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push和pop

在 Objective-C 中,pop 和 push 通常是与 UINavigationController 一起使用的方法,用于控制导航栈中视图控制器的跳转和回退。

• push 和 pop 通常成对使用,用于实现导航栈的前进和后退功能。
• 当用户进入新的视图控制器时,使用 push 方法将其加入导航栈;
• 当用户需要返回上一个视图控制器时,使用 pop 方法从导航栈中移除当前视图控制器。

push的代码格式：

[self.navigationController pushViewController:two animated:YES];

pop的代码格式：

//返回上一视图控制器
[self.navigationController popViewControllerAnimated:YES];
//返回根视图控制器
[self.navigationController popToRootViewControllerAnimated:YES];
//返回到指定的控制器
[self.navigationController popToViewController:one animated:YES];

present和dismiss

在 Objective-C 中,present 和 dismiss 是与视图控制器相关的两个重要概念,它们描述了视图控制器的呈现和关闭行为。present 用于以模态方式呈现一个新的视图控制器。dismiss 用于关闭当前模态呈现的视图控制器,返回到上一级视图控制器。

区别与联系：

• present 和 dismiss 是相对的概念,present 用于呈现新的视图控制器,dismiss 用于关闭当前视图控制器。
• 通常情况下,一个视图控制器被 present 之后,需要通过 dismiss 方法来关闭自己,返回到上一级视图控制器。

示例代码：

[self presentViewController:three animated:YES completion:nil];

[self dismissViewControllerAnimated:YES completion:nil];

示例程序

VCone.m:

#import "VCone.h"
#import "VCtwo.h"
@interface VCone ()@end@implementation VCone
@synthesize item = _item;
- (void)viewDidLoad {[super viewDidLoad];self.view.backgroundColor = [UIColor redColor];_item = [[UIBarButtonItem alloc] initWithTitle:@"下一页" style:UIBarButtonItemStylePlain target:self action:@selector(pressRight)];self.navigationItem.rightBarButtonItem = _item;
}-(void) pressRight
{VCtwo* two = [[VCtwo alloc] init];[self.navigationController pushViewController:two animated:YES];}/*
#pragma mark - Navigation// In a storyboard-based application, you will often want to do a little preparation before navigation
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {// Get the new view controller using [segue destinationViewController].// Pass the selected object to the new view controller.
}
*/@end

VCtwo.m:

#import "VCtwo.h"
#import "VCone.h"
#import "VCthree.h"
@interface VCtwo ()@end@implementation VCtwo
@synthesize btn = _btn;
@synthesize btn1 = _btn1;
- (void)viewDidLoad {[super viewDidLoad];self.view.backgroundColor = [UIColor greenColor];_btn = [[UIBarButtonItem alloc] initWithTitle:@"上一页" style:UIBarButtonItemStylePlain target:self action:@selector(press)];self.navigationItem.leftBarButtonItem = _btn;_btn1 = [[UIBarButtonItem alloc] initWithTitle:@"下一页" style:UIBarButtonItemStylePlain target:self action:@selector(pressright)];self.navigationItem.rightBarButtonItem = _btn1;
}-(void) press
{[self.navigationController popViewControllerAnimated:YES];
}-(void) pressright
{VCthree* three = [[VCthree alloc] init];[self presentViewController:three animated:YES completion:nil];
}/*
#pragma mark - Navigation// In a storyboard-based application, you will often want to do a little preparation before navigation
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {// Get the new view controller using [segue destinationViewController].// Pass the selected object to the new view controller.
}
*/@end

VCthree.m:

#import "VCthree.h"
#import "VCtwo.h"
@interface VCthree ()@end@implementation VCthree- (void)viewDidLoad {[super viewDidLoad];// Do any additional setup after loading the view.self.view.backgroundColor = [UIColor yellowColor];
}-(void) touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event
{[self dismissViewControllerAnimated:YES completion:nil];
}/*
#pragma mark - Navigation// In a storyboard-based application, you will often want to do a little preparation before navigation
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {// Get the new view controller using [segue destinationViewController].// Pass the selected object to the new view controller.
}
*/@end

效果图：