iOS - Navigation Bar


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Use of Navigation Bar

Navigation bar contains the navigation buttons of a navigation controller, which is a stack of view controllers which can be pushed and popped. Title on the navigation bar is the title of the current view controller.

Sample Code and Steps

Step 1 − Create a view based application.

Step 2 − Now, select the App Delegate.h and add a property for navigation controller as follows −

#import <UIKit/UIKit.h>

@class ViewController;

@interface AppDelegate : UIResponder <UIApplicationDelegate>

@property (strong, nonatomic) UIWindow *window;

@property (strong, nonatomic) ViewController *viewController;

@property (strong, nonatomic) UINavigationController *navController;

@end

Step 3 − Now update the application:didFinishLaunchingWithOptions: method in AppDelegate.m file, to allocate the navigation controller and makes it window's root view controller as follows −

- (BOOL)application:(UIApplication *)application 
   didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
   self.window = [[UIWindow alloc] initWithFrame:
   [[UIScreen mainScreen] bounds]];
   
   // Override point for customization after application launch.
   self.viewController = [[ViewController alloc] 
   initWithNibName:@"ViewController" bundle:nil];
   
   //Navigation controller init with ViewController as root
   UINavigationController *navController = [[UINavigationController alloc]
   initWithRootViewController:self.viewController];
   self.window.rootViewController = navController;
   [self.window makeKeyAndVisible];
   return YES;
}

Step 4 − Add a new class file TempViewController by selecting FileNewFile... → Objective C Class and then name the Class as TempViewController with subclass UIViewController.

Step 5 − Add a UIButton navButon in ViewController.h as follows −

// ViewController.h
#import <UIKit/UIKit.h>

@interface ViewController : UIViewController {
   UIButton *navButton;
}
@end

Step 6 − Add a method addNavigationBarItem and call the method in viewDidLoad.

Step 7 − Create a method for navigation item action.

Step 8 − We also need to create another method to push another view controller TempViewController.

Step 9 − The updated ViewController.m is as follows −

// ViewController.m
#import "ViewController.h"
#import "TempViewController.h"
@interface ViewController ()

@end
@implementation ViewController

- (void)viewDidLoad {
   [super viewDidLoad];
   [self addNavigationBarButton];
   //Do any additional setup after loading the view, typically from a nib
}

- (void)didReceiveMemoryWarning {
   [super didReceiveMemoryWarning];
   // Dispose of any resources that can be recreated.
}

-(IBAction)pushNewView:(id)sender {
   TempViewController *tempVC =[[TempViewController alloc]
   initWithNibName:@"TempViewController" bundle:nil];
   [self.navigationController pushViewController:tempVC animated:YES];
}

-(IBAction)myButtonClicked:(id)sender {
   // toggle hidden state for navButton
   [navButton setHidden:!nav.hidden];
}

-(void)addNavigationBarButton {
   UIBarButtonItem *myNavBtn = [[UIBarButtonItem alloc] initWithTitle:
   @"MyButton" style:UIBarButtonItemStyleBordered target:
   self action:@selector(myButtonClicked:)];
   
   [self.navigationController.navigationBar setBarStyle:UIBarStyleBlack];
   [self.navigationItem setRightBarButtonItem:myNavBtn];
   
   // create a navigation push button that is initially hidden
   navButton = [UIButton buttonWithType:UIButtonTypeRoundedRect];
   [navButton setFrame:CGRectMake(60, 50, 200, 40)];
   [navButton setTitle:@"Push Navigation" forState:UIControlStateNormal];
   [navButton addTarget:self action:@selector(pushNewView:) 
   forControlEvents:UIControlEventTouchUpInside];
   [self.view addSubview:navButton];
   [navButton setHidden:YES];
}
@end

Step 10 − When we run the application we'll get the following output −

iOS Tutorial

Step 11 − On clicking the navigation button MyButton, the push navigation button visibility is toggled.

Step 12 − On clicking the push navigation button, another view controller is pushed as shown below.

iOS Tutorial
ios_ui_elements.htm

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