代理传值代理传值原理
代理(delegate)传值 ---- 顾名思义就是委托别人办事，就是当一件事情发生后，自己不处理，让别人来处理。
//代理传值
注意:从后往前传(如果从前往后传,会传不成功)
//流程:
1.后一个界面定义一个协议,并且定义一个属性叫delegate
2.在前一个界面进入后一个界面的瞬间,(即:创建完成一个界面之后),让前一个界面作为后一个界面的delegate
3.前一个界面实现代理方法
4.后一个界面在合适的机会, 让代理, 执行,代理方法 (传的值以参数的形式 含在代理方法里)
代码如下:
[objc] view plaincopy
#import "FirstViewController.h"
#import "SecondViewController.h"
#import "UIButton+Create.h"
@interface FirstViewController ()
{
UILabel * _label;
}
@end
@implementation FirstViewController
- (void)dealloc
{
[_label release];
[super dealloc];
}
- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
if (self) {
// Custom initialization
}
return self;
}
- (void)viewDidLoad
{
[super viewDidLoad];
self.view.backgroundColor = [UIColor redColor];
self.navigationItem.title = @"首页";
self.view.userInteractionEnabled = YES;
/**
* 1.创建一个UIButton,
* 2.并添加响应事件,从首页跳转到第二个页面.
*/
UIButton * button = [UIButton systemButtonWithFrame:CGRectMake(100, 120, 50, 50) title:@"Push" target:self action:@selector(didClickButtonAction)];
button.userInteractionEnabled = YES;
[self.view addSubview:button];
/**
* 1.在第1个界面创建一个UILabel
* 2.把第二页输入框输入的字符串,通过代理方法传过来
* 3.然后通过赋值给UILabel
*/
_label = [[UILabel alloc]initWithFrame:CGRectMake(50, 80, 200, 30)];
_label.backgroundColor = [UIColor greenColor];
[self.view addSubview:_label];
// Do any additional setup after loading the view.
}
- (void)didClickButtonAction
{
/**
* 1.用push的方法推出下一个页面
* 2.把第二页输入框输入的字符串,通过代理方法传过来
* 3.从而实现把首页输入框输入的字符串,传到第二页的UILabel上.
*/
SecondViewController * secondVC = [[SecondViewController alloc]init];
secondVC.delegate = self;//确认代理
[self.navigationController pushViewController:secondVC animated:YES];
[secondVC release];
}
//实现代理方法
- (void)passByValueSecondVC:(SecondViewController *)secondVC text:(NSString *)text
{
_label.text = text;
}
- (void)didReceiveMemoryWarning
{
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
@end
[objc] view plaincopy
#import <UIKit/UIKit.h>
@class SecondViewController;
@protocol secondViewControllerDelegate <NSObject>
- (void)passByValueSecondVC:(SecondViewController *)secondVC text:(NSString *)text;
@end
@interface SecondViewController : UIViewController
@property (nonatomic,assign)id<secondViewControllerDelegate>delegate;
@end
[objc] view plaincopy
#import "SecondViewController.h"
#import "UIButton+Create.h"
#import "FirstViewController.h"
@interface SecondViewController ()
{
UITextField * _textField;//创建一个输入框
}
@end
@implementation SecondViewController
- (void)dealloc
{
[_textField release];
[super dealloc];
}
- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
if (self) {
// Custom initialization
}
return self;
}
- (void)viewDidLoad
{
[super viewDidLoad];
self.view.backgroundColor = [UIColor orangeColor];
self.navigationItem.title = @"第二页";
/**
* 1.创建一个UIButton,
* 2.并添加响应事件,从第二个页面返回到首页.
*/
UIButton * button = [UIButton systemButtonWithFrame:CGRectMake(100, 120, 50, 50) title:@"Back" target:self action:@selector(didClickButtonAction)];
[self.view addSubview:button];
/**
* 1.在第二个界面创建一个输入框
*
*/
_textField = [[UITextField alloc]initWithFrame:CGRectMake(50, 80, 200, 30)];
_textField.borderStyle = UITextBorderStyleRoundedRect;
[self.view addSubview:_textField];
// Do any additional setup after loading the view.
}
- (void)didClickButtonAction
{
//调用代理方法,_textField.text传值
[_delegate passByValueSecondVC:self text:_textField.text];
[self.navigationController popToRootViewControllerAnimated:YES];
}
- (void)didReceiveMemoryWarning
{
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
@end