手势识别器（UIGestureRecognizer）- UITapGestureRecognizer(敲击)

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本文介绍如何使用UIGestureRecognizer实现常见的手势识别，包括敲击、拖拽等，并通过示例代码展示了如何将手势识别器添加到UIImageView上。

为了完成手势识别，必须借助于手势识别器----UIGestureRecognizer

利用UIGestureRecognizer，能轻松识别用户在某个view上面做的一些常见手势

UIGestureRecognizer是一个抽象类，定义了所有手势的基本行为，使用它的子类才能处理具体的手势

UITapGestureRecognizer(敲击)

UIPinchGestureRecognizer(捏合，用于缩放)

UIPanGestureRecognizer(拖拽)

UISwipeGestureRecognizer(轻扫)

UIRotationGestureRecognizer(旋转)

UILongPressGestureRecognizer(长按)

#import "ViewController.h"

@interface ViewController ()
@property (weak, nonatomic) IBOutlet UIImageView *imageView;

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    
    // 给imageView添加手势
    self.imageView.userInteractionEnabled = YES;
    
    // 创建『敲击』手势
    UITapGestureRecognizer *tap = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(tap:)];
    // 双击触发
//    tap.numberOfTapsRequired = 2;
    [self.imageView addGestureRecognizer:tap];
}

- (void)tap:(UITapGestureRecognizer *)recognizer
{
    NSLog(@"敲击了");
}

@end

一些代理方法：

//
//  ViewController.m


#import "ViewController.h"

@interface ViewController ()<UIGestureRecognizerDelegate>
@property (weak, nonatomic) IBOutlet UIImageView *imageView;

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    
    // 给imageView添加手势
    self.imageView.userInteractionEnabled = YES;
    
    // 创建『敲击』手势
    UITapGestureRecognizer *tap = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(tap:)];
    // 双击触发
//    tap.numberOfTapsRequired = 2;
    
    tap.delegate = self; // 设置代理为当前控制器
    
    [self.imageView addGestureRecognizer:tap];
}

- (void)tap:(UITapGestureRecognizer *)recognizer
{
    NSLog(@"敲击了");
}

#pragma mark - <UIGestureRecognizerDelegate>
/**
 *  是否允许开始触发手势
 *
 *  @param gestureRecognizer 手势识别器
 *
 *  @return 返回YES可以触发，返回NO不能触发
 */
- (BOOL)gestureRecognizerShouldBegin:(UIGestureRecognizer *)gestureRecognizer
{
    NSLog(@"先来到这里");
    return YES;
}

/**
 *  是否允许同事支持多个手势(默认不支持多个手势)
 */
- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldRequireFailureOfGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer
{
    return NO;
}

/**
 *  是否允许接收手指的触摸点(通过这方法可以控制一个控件左边能点击，右边不能点击)
 */
- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldReceiveTouch:(UITouch *)touch
{
    CGPoint currentPoint = [touch locationInView:self.imageView];
    if (currentPoint.x < self.imageView.bounds.size.width * 0.5) {
        return YES;
    }else{
        return NO;
    }

}


@end