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];
}
@end7.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:
