iPhone开发之NavigationController

在上图中红线框住的就是导航栏，应用也很广泛，系统自带应用也在用它。如何从零创建一个导航栏应用。
新建项目，可以选择“Master-Detail Application”，但是默认就创建了TableView视图，这个我们不需要，所以还是从空项目创建，选择“Empty Appliction”，项目命名为“NavigationDemo”
新建一个视图，“New file..” -> “UIViewController subclass”，命名为RootViewController，并勾选“With XIB for user interface”
修改AppDelegate.h和AppDelegate.m源代码

//  AppDelegate.h
 
#import <UIKit/UIKit.h>
 
@interface AppDelegate : UIResponder <UIApplicationDelegate>
{
    UINavigationController *navController;
}
 
@property (strong, nonatomic) UIWindow *window;
 
@end

//  AppDelegate.m
 
#import "AppDelegate.h"
#import "RootViewController.h"
 
@implementation AppDelegate
 
@synthesize window = _window;
 
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
    navController = [[UINavigationController alloc] init];
    RootViewController *rootViewController = [[RootViewController alloc] init];
 
 
    // 这时navController会增加rootViewController的引用计数
    [navController pushViewController:rootViewController animated:NO];
    [self.window addSubview:navController.view];
    [self.window makeKeyAndVisible];
	// 所以这里可以release先前的引用，UINavigationController它会掌控rootViewController
	[rootViewController release];
    return YES;
}
 
...
 
- (void)dealloc
{
    [navController release];
    [self.window release];
    [super dealloc];
}
 
@end

这时候运行只是一个空的导航栏程序，咋都没有，接下来我们添加第二个视图并设置标题文字
新建一个视图，“New file..” -> “UIViewController subclass”，命名为SecondViewController，并勾选“With XIB for user interface”
在RootViewController.xib中添加一个按钮并绑定到(IBAction)displaySecondView

//  AppDelegate.m
 
 
#import "AppDelegate.h"
#import "RootViewController.h"
 
@implementation AppDelegate
 
@synthesize window = _window;
 
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
    navController = [[UINavigationController alloc] init];
    RootViewController *rootViewController = [[RootViewController alloc] init];
	// 修改 rootViewController 标题
    rootViewController.title = @"Root View";
 
    // Override point for customization after application launch.
    [navController pushViewController:rootViewController animated:NO];  
    [self.window addSubview:navController.view];
    [self.window makeKeyAndVisible];
 
    [rootViewController release];
 
    return YES;
}

//  RootViewController.h
 
#import <UIKit/UIKit.h>
 
@interface RootViewController : UIViewController
 
- (IBAction)displaySecondView:(id)sender;
 
@end

//  RootViewController.m
 
#import "RootViewController.h"
#import "SecondViewController.h"
 
@implementation RootViewController
 
...
 
- (void)displaySecondView:(id)sender
{
    SecondViewController *secondViewController = [[SecondViewController alloc] init];
	// 向视图询问它的导航控制器，因为在AppDelegate.m中我们已经在navController中rootViewController，
	// 所以这里我们询问rootViewController的导航控制器就会返回先前navController指针，如果没有就返回空
    [self.navigationController pushViewController:secondViewController animated:YES];
	// 设置 secondViewController 标题
    secondViewController.title = @"Second View";
 
    [secondViewController release];
}
 
@end

运行程序，当点击按钮，动画切换到secondViewController，导航栏自动显示返回rootViewController按钮。

我们看第一张截图，左右各有一个按钮，那么这两个按钮是怎么创建的，UINavigationController上面的区域叫UINavigationItem，UINavigationItem中可以添加UIBarButtonItem，创建界面最好的时机就是在- (void)viewDidLoad方法中.

//  RootViewController.m
 
#import "RootViewController.h"
#import "SecondViewController.h"
 
@implementation RootViewController
 
...
- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view from its nib.
    UIBarButtonItem *testButton = [[UIBarButtonItem alloc] initWithTitle:@"test" style:UIBarButtonItemStyleBordered target:self action:@selector(testClicked:)];
    self.navigationItem.leftBarButtonItem = testButton;
    [testButton release];
}
...

这时候点击导航栏上的“test”按钮没有任何行为，因为我们还没有创建action testClicked方法

//  RootViewController.m
 
#import "RootViewController.h"
#import "SecondViewController.h"
 
@implementation RootViewController
...
 
- (void)testClicked:(id)sender
{
    NSLog(@"test button clicked.");
}
 
...

有时候我们可能想创建下面的按钮，右边的按钮上面有个小十字，这些系统小图标是iPhone内部预设的，下面来看看这些按钮.

//  RootViewController.m
 
#import "RootViewController.h"
#import "SecondViewController.h"
 
@implementation RootViewController
 
...
- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view from its nib.
    UIBarButtonItem *testButton = [[UIBarButtonItem alloc] initWithTitle:@"test" style:UIBarButtonItemStyleBordered target:self action:@selector(testClicked:)];
    self.navigationItem.leftBarButtonItem = testButton;
 
    UIBarButtonItem *addButton =[[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemAdd target:self action:@selector(addClicked:)];
    self.navigationItem.rightBarButtonItem = addButton;
 
    [testButton release];
    [addButton release];
}
 
...
 
- (void)addClicked:(id)sender
{
    NSLog(@"add button clicked.");
}
@end

创建这些按钮很方便，只要打入UIBarButtonSystemItem，Xcode会自动补全，后面列出的都是系统预设按钮。
还有一些按钮按钮和行为，系统已经帮我们定义好了，Edit和Done按钮行为，我们只要实现它就好了

//  RootViewController.m
 
#import "RootViewController.h"
#import "SecondViewController.h"
 
@implementation RootViewController
 
...
 
- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view from its nib.
    UIBarButtonItem *testButton = [[UIBarButtonItem alloc] initWithTitle:@"test" style:UIBarButtonItemStyleBordered target:self action:@selector(testClicked:)];
    self.navigationItem.leftBarButtonItem = testButton;
 
    self.navigationItem.rightBarButtonItem = self.editButtonItem;
 
    [testButton release];
}
 
...
 
- (void)setEditing:(BOOL)editing animated:(BOOL)animated
{
    [super setEditing:editing animated:animated];
    if (editing) {
        NSLog(@"editing");
    } else {
        NSLog(@"done");
    }
}
 
@end

有时候我们会在导航栏上看到这样的按钮排列，这个又是怎么实现的

//  RootViewController.m
 
#import "RootViewController.h"
#import "SecondViewController.h"
 
@implementation RootViewController
 
...
 
- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view from its nib.
    UIBarButtonItem *testButton = [[UIBarButtonItem alloc] initWithTitle:@"test" style:UIBarButtonItemStyleBordered target:self action:@selector(testClicked:)];
    self.navigationItem.leftBarButtonItem = testButton;
 
    self.navigationItem.rightBarButtonItem = self.editButtonItem;
    NSArray *segmentButtons = [NSArray arrayWithObjects:@"升序", @"降序", nil];
    UISegmentedControl *segmentedController = [[UISegmentedControl alloc] initWithItems:segmentButtons];
    segmentedController.segmentedControlStyle = UISegmentedControlStyleBar;
    [segmentedController addTarget:self action:@selector(segmentAction:) forControlEvents:UIControlEventValueChanged];
    self.navigationItem.titleView = segmentedController;
 
    [testButton release];
    [segmentedController release];
}
 
...
- (void)segmentAction:(id)sender
{
    switch ([sender selectedSegmentIndex]) {
        case 0:
            NSLog(@"button 0 clicked");
            break;
 
        case 1:
            NSLog(@"button 1 clicked");
            break;
 
        default:
            break;
    }
}
...
@end

返回按钮的定制，如果导航栏的标题很长的话，返回按钮的长度也会变长，而我们并不希望这样的事发生，我们可以设置返回按钮的标题来达到目的，关键是我们要返回哪个视图控制器，就在哪个视图控制器类里修改。

//  RootViewController.m
 
#import "RootViewController.h"
#import "SecondViewController.h"
 
@implementation RootViewController
...
- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view from its nib.
    ...
    UIBarButtonItem *backButton = [[UIBarButtonItem alloc] initWithTitle:@"Root" style:UIBarButtonItemStylePlain target:nil action:nil];
    self.navigationItem.backBarButtonItem = backButton;
 
    [backButton release];
}
...
@end