iOS多界面传值之--通知传值

通知传值

通知传值也是逆向传值的一种,即第二界面向第一界面传值
谁要监听值的变化，谁就注册通知 特别要注意，通知的接受者必须存在这一条件
1.注册通知
2.通知中心发送通知消息,其中name(通知名)前后要保持一致性
3.实现通知内部的方法,并实现传值
4.消息发送完之后,要移除通知

5.新建一个继承与UIViewController的SecondViewController,然后在.m文件中分别声明UITextField 和 UIButton 这两个属性.再用懒加载的方法分别创建UITextField 和 UIbutton

#import "SecondViewController.h"

@interface SecondViewController ()
@property (nonatomic,strong) UITextField *textF;
@property (nonatomic,strong) UIButton *backBtn;


@end

@implementation SecondViewController

-(UITextField *)textF{

    if (!_textF) {

        _textF = [[UITextField alloc]initWithFrame:CGRectMake(0, 100, self.view.bounds.size.width, 50)];
        _textF.borderStyle = UITextBorderStyleRoundedRect;
        _textF.backgroundColor = [UIColor whiteColor];

    }
    return _textF;
}


-(UIButton *)backBtn{

    if (!_backBtn) {

        _backBtn = [UIButton buttonWithType:UIButtonTypeRoundedRect];
        _backBtn.frame = CGRectMake(20, 200, self.view.bounds.size.width-40,40);

        _backBtn.backgroundColor = [UIColor blueColor];
        _backBtn.tintColor = [UIColor whiteColor];
        _backBtn.titleLabel.font = [UIFont systemFontOfSize:25.0];

        [_backBtn setTitle:@"Back" forState:UIControlStateNormal];
        [_backBtn addTarget:self action:@selector(backBtn:) forControlEvents:UIControlEventTouchUpInside];

    }
    return _backBtn;

}

- (void)viewDidLoad {
    [super viewDidLoad];
    self.view.backgroundColor = [UIColor cyanColor];

    [self.view addSubview:self.textF];
    [self.view addSubview:self.backBtn];



}

6.实现一下BUtton里面的点击事件的方法,并且在这个方法里面进行发送通知消息

-(void)backBtn:(UIButton *)sender{

//    发送通知
    [[NSNotificationCenter defaultCenter]postNotificationName:@"ChangeValue" object:nil userInfo:@{@"Value":_textF.text}];
    NSLog(@"%@",self.textF.text);
    [self dismissViewControllerAnimated:YES completion:nil];

}


@end

7.回到ViewController.m中,导入一下头文件.并且是声明属性,创建UItextField 和 UIbutton,在viewDidLoad里面注册监听者…

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

@interface ViewController ()
@property (nonatomic,strong) UITextField *textField;
@property (nonatomic,strong) UIButton *nextBtn;


@end


@implementation ViewController
-(UITextField *)textField{

    if (!_textField) {
        _textField = [[UITextField alloc]initWithFrame:CGRectMake(0, 100, self.view.bounds.size.width, 50)];
        _textField.borderStyle = UITextBorderStyleRoundedRect;
        _textField.backgroundColor = [UIColor whiteColor];

    }
    return _textField;
}

-(UIButton *)nextBtn{

    if (!_nextBtn) {

        _nextBtn = [UIButton buttonWithType:UIButtonTypeRoundedRect];
        _nextBtn.frame = CGRectMake(20, 200, self.view.bounds.size.width - 40, 44);

        _nextBtn.backgroundColor = [UIColor blueColor];
        _nextBtn.titleLabel.font = [UIFont systemFontOfSize:25.0];
        _nextBtn.tintColor = [UIColor whiteColor];

        [_nextBtn setTitle:@"Next" forState:UIControlStateNormal];
        [_nextBtn addTarget:self action:@selector(nextBtn:) forControlEvents:UIControlEventTouchUpInside];

    }
    return _nextBtn;
}

- (void)viewDidLoad {
    [super viewDidLoad];

    /**
     通知传值(逆向传值 --> 第二个界面传值到第一个界面)
     s
     1、注册通知

     2、通知中心发送一条消息通知，其中name前后一定要一样

     3、实现通知中心内部的方法，并实现传值

     4、消息发送完，要移除掉。（页面将要消失的时候）
     */
    self.navigationItem.title = @"通知传值";
    self.view.backgroundColor = [UIColor yellowColor];

    [self.view addSubview:self.textField];
    [self.view addSubview:self.nextBtn];


//    注册监听者
    /**
     *  addObserver 注册监听者,一般都是控制器本身去监听一个通知
     *
     *  selector 当监听到通知的时候执行的方法
     *
     *  name 通知的名字,要和发送的通知的对象的名字一致
     */
    [[NSNotificationCenter defaultCenter]addObserver:self selector:@selector(ChangeTextFText:) name:@"ChangeValue" object:nil];


}

8.实现Button的点击事件方法和移除通知

-(void)ChangeTextFText:(NSNotification *)notification{

    NSDictionary *dict = notification.userInfo;
    NSLog(@"dict = %@",dict);
    _textField.text = dict[@"Value"];

}


-(void)nextBtn:(UIButton *)sender{
    SecondViewController *secondVC = [[SecondViewController alloc]init];
    [self presentViewController:secondVC animated:YES completion:nil];



}

//移除通知
-(void)dealloc{

    [[NSNotificationCenter defaultCenter]removeObserver:self];

}

@end

9.模拟器运行效果如下: