程序猿的开心一刻###

蔺相如，司马相如；魏无忌，长孙无忌。下列哪一组对应关系与此类似？
a，PHP，Python；b，JSP，servlet；c，java，java script ；d，C，C++

请在评论区输入答案，接下来进入正题

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Java接口#

参考文章：Java回调机制趣解

接口是什么：#####

• Java不支持多重继承，但可以实现多个接口。
• 接口定义了某一批类所要遵守的规范，只规定这些类里必须提供某些方法。
• 接口并不是类，编写接口的方式和类很相似，但是它们属于不同的概念。
• 类描述对象的属性和方法，接口则包含类要实现的方法。
• 接口可以多继承

接口的作用：#####

• 扩展性： 如果业务逻辑发生变化需要新增类的方法，就可以在不改变原来已经写好的代码基础上新增一个类来实现接口中定义的函数来实现。
• 规范性：告诉开发人员你需要实现哪些业务，并可以将命名规范限制住。
• 安全性：接口是实现软件松耦合的重要手段，它描叙了系统对外的所有服务，而不涉及任何具体的实现细节。

接口实例一：回调传值

接口文件代码：

public interface Listener {
    void send(String s);
}

Info.java文件代码

public class Info {
    public Listener mListener;

    public Info(Listener mListener){
        this.mListener = mListener;
    }

    public void sends(){
        mListener.send("haha");
    }
}

要实现接口里的方法的MainActivity.java文件代码

public class MainActivity extends AppCompatActivity implements Listener{
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        Info info = new Info(this);
        info.sends();
    }
    @Override
    public void send(String s) {
        System.out.println(s);
    }
}

输出结果####

1.png

思考：Java中接口和抽象类的区别？

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Objective-C协议#

协议就是定义一套方法，遵守协议的类要去实现协议里的方法。

iOS实例一 ：控制器之间逆向传值###

控制器一.m文件代码：

#import "ViewController.h"
#import "SecondViewController.h"
@interface ViewController ()<MyProtocol>
@property(nonatomic,strong)UITextView* textView1;
@end

@implementation ViewController

//此方法只加载一次，类中成员对象和变量的初始化都会放在这个方法中
- (void)viewDidLoad {
    [super viewDidLoad];
    self.view.backgroundColor = [UIColor blueColor];
    
    _textView1 = [[UITextView alloc] initWithFrame:CGRectMake(0, 100, 320, 30)];
    _textView1.font = [UIFont systemFontOfSize:15];
    _textView1.textColor = [UIColor whiteColor];
    _textView1.backgroundColor = [UIColor blackColor];
    [self.view addSubview:_textView1];
    
    UIButton *button1 = [UIButton buttonWithType:UIButtonTypeCustom];
    button1.frame = CGRectMake(0, 50, 320, 30);
    button1.titleLabel.font = [UIFont systemFontOfSize:17];
    [button1 setTitle:@"点击按钮，去显示控制器二" forState:UIControlStateNormal];
    button1.backgroundColor = [UIColor blackColor];
    [button1 addTarget:self action:@selector(click) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:button1];
}

-(void)showMessage:(NSString *)str{
    _textView1.text = str;
}

-(void)click{
    SecondViewController *vc = [[SecondViewController alloc] init];
    vc.delegate = self;
    [self presentViewController:vc animated:YES completion:nil];
}

@end

控制器二.h文件代码

#import <UIKit/UIKit.h>
//定义协议
@protocol MyProtocol <NSObject>
//必须实现
@required
-(void)showMessage:(NSString*)str;
//可选择实现
@optional
-(void)showtext:(NSString*)str;

@end

@interface SecondViewController : UIViewController

@property(nonatomic,weak) id<MyProtocol> delegate;

@end

控制器二.m文件代码

#import "SecondViewController.h"

@interface SecondViewController ()
@property(nonatomic,strong)UITextField *textField1;
@end

@implementation SecondViewController

//此方法只加载一次，类中成员对象和变量的初始化都会放在这个方法中
- (void)viewDidLoad {
    [super viewDidLoad];
    self.view.backgroundColor = [UIColor greenColor];

    _textField1 = [[UITextField alloc] initWithFrame:CGRectMake(0, 100, 320, 30)];
    _textField1.font = [UIFont systemFontOfSize:15];
    _textField1.textColor = [UIColor whiteColor];
    _textField1.backgroundColor = [UIColor blackColor];
    [self.view addSubview:_textField1];
    
    UIButton *button1 = [UIButton buttonWithType:UIButtonTypeCustom];
    button1.frame = CGRectMake(0, 50, 320, 30);
    button1.titleLabel.font = [UIFont systemFontOfSize:17];
    [button1 setTitle:@"点击按钮，去显示控制器一" forState:UIControlStateNormal];
    button1.backgroundColor = [UIColor blackColor];
    [button1 addTarget:self action:@selector(click) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:button1];
}

-(void)click{
    [_delegate showMessage:_textField1.text];
    
    [self dismissViewControllerAnimated:YES completion:nil];
}

@end

效果演示###

未命名.gif

iOS实例二 ：View让Controller帮它实现跳转###

FirstView.h文件代码

#import <UIKit/UIKit.h>
//定义协议
@protocol FirstViewDelegate <NSObject>
//必须实现
@required
-(void)jumpViewController;
//可选择实现
@optional
-(void)showtext:(NSString*)str;
@end

@interface FirstView : UIView
@property(nonatomic,weak) id<FirstViewDelegate> delegate;
@end

FirstView.m文件代码

#import "FirstView.h"
@implementation FirstView
-(id)initWithFrame:(CGRect)frame{
    if(self = [super initWithFrame:frame]){
        UIButton *button1 = [UIButton buttonWithType:UIButtonTypeCustom];
        button1.frame = CGRectMake(0, 50, 320, 30);
        button1.titleLabel.font = [UIFont systemFontOfSize:17];
        [button1 setTitle:@"点击按钮，去显示控制器二" forState:UIControlStateNormal];
        button1.backgroundColor = [UIColor blackColor];
        [button1 addTarget:self action:@selector(click) forControlEvents:UIControlEventTouchUpInside];
        [self addSubview:button1];
    }
    return self;
}

-(void)click{
    [_delegate jumpViewController];
}

@end

ViewController.m文件代码

#import "ViewController.h"
#import "FirstView.h"
#import "SecondViewController.h"
@interface ViewController ()<FirstViewDelegate>

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    self.view.backgroundColor = [UIColor blueColor];
    FirstView *firstView = [[FirstView alloc] initWithFrame:CGRectMake(0, 0, 320, 568)];
    firstView.delegate = self;
    [self.view addSubview:firstView];
  
}

-(void)jumpViewController{
    SecondViewController *vc = [[SecondViewController alloc] init];
    [self presentViewController:vc animated:YES completion:nil];
}

@end

效果演示###

未命名.gif