iOS present效果

共同点：

present和朴实方法都可以用于推出新的界面，present和dismiss对应使用，push和pop对应使用。

不同点：

present弹出的视图是模态视图（是一个临时视图）并且模式情况下不是全屏显示的；而push由视图栈控制，每一个视图都入栈，调用之前的视图则需要出栈。
present只能逐级返回；而push可以返回任意一层。

使用方法：

使用UINavigationController时使用push方法，代码如下：

[self.navigationController pushViewController:xxx animated:BOOL];

返回时使用pop方法，代码如下：

[self.navigationController popViewControllerAnimated:BOOL];

不使用导航栏的时候使用present方法，代码如下：

[self presentViewController:xxx animated:BOOL completion:nil];

返回时使用dismiss方法，代码如下：

[self dismissViewControllerAnimated:BOOL completion:nil];

下面我们用一个小小的demo来实际使用这几种方法，流程如下：
（1）A视图中创建一个按钮点击后present到B视图。
（2）B视图中创建两个按钮，一个点击后present到C视图，一个点击后push到C视图。
（3）C视图中创建两个按钮，一个点击后dismiss到B视图，一个点击后pop到B视图。

代码如下：
A视图（ViewController）present到B视图（SecondViewController）：

#import "ViewController.h"
#import "SecondViewController.h"

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view.
    
    self.view.backgroundColor = [UIColor orangeColor];
    UIButton *testButton = [UIButton buttonWithType:UIButtonTypeRoundedRect];
    [testButton setTitle:@"跳到B界面" forState:UIControlStateNormal];
    [testButton setTitleColor:[UIColor blackColor] forState:UIControlStateNormal];
    testButton.frame = CGRectMake([UIScreen mainScreen].bounds.size.width / 3, [UIScreen mainScreen].bounds.size.height / 3, [UIScreen mainScreen].bounds.size.width / 4, 50);
    
    [testButton addTarget:self action:@selector(pressButton) forControlEvents:UIControlEventTouchUpInside]; 
     
    [self.view addSubview:testButton];
}

//按钮的点击事件
- (void) pressButton {
    NSLog(@"pressButton TO B");
    SecondViewController *second = [[SecondViewController alloc] init];
    UINavigationController *navigation = [[UINavigationController alloc] initWithRootViewController:second];
    navigation.modalPresentationStyle = UIModalPresentationFullScreen;
    [self presentViewController:navigation animated:YES completion:nil];
}

@end

B视图（SecondViewController）的两个跳转到C视图（ThirdViewController）的按钮：

#import "SecondViewController.h"
#import "ThirdViewController.h"

@interface SecondViewController ()

@end

@implementation SecondViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view.
    
    self.view.backgroundColor = [UIColor yellowColor];
    UIButton *testButton = [UIButton buttonWithType:UIButtonTypeRoundedRect];
    [testButton setTitle:@"点击跳转C界面nav" forState:UIControlStateNormal];
    [testButton setTitleColor:[UIColor blackColor] forState:UIControlStateNormal];
    [testButton addTarget:self action:@selector(pressButton) forControlEvents:UIControlEventTouchUpInside];
    testButton.frame = CGRectMake([UIScreen mainScreen].bounds.size.width / 4, [UIScreen mainScreen].bounds.size.height / 4, [UIScreen mainScreen].bounds.size.width / 2, 50);
    [self.view addSubview:testButton];
    
    UIButton *testButtonSecond = [UIButton buttonWithType:UIButtonTypeRoundedRect];
    [testButtonSecond setTitle:@"点击跳转C界面present" forState:UIControlStateNormal];
    [testButtonSecond setTitleColor:[UIColor blackColor] forState:UIControlStateNormal];
    [testButtonSecond addTarget:self action:@selector(pressButtonSecond) forControlEvents:UIControlEventTouchUpInside];
    testButtonSecond.frame = CGRectMake([UIScreen mainScreen].bounds.size.width / 4, [UIScreen mainScreen].bounds.size.height / 3, [UIScreen mainScreen].bounds.size.width / 2, 50);
    [self.view addSubview:testButtonSecond];
}

//push到C界面
- (void) pressButton {
    NSLog(@"pressButtonPush");
    ThirdViewController *third = [[ThirdViewController alloc] init];
    third.modalPresentationStyle = UIModalPresentationFullScreen;
    [self.navigationController pushViewController:third animated:YES];
}

//present到C界面
- (void) pressButtonSecond {
    NSLog(@"pressButtonPresent");
    ThirdViewController *third = [[ThirdViewController alloc] init];
    third.modalPresentationStyle = UIModalPresentationFullScreen;
    [self presentViewController:third animated:YES completion:nil];
}

@end

C视图（ThirdViewController）的两个返回按钮：

#import "ThirdViewController.h"

@interface ThirdViewController ()

@end

@implementation ThirdViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view.
    
    self.view.backgroundColor = [UIColor whiteColor];
    UIButton *testButton = [UIButton buttonWithType:UIButtonTypeRoundedRect];
    [testButton setTitle:@"back With pop" forState:UIControlStateNormal];
    [testButton setTitleColor:[UIColor blackColor] forState:UIControlStateNormal];
    [testButton addTarget:self action:@selector(pressButton) forControlEvents:UIControlEventTouchUpInside];
    testButton.frame = CGRectMake([UIScreen mainScreen].bounds.size.width / 4, [UIScreen mainScreen].bounds.size.height / 4, [UIScreen mainScreen].bounds.size.width / 2, 50);
    [self.view addSubview:testButton];
    
    UIButton *testButtonSecond = [UIButton buttonWithType:UIButtonTypeRoundedRect];
    [testButtonSecond setTitle:@"back With dismiss" forState:UIControlStateNormal];
    [testButtonSecond setTitleColor:[UIColor blackColor] forState:UIControlStateNormal];
    [testButtonSecond addTarget:self action:@selector(pressButtonSecond) forControlEvents:UIControlEventTouchUpInside];
    testButtonSecond.frame = CGRectMake([UIScreen mainScreen].bounds.size.width / 4, [UIScreen mainScreen].bounds.size.height / 3, [UIScreen mainScreen].bounds.size.width / 2, 50);
    [self.view addSubview:testButtonSecond];
}

//使用pop返回
- (void) pressButton {
    NSLog(@"backpop");
    [self.navigationController popViewControllerAnimated:YES];
}

//使用dismiss返回
- (void) pressButtonSecond {
    NSLog(@"backdismiss");
    [self dismissViewControllerAnimated:YES completion:nil];
}

@end

运行结果如下：

当我们使用导航栏从B视图push到C视图，再点击第一个按钮（用pop方法返回）：

C视图界面如下：

点击第一个按钮后结果：

我们跳转到了B界面

但是当我们在C视图界面点击第二个按钮（用dismiss方法返回）后的运行结果：

我们返回到了A视图界面

当我们从B视图界面点击第二个按钮（用present方法跳转到C视图）后再点击第一个按钮（用pop方法返回）的结果如下：

我们可以看到，点击后并没有发生界面跳转，当前界面还是C视图界面，这是因为pop方法是导航栏才能使用的方法，我们没有使用导航栏的push方法而使用了present方法，结果是C视图界面中就没有导航栏，也就无法使用pop方法。但是此时我们点击C视图界面的第二个按钮（用dismiss方法返回）后的结果如下：

我们跳转到了B视图界面。