UINavigationBar的使用

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新建工程，工程名为UINavigationBarTest

1）增加ViewController成员变量
@implementation ViewController
NSInteger count;
UINavigationBar* navBar;

2）在ViewController.m中创建导航项

-(UINavigationItem*)makeNavItem{

    UINavigationItem* navItem=[[UINavigationItem alloc]initWithTitle:nil];
    navItem.title=[NSString stringWithFormat: @"第[%d]个导航项",count];
    UIBarButtonItem* leftBtn=[[UIBarButtonItem alloc]initWithBarButtonSystemItem:UIBarButtonSystemItemAdd target:self  action:@selector(push)];
    [navItem setLeftBarButtonItem:leftBtn];
    UIBarButtonItem* rightBtn=[[UIBarButtonItem alloc]initWithBarButtonSystemItem:UIBarButtonSystemItemCancel target:self  action:@selector(pop)];
    [navItem setRightBarButtonItem:rightBtn];

    return navItem;
}

3）创建压栈函数

-(void)push{
    [navBar pushNavigationItem:[self makeNavItem]animated:YES];
    count++;

}

4）创建出栈函数

-(void)pop{
    if(count>2){
        count--;
        [navBar popNavigationItemAnimated:YES];
    }else{
        UIAlertView* alert=[[UIAlertView alloc]initWithTitle:@"提示" message:@"只剩下最后一个导航项，不能再出栈了"delegate:nil cancelButtonTitle:@"确定"otherButtonTitles:nil];
        [alert show];
    }
}

5）重载viewDidLoad方法

- (void)viewDidLoad {
    [super viewDidLoad];
    CGRect rect=[[UIScreen mainScreen]bounds];
    CGSize windowSize=rect.size;
    CGFloat windowWidth=windowSize.width;

    count=1;
    navBar=[[UINavigationBar alloc] initWithFrame:CGRectMake(0, 20, windowWidth, 44)];
    [self.view addSubview:navBar];
    [self push];
    // Do any additional setup after loading the view, typically from a nib.
}

此时可以看到

注意nil参数,为了兼容swift,所以Xcode里设置了nonnull/nullable
不嫌麻烦的话可以重写这个方法:
UINavigationItem *navItem = [[UINavigationItem alloc] initWithTitle:@””];
嫌烦的可以直接加上这段

需在count前加上int
navItem.title=[NSString stringWithFormat: @”第[%d]个导航项”,(int)count];

此时运行程序