ViewController的Present使用效果

今年十一没有出去，其实以往的十一也没有出去。好吧，具体的说，五一也没有出去，再详细的说，就是春节的长假也没有出去，严格的说，自从有五一，十一，春节的假期以来，只有一个五一出去过一次，那是在认识媳妇的时候去的，之前和之后就再也没有了，人太多，凑啥热闹，有那功夫还不如在家敲敲代码充充电来的实在。
今年开始学习ios了，刚开始学啊，前面记录了几篇比较水的日志，今天来点相对有技术含量的，是相对啊，也不枉我看了一天的文档。还有就是我下了一个制作gif的小工具看看能不能用在这篇文档中。
看完ViewController的文档知道了一个事实，就是ViewController切换可以用2种方式，一种是直接在ViewController中调用Present的方法，另一种就是用NavigationController。一步一步来吧，这里先记录使用Presentation切换ViewController的方法。
其实很简单，就是先创建一个工程，然后添加一个class，暂时取名为SecondViewController，用来描述第2个页面，这样算上新建工程中已有的就有两个页面了，就可以在它们之间切来切去了。建好的工程如下图所以：

接下来上代码，先是ViewController类的：

//
// ViewController.h
// test-viewcontroller-presention
//
// Created by ChrisBluez on 10/2/16.
// Copyright © 2016 ChrisBluez. All rights reserved.
//

#import <UIKit/UIKit.h>

@interface ViewController : UIViewController


@end

//
// ViewController.m
// test-viewcontroller-presention
//
// Created by ChrisBluez on 10/2/16.
// Copyright © 2016 ChrisBluez. All rights reserved.
//

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

@interface ViewController ()

@end

@implementation ViewController



- (void)viewDidLoad {

// 创建一个按钮
UIButton *btn1 = [UIButton buttonWithType:UIButtonTypeRoundedRect];
    btn1.frame = CGRectMake(38, 100, 300, 30);
    [btn1 setTitle:@"jump to the second page" forState:UIControlStateNormal];
    btn1.backgroundColor = [UIColor whiteColor];
self.view.backgroundColor = [UIColor redColor];
    [btn1 addTarget:self action:@selector(jumpto) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:btn1];

    [super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
}


- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}

- (void) jumpto
{
    SecondViewController *sec = [[SecondViewController alloc] init];
    [self presentViewController:sec animated:YES completion:nil];
}

@end

简单说明，就是在第1个View上创建了一个按钮，并且指定了点击这个按钮后需要执行的方法jumpto()，在这个方法中创建了一个SecondViewController的实例，然后present它，就把SecondViewcontroller推出来了，从而切换到了SecondViewController维护的第2个页面。下面看SecondViewController的代码：

//
// SecondViewController.h
// test-viewcontroller-presention
//
// Created by ChrisBluez on 10/2/16.
// Copyright © 2016 ChrisBluez. All rights reserved.
//

#import <UIKit/UIKit.h>

@interface SecondViewController : UIViewController

@end

//
// SecondViewController.m
// test-viewcontroller-presention
//
// Created by ChrisBluez on 10/2/16.
// Copyright © 2016 ChrisBluez. All rights reserved.
//

#import "SecondViewController.h"

@interface SecondViewController ()

@end

@implementation SecondViewController

- (void)viewDidLoad {
// 创建一个按钮
UIButton *btn1 = [UIButton buttonWithType:UIButtonTypeRoundedRect];
    btn1.frame = CGRectMake(38, 100, 300, 30);
    [btn1 setTitle:@"jump to the first page" forState:UIControlStateNormal];
    btn1.backgroundColor = [UIColor whiteColor];
self.view.backgroundColor = [UIColor blueColor];
    [btn1 addTarget:self action:@selector(backto) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:btn1];

    [super viewDidLoad];
// Do any additional setup after loading the view.
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}

- (void) backto
{
    [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

同样是定义一个按钮，点击之后把自己dismiss了。
这里使用的present在ViewController的官方文档中有具体的描述，参考链接为：https://developer.apple.com/library/content/featuredarticles/ViewControllerPGforiPhoneOS/PresentingaViewController.html#//apple_ref/doc/uid/TP40007457-CH14-SW1
查看 Presenting Versus Showing a View Controller 及后面的相关章节。

上面代码执行的效果如下：