Java接口 == Objective-C協議

程序猿的開心一刻

藺相如，司馬相如；魏無忌，長孫無忌。下列哪一組對應關係與此相似？
a，PHP，Python；b，JSP，servlet；c，java，java script ；d，C，C++

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Java接口

參考文章：Java回調機制趣解

接口是什麼：

• Java不支持多重繼承，但能夠實現多個接口。
• 接口定義了某一批類所要遵照的規範，只規定這些類裏必須提供某些方法。
• 接口並非類，編寫接口的方式和類很類似，可是它們屬於不一樣的概念。
• 類描述對象的屬性和方法，接口則包含類要實現的方法。
• 接口能夠多繼承

接口的做用：

• 擴展性： 若是業務邏輯發生變化須要新增類的方法，就能夠在不改變原來已經寫好的代碼基礎上新增一個類來實現接口中定義的函數來實現。
• 規範性：告訴開發人員你須要實現哪些業務，並能夠將命名規範限制住。
• 安全性：接口是實現軟件鬆耦合的重要手段，它描敘了系統對外的全部服務，而不涉及任何具體的實現細節。

接口實例一：回調傳值

接口文件代碼：

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

Info.java文件代碼

public class Info {
    public Listener mListener;

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

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

要實現接口裏的方法的MainActivity.java文件代碼

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);
    }
}複製代碼

輸出結果

1.png

思考：Java中接口和抽象類的區別？

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Objective-C協議

協議就是定義一套方法，遵照協議的類要去實現協議裏的方法。

iOS實例一 ：控制器之間逆向傳值

控制器一.m文件代碼：

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

@implementation ViewController

//此方法只加載一次，類中成員對象和變量的初始化都會放在這個方法中
- (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:@"點擊按鈕，去顯示控制器二" 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複製代碼

控制器二.h文件代碼

#import <UIKit/UIKit.h>
//定義協議
@protocol MyProtocol <NSObject>
//必須實現
@required
-(void)showMessage:(NSString*)str;
//可選擇實現
@optional
-(void)showtext:(NSString*)str;

@end

@interface SecondViewController : UIViewController

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

@end複製代碼

控制器二.m文件代碼

#import "SecondViewController.h"

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

@implementation SecondViewController

//此方法只加載一次，類中成員對象和變量的初始化都會放在這個方法中
- (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:@"點擊按鈕，去顯示控制器一" 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複製代碼

效果演示

未命名.gif

iOS實例二 ：View讓Controller幫它實現跳轉

FirstView.h文件代碼

#import <UIKit/UIKit.h>
//定義協議
@protocol FirstViewDelegate <NSObject>
//必須實現
@required
-(void)jumpViewController;
//可選擇實現
@optional
-(void)showtext:(NSString*)str;
@end

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

FirstView.m文件代碼

#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:@"點擊按鈕，去顯示控制器二" forState:UIControlStateNormal];
        button1.backgroundColor = [UIColor blackColor];
        [button1 addTarget:self action:@selector(click) forControlEvents:UIControlEventTouchUpInside];
        [self addSubview:button1];
    }
    return self;
}

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

@end複製代碼

ViewController.m文件代碼

#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複製代碼

效果演示

未命名.gif