Im new to iphone development and after lots of reading on it im still trying to figure out how UIViews operate properly. I have been playing about with it and i this is where i am at so far:
I have created a new xcode project using the view-based application. I have my MMAppViewController classes and i created a new UIViewController subclass called "Level1View".
There is a button titled "Level 1" that takes me to the "Level1View" viewController. In this viewController there is there is a "next" button, a "main menu" button (that returns to MMAppViewController) and there is a label, currently titled "Level 1".
My problem is that the code i have used to change the title of label does not work! Does anyone know why this is? Here is my code:
#class MMAppViewController;
#interface MMAppAppDelegate : NSObject <UIApplicationDelegate> {
UIWindow *window;
MMAppViewController *viewController;
}
#property (nonatomic, retain) IBOutlet UIWindow *window;
#property (nonatomic, retain) IBOutlet MMAppViewController *viewController;
#end
and
#implementation MMAppViewController
-(IBAction)pushLevel1{
Level1View *level1View = [[Level1View alloc] initWithNibName:nil bundle:nil];
[self presentModalViewController:level1View animated:YES];
}
...
and
#import <UIKit/UIKit.h>
#interface Level1View : UIViewController {
IBOutlet UILabel *labelTitle;
}
-(IBAction)pushBack;
-(IBAction)pushNext;
#end
and
#import "Level1View.h"
#import "MMAppViewController.h"
#implementation Level1View
-(IBAction)pushBack{
MMAppViewController *MainView = [[MMAppViewController alloc] initWithNibName:nil bundle:nil];
[self presentModalViewController:MainView animated:YES];
}
-(IBAction)pushNext{
[labelTitle setText:(#"Thanks for playing :)")];
}
- (void)didReceiveMemoryWarning {
...
Currently the app runs but the label wont change when i hit the "next" button. Can anyone help?
are you sure a UINavigationController isn't a better tool for the job you want to do? That will make it easy for you to manage a stack of UIView objects.
That said, have you tried adding logging to make sure your pushNext method is getting called? where is labelTitle declared? Did you use a XIB or not?
Did you bind the Label in Interface Builder to the labelTitle outlet in your Level1View?
If you forget that step, the outlets won't work. Even after several years, I still forget this step sometimes.
--Mike
are you sure you connected the label in IB?
and if you set a property "#property (nonatomic, retain) IBOutlet UILabel *labelTitle;" in Level1View.h you can access it from Main View:
Level1View *level1View = [[Level1View alloc] initWithNibName:nil bundle:nil];
[self presentModalViewController:level1View animated:YES];
level1View.labelTitle.text = #"something";
[level1View release];
The other thing you shouldn't present the Main View Controller again instead dismiss the Level1View with:
#implementation Level1View
-(IBAction)pushBack{
[self dismissModalViewControllerAnimated:YES];
}
//
and maybe the problem is [[Level1View alloc] initWithNibName:nil bundle:nil] you have to specify the nib you want to load e.g. [[Level1View alloc] initWithNibName:#"Level1View" bundle:nil]
Declare labelTitle as a property in your header file, and synthesize labelTitle in your .m - as long as labelTitle is hooked up through interface builder the rest of your code is fine.
.h
#property (nonatomic, retain) IBOutlet UILabel *labelTitle;
.m
#synthesize labelTitle;
Then your setter call will work. (also, dot-notation works for synthesized properties so you may as well use it)
change
[labelTitle setText:(#"Thanks for playing :)")];
to
labelTitle.text = #"Thanks for playing :)";
Synthesizing a property will create setter and getter methods at runtime. Read: The Objective-C Programming Language
Related
I have my ViewController.h/m and another class Keyboard.h/m.
In my ViewController.h I have an UILabel:
#interface ViewController : UIViewController{
UILabel *label;
}
#property (nonatomic, retain) IBOutlet UILabel *label;
and my ViewController.m looks so
#import "ViewController.h"
#synthesize label;
...
Now I want to change the label from Keyboard.m.
I have tried something like this:
#import "ViewController.h"
...
ViewController *vc;
vc.label.text = #"text";
it compiles without any errors but the label doesn't change
It's very error prone that you're doing here.
ViewController *vc;
declares a pointer, but this won't be initialized; so when you're accessing its property vc.label.text, objc_messageSend() will be passed a bogus pointer, so it can potentially crash! (you're lucky if id didn't do so.)
Anyways: if you have done it well, like ViewController *vc = [[ViewController alloc] init]; creating a new instance wouldn't have affected the other instance. You have to store the pointer to your instance somewhere, e. g. set a #property (retain) ViewContrller *vc; to your application's app delegate object, and access it through that property like this:
[(MyAppDelegate *)[[UIApplication sharedApplication] delegate] vc].label.text = #"new text";
that way it should work.
Hope it helps.
How are you initiating your vc variable? I am guessing that is where the error is coming from. Try doing:
vc = [[ViewController alloc] initWithNibName:# ViewController"];
If you are already doing that, make sure your IBOutlet is hooked up correctly. You are setting the variable correctly so the error must be coming from somewhere else.
I have an existing TableViewController as follows
// TableViewController.h
#interface TableViewController : UITableViewController { NSArray *dataArray; }
#property (nonatomic, retain) NSArray *dataArray;
And a navAppDelegate - to be specific:
// navAppDelegate.h
#import <UIKit/UIKit.h>
#interface navwAppDelegate : NSObject
<UIApplicationDelegate, UINavigationControllerDelegate> {
UIWindow *window;
IBOutlet UINavigationController *navigationController;}
#property (nonatomic, retain) IBOutlet UIWindow *window;
#property (nonatomic, retain) UINavigationController *navigationController;
// navAppDelegate.m
#import "navAppDelegate.h"
#implementation navigationtableviewAppDelegate
#synthesize window, navigationController;
- (void)applicationDidFinishLaunching:(UIApplication *)application
{
[window makeKeyAndVisible];
[window addSubview:[navigationController view]];
}
Now, I simply added the files to an existing project, except I put the content of (void)applicationDidFinishLaunching{} in a (void)viewDidLoad{} since it's a view from now on and not a window (right?). It doesn't work and my guess is that I have to change all the window calls from above to a view? What am I making here fundamentally wrong?
I'm making a call from
// StartOffHere.m
- (void)LetsGoButtonTouched {
navAppDelegate *newview = [[navAppDelegate alloc] initWithNibName:nil bundle:nil]; // I get a SIGABRT here
[[self navigationController] pushViewController: newview animated: YES];
}
- (void)LetsGoButtonTouched {
TableViewController *tableViewController = [[TableViewController alloc] init];
[[self navigationController] pushViewController:tableViewController animated: YES];
}
Try that. Is that what you wanted to happen?
If so, what I have done is created a new instance of your table view controller and pushed that. In your original code, you were trying to push on the app delegate which cannot be done; the app delegate is not a view controller. TableViewController, your subclass of UITableViewController, is though, so you can use this for the pushViewController: method - and the table view will appear on screen.
Thanks Benjamin. Excellent. But it didn't work quite that way though - after two hard days I managed it to run. For those who are interesed, here's what I did:
If you want to add an existing TableViewController with a NavigationController you'll only need the TableViewController and the DetailViewController files. Forget the AppDelegate.
Do twice new file -> Subclass and copy your existing code into identical TableViewController .h/.m/.xib - and DetailViewController .h/.m/.xib respectively.
When you make the method call you have to integrate both the TableViewController and the NavigationController - like this:
- (void)LetsGoButtonTouched {
TableViewController *tvc = [[[TableViewController alloc] init] autorelease];
UINavigationController *navigationController = [[[UINavigationController alloc] initWithRootViewController:tvc]autorelease];
[self presentModalViewController:navigationController animated:YES];
By the way, this question gave me the hint:
Add a UINavigationBar to a UITableViewController without a UINavigationController
I'm my class i've added a an instance of my view controller, created a property and then synthesized it in my implementation file. I am trying to update the UIlabel in the view controller like this,
NSString *currentChar = [[NSString alloc] initWithFormat:#"%c", ch];
viewController.outputLabel.text = currentChar;
[currentChar release];
My problem is that everything builds without any errors or warnings but the label just doesn't get updated, what am I doing wrong. I'd really appreciate some help on this one.
Are you sure you're referencing the existing viewController and you didn't instantiate a new one? Your property is not declared as copy, correct?
textProcessor.h / .m
#interface textProcessor : NSObject {
MainViewController *mainView;
}
#property (retain) MainViewController *mainView;
#end
#implementation textProcessor;
#synthesize mainView;
MainViewController.h / .m
#interface MainViewController : UIViewController {
UILabel *myLabel;
}
#property (retain) UILabel myLabel;
#end
#implementation MainViewController
#synthesize myLabel;
When you are initializing your textProcessor class, and you set the value for "mainView" like
-(void)viewDidLoad {
[super viewDidLoad];
textProcessor *proc = [[textProcessor alloc] init];
proc.mainView = self;
//note that you are not doing this:
//MainViewController *mainView = [[MainViewController alloc] init];
//proc.mainView = mainView;
//that was creating a new instance variable instead of using self, the existing one
[textProcessor release];
}
Have you created your label in IB? If you are using IB you have to create an IBOutlet for your UILabel. You then make a connection between the UILabel in IB to your IBOutlet in your class.
Have you tried calling the setNeedsDisplay method on the view? Also you may want to try using the setText method instead of assigning directly to the property.
I have a MyAppAppDelegate, it contains a window, and a UITabBarController.
#interface MyAppAppDelegate : NSObject <UIApplicationDelegate> {
UIWindow *window;
IBOutlet UITabBarController *rootController;
}
#property (nonatomic, retain) IBOutlet UIWindow *window;
#property (nonatomic, retain) IBOutlet UITabBarController *rootController;
#end
And I have View A, that contain a button to switch to View B. It is the .h file:
#import <UIKit/UIKit.h>
#class MyAppAppDelegate;
#class ViewBController;
#interface ViewAController : UIViewController {
IBOutlet UIView *view;
IBOutlet UIButton *switchToViewBButton;
}
#property (retain, nonatomic) UIView *view;
#property (retain, nonatomic) UIButton *switchToViewBButton;
-(IBAction) startSwitching: (id)sender;
#end
And it is the.m file:
#import "ViewAController.h"
#import "ViewBController.h"
#import "MyAppAppDelegate.h"
#implementation ViewAController
/*skip the default generated codes*/
-(IBAction) startClock: (id)sender{
NSLog(#"Start Switching");
[rootController presentModalViewController:ViewBController animated:YES];
}
Plz notice that the ViewB is not enable to display on UITabBarController, it only appear, when the ViewA button is clicked. Also, I found that the debugger tell me that the rootController is undeclared. but I already import MyAppDelegate to the file. thz a lot... ...
You need to synthesize the rootController instance:
#synthesize rootController;
Then it should work. Put this line of code below the implementation line in the .m file. There is no reason why you should be getting the second error, so try my solution and then tell us what happened.
Also, please try to write in complete sentences. In my experience, if you write well in a forum post, you will gain more respect from people who might help you.
No you need to do something like this:
ViewBController* vc = [[ViewBController alloc] initWithNib: #"ViewBController" mainBundle: nil];
if (vc != nil) {
[rootController presentModalViewController: vc animated:YES];
[vc release];
}
The mistake that you are making is that you are passing presentModalViewController: the class of the ViewBController. Instead it needs an instance.
ViewBController* viewBController = [[[ViewBController alloc] initWithNibName: #"NameOfViewBControllerNibFile" bundle:nil] autorelease];
[self presentModalViewController:viewBController animated:YES];
You can not access rootController from ViewAController, because it is a property of MyAppAppDelegate, not ViewAController. If you want to access the UITabBarController in charge of ViewAController, then inside ViewAController you use self.tabBarController
So if you want the UITabBarController to do the above, change it to
ViewBController* viewBController = [[[ViewBController alloc] initWithNib: #"NameOfViewBControllerNibFile" mainBundle: nil] autorelease];
[self.tabBarController presentModalViewController:viewBController animated:YES];
ViewBController *vc = [[[ViewBController alloc] initWithNib:#"ViewBController"
mainBundle:nil] autorelease];
MyAppDelegate *appDelegate = (MyAppAppDelegate *)[UIApplication sharedApplication].delegate;
[appDelegate.rootController presentModalViewController:vc animated:YES];
I'm a beginner programmmer, this is for xcode - iPhone. although i made alot of my iPhone app but i seem to lack some understanding of how a simple communication might work.
Specially when I've got 2 ViewControllers.
And I wana call one function of a ViewController from another ViewController. Both are under a tabbarController. What I want to achieve is When I'm in ViewA, after tapping on a tableCell, I Should Invoke a method of ViewB and the NavigationBar of ViewB pushes to viewDetail.
The Following is the code i'm using
in ViewControllerA.h (where I'm calling a method)
#class ViewControllerB;
#interface SmartDDxViewController : UIViewController {
IBOutlet UITableView *tableView;
ViewControllerB *xViewController;
}
#property (nonatomic, retain) UITableView *tableView;
#property (nonatomic, retain) ViewControllerB *xViewController;
And this is what I use to invoke it..ViewControllerA.m
ViewControllerB *ddViewController = [[ViewControllerB alloc] init];
self.xViewController = ddViewController;
[xViewController InitialiseDetailWithId:2 title:#"HEYA"];
Heres the InitialiseDetailWithId code: in ViewControllerB.m
-(void)InitialiseDetailWithId:(NSInteger)pkey title:(NSString *)tt{
NSLog(#"InitialiseDetailC=========================================");
AppDelegate *appDelegate = (Smart_DifferentialsAppDelegate *)[[UIApplication sharedApplication] delegate];
[appDelegate GetConditionDetailsWithId:pkey];
DDisViewController *viewController= [[DDisViewController alloc] initWithNibName:#"DetailView" bundle:nil];
viewController.title = tt;
[self.NavBar pushViewController:viewController animated:YES];
//[tt release];
[viewController release];
viewController = nil;
[self say:#"HEYA"]; //this is ALERTVIEW box that displays HEYA
}
I'm getting all information fine, and the alertview does get displayed. But when I chose that View in TabBar, its not pushed.
Do not use direct access between view controllers, instead use the delegate pattern. Define your controller like this:
#protocol ViewControllerAInitDelegate;
#interface ViewControllerA : UIViewController {
IBOutlet UITableView *tableView;
id<ViewControllerAInitDelegate> initDelegate;
}
#property (nonatomic, retain) UITableView *tableView;
#property (nonatomic, assign) ViewControllerAInitDelegate *initDelegate;
#end
#protocol ViewControllerInitDelegate
-(void)initializeDetailWithId:(NSInteger)pkey title:(NSString)tt;
#end
So in
Now let your application delegate conform to the ViewControllerInitDelegate protocol. It should look something like this:
#interface AppDelegate : NSObject <UIApplicationDelegate, ViewControllerInitDelegate> {
IBOutlet UITabBarControler* tabBarController;
IBOutlet ViewControllerA* controllerA;
IBOutlet ViewControllerB* controllerB;
}
#end;
The AppDelegate should know about both ViewControllerA, and ViewControllerB, but neither of the view controller should know about each other. This way it will be much easier to debug and extend your app.
//current view controller index
int currentVCIndex = [self.navigationController.viewControllers indexOfObject:self.navigationController.topViewController];
//previous view controller (index -1)
AccountViewController *account = (AccountViewController *)[self.navigationController.viewControllers objectAtIndex:currentVCIndex - 1];
(access to anything you want)
account.property = object;
[account doSmthng];
In each of your view controllers, you might want to add a instance variable/property to keep track of the other view controller.
you might have for example:
#interface ThisViewController : UIViewController {
SomeViewController *sViewController;
// other instance variables
}
#property (nonatomic, retain) SomeViewController *sViewController;
This not only makes it easier to call methods from the other view controller and access its public properties, but it also allows you an easier way of flipping between the two (with or without animation).