UI delegate

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代理模式：

一个委托人

一份协议

一个代理者

1、

#import "AppDelegate.h"
//2、设置协议
@interface AppDelegate () <UITextFieldDelegate>

@end

@implementation AppDelegate

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    // Override point for customization after application launch.
#pragma mark ======= 1、创建窗口 ========================
    self.window = [[UIWindow alloc]initWithFrame:[UIScreen mainScreen].bounds];

    self.window.backgroundColor = [UIColor whiteColor];

    [self.window makeKeyAndVisible];

#pragma mark ======== 2、创建一个文本编辑框 ================
    UITextField *textField = [[UITextField alloc]initWithFrame:CGRectMake(50, 100, 200, 30)];

    textField.placeholder = @"编辑";

    [self.window addSubview:textField];

#pragma mark ========= 设置代理 =========================
    //1、将当前类对象设置为输入框的代理
    textField.delegate = self;
    //2、遵从协议
    //3、实现协议方法

    //第一响应者:first responder

    return YES;
}
//3、实现协议方法===参数:设置代理的人
-(BOOL)textFieldShouldReturn:(UITextField *)textField
{
    //释放第一响应者
    [textField resignFirstResponder];

    return YES;

}

2、

#import <UIKit/UIKit.h>

@interface MyAppDelegate : UIResponder <UIApplicationDelegate>

@property(nonatomic,strong) UIWindow *window;

@end

3、

#import "MyAppDelegate.h"

@implementation MyAppDelegate

-(BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions{

    self.window = [[UIWindow alloc]initWithFrame:[UIScreen mainScreen].bounds];
    self.window.backgroundColor = [UIColor whiteColor];


    [self.window makeKeyAndVisible];

    UILabel *label = [[UILabel alloc]initWithFrame:CGRectMake(50, 80, 200, 50)];
    label.text = @"自己写的AppDelegate";
    label.textColor = [UIColor redColor];

    [self.window addSubview:label];

    return YES;
}
@end

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