UINavigationController练习

#import "AppDelegate.h"
#import <UIKit/UIKit.h>
#import "RootViewController.h"
@interface AppDelegate ()

@end

@implementation AppDelegate

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {

float sysVersion=[[UIDevice currentDevice]systemVersion].floatValue;
if (sysVersion>=8.0) {
UIUserNotificationType type=UIUserNotificationTypeBadge | UIUserNotificationTypeAlert | UIUserNotificationTypeSound;
UIUserNotificationSettings *setting=[UIUserNotificationSettings settingsForTypes:type categories:nil];
[[UIApplication sharedApplication]registerUserNotificationSettings:setting];
}

UIWindow* w = [[UIWindow alloc] initWithFrame:[UIScreen mainScreen].bounds];
w.backgroundColor = [UIColor whiteColor];
self.window = w;
RootViewController* r =[[RootViewController alloc] init];
UINavigationController* navBar = [[UINavigationController alloc] initWithRootViewController:r];
w.rootViewController = navBar;
[w makeKeyAndVisible];
return YES;
}

#import <UIKit/UIKit.h>

@interface RootViewController : UIViewController

@end

#import "RootViewController.h"
#import "SecondViewController.h"

@implementation RootViewController
-(void)viewWillAppear:(BOOL)animated
{
self.navigationController.navigationBar.barStyle = UIBarStyleBlack;
[self.navigationController setToolbarHidden:NO animated:YES];
}
-(void)viewDidLoad
{
[super viewDidLoad];

UIButton* btn = [UIButton buttonWithType:UIButtonTypeCustom];
[btn setFrame:CGRectMake(20, 64, 80, 40)];
[btn setBackgroundColor:[UIColor brownColor]];
[btn setTitle:@"添加" forState:UIControlStateNormal];
[btn addTarget:self action:@selector(BtnClicked:) forControlEvents:UIControlEventTouchUpInside];
[self.view addSubview:btn];

UIBarButtonItem* BarBtn = [[UIBarButtonItem alloc] initWithTitle:@"随机背景" style:UIBarButtonItemStylePlain target:self action:@selector(onClick:)];
self.navigationItem.leftBarButtonItem = BarBtn;

@try {
UINavigationItem* item = self.navigationController.navigationBar.items[0];
NSLog(@"%p",self.navigationItem);
NSLog(@"%p",item);
item.title = @"HelloWorld";
}
@catch (NSException *exception) {
NSLog(@"%@",exception.description);
}
@finally {

}
}
-(void)onClick:(UIBarButtonItem*) ABarBtn
{
CGFloat r = ( arc4random() % 256 / 256.0 );
CGFloat g = ( arc4random() % 256 / 256.0 );
CGFloat b = ( arc4random() % 256 / 256.0 );
UIColor* c2 = [UIColor colorWithRed:r green:g blue:b alpha:1];

self.view.backgroundColor = c2;
}
-(void)BtnClicked:(UIButton*)abtn
{
SecondViewController* sec = [[SecondViewController alloc] init];
[self.navigationController pushViewController:sec animated:NO];
}
@end

#import <UIKit/UIKit.h>

@interface SecondViewController : UIViewController

@end

#import "SecondViewController.h"

@implementation SecondViewController

-(void)viewDidLoad
{
[super viewDidLoad];
self.view.backgroundColor = [UIColor blueColor];
}
-(void)viewWillAppear:(BOOL)animated
{
UINavigationItem* item = self.navigationController.navigationBar.items[1];
[self.navigationController setToolbarHidden:YES animated:YES];
item.title = @"HelloWorldSec";
}
@end

个人对这个ui组件使用的理解

1，虽然UINavigationController继承于UIViewController,但是UIViewController保留了访问导航的属性，这样方便了各自实例的通讯。

2，自己写的类，如果要继承于UIViewController的话，最好直接继承，如果继承UITabViewController，虽然也有UINavigationController属性，但访问不到，为nil.

3，UINavigationController是栈管理的方式。

4，UINavigationController会为每一个实例创建个UINavigationItem.通过self.navigationItem与self.navigationController.navigationBar.item[0]的访问一样.

5，对navigationBar的设置都是全局的，不管在显示哪个ViewController.
6，这个navigationBar与Controller的View坐标重叠，如果新建subview，并且要显示出来，那么就得要考虑navigationBar的默认高度44.