1、手势识别器——UIGestureRecognizer 介绍
在ios开发中，除了有关触摸的这组方法来控制使用用者的手指触控外，还可以用UIGestureRecognizer的衍生类来进行判断。
用UIGestureRecognizer的好处在于有现成的手势，开发者不用自己计算手指移动轨迹，创建了这些手势识别器之后可以调用视图的addGestureRecognizer:方法，将手势识别器注册到某个视图组件上。
UIGestureRecognizer是在Touch的基础上封装出来的。
UIGestureRecognizer的子类类别有以下几种：

• UIPanGestureRecognizer（拖动识别器）
• UIPinchGestureRecognizer（捏合识别器）
• UIRotationGestureRecognizer（旋转识别器）
• UITapGestureRecognizer（轻拍识别器）
• UILongPressGestureRecognizer（长按识别器）
• UISwipeGestureRecognizer（扫动识别器）

2、各个手势的例子：

#import "ViewController.h"

@interface ViewController ()<UINavigationControllerDelegate,UIImagePickerControllerDelegate>

@property (weak, nonatomic) IBOutlet UIView *targetView;

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    //单击
    UITapGestureRecognizer *singleTap = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(singleTapAction:)];
    [self.view addGestureRecognizer:singleTap];
    //双击
    UITapGestureRecognizer *doubleTap = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(doubleTapAction:)];
    doubleTap.numberOfTapsRequired = 2;
    [self.view addGestureRecognizer:doubleTap];
    //单击要想执行必须双击失效（如果双击确定偵測失败才會触发单击）
    [singleTap requireGestureRecognizerToFail:doubleTap];
    //长按手势
    UILongPressGestureRecognizer *longPress = [[UILongPressGestureRecognizer alloc] initWithTarget:self action:@selector(longPressAction:)];
    [self.targetView addGestureRecognizer:longPress];
    //捏合手势
    UIPinchGestureRecognizer *pinchGesture = [[UIPinchGestureRecognizer alloc] initWithTarget:self action:@selector(pinchGestureAction:)];
    [self.targetView addGestureRecognizer:pinchGesture];
    //拖拽
    UIPanGestureRecognizer *panGesture = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(panAction:)];
    [self.targetView addGestureRecognizer:panGesture];
    //旋转
    UIRotationGestureRecognizer *rotation = [[UIRotationGestureRecognizer alloc] initWithTarget:self action:@selector(rotationAction:)];
    [self.targetView addGestureRecognizer:rotation];
    //缩放要想执行 必须旋转失效（如果旋转确定偵測失败才會触发缩放）
    [pinchGesture requireGestureRecognizerToFail:rotation];
    //左横扫
    UISwipeGestureRecognizer *leftSwipeGesture = [[UISwipeGestureRecognizer alloc] initWithTarget:self action:@selector(swipAction:)];
    [self.view addGestureRecognizer:leftSwipeGesture];    
    leftSwipeGesture.direction = UISwipeGestureRecognizerDirectionLeft;
    //右横扫
    UISwipeGestureRecognizer *rightSwipeGesture = [[UISwipeGestureRecognizer alloc] initWithTarget:self action:@selector(swipAction:)];
    [self.view addGestureRecognizer:rightSwipeGesture];    
    rightSwipeGesture.direction = UISwipeGestureRecognizerDirectionRight;
    //下横扫
    UISwipeGestureRecognizer *downSwipeGesture = [[UISwipeGestureRecognizer alloc] initWithTarget:self action:@selector(swipAction:)];
    [self.view addGestureRecognizer:downSwipeGesture];    
    downSwipeGesture.direction = UISwipeGestureRecognizerDirectionDown;
    //上横扫
    UISwipeGestureRecognizer *upSwipeGesture = [[UISwipeGestureRecognizer alloc] initWithTarget:self action:@selector(swipAction:)];
    [self.view addGestureRecognizer:upSwipeGesture];
    upSwipeGesture.direction = UISwipeGestureRecognizerDirectionUp;

}
#pragma mark -----横扫
-(void)swipAction:(UISwipeGestureRecognizer *)sender{
    CATransition *animation = [CATransition animation];//创建CATransition对象
    animation.delegate = self;
    animation.duration = 1.0f;//动画持续时间
    animation.timingFunction = UIViewAnimationCurveEaseInOut;//速度控制函数，控制动画运行的节奏
    animation.type = kCATransitionMoveIn; //设置运动type
    switch (sender.direction) {
        case UISwipeGestureRecognizerDirectionRight: //向右滑
        {
            animation.subtype = kCATransitionFromLeft;//视图从左开始
        }
            break;
        case UISwipeGestureRecognizerDirectionLeft:
        {
            animation.subtype = kCATransitionFromRight;//视图向左滑
        }
            break;
        case UISwipeGestureRecognizerDirectionUp://向上滑
        {
            animation.subtype = kCATransitionFromTop;
        }
            break;
        case UISwipeGestureRecognizerDirectionDown: //向下滑
        {
            animation.subtype = kCATransitionFromBottom;
        
        }
            break;
        default:
            break;
    }
    [sender.view.layer addAnimation:animation forKey:@"move in"];
}
#pragma mark ------ 拖拽
-(void)panAction:(UIPanGestureRecognizer *)sender{
    //当手势按在视图上面的点，转为父系坐标 拿到中心点
    /*CGPoint translatedPoint=[sender translationInView:self.view];
    CGFloat firstX;
    CGFloat firstY;
     if ([sender state]==UIGestureRecognizerStateBegan) {
         firstX=[sender.view center].x;
         firstY=[sender.view center].y;
     
     }
     translatedPoint=CGPointMake(firstX+translatedPoint.x, firstY+translatedPoint.y);
     [sender.view setCenter:translatedPoint];*/
    //中心拖拽
    //当你的状态不等于结束状态，不等于失败状态
    /*if (sender.state != UIGestureRecognizerStateEnded && sender.state != UIGestureRecognizerStateFailed) {
        CGPoint location = [sender locationInView:sender.view.superview];
        sender.view.center = location;
    }*/

    //视图前置操作
    [sender.view.superview bringSubviewToFront:sender.view];
    //拖拽
    CGPoint center = sender.view.center;
    CGFloat cornerRadius = sender.view.frame.size.width / 2;
    CGPoint translation = [sender translationInView:self.view];
     //NSLog(@"%@", NSStringFromCGPoint(translation));
    sender.view.center = CGPointMake(center.x + translation.x,center.y +translation.y);
    [sender setTranslation:CGPointZero inView:self.view];
    //动画效果
    if (sender.state == UIGestureRecognizerStateEnded) {
        //计算速度向量的长度，当他小于200时，滑行会很短
        CGPoint velocity = [sender velocityInView:self.view];
        CGFloat magnitude = sqrtf((velocity.x * velocity.x) + (velocity.y * velocity.y));
        CGFloat slideMult = magnitude / 200;
    
        //基于速度和速度因素计算一个终点
        float slideFactor = 0.1 * slideMult;
        CGPoint finalPoint = CGPointMake(center.x + (velocity.x * slideFactor),center.y + (velocity.y * slideFactor));
        //限制最小［cornerRadius］和最大边界值［    self.view.bounds.size.width - cornerRadius］，以免拖动出屏幕界限
        finalPoint.x = MIN(MAX(finalPoint.x, cornerRadius),self.view.bounds.size.width - cornerRadius);
        finalPoint.y = MIN(MAX(finalPoint.y, cornerRadius),self.view.bounds.size.height - cornerRadius);
        [UIView animateWithDuration:slideFactor*2 delay:0 options:UIViewAnimationOptionCurveEaseOut
     animations:^{
             sender.view.center = finalPoint;
        }
         completion:nil];

    }

}
#pragma mark ----- 旋转
-(void)rotationAction:(UIRotationGestureRecognizer *)sender{
    sender.view.transform = CGAffineTransformRotate(sender.view.transform, sender.rotation);
    sender.rotation=10.0;//旋转速度
}

#pragma mark ----- 缩放
-(void)pinchGestureAction:(UIPinchGestureRecognizer *)sender{
    NSLog(@"xxx");
    sender.view.transform=CGAffineTransformMakeScale(sender.scale, sender.scale);
}
# pragma mark -----长按
-(void)longPressAction:(UILongPressGestureRecognizer *)sender{
    if (sender.state == UIGestureRecognizerStateEnded) {
        UIAlertController *alertController = [UIAlertController alertControllerWithTitle:@"标题" message:@"选择照片" preferredStyle:UIAlertControllerStyleActionSheet];
        UIAlertAction *photoAction = [UIAlertAction actionWithTitle:@"拍照" style:UIAlertActionStyleDestructive handler:^(UIAlertAction * _Nonnull action) {
            NSLog(@"调用照相机");
            if ([UIImagePickerController isSourceTypeAvailable:UIImagePickerControllerSourceTypeCamera]) {
                UIImagePickerController *imagepicker = [[UIImagePickerController alloc] init];
                imagepicker.sourceType = UIImagePickerControllerSourceTypeCamera;
                imagepicker.delegate = self;
                imagepicker.allowsEditing = YES;//允许图片被编辑
                imagepicker.modalTransitionStyle = UIModalTransitionStyleFlipHorizontal;
                [self presentViewController:imagepicker animated:NO completion:nil];
            
            }
        }];
        [alertController addAction:photoAction];
        UIAlertAction *libraryAction=[UIAlertAction actionWithTitle:@"相册" style:UIAlertActionStyleDefault handler:^(UIAlertAction * _Nonnull action) {
            NSLog(@"调用本地相册");
            if ([UIImagePickerController isSourceTypeAvailable:UIImagePickerControllerSourceTypePhotoLibrary]) {
                UIImagePickerController *picker =
                [[UIImagePickerController alloc] init];
                picker.delegate=self;
                picker.allowsEditing = YES;
                picker.sourceType = UIImagePickerControllerSourceTypePhotoLibrary;
               [self presentViewController:picker animated:NO completion:nil];
            
            }
         }];
        [alertController addAction:libraryAction];
        UIAlertAction *cancleAction=[UIAlertAction actionWithTitle:@"取消" style:UIAlertActionStyleCancel handler:^(UIAlertAction * _Nonnull action) {
            NSLog(@"取消");
            }];
        [alertController addAction:cancleAction];
        [self presentViewController:alertController animated:YES completion:nil];
    }
}
#pragma mark ---- 单击
-(void)singleTapAction:(UITapGestureRecognizer *)sender{
    NSLog(@"单击");
    //改变背景颜色
    if (sender.view.backgroundColor==[UIColor whiteColor]) {
        sender.view.backgroundColor=[UIColor cyanColor];
    }else{
        sender.view.backgroundColor=[UIColor whiteColor];
    }
}  
#pragma mark------- 双击
-(void)doubleTapAction:(UITapGestureRecognizer *)sender{
    NSLog(@"双击");
}

@end