's call him SecVC. so when i am trying to do the popViewControllerAnimated i want to pass some data from the SecVC to the MainVc.. i know i can do it with appDelegate Param or with singletons class but my question is : can i do it with more Elegant solution? like i use prepareForSegue and use local parmeters..
Thank you...
The best way to do it is by using a delegate.
//SecVCDelegate.h
#import <Foundation/Foundation.h>
#protocol SecVSDelegate <NSObject>
#optional
- (void)secVCDidDismisWithData:(NSObject*)data;
#end
//SecVC.h
#import <UIKit/UIKit.h>
#import "SecVSDelegate.h"
#interface SecVC : UIViewController
/** Returns the delegate */
#property (nonatomic, assign) id<SecVSDelegate> delegate;
#end
//SecVC.M
...
- (void) dealloc
{
...
delegate = nil
...
}
When ever you popViewControllerAnimated, right after it (or before it) you do this
if(_delegate && [_delegate respondsToSelector:#selector(secVCDidDismisWithData:)])
{
[_delegate secVCDidDismisWithData:myDataObject];
}
And in the MainVC you must be certain that you implement the delegate function
//MainVC.m
- (void)secVCDidDismisWithData
{
//do whatever you want with the data
}
To avoid any warnings you must tell that the MainVC class implements the delegate like this:
//MainVC.h
#import "SecVCDelegate.h"
...
#interface MainVC : UIViewController <SecVCDelegate>
...
secVCInstance.delegate = self;
[self.navigationController pushViewController:secVCInstance];
...
While I agree that the best option is to use Delegate,
but still if any one is looking for something different, he can use NSNotificationCenter as an alternative.
In viewDidLoad of MainVC:
- (void)viewDidLoad
{
[super viewDidLoad];
[[NSNotificationCenter defaultCenter] addObserver:self
selector:#selector(recvData:)
name:#"SecVCPopped"
object:nil];
}
And add method recvData in MainVC.m
- (void) recvData:(NSNotification *) notification
{
NSDictionary* userInfo = notification.userInfo;
int messageTotal = [[userInfo objectForKey:#"total"] intValue];
NSLog (#"Successfully received data from notification! %i", messageTotal);
}
Now in SecVC, before popping, add this line
NSMutableDictionary* userInfo = [NSMutableDictionary dictionary];
[userInfo setObject:[NSNumber numberWithInt:messageTotal] forKey:#"total"];
NSNotificationCenter* nc = [NSNotificationCenter defaultCenter];
[nc postNotificationName:#"SecVCPopped" object:self userInfo:userInfo];
I would do it in one of the following ways, but I'm not sure if it's elegant enough...
In SecVC, add an #property MainVC *mainVC; Use [self.mainVC setSomeValue:...]; before calling [self.navigationController popViewControllerAnimated:...];
Use [self.navigationController viewControllers]; to find out the MainVC *mainVC, and call [mainVC setSomeValue:...]; before the line of code that pop the ViewController.
Is this what you want?
I simply set up a protocol in the view being dismissed (example in Swift):
protocol ExampleTableViewControllerDismissDelegate {
func didDismiss(withData: Any)
}
var delegate: SearchableTableViewControllerDismissDelegate?
You can then call this when you dismiss/pop your view like this
self.navigationController?.popViewController(animated: true)
delegate?.didDismiss(withData: Any)
Then in the view being dismissed to (the parent in the hierarchy), we can conform to the delegate and essentially get a callback with the data after the view has been dismissed.
//MARK: ExampleTableViewControllerDismissDelegate
func didDismiss(withData: Any) {
//do some funky stuff
}
And don't forget to subscribe to the delegate in the parent view by using
viewController.delegate = self
There is another way to pass data between views including popViewControllerAnimated and it's with a global var instance, so If you modify that Var in your detail view and after do the popViewControllerAnimated, you can call the new data in the viewWillAppear method.
The first step is declare the Global var in main.h
NSMutableArray * layerList;
And now you have to call it in detail view.
SecondView.m
extern NSString *layerList;
SecondView.h
-(void)back{
layerList = #"Value to send";
[self.navigationController popViewControllerAnimated:YES];
}
Now you can use the information in the Master View after detect the pop action.
FirstView.m
extern NSString *layerList;
FirstView.h
-(void)viewWillAppear:(BOOL)animated{
NSLog(#"This is what I received: %#",layerList);
}
I have been trying for days to get this code to work, but I have no idea what I am doing wrong. Everytime the app wakes up from sleep, or the user closes the app and opens it again (without closing the app from multitasking), I want a label value to change.
In my applicationDidBecomeActive, I am running a counter, which I want to display on whatever viewcontroller is open at that moment.
Code:
- (void)applicationDidBecomeActive:(UIApplication *)application {
counter = counter + 1;
W1G1 *view1 = [[[W1G1 alloc] initWithNibName:#"W1G1" bundle:nil] retain];
[view1 setlabel];
}
In my viewcontroller W1G1, I have the following code:
Code:
- (void) setlabel {
NSString *string = [NSString stringWithFormat:#"%d", counter];
vocabword.text = string;
}
I have imported W1G1 in my appdelegate, but the code does not run :( Please help!
Thanks
In the AppDelegate.m file, where you have
- (void)applicationDidBecomeActive:(UIApplication *)application {
counter = counter + 1;
W1G1 *view1 = [[[W1G1 alloc] initWithNibName:#"W1G1" bundle:nil] retain];
[view1 setlabel];
}
the variable counter being incremented is confined to the AppDelegate. In other words, your view controller doesn't know that it has been incremented.
I would suggest that you use NSUserDefaults to store the value of counter so that you can easily pass it between these view controllers. Either that, or you could allow for an input into the method setLabel, e.g.
- (void) setlabel:(int)counter {
NSString *string = [NSString stringWithFormat:#"%d", counter];
vocabword.text = string;
}
and then in the AppDelegate you'll want to do:
- (void)applicationDidBecomeActive:(UIApplication *)application {
counter = counter + 1;
W1G1 *view1 = [[[W1G1 alloc] initWithNibName:#"W1G1" bundle:nil] retain];
[view1 setlabel:counter]; // <-- now you're using counter
[self.window addSubview:view1];
}
1) When you say 'the code does not run' do you mean that? That is, if you put NSLogs in applicationDidBecomeActive: and in setLabel does it show the code is run?
2) I would suspect the code is running. But your code won't "show the counter on whatever view controller is open at that moment". Your code creates a new view (view1), but that view won't be displayed. It is not added as a subview to anything. Your code will also leak. You create a W1G1 object, but it is never released and you throw away any reference you have to it.
To achieve what you want, you could add a subview to the application's window. Depending how your app delegate is set up, something like the following should do the trick:
counter++;
W1G1 *viewController1 = [[W1G1 alloc] initWithNibName:#"W1G1" bundle:nil];
[viewController1 setlabel: counter];
[[self window] addSubview: [viewController1 view]]
// you'll want to save a reference to the viewController somehow so you can release it at a later date
Then in W1G1
- (void) setlabel: (int) counter;
{
NSString *string = [NSString stringWithFormat:#"%d", counter];
vocabword.text = string;
}
There are, of course, lots of other approaches you could take towards this problem. And you'll need some strategy for removing the W1G1 view that you are adding at some stage, otherwise you'll just get more and more views added.
Update: You ask (in comments) how to keep track of your viewController throughout lifetime of the app... One approach is to keep track of it in your appDelegate. In the header have something like:
#class W1G1;
#interface MyAppDelegate : : NSObject <UIApplicationDelegate>
{
// other decelerations
int counter;
W1G1 * _myW1G1
}
#property (nonatomic, retain) W1G1* theW1G1
In the .m file include
#synthesize theW1G1 = _myW1G1;
Probably in application:didFinishLaunchingWithOptions: create the viewController, set the property to refer to it, and add its view to the view hierarchy.
W1G1* theViewController = [[W1G! alloc] initWithNibName: #"W1G1" bundle: nil];
[[self window] addSubview: [theViewController view]];
[self setTheW1G1: theViewController];
[theViewController release];
Then when you want to access the viewController again from with the app delegate use [self theW1G1], e.g.
[[self W1G1] setlabel: counter];