UINavigationBar的创建

步骤：左右button －set方法－ navitem －push方法－ navbar －add方法－ VC的view上

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    
    UITextView *uitv = [[UITextView alloc]init];
    uitv.frame = CGRectMake(0, 20+44, 320, 640-44-20);
    uitv.bounces = YES;
    uitv.autocapitalizationType = UITextAutocapitalizationTypeNone;
    uitv.autocorrectionType = UITextAutocorrectionTypeNo;
    [self.view addSubview:uitv];
//    uitv.delegate = self.view;
//    1、首先创建navbar的frame
    UINavigationBar *navbar = [[UINavigationBar alloc]initWithFrame:CGRectMake(0, 20, 320, 44)];
//    2、创建navitem装载功能按键
    UINavigationItem *navitem = [[UINavigationItem alloc]initWithTitle:nil];
//    3、创建左右两个按钮
    UIBarButtonItem *leftbtn = [[UIBarButtonItem alloc]initWithTitle:@"Back" style:UIBarButtonItemStylePlain target:self action:@selector(finishEdit)];
    UIBarButtonItem *rightbtn = [[UIBarButtonItem alloc]initWithTitle:@"Done" style:UIBarButtonItemStyleDone target:self action:@selector(finishEdit)];
//    4、赋予navitem标题
    [navitem setTitle:@"MY NOTE"];
//    5、push navitem到navbar
    [navbar pushNavigationItem:navitem animated:YES];
//    6、set按钮到navitem
    [navitem setLeftBarButtonItem:leftbtn];
    [navitem setRightBarButtonItem:rightbtn];
//    7、navbar子视图放到VC上
    [self.view addSubview:navbar];
    
//    navbar.items = [NSArray arrayWithObject:self.navigationItem];
//    done = [[UIBarButtonItem alloc]initWithBarButtonSystemItem:UIBarButtonItemStyleDone target:self action:@selector(finishEdit)];
    
}