Java介面 == Objective-C協議

史耀傑發表於2017-04-26
JavaObject協議

程式猿的開心一刻

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類似？
a，PHP，Python；b，JSP，servlet；c，java，java script ；d，C，C++

請在評論區輸入答案，接下來進入正題

Java介面

參考文章：Java回撥機制趣解

介面是什麼：
  • Java不支援多重繼承，但可以實現多個介面。
  • 介面定義了某一批類所要遵守的規範，只規定這些類裡必須提供某些方法。
  • 介面並不是類，編寫介面的方式和類很相似，但是它們屬於不同的概念。
  • 類描述物件的屬性和方法，介面則包含類要實現的方法。
  • 介面可以多繼承
介面的作用：
  • 擴充套件性： 如果業務邏輯發生變化需要新增類的方法，就可以在不改變原來已經寫好的程式碼基礎上新增一個類來實現介面中定義的函式來實現。
  • 規範性：告訴開發人員你需要實現哪些業務，並可以將命名規範限制住。
  • 安全性：介面是實現軟體鬆耦合的重要手段，它描敘了系統對外的所有服務，而不涉及任何具體的實現細節。

介面例項一：回撥傳值

介面檔案程式碼：

public interface Listener {
    void send(String s);
}複製程式碼

Info.java檔案程式碼

public class Info {
    public Listener mListener;

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

    public void sends(){
        mListener.send("haha");
    }
}複製程式碼

要實現介面裡的方法的MainActivity.java檔案程式碼

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);
    }
}複製程式碼

輸出結果

Java介面 == Objective-C協議
1.png

思考：Java中介面和抽象類的區別？

Objective-C協議

協議就是定義一套方法，遵守協議的類要去實現協議裡的方法。

iOS例項一 ：控制器之間逆向傳值

控制器一.m檔案程式碼：

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

@implementation ViewController

//此方法只載入一次，類中成員物件和變數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:@"點選按鈕，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複製程式碼

控制器二.h檔案程式碼

#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複製程式碼

控制器二.m檔案程式碼

#import "SecondViewController.h"

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

@implementation SecondViewController

//此方法只載入一次，類中成員物件和變數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:@"點選按鈕，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複製程式碼

效果演示

Java介面 == Objective-C協議
未命名.gif

iOS例項二 ：View讓Controller幫它實現跳轉

FirstView.h檔案程式碼

#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複製程式碼

FirstView.m檔案程式碼

#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:@"點選按鈕，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複製程式碼

ViewController.m檔案程式碼

#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複製程式碼

效果演示

Java介面 == Objective-C協議
未命名.gif

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