I am looking to replace the back button in the UINavigationController throughout my application. My requirements is that this back button be defined in one XIB and if possible, the code to set it is in one place.
I have seen various methods that set the property self.navigationItem.backBarButtonItem to be a UIBarButtomItem with the custom button as it's view, e.g. [[UIBarButtonItem alloc] initWithCustomView:myButton];
My first thought was to create a global category (not sure if that's the term, I'm new to Objective-C as you might have guessed) that implements 'ViewDidLoad' for all my UINavigationControllers, and setting this property. My problem is loading the XIB to this button that I create at runtime.
Does anyone have a suggestion on a neat way of doing this (I guess it must be a common thing to do, and I can't imagine repeating code in all my screens). I have considered creating a UINavigationController subclass, however I wasn't sure how this would effect my custom implementations of ViewDidLoad.
Any advice much appreciated. Also I need to target >= iOS4 (the appearance API is iOS5 only).
I prefer to not force inheritance where possible so you could do this with two categories
#interface UIViewController (backButtonAdditions)
- (void)ps_addBackbutton;
#end
#implementation UIViewController (backButtonAdditions)
- (void)ps_addBackbutton;
{
// add back button
}
#end
#interface UINavigationController (backButtonAdditions)
- (void)ps_pushViewController:(UIViewController *)viewController animated:(BOOL)animated;
#end
#implementation UINavigationController (backButtonAdditions)
- (void)ps_pushViewController:(UIViewController *)viewController animated:(BOOL)animated;
{
[viewController ps_addBackbutton];
[self pushViewController:viewController animated:animated];
}
#end
Now #import these files as appropriate and instead of using
[self.navigationController pushViewController:aViewController YES];
use
[self.navigationController ps_pushViewController:aViewController YES];
Disclaimer
I free styled this in the browser so you may need to tweak it
I had the same issue in my current project, the solution I came up with was to create a MYBaseViewController base class without xib and there in viewDidLoad programmatically (if you want to init barButtonItem with custom view, you are not able to create in xib anyways) create a customBackButton (and of course release it and set to nil viewDidUnload.
This works good for me because this way I can create xibs for all my other viewControllers that are subclasses of MYBaseViewController(if you created a view for base class in nib you would not be able to create a nib for a subclass).
Related
I am a newbie in iPhone application development.
I am developing an iPad application. It contains a menu bar on top, clicking on which retrieves a sub view. The sub view consists of UIPickerView. Upon selecting a row from UIPickerView, navigates to another UIViewController.
The UIPickerView methods are written in a separate class (As this functionality comes throughout the app, I made it a general one). So,
[self.navigationController pushViewController:controller animated:YES];
will not work for me!
I was able to get the name of the class to be pushed (It changes according to the selection made). Is there any way I can do it?
Thanks In Advance :-)
I guess what you really want is to create an object from a classname
The simple answer is
[[NSClassFromString(className) alloc] init...]
For a more thorough answer you should look at Create object from NSString of class name in Objective-C
You can use delegate method (delegate methods allows communication between objects) to implement this scenario
For example in your UIPicker(.h) class define a delegate protocol as follows
#protocol pickerProtocol;
#interface MyPicker : NSObject {
id <pickerProtocol> pickerDelegate;
}
#property(nonatomic,retain) id <pickerProtocol> pickerDelegate;
#end
#protocol pickerProtocol
- (void) pushViewController;
#end
And call this delegate method when selecting a row from UIPickerView
[pickerDelegate pushViewController];
Then in all view controller that uses picker write the implementation of the delegate method
- (void) pushViewController {
[self.navigationController pushViewController:controller animated:YES];
}
dont for get to set the delegate as follows
MyPicker *picker = [MyPicker alloc]init];
picker.pickerDelegate = self;
Let's say I have a view controller called vc1, which a synthesized property called property1, and i wants to access it from another view controller (vc2) and change it from vc2.
Now the methods created by the #syntisize to change and get properties are instance methods, so how can I get to them fro another view controller (do view controllers have instances in the app, and if so, what are they?)
Just to be clear I am using storyboards, so I never really instantiate the view controllers...
VC1.m:
-(void) yourMethod {
...
}
VC2.m
YOURViewController * vc2 = [[YOURViewController alloc]init];
[vc yourMethod];
[vc release];
Make sure to import your YOURViewController in your other view .m file
Something like that should work.
Or if you're having problems, try this tutorial here:
Tutorial on How-To Pass Data Between Two View Controllers
Hope this helps :)
While you can do it the way you describe, I think the common technique (assuming VC1 has a segue to VC2) is a bit different, where VC2 will have a property that will be set by prepareForSegue. See Configuring the Destination Controller When a Segue is Triggered in the View Controller Programming Guide.
You will need to link the storyboard views with the viewcontrollers so the view for vc1 would use the class vc1 etc for the rest (I assume you have done this because this is important when coding for different views)
Then all you need to do is where ever you are calling the properties so lets say the viewDidLoad method, declare the view controller like this:
- (void) viewDidLoad {
vc1 *viewController;
// Now you change the variable I'll presume its a UILabel so I'll change its text [viewController.property1 setText:#"I changed a different views UILabel"];
}
Let me know whether this works... Its worked for me before so should work
I am trying to open a ViewController from within another ViewController if certain conditions are met. The code seems to run without error but the view is never shown. I am new to xcode 4 /ios 5 so I must be missing something.
Here is the code responsible for opening the second viewcontroller:
CreateUserViewController *createUserController = [[CreateUserViewController alloc] initWithNibName:#"CreateUserView" bundle:[NSBundle mainBundle] keyWrapper:keyChainWrapper];
[self presentViewController:createUserController animated:YES completion:nil];
In my project I have a xib called, "CreateUserView". I have added a view controller to this xib and assigned it to, "CreateUserViewController".
Also I noticed in the apple documentation that is shows setting the delegate of the viewcontroller to be presented. But it seems that no property called, "delegate" is on the viewcontroller object. Is this documentation old? This is the document I am trying to use (section 9-1):
View Controller Programming
Can someone give me a hint? Thanks..
edit Adding Custom Constructor
-(id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil keyWrapper:(KeychainItemWrapper *)keyWrapper
{
self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
if(self){
[self setKeyChainWrapper:keyWrapper];
}
return self;
}
Regarding CreateUserView.xib: you don't want to put a CreateUserViewController object in the nib. You want to set the custom class of the File's Owner placeholder to CreateUserViewController. Then you need to connect the view outlet of File's Owner to the top-level view in the nib.
Regarding the delegate property: The UIViewController class doesn't have its own delegate property. The idea is that you add a delegate property to your subclass of UIViewController. The delegate provides a way for your presented view controller to pass custom information back to the presenting view controller.
Why would you want to do that? Let's consider the code you posted. I'll assume you have a UserListViewController that shows a list of User objects, and has a "Create new user" button. When the user touches the "Create new user" button, you create a CreateUserViewController and present it.
The user interacts with the CreateUserViewController to set the attributes of the new User object - name, rank, hairstyle, etc. Then he touches a "Done" button. Your CreateUserViewController creates the new User object and puts it in the database. Then it needs to dismiss itself, so the UserListViewController's list of User objects will appear again.
But you want the User list to include the newly created User object and you want to scroll the list so that the new User is on the screen. So you need a way to have your CreateUserViewController tell the UserListViewController about the newly created User object. This is where the delegate comes in.
You define a protocol like this:
#protocol CreateUserViewControllerDelegate
- (void)didCreateUser:(User *)user;
#end
and you give your CreateUserViewController a delegate property:
#interface CreateUserViewController
#property (weak, nonatomic) id<CreateUserViewControllerDelegate> delegate;
// ...
When your CreateUserViewController's "Done" button is touched, you notify your delegate of the new User:
- (IBAction)doneButtonWasTouched:(id)sender {
User *user = [self createUser];
[self.delegate didCreateUser:user];
[self dismissViewControllerAnimated:YES completion:nil];
}
In your UserListViewController, you adopt and implement the protocol:
#interface UserListViewController <CreateUserViewControllerDelegate, UITableViewDelegate, UITableViewDataSource>
// ...
#end
#implementation UserListViewController
- (void)didCreateUser:(User *)user {
NSIndexPath *indexPath = [NSIndexPath indexPathForRow:[self.users count] inSection:0];
[self.users addObject:user];
[self.tableView insertRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation: UITableViewRowAnimationAutomatic];
[self.tableView scrollToRowAtIndexPath:indexPath atScrollPosition: UITableViewScrollPositionNone animated:YES];
}
and when you need to present a CreateUserViewController, you set the new controller's delegate to the UserListViewController:
- (IBAction)createUserButtonWasTouched:(id)sender {
CreateUserViewController *createUserController = [[CreateUserViewController alloc] initWithNibName:#"CreateUserView" bundle:[NSBundle mainBundle] keyWrapper:keyChainWrapper];
createUserController.delegate = self;
[self presentViewController:createUserController animated:YES completion:nil];
}
In iOS5 the method for pushing new view controllers was really changed around quite a bit from iOS4 and Xcode 3. In summary, storyboards are now used to create your application view controller flow. Even though you may use standalone .xib files to build an application it is much less common in iOS5.
Anyway, the main method for pushing new view controllers onto the screen is done using segues. Check out this tutorial for an introduction: http://www.raywenderlich.com/5138/beginning-storyboards-in-ios-5-part-1
It does a good job on explaining how to create a storyboard and use segues. You can still present view controllers in code "the old way" but it is much much less common now with the introduction of these new technologies. There are also some absolutely awesome tutorials on iTunes U - search for CS193P. It's the Stanford Introductory class to Objective-C and programming for iOS. This should get you started and maybe help you think of a way to push your createUserController in a way more up to speed with iOS5.
UPDATE
I just wanted to add. If you configure your program to use storyboards and segues you can use the method performSegueWithIdentifier:sender: to perform the segue to your createUserController view if the proper conditions are met. See the Apple API for UIViewController for information on how to use this method.
If you add a subview to a view or add a view to a window, how does iOS know which controller this view belongs too?
Easy example:
Have a UIView without UIViewController and add it to the window [window addSubView:myView] --> it will not rotate.
Now use a UIViewController, have it implement shouldAutoRotateToInterfaceOrientation: and add the controller's view to the window: [window addSubView:myController.view] --> magically, the view will adjust to interface orientation.
But look at the code: in both cases a UIView was added. How can iOS possibly be aware that in the second case a UIViewController was involved?
I'm interested in how this is done internally. My best guess is that UIViewController.view is a setter which adds the controller to an internal array of controllers or assigns itself to some internal variable which holds the currently active controller.
Simple. Look in UIView.h. It's right there. Each UIView has a pointer back to a UIViewController (which is apparently referred to as the "viewDelegate").
Dave DeLong is correct (and gets +1) as it is clearly defined UIView.h as #package so anything in UIKit can access it.
Here is an example of accessing that variable for educational purposes only (obviously you will not do this in a real application).
SomeAppDelegate.m
#synthesize navigationController=_navigationController;
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
// Override point for customization after application launch.
// Add the navigation controller's view to the window and display.
self.window.rootViewController = self.navigationController;
[self.window makeKeyAndVisible];
//DO NOT TRY THIS AT HOME
UIView *mynavview = self.navigationController.view;
//Guaranteed _viewDelegate atleast in iOS 4.3
Ivar ivar = class_getInstanceVariable([UIView class], "_viewDelegate");
UIViewController *controller = object_getIvar(mynavview, ivar);
NSLog(#"controller = self.navigationController? %#", controller == self.navigationController ? #"Yes" : #"No");
return YES;
}
UIViewController has a private class method (called controllerForView:, I believe) which is used to find the view's controller. Internally, there is probably a table used to connect the two together, and this method simply finds the proper location in that table and returns its value. When the result is nil, the default implementation will be used (don't rotate).
If you want to be sure about the name of the method, set a breakpoint in -[UIView becomeFirstResponder], tap on a text field, and step through the code until it shows up in the call stack. I suggest using becomeFirstResponder because it is easier to control than most things which get the view controller.
So I'm trying to do this exercise where I need to set a delegate for the main window. The purpose is to make sure that when the user resizes the window, it's always twice as wide as it is high.
This is my AppController.h file:
#import <Cocoa/Cocoa.h>
#interface AppController : NSObject
{
NSWindow *windowWillResize;
}
#end
and this is my AppController.m file:
#import "AppController.h"
#implementation AppController
- (id) init
{
[super init];
windowWillResize = [[NSWindow alloc] init];
[windowWillResize setDelegate:self];
return self;
}
- (NSSize) windowWillResize:(NSWindow *)sender
toSize:(NSSize)frameSize;
{
NSLog(#"size is changing");
return frameSize;
}
#end
However, I can remove the line
[windowWillResize setDelegate:self];
since I set the delegate in Interface Builder, but I'm not sure why this works.
How does windowWillResize know that I'm referring to the main application window since I'm doing a completely new
windowWillResize = [[NSWindow alloc] init];
I have a feeling that I am completely doing this wrong. Could someone point me in the right direction? Thanks!
Indeed, you don't need to create a NSWindow *windowWilResize since a newly created Cocoa app already has a main window. You don't need to implement an -init method either.
You only need to set you appController as a delegate of your main window in Interface Builder and to implement the -windowWillResize: method in your appController.
If you are familiar with french language, you can take a look at a blog entry I have written on this subject: Délégation en Cocoa.
You're leaking an instance of NSWindow. In -init you create an NSWindow instance. However, that is not used because when the NIB loads, it sets up all the connections that you specified in Interface Builder and you start using the window from the NIB instead. Do not create a window object in code - Interface Builder does it for you! :-)
In fact, it's not quite "instead"; your app controller is now the delegate for both NSWindow instances - the one that comes from the NIB and the one you instantiated in -init. However as the in-code NSWindow is never used anywhere else, it's still redundant and should be removed.
If you just want to maintain the aspect ratio of the window you can use either of these two NSWindow methods:
setAspectRatio:(NSSize)
setContentAspectRatio:(NSSize)
The first method locks the entire window size, including the title bar. The second one just the content. You can call this method during the initialization of your window inside the delegate (for example: -applicationDidFinishLaunching)