IOS(UI)_委托传值

ViewController.m

#import "ViewController.h"#import "NextViewController.h"@interface ViewController ()<NextProtocol>{    UILabel *_label;}@end@implementation ViewController- (void)viewDidLoad {    [super viewDidLoad];    self.view.backgroundColor = [UIColor whiteColor];    self.title = @"ViewController";    _label = [UILabel new];    _label.text = @"LOL";    _label.backgroundColor = [UIColor yellowColor];    _label.textAlignment = NSTextAlignmentCenter;    _label.translatesAutoresizingMaskIntoConstraints = NO;    [self.view addSubview:_label];    NSLayoutConstraint *constraint1 = [NSLayoutConstraint constraintWithItem:_label attribute:NSLayoutAttributeTop relatedBy:NSLayoutRelationEqual toItem:self.view attribute:NSLayoutAttributeTop multiplier:1 constant:100];    [self.view addConstraint:constraint1];    NSLayoutConstraint *constraint2 = [NSLayoutConstraint constraintWithItem:_label attribute:NSLayoutAttributeCenterX relatedBy:NSLayoutRelationEqual toItem:self.view attribute:NSLayoutAttributeCenterX multiplier:1 constant:0];    [self.view addConstraint:constraint2];    NSLayoutConstraint *constraint3 = [NSLayoutConstraint constraintWithItem:_label attribute:NSLayoutAttributeWidth relatedBy:NSLayoutRelationEqual toItem:nil attribute:NSLayoutAttributeWidth multiplier:1 constant:200];    [self.view addConstraint:constraint3];    NSLayoutConstraint *constraint4 = [NSLayoutConstraint constraintWithItem:_label attribute:NSLayoutAttributeHeight relatedBy:NSLayoutRelationEqual toItem:nil attribute:NSLayoutAttributeHeight multiplier:1 constant:30];    [self.view addConstraint:constraint4];    UIButton *pushButton = [UIButton buttonWithType:UIButtonTypeCustom];    [pushButton setTitle:@"push" forState:UIControlStateNormal];    [pushButton setTitleColor:[UIColor purpleColor] forState:UIControlStateNormal];    pushButton.translatesAutoresizingMaskIntoConstraints = NO;    [pushButton addTarget:self action:@selector(pushBtnAction:) forControlEvents:UIControlEventTouchUpInside];    [self.view addSubview:pushButton];    NSLayoutConstraint *constraint11 = [NSLayoutConstraint constraintWithItem:pushButton attribute:NSLayoutAttributeTop relatedBy:NSLayoutRelationEqual toItem:_label attribute:NSLayoutAttributeBottom multiplier:1 constant:50];    [self.view addConstraint:constraint11];    NSLayoutConstraint *constraint12 = [NSLayoutConstraint constraintWithItem:pushButton attribute:NSLayoutAttributeCenterX relatedBy:NSLayoutRelationEqual toItem:self.view attribute:NSLayoutAttributeCenterX multiplier:1 constant:0];    [self.view addConstraint:constraint12];    NSLayoutConstraint *constraint13 = [NSLayoutConstraint constraintWithItem:pushButton attribute:NSLayoutAttributeWidth relatedBy:NSLayoutRelationEqual toItem:nil attribute:NSLayoutAttributeWidth multiplier:1 constant:100];    [self.view addConstraint:constraint13];    NSLayoutConstraint *constraint14 = [NSLayoutConstraint constraintWithItem:pushButton attribute:NSLayoutAttributeHeight relatedBy:NSLayoutRelationEqual toItem:nil attribute:NSLayoutAttributeHeight multiplier:1 constant:30];    [self.view addConstraint:constraint14];}#pragma mark ----------------------(void)pushBtnAction:(UIButton *)sender{    NextViewController *nextViewController = [[NextViewController alloc]init];   // nextViewController.text = _label.text;    [self.navigationController pushViewController:nextViewController animated:YES];    //=====让ViewController遵循协议    nextViewController.delegate = self;}//调用协议里面的方法-(void)transferString:(NSString *)string{    _label.text = string;}- (void)didReceiveMemoryWarning {    [super didReceiveMemoryWarning];    // Dispose of any resources that can be recreated.}@end/* 从A页面推到B页面,然后B页面要回传值给A页面。 若使用委托传值的方式。那么首先需要在定义一个协议,然后在B页面定义一个循序该协议的代理的属性 判断代理是否存在并且代理是否循序协议。若存在,再调用协议里面的方法。 在A页面,让A页面遵循该协议,让后让B页面的对象的代理 = self 最后再实现一些协议里面的方法,并以此获得回传的参数 */

NextViewController.h

#import <UIKit/UIKit.h>//委托模式在UI中属于回调传值=============@protocol NextProtocol <NSObject>//在委托里面定义一个方法=============-(void)transferString:(NSString *)string;@end@interface NextViewController : UIViewController@property(nonatomic,strong)NSString *text;//定义一个协议 =======@property (nonatomic,assign)id<NextProtocol>delegate;@end

NextViewController.m

#import "NextViewController.h"//调用TextField API里面的协议 用来取消第一响应者@interface NextViewController ()<UITextFieldDelegate>@end@implementation NextViewController- (void)viewDidLoad {    [super viewDidLoad];    self.view.backgroundColor = [UIColor whiteColor];    self.title = @"NextViewController";    UILabel *label = [UILabel new];    label.backgroundColor = [UIColor yellowColor];    label.text = self.text;    label.textAlignment = NSTextAlignmentCenter;    label.translatesAutoresizingMaskIntoConstraints = NO;    [self.view addSubview:label];    NSLayoutConstraint *constraint1 = [NSLayoutConstraint constraintWithItem:label attribute:NSLayoutAttributeTop relatedBy:NSLayoutRelationEqual toItem:self.view attribute:NSLayoutAttributeTop multiplier:1 constant:100];    [self.view addConstraint:constraint1];    NSLayoutConstraint *constraint2 = [NSLayoutConstraint constraintWithItem:label attribute:NSLayoutAttributeCenterX relatedBy:NSLayoutRelationEqual toItem:self.view attribute:NSLayoutAttributeCenterX multiplier:1 constant:0];    [self.view addConstraint:constraint2];    NSLayoutConstraint *constraint3 = [NSLayoutConstraint constraintWithItem:label attribute:NSLayoutAttributeWidth relatedBy:NSLayoutRelationEqual toItem:nil attribute:NSLayoutAttributeWidth multiplier:1 constant:200];    [self.view addConstraint:constraint3];    NSLayoutConstraint *constraint4 = [NSLayoutConstraint constraintWithItem:label attribute:NSLayoutAttributeHeight relatedBy:NSLayoutRelationEqual toItem:nil attribute:NSLayoutAttributeHeight multiplier:1 constant:30];    [self.view addConstraint:constraint4];    UITextField *textField = [[UITextField alloc]init];    textField.layer.borderColor = [UIColor lightGrayColor].CGColor;    textField.layer.borderWidth = 1.0;    textField.layer.cornerRadius = 5.0;    textField.layer.masksToBounds = YES;    //让谁遵循委托==============    textField.delegate = self;    textField.placeholder = @"请输入要传的值..";    textField.tag = 2000;    textField.translatesAutoresizingMaskIntoConstraints = NO;    [self.view addSubview:textField];    NSLayoutConstraint *constraint11 = [NSLayoutConstraint constraintWithItem:textField attribute:NSLayoutAttributeCenterX relatedBy:NSLayoutRelationEqual toItem:self.view attribute:NSLayoutAttributeCenterX multiplier:1 constant:0];    [self.view addConstraint:constraint11];    NSLayoutConstraint *constraint12 = [NSLayoutConstraint constraintWithItem:textField attribute:NSLayoutAttributeTop relatedBy:NSLayoutRelationEqual toItem:self.view attribute:NSLayoutAttributeTop multiplier:1 constant:300];    [self.view addConstraint:constraint12];    NSLayoutConstraint *constraint13 = [NSLayoutConstraint constraintWithItem:textField attribute:NSLayoutAttributeWidth relatedBy:NSLayoutRelationEqual toItem:nil attribute:NSLayoutAttributeWidth multiplier:1 constant:200];    [self.view addConstraint:constraint13];    NSLayoutConstraint *constraint14 = [NSLayoutConstraint constraintWithItem:textField attribute:NSLayoutAttributeHeight relatedBy:NSLayoutRelationEqual toItem:nil attribute:NSLayoutAttributeHeight multiplier:1 constant:30];    [self.view addConstraint:constraint14];    UIButton *pushButton = [UIButton buttonWithType:UIButtonTypeCustom];    [pushButton setTitle:@"back" forState:UIControlStateNormal];    [pushButton setTitleColor:[UIColor purpleColor] forState:UIControlStateNormal];//为按钮添加点击事件    [pushButton addTarget:self action:@selector(backBtnAction:) forControlEvents:UIControlEventTouchUpInside];    pushButton.translatesAutoresizingMaskIntoConstraints = NO;    [self.view addSubview:pushButton];    NSLayoutConstraint *constraint21 = [NSLayoutConstraint constraintWithItem:pushButton attribute:NSLayoutAttributeCenterX relatedBy:NSLayoutRelationEqual toItem:self.view attribute:NSLayoutAttributeCenterX multiplier:1 constant:0];    [self.view addConstraint:constraint21];    NSLayoutConstraint *constraint22 = [NSLayoutConstraint constraintWithItem:pushButton attribute:NSLayoutAttributeTop relatedBy:NSLayoutRelationEqual toItem:self.view attribute:NSLayoutAttributeTop multiplier:1 constant:360];    [self.view addConstraint:constraint22];    NSLayoutConstraint *constraint23 = [NSLayoutConstraint constraintWithItem:pushButton attribute:NSLayoutAttributeWidth relatedBy:NSLayoutRelationEqual toItem:nil attribute:NSLayoutAttributeWidth multiplier:1 constant:60];    [self.view addConstraint:constraint23];    NSLayoutConstraint *constraint24 = [NSLayoutConstraint constraintWithItem:pushButton attribute:NSLayoutAttributeHeight relatedBy:NSLayoutRelationEqual toItem:nil attribute:NSLayoutAttributeHeight multiplier:1 constant:30];    [self.view addConstraint:constraint24];}#pragma mark ------------------(void)backBtnAction:(UIButton *)sender{    UITextField *textField = (UITextField *)[self.view viewWithTag:2000];    //判断textFiel里面的内容是否为空    if (textField.text.length == 0)    {        NSLog(@"请输入回传值,亲");        UIAlertController *alertController = [UIAlertController alertControllerWithTitle:@"提示" message:@"请输入回传值,亲" preferredStyle:UIAlertControllerStyleAlert];        UIAlertAction *action = [UIAlertAction actionWithTitle:@"OK" style:UIAlertActionStyleDefault handler:^(UIAlertAction * _Nonnull action) {        }];        [alertController addAction:action];//        UIAlertAction *action1 = [UIAlertAction actionWithTitle:@"确定" style:UIAlertActionStyleDefault handler:^(UIAlertAction * _Nonnull action) {//            //        }];//        [alertController addAction:action1];//        //        UIAlertAction *action2 = [UIAlertAction actionWithTitle:@"确定2" style:UIAlertActionStyleDefault handler:^(UIAlertAction * _Nonnull action) {//            //        }];//        [alertController addAction:action2];        [self presentViewController:alertController animated:YES completion:^{        }];    }    else    {        //判断是否遵循协议=====================        if (self.delegate && [self.delegate conformsToProtocol:@protocol(NextProtocol)])        {            //遵循协议之后 调用协议里面的方法把text的值传过去            [self.delegate transferString:textField.text];        }        //返回跳转的UIViewController        [self.navigationController popViewControllerAnimated:YES];    }}#pragma mark ---------UITextFieldDelegate(当按键盘return键是取消第一响应者)---------- (BOOL)textFieldShouldReturn:(UITextField *)textField{    //    [textField resignFirstResponder];    return YES;}- (void)didReceiveMemoryWarning {    [super didReceiveMemoryWarning];    // Dispose of any resources that can be recreated.}@end