Basically, I have a TabBarController and some sub-views attached to this controller. The TabBarController has some properties that I would like to access in the sub-views.
Here's what I have :
MyTabBarController's .m
-(void)setDetails:(id)sender
{
self.myVariable = #"This is a test";
NSLog(#"Here I set my variable");
}
- (void)viewDidLoad
{
NSLog(#"[LOAD] My Tab Bar Controller");
[self setDetails:nil];
}
First subView's .m
- (void)viewDidLoad
{
NSLog(#"[LOAD] FirstViewController");
MyTabBarController *myTBC = (MyTabBarController *)self.tabBarController;
self.headerName.text = myTBC.myViariable; // Here I just set the UILabel's text
NSLog(#"Header name = %#", self.headerName);
}
Here's what I have in the logs :
2012-08-07 11:43:23.001 MyFirstproject[23632:15203] [LOAD] My Tab Bar Controller
2012-08-07 11:43:23.012 MyFirstproject[23632:15203] [LOAD] FirstViewController
2012-08-07 11:43:23.072 MyFirstproject[23751:15203] Header name = (null)
2012-08-07 11:43:23.116 MyFirstproject[23751:15203] Here I set my variable
My question is : As I can see in the logs, the viewDidLoad function of MyTabBarController is called before the FirstViewController's one. However, it seems the function setDetails of MyTabBarController is called after the function viewDidLoad of the FirstViewController.
How can this be possible ? Is there something I'm doing wrong here ?
Thanks !
Try to put the code for firstViewController in viewDidAppear method instead of viewDidLoad
Happy Coding :)
And for the difference bet'n those two just check it out the documentation regarding it on Apple's developer site :)
Formally viewDidLoad call's once at the time of loading the view
And viewDidAppearcall's when ever the view is about to appeared on the screen :)
Happy Coding :)
Related
I was trying to push a viewcontroller B into navigation controller from A and then assigning some properties of B in A.
In this case, the assigning of properties was done and then viewDidLoad of viewcontroller A was executed.
Here, assigning properties in A should be done only after viewDidLoad of A has done.
For example,
[b.navController pushViewController:a animated:YES];
a.status = #"loaded";
Here, status was assigned first and then viewDidLoad of A was executed.
This happens only in iOS 7 whereas in iOS6 it works fine.
Can anyone please let me know where the problem is?
UPDATE: For me in some cases in iOS7, Push view is not working. How cna I debug and fix it?
Just access the viewcontroller.view (set any thing immediately after the alloc) property after the alloc init;
Which will loadview/viewdidload.
See Apple Documentation
In my experience, a UIViewController view is loaded lazily, no matter which iOS version you're working on. If you want to trigger a view load, and therefore its UIViewController viewDidLoad, you should access the view after the UIViewController is allocated. For example:
UIViewController *aViewController = [[CustomViewController alloc] init];
[aViewController view];
Make sure you don't code it as
aViewController.view
since that would generate a compiler warning.
So, in your case it would have to be something like this:
...
CustomViewController *a = [[CustomViewController alloc] init];
[b.navController pushViewController:a animated:YES];
[a view];
a.status = #"loaded";
Let me know if you have further problems with it.
You can know when a View Controller has been pushed onto the stack by implementing the UINavigationControllerDelegate and setting yourself as the delegate self.navigationController.delegate = self; then you will get this callback after every push
navigationController:didShowViewController:animated:
So you can check if the shown viewController is the one your interested in, then set your a.status.
I would suggest you call a delegate method once the view is loaded.
Set the delegate to be controller B.
and after viewDidLoad finishes (in controller A) call the delegate method. You can even pass parameters as you wish to the delegate.
Here's some example code:
Controller B:
a.delegate = self;
[b.navigationController pushViewController:a animated:YES];
Implement the delegate method:
- (void)controllerIsLoaded:(ControllerA *)controllerA status:(NSString *)status
{
a.status = status;
}
Controller A .h file:
#class ControllerA;
#protocol ControllerADelegate <NSObject>
- (void)controllerIsLoaded:(ControllerA *)controllerA status:(NSString *)status;
#end
#interface ControllerA : UIViewController
#property (nonatomic, weak) id <ControllerADelegate> delegate;
Controller A .m file:
- (void)viewDidLoad:(BOOL)animated
{
[super viewDidLoad:animated];
/* your viewDidLoad code here... */
if ([_delegate respondsToSelector:#selector(controllerIsLoaded:status)])
[_delegate controllerIsLoaded:self status:#"Loaded"];
}
Turn off animation for ios7, in my case its work
[b.navController pushViewController:a animated:NO];
a.status = #"loaded";
No documentation provides enough information to know exactly when viewDidLoad would be called.
UIViewController's documentation just says this
This method is called after the view controller has loaded its view hierarchy into memory
I would suggest that you create a custom initializer like this
- (id)initWithStatus:(NSString *)status {
}
But, if you are trying to use this variable to check if the viewController's view has 'loaded' or not, it may not be possible to do that because the pushViewController or presentViewController methods are not guaranteed to be synchronous.
Even in iOS 6, there was no explicit guarantee that the view would be loaded as soon as that method returned.
Please write the code in viewWillAppear method instead of viewDidLoad in next class i.e. where you are pushing the object to
-(void)viewWillAppear:(BOOL)animated
{
}
I'm understand of your question like this:
B *b = [[B alloc] init];
b.status = #"loaded";
[self.navigationController pushViewController:b animated:Yes];
If you want to pass a value from one controller to another means, you have to assign a value before using pushViewController method.
I have a little problem, because I can't pass data to another view controller.
-(void)barcodeData:(NSString *)barcode type:(int)type
{
mainTabBarController.selectedViewController=self;
[status setString:#""];
[status appendFormat:#"Type: %d\n",type];
[status appendFormat:#"Type text: %#\n",[dtdev barcodeType2Text:type]];
[status appendFormat:#"Barcode: %#",barcode];
[displayText setText:status];
codede1String = barcode;
NSLog(#"%#",codede1String);
[self updateBattery];
}
In the code above I put a barcode in the String codeString1. So far no problem, but when I send this data to the other viewController barCodeString suddenly is NULL.
I pass data to viewcontroller like this:
-(void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender{
if ([segue.identifier isEqualToString:#"barcode"]) {
main =[ segue destinationViewController];
main.code1.text = codede1String;
}
}
So how do I solve this problem?
I assume that code1 is a text field, text view or label. If so, the reason this doesn't work, is that the outlets for main are not yet set at the time of prepareForSegue. You need to create a string property in main and set its value to code1String in prepareForSegue. Then, in main's viewDidLoad or viewDidAppear, set code1's text value to that string.
Note that IBOutlets of the destination view controller are not set yet in prepareForSegue. So if main.code1 represents a UILabel, it will be nil because the view is not yet loaded. You should pass the string directly using a setter method: [main setCodeString:codede1String] and then configure the user interface in viewDidLoad: self.code1.text = [self codeString].
Do this in the viewDidLoad of the view controller, then it works fine
- (void)viewDidLoad
{
codedeString=[[NSString alloc] init];
}
Try doing this, it helped me once for the same kinda issue (but with xibs)
Add one more line, just before any assignments
[main.view setAlpha:1.0f];
main.code1.text = codede1String;
Hope this will help you as well.
Wondering how I can set properties of view controllers that are already on the NavigationController's stack
My situation:
I want to set up an image uploading flow like this
(Navigation Stack)
RootViewController -> TakePictureViewController -> EditPictureViewController -> UploadPictureViewController
When user confirms the upload from the UploadPictureViewController, rather than start to upload, I want to set an NSDictionary property on RootViewController which contains the upload query, then pop the navigation stack back down to the RootViewController and have it handle initiating and status reporting of the query.
Here's my code in the uploadpictureviewcontroller, currently, the code does pop to the right view controller, but the uploadPackage property is still nil, also I have tried to -setUploadPackage
RootViewController *rvc = (RootViewController *)[self.navigationController.viewControllers objectAtIndex:0];
rvc.uploadPackage = uploadPackage;
[self.navigationController popToViewController:rvc animated:YES];
All help appreciated, thanks.
try using [self.navigationController popToRootViewControllerAnimated:YES]. That should do it.
EDIT:
If you have only one instance of RootViewController, then you can set it up as a singleton and therefore you can access it from any other controller (just like the appDelegate). To do so you need to add the following to your RootViewController.m under synthesize...; :
static RootViewController *rootViewController;
+(id)sharedRootController {
return rootViewController;
}
inside your init method for RootViewController add the following line:
rootViewController = self;
now back to your UploadPictureViewController you can set the uploadPackage like this:
RootViewController *rvc = [RootViewController sharedRootController];
rvc.uploadPackage = uploadPackage;
Please note that you should NOT use the singleton method if there is to be more than one instance of RootViewController.
hope this helps!
I have a TabBarController which is set up with multiple ViewControllers at launch. When the user clicks a button I want to send them to a different ViewController in the TabBarController, and pass data through a delegate.
I have a protocol and delegate set up. However, when do you set the delegate since all the ViewControllers are in the TabBarController
Is this possible, how can I pass data to another ViewController in the TabBar when the user clicks a button. Any ideas, I'd really like to use a delegate.
- (IBAction)sendData:(id)sender
{
[self.delegate setStringData:strData];
self.tabBarController.selectedIndex = 0;
}
Edit:
So let's say I have a TabBarController with two ViewControllers called ViewControllerOne and ViewControllerTwo.
I have ViewControllerTwo set up as the delegate and protocol. This is the ViewController that will send data to ViewControllerOne after the button is pressed. ViewControllerOne implements protocol and contains the method setStringData which should be called after the button in ViewControllerTwo is pressed.
From a UIViewController you want to change the selected tab bar index and pass data.
I suggest you add a function in you app delegate for this.
That way your UIViewController won't be tied with a UITabBar (if tomorrow you want to use a different UI idiom, you will just have to change the implementation of your function in your app delegate).
To pass data, i you could try to introspection in your function : you take the current UIViewController of the new selected tab index, verify it responds to your selector and call the function.
Edit :
Let's assume your 'just' have to change the selected tabBar index (e.g. your UIViewController will always be the same on the new tab bar index).
In your first View Controller :
- (IBAction)sendData:(id)sender
{
UIApplicationDelegate * appDelegate = [[UIApplication sharedApplication] delegate];
if ([appDelegate respondToSelector:#selector(goToFirstTabBarWithData:)])
{
[appDelegate performSelector:#selector(goToFirstTabBarWithData:) withObject: strData];
}
}
In your Appdelegate :
- (void)goToFirstTabBarWithData:(NSString *)data
{
self.tabBarController.selectedIndex = 0;
UIViewController * vc = [self.tabBarController.viewControllers objectAtIndex:0];
if ([vc respondToSelector:#selector(setStringData:)])
{
[vc performSelector:#selector(setStringData:) withObject:data];
}
}
In your second View controller (the one you will arrive on) :
- (void)setStringData:(NSString *)data
{
// Do something...
}
I found a simpler solution to my problem. Inside of ViewControllerTwo, I just create an instance of ViewControllerOne and pass it that data I need. Then I change the tabBarController index to ViewControllerOne.
For example:
// A method inside of ViewControllerTwo
ViewController *viewcontrollerOne = [ViewcontrollerOne alloc] init];
[viewcontrollerOne setStringData:str];
[viewcontrollerOne release];
self.tabBarController.selectedIndex = 0;
I have application
I want a button to open another screen with done button
after click this button a data be transfered from the current screen to the previous one
like opening options screen , how to let the main view know the changes be done on this subview
Best regards
You can use properties for this.
Create a property in the second class: .h file
#interface DetailViewController : UIViewController {
NSString *head;
}
#property(nonatomic,retain)NSString *head;
#end
in .m file
#synthesize head;
Now in your firstviewcontroller or first class
if (dt==nil) {
DetailViewController *d = [[DetailViewController alloc]initWithNibName:#"Detailview" bundle:nil];
self.dt = d;
[d release];
}
dt.head=itemsum;
[self.navigationController pushViewController:self.dt animated:YES];
Suppose you have to pass NSString to other class then declare one Nsstring in second class and make accessor method for nsstring and then call this code from first view controller
yournextviewcontroller *viewcontroller = [[yournextviewcontroller alloc] initWithNibName:#"yournextviewcontroller" bundle:nil];
viewcontroller.Stringname = name;
[self.navigationController viewcontroller:evernotebook animated:YES];
You can take UIView as IBOutlet in the same ViewController. Show that view with click on Button like
IBOutlet UIView *yourAnotherScreenView; //Bind this to your view in XIB file.
[self.view addSubView:yourAnotherScreenView];
[self.view bringSubViewtoFront:yourAnotherScreenView];
Take Done button on the view and wireup the action event in the same controller and do the necessary stuff as required.
Use the simple delegate concept of Objective-C .
Check very simple answers in the below post for using delegate in Objective-C .
How do I set up a simple delegate to communicate between two view controllers?