#import <UIKit/UIKit.h>
#import "SecondViewController.h"
@interface FirstViewController : UIViewController<UITextFieldDelegate,postValue>

@property(strong,nonatomic) UITextField *textName;
@property(strong,nonatomic) UIButton *nextbutton;

@end

#import "FirstViewController.h"

@interface FirstViewController ()

@end

@implementation FirstViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    self.view.backgroundColor=[UIColor redColor];
    self.textName=[[UITextField alloc] initWithFrame:CGRectMake(100, 100, 200,50)];
    self.textName.borderStyle=UITextBorderStyleLine;
    self.textName.delegate=self;
    [self.view addSubview:self.textName];
    
    self.nextbutton=[[UIButton alloc] initWithFrame:CGRectMake(200, 200, 100, 50)];
    [self.nextbutton setTitle:@"下一页" forState:UIControlStateNormal];
    self.nextbutton.backgroundColor=[UIColor grayColor];
    [self.nextbutton addTarget:self action:@selector(nextPage) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:self.nextbutton];
    
}

-(BOOL)textFieldShouldReturn:(UITextField *)textField
{
    if ([textField isFirstResponder]) {
        [textField resignFirstResponder];
    }
    
    return YES;
}

-(void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event
{
    [self.textName resignFirstResponder];
}

-(void)nextPage
{
    SecondViewController *secondVc=[[SecondViewController alloc] init];
    secondVc.str=self.textName.text;
    secondVc.deletage=self;
    [self presentViewController:secondVc animated:YES completion:nil];
}

-(void)postValue:(NSString *)str
{
    self.textName.text=str;
}

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

@end

#import <UIKit/UIKit.h>

  // 创建协议

@protocol postValue <NSObject>

-(void)postValue:(NSString *)str;

@end

@interface SecondViewController : UIViewController<UITextFieldDelegate>

@property(strong,nonatomic) UITextField *textInfo;
@property(strong,nonatomic) UIButton *backbutton;
@property(strong,nonatomic) NSString *str;

@property(strong,nonatomic) id<postValue> deletage;

@end

#import "SecondViewController.h"

@interface SecondViewController ()

@end

@implementation SecondViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    self.view.backgroundColor=[UIColor colorWithRed:0.541 green:0.878 blue:0.831 alpha:1.000];
    
    self.textInfo=[[UITextField alloc] initWithFrame:CGRectMake(100, 100, 200, 50)];
    self.textInfo.borderStyle=UITextBorderStyleLine;
    self.textInfo.text=self.str;
    self.textInfo.delegate=self;
    
    [self.view addSubview:self.textInfo];
    
    self.backbutton=[[UIButton alloc] initWithFrame:CGRectMake(100, 200, 100, 50)];
    [self.backbutton setTitle:@"上一页" forState:UIControlStateNormal];
    self.textInfo.text=self.str;
    [self.backbutton addTarget:self action:@selector(backPage) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:self.backbutton];
    
}

-(BOOL)textFieldShouldReturn:(UITextField *)textField
{
    if ([textField isFirstResponder]) {
        [textField resignFirstResponder];
    }
    
    return YES;
}

-(void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event
{
    [self.textInfo resignFirstResponder];
}


-(void)backPage
{
    if (self.deletage!=0) {
        [self.deletage postValue:self.textInfo.text];
    }
    
    [self dismissViewControllerAnimated:YES completion:nil];
}

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

#import <UIKit/UIKit.h>
#import"FirstViewController.h"
@interface AppDelegate : UIResponder <UIApplicationDelegate>

@property (strong, nonatomic) UIWindow *window;

@end

#import "AppDelegate.h"

@interface AppDelegate ()

@end

@implementation AppDelegate

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    FirstViewController *firstVc=[[FirstViewController alloc] init];
    
    self.window.rootViewController=firstVc;
    
    return YES;
}
.......

@end