iOS多界面傳值之--通知傳值

通知傳值

通知傳值也是逆向傳值的一種,即第二界面向第一界面傳值
誰要監聽值的變化，誰就註冊通知 特別要注意，通知的接受者必須存在這一條件
1.註冊通知
2.通知中心發送通知消息,其中name(通知名)前後要保持一致性
3.實現通知內部的方法,並實現傳值
4.消息發送完之後,要移除通知

5.新建一個繼承與UIViewController的SecondViewController,然後在.m文件中分別聲明UITextField 和 UIButton 這兩個屬性.再用懶加載的方法分別創建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.實現一下BUtton裏面的點擊事件的方法,並且在這個方法裏面進行發送通知消息

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

//    發送通知
    [[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,導入一下頭文件.並且是聲明屬性,創建UItextField 和 UIbutton,在viewDidLoad裏面註冊監聽者…

#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];

    /**
     通知傳值(逆向傳值 --> 第二個界面傳值到第一個界面)
     s
     1、註冊通知

     2、通知中心發送一條消息通知，其中name前後一定要一樣

     3、實現通知中心內部的方法，並實現傳值

     4、消息發送完，要移除掉。（頁面將要消失的時候）
     */
    self.navigationItem.title = @"通知傳值";
    self.view.backgroundColor = [UIColor yellowColor];

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


//    註冊監聽者
    /**
     *  addObserver 註冊監聽者,一般都是控制器本身去監聽一個通知
     *
     *  selector 當監聽到通知的時候執行的方法
     *
     *  name 通知的名字,要和發送的通知的對象的名字一致
     */
    [[NSNotificationCenter defaultCenter]addObserver:self selector:@selector(ChangeTextFText:) name:@"ChangeValue" object:nil];


}

8.實現Button的點擊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.模擬器運行效果如下: