iOS 手势操作：拖动、捏合、旋转、点按、长按、轻扫、自定义

1、UIGestureRecognizer 介绍

手势识别在 iOS 中非常重要，他极大地提高了移动设备的使用便捷性。

iOS 系统在 3.2 以后，他提供了一些常用的手势（UIGestureRecognizer 的子类），开发者可以直接使用他们进行手势操作。

• UIPanGestureRecognizer（拖动）

• UIPinchGestureRecognizer（捏合）

• UIRotationGestureRecognizer（旋转）

• UITapGestureRecognizer（点按）

• UILongPressGestureRecognizer（长按）

• ​UISwipeGestureRecognizer（轻扫）

另外，可以通过继承 UIGestureRecognizer 类，实现自定义手势（手势识别器类）。

PS：自定义手势时，需要 #import <UIKit/UIGestureRecognizerSubclass.h>，一般需实现如下方法：

 - (void)reset;

 - (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event;
 - (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event;
 - (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event;
 - (void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event;
 //以上方法在分类 UIGestureRecognizer (UIGestureRecognizerProtected) 中声明，更多方法声明请自行查看

UIGestureRecognizer 的继承关系如下：

2、手势状态

在六种手势识别中，只有一种手势是离散型手势，他就是 UITapGestureRecognizer。

离散型手势的特点就是：一旦识别就无法取消，而且只会调用一次手势操作事件（初始化手势时指定的回调方法）。

​换句话说其他五种手势是连续型手势，而连续型手势的特点就是：会多次调用手势操作事件，而且在连续手势识别后可以取消手势。从下图可以看出两者调用操作事件的次数是不同的：

手势状态枚举如下：

 typedef NS_ENUM(NSInteger, UIGestureRecognizerState) {
     UIGestureRecognizerStatePossible,   // 尚未识别是何种手势操作（但可能已经触发了触摸事件），默认状态
     UIGestureRecognizerStateBegan,      // 手势已经开始，此时已经被识别，但是这个过程中可能发生变化，手势操作尚未完成
     UIGestureRecognizerStateChanged,    // 手势状态发生转变
     UIGestureRecognizerStateEnded,      // 手势识别操作完成（此时已经松开手指）
     UIGestureRecognizerStateCancelled,  // 手势被取消，恢复到默认状态
     UIGestureRecognizerStateFailed,     // 手势识别失败，恢复到默认状态
     UIGestureRecognizerStateRecognized = UIGestureRecognizerStateEnded // 手势识别完成，同UIGestureRecognizerStateEnded
 };

• 对于离散型手势 UITapGestureRecgnizer 要么被识别，要么失败，点按（假设点按次数设置为1，并且没有添加长按手势）下去一次不松开则此时什么也不会发生，松开手指立即识别并调用操作事件，并且状态为3（已完成）。

• 但是连续型手势要复杂一些，就拿旋转手势来说，如果两个手指点下去不做任何操作，此时并不能识别手势（因为我们还没旋转）但是其实已经触发了触摸开始事件，此时处于状态0；如果此时旋转会被识别，也就会调用对应的操作事件，同时状态变成1（手势开始），但是状态1只有一瞬间；紧接着状态变为2（因为我们的旋转需要持续一会），并且重复调用操作事件（如果在事件中打印状态会重复打印2）；松开手指，此时状态变为3，并调用1次操作事件。

3、使用手势的步骤

使用手势很简单，分为三步：

1. 创建手势识别器对象实例。创建时，指定一个回调方法，当手势开始，改变、或结束时，执行回调方法。

2. 设置手势识别器对象实例的相关属性（可选部分）

3. 添加到需要识别的 View 中。每个手势只对应一个 View，当屏幕触摸在 View 的边界内时，如果手势和预定的一样，那就会执行回调方法。

PS：一个手势只能对应一个 View，但是一个 View 可以有多个手势。建议在真机上测试这些手势，模拟器操作不太方便，可能导致认为手势失效的情况。（模拟器测试捏合和旋转手势时，按住 option 键，再用触摸板或鼠标操作）

4、举例说明

功能描述：

附加到两个图片视图 UIImageView 的有『拖动』、『捏合』、『旋转』、『点按』；

而『轻扫』和『自定义手势 KMGestureRecognizer』附加在根视图 UIView 中。

1. 拖动：进行当前图片视图位置移动

2. 捏合：进行当前图片视图缩放

3. 旋转：进行当前图片视图角度旋转

4. 点按：双击恢复当前图片视图的缩放、角度旋转、不透明度

5. 长按：设置当前图片视图的不透明度为0.7

6. 轻扫：左右轻扫设置两个图片视图为居中，同时以垂直居中的特定偏移量定位

7. 自定义手势：挠痒功能，左右扫动共3次或以上，设置两个图片视图为居中，同时以水平居中的特定偏移量定位

效果如下：

KMGestureRecognizer.h

 #import <UIKit/UIKit.h>

 typedef NS_ENUM(NSUInteger, Direction) {
     DirectionUnknown,
     DirectionLeft,
     DirectionRight
 };

 @interface KMGestureRecognizer : UIGestureRecognizer
 @property (assign, nonatomic) NSUInteger tickleCount; //挠痒次数
 @property (assign, nonatomic) CGPoint currentTickleStart; //当前挠痒开始坐标位置
 @property (assign, nonatomic) Direction lastDirection; //最后一次挠痒方向

 @end

KMGestureRecognizer.m

 #import "KMGestureRecognizer.h"
 #import <UIKit/UIGestureRecognizerSubclass.h>

 @implementation KMGestureRecognizer
 #define kMinTickleSpacing 20.0
 #define kMaxTickleCount 3

 - (void)reset {
     _tickleCount = ;
     _currentTickleStart = CGPointZero;
     _lastDirection = DirectionUnknown;

     if (self.state == UIGestureRecognizerStatePossible) {
         self.state = UIGestureRecognizerStateFailed;
     }
 }

 - (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
     UITouch *touch = [touches anyObject];
     _currentTickleStart = [touch locationInView:self.view]; //设置当前挠痒开始坐标位置
 }

 - (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
     //『当前挠痒开始坐标位置』和『移动后坐标位置』进行 X 轴值比较，得到是向左还是向右移动
     UITouch *touch = [touches anyObject];
     CGPoint tickleEnd = [touch locationInView:self.view];
     CGFloat tickleSpacing = tickleEnd.x - _currentTickleStart.x;
     Direction currentDirection = tickleSpacing <  ? DirectionLeft : DirectionRight;

     //移动的 X 轴间距值是否符合要求，足够大
     if (ABS(tickleSpacing) >= kMinTickleSpacing) {
         //判断是否有三次不同方向的动作，如果有则手势结束，将执行回调方法
         if (_lastDirection == DirectionUnknown ||
             (_lastDirection == DirectionLeft && currentDirection == DirectionRight) ||
             (_lastDirection == DirectionRight && currentDirection == DirectionLeft)) {
             _tickleCount++;
             _currentTickleStart = tickleEnd;
             _lastDirection = currentDirection;

             if (_tickleCount >= kMaxTickleCount && self.state == UIGestureRecognizerStatePossible) {
                 self.state = UIGestureRecognizerStateEnded;
                 //NSLog(@"自定义手势成功，将执行回调方法");
             }
         }
     }
 }

 - (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {
     [self reset];
 }

 - (void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event {
     [self reset];
 }

 @end

ViewController.h

 #import <UIKit/UIKit.h>
 #import "KMGestureRecognizer.h"

 @interface ViewController : UIViewController
 @property (strong, nonatomic) UIImageView *imgV;
 @property (strong, nonatomic) UIImageView *imgV2;
 @property (strong, nonatomic) KMGestureRecognizer *customGestureRecognizer;

 @end

ViewController.m

 #import "ViewController.h"

 @interface ViewController ()
 - (void)handlePan:(UIPanGestureRecognizer *)recognizer;
 - (void)handlePinch:(UIPinchGestureRecognizer *)recognizer;
 - (void)handleRotation:(UIRotationGestureRecognizer *)recognizer;
 - (void)handleTap:(UITapGestureRecognizer *)recognizer;
 - (void)handleLongPress:(UILongPressGestureRecognizer *)recognizer;
 - (void)handleSwipe:(UISwipeGestureRecognizer *)recognizer;
 - (void)handleCustomGestureRecognizer:(KMGestureRecognizer *)recognizer;

 - (void)bindPan:(UIImageView *)imgVCustom;
 - (void)bindPinch:(UIImageView *)imgVCustom;
 - (void)bindRotation:(UIImageView *)imgVCustom;
 - (void)bindTap:(UIImageView *)imgVCustom;
 - (void)bindLongPress:(UIImageView *)imgVCustom;
 - (void)bindSwipe;
 - (void)bingCustomGestureRecognizer;
 - (void)layoutUI;
 @end

 @implementation ViewController

 - (void)viewDidLoad {
     [super viewDidLoad];

     [self layoutUI];
 }

 - (void)didReceiveMemoryWarning {
     [super didReceiveMemoryWarning];
     // Dispose of any resources that can be recreated.
 }

 #pragma mark - 处理手势操作
 /**
  *  处理拖动手势
  *
  *  @param recognizer 拖动手势识别器对象实例
  */
 - (void)handlePan:(UIPanGestureRecognizer *)recognizer {
     //视图前置操作
     [recognizer.view.superview bringSubviewToFront:recognizer.view];

     CGPoint center = recognizer.view.center;
     CGFloat cornerRadius = recognizer.view.frame.size.width / ;
     CGPoint translation = [recognizer translationInView:self.view];
     //NSLog(@"%@", NSStringFromCGPoint(translation));
     recognizer.view.center = CGPointMake(center.x + translation.x, center.y + translation.y);
     [recognizer setTranslation:CGPointZero inView:self.view];

     if (recognizer.state == UIGestureRecognizerStateEnded) {
         //计算速度向量的长度，当他小于200时，滑行会很短
         CGPoint velocity = [recognizer velocityInView:self.view];
         CGFloat magnitude = sqrtf((velocity.x * velocity.x) + (velocity.y * velocity.y));
         CGFloat slideMult = magnitude / ;
         //NSLog(@"magnitude: %f, slideMult: %f", magnitude, slideMult); //e.g. 397.973175, slideMult: 1.989866

         //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);

         //使用 UIView 动画使 view 滑行到终点
         [UIView animateWithDuration:slideFactor*
                               delay:
                             options:UIViewAnimationOptionCurveEaseOut
                          animations:^{
                              recognizer.view.center = finalPoint;
                          }
                          completion:nil];
     }
 }

 /**
  *  处理捏合手势
  *
  *  @param recognizer 捏合手势识别器对象实例
  */
 - (void)handlePinch:(UIPinchGestureRecognizer *)recognizer {
     CGFloat scale = recognizer.scale;
     recognizer.view.transform = CGAffineTransformScale(recognizer.view.transform, scale, scale); //在已缩放大小基础下进行累加变化；区别于：使用 CGAffineTransformMakeScale 方法就是在原大小基础下进行变化
     recognizer.scale = 1.0;
 }

 /**
  *  处理旋转手势
  *
  *  @param recognizer 旋转手势识别器对象实例
  */
 - (void)handleRotation:(UIRotationGestureRecognizer *)recognizer {
     recognizer.view.transform = CGAffineTransformRotate(recognizer.view.transform, recognizer.rotation);
     recognizer.rotation = 0.0;
 }

 /**
  *  处理点按手势
  *
  *  @param recognizer 点按手势识别器对象实例
  */
 - (void)handleTap:(UITapGestureRecognizer *)recognizer {
     UIView *view = recognizer.view;
     view.transform = CGAffineTransformMakeScale(1.0, 1.0);
     view.transform = CGAffineTransformMakeRotation(0.0);
     view.alpha = 1.0;
 }

 /**
  *  处理长按手势
  *
  *  @param recognizer 点按手势识别器对象实例
  */
 - (void)handleLongPress:(UILongPressGestureRecognizer *)recognizer {
     //长按的时候，设置不透明度为0.7
     recognizer.view.alpha = 0.7;
 }

 /**
  *  处理轻扫手势
  *
  *  @param recognizer 轻扫手势识别器对象实例
  */
 - (void)handleSwipe:(UISwipeGestureRecognizer *)recognizer {
     //代码块方式封装操作方法
     void (^positionOperation)() = ^() {
         CGPoint newPoint = recognizer.view.center;
         newPoint.y -= 20.0;
         _imgV.center = newPoint;

         newPoint.y += 40.0;
         _imgV2.center = newPoint;
     };

     //根据轻扫方向，进行不同控制
     switch (recognizer.direction) {
         case UISwipeGestureRecognizerDirectionRight: {
             positionOperation();
             break;
         }
         case UISwipeGestureRecognizerDirectionLeft: {
             positionOperation();
             break;
         }
         case UISwipeGestureRecognizerDirectionUp: {
             break;
         }
         case UISwipeGestureRecognizerDirectionDown: {
             break;
         }
     }
 }

 /**
  *  处理自定义手势
  *
  *  @param recognizer 自定义手势识别器对象实例
  */
 - (void)handleCustomGestureRecognizer:(KMGestureRecognizer *)recognizer {
     //代码块方式封装操作方法
     void (^positionOperation)() = ^() {
         CGPoint newPoint = recognizer.view.center;
         newPoint.x -= 20.0;
         _imgV.center = newPoint;

         newPoint.x += 40.0;
         _imgV2.center = newPoint;
     };

     positionOperation();
 }

 #pragma mark - 绑定手势操作
 /**
  *  绑定拖动手势
  *
  *  @param imgVCustom 绑定到图片视图对象实例
  */
 - (void)bindPan:(UIImageView *)imgVCustom {
     UIPanGestureRecognizer *recognizer = [[UIPanGestureRecognizer alloc] initWithTarget:self
                                                                                  action:@selector(handlePan:)];
     [imgVCustom addGestureRecognizer:recognizer];
 }

 /**
  *  绑定捏合手势
  *
  *  @param imgVCustom 绑定到图片视图对象实例
  */
 - (void)bindPinch:(UIImageView *)imgVCustom {
     UIPinchGestureRecognizer *recognizer = [[UIPinchGestureRecognizer alloc] initWithTarget:self
                                                                                      action:@selector(handlePinch:)];
     [imgVCustom addGestureRecognizer:recognizer];
     //[recognizer requireGestureRecognizerToFail:imgVCustom.gestureRecognizers.firstObject];
 }

 /**
  *  绑定旋转手势
  *
  *  @param imgVCustom 绑定到图片视图对象实例
  */
 - (void)bindRotation:(UIImageView *)imgVCustom {
     UIRotationGestureRecognizer *recognizer = [[UIRotationGestureRecognizer alloc] initWithTarget:self
                                                                                            action:@selector(handleRotation:)];
     [imgVCustom addGestureRecognizer:recognizer];
 }

 /**
  *  绑定点按手势
  *
  *  @param imgVCustom 绑定到图片视图对象实例
  */
 - (void)bindTap:(UIImageView *)imgVCustom {
     UITapGestureRecognizer *recognizer = [[UITapGestureRecognizer alloc] initWithTarget:self
                                                                                  action:@selector(handleTap:)];
     //使用一根手指双击时，才触发点按手势识别器
     recognizer.numberOfTapsRequired = ;
     recognizer.numberOfTouchesRequired = ;
     [imgVCustom addGestureRecognizer:recognizer];
 }

 /**
  *  绑定长按手势
  *
  *  @param imgVCustom 绑定到图片视图对象实例
  */
 - (void)bindLongPress:(UIImageView *)imgVCustom {
     UILongPressGestureRecognizer *recognizer = [[UILongPressGestureRecognizer alloc] initWithTarget:self action:@selector(handleLongPress:)];
     recognizer.minimumPressDuration = 0.5; //设置最小长按时间；默认为0.5秒
     [imgVCustom addGestureRecognizer:recognizer];
 }

 /**
  *  绑定轻扫手势；支持四个方向的轻扫，但是不同的方向要分别定义轻扫手势
  */
 - (void)bindSwipe {
     //向右轻扫手势
     UISwipeGestureRecognizer *recognizer = [[UISwipeGestureRecognizer alloc] initWithTarget:self
                                                                                      action:@selector(handleSwipe:)];
     recognizer.direction = UISwipeGestureRecognizerDirectionRight; //设置轻扫方向；默认是 UISwipeGestureRecognizerDirectionRight，即向右轻扫
     [self.view addGestureRecognizer:recognizer];
     [recognizer requireGestureRecognizerToFail:_customGestureRecognizer]; //设置以自定义挠痒手势优先识别

     //向左轻扫手势
     recognizer = [[UISwipeGestureRecognizer alloc] initWithTarget:self
                                                            action:@selector(handleSwipe:)];
     recognizer.direction = UISwipeGestureRecognizerDirectionLeft;
     [self.view addGestureRecognizer:recognizer];
     [recognizer requireGestureRecognizerToFail:_customGestureRecognizer]; //设置以自定义挠痒手势优先识别
 }

 /**
  *  绑定自定义挠痒手势；判断是否有三次不同方向的动作，如果有则手势结束，将执行回调方法
  */
 - (void)bingCustomGestureRecognizer {
     //当 recognizer.state 为 UIGestureRecognizerStateEnded 时，才执行回调方法 handleCustomGestureRecognizer:

     //_customGestureRecognizer = [KMGestureRecognizer new];
     _customGestureRecognizer = [[KMGestureRecognizer alloc] initWithTarget:self
                                                                     action:@selector(handleCustomGestureRecognizer:)];
     [self.view addGestureRecognizer:_customGestureRecognizer];
 }

 - (void)layoutUI {
     //图片视图 _imgV
     UIImage *img = [UIImage imageNamed:@"Emoticon_tusiji_icon"];
     CGFloat cornerRadius = img.size.width;
     _imgV = [[UIImageView alloc] initWithImage:img];
     _imgV.frame = CGRectMake(20.0, 20.0,
                              cornerRadius * , cornerRadius * );
     _imgV.userInteractionEnabled = YES;
     _imgV.layer.masksToBounds = YES;
     _imgV.layer.cornerRadius = cornerRadius;
     _imgV.layer.borderWidth = 2.0;
     _imgV.layer.borderColor = [UIColor grayColor].CGColor;
     [self.view addSubview:_imgV];

     //图片视图 _imgV2
     img = [UIImage imageNamed:@"Emoticon_tusiji_icon2"];
     cornerRadius = img.size.width;
     _imgV2 = [[UIImageView alloc] initWithImage:img];
     _imgV2.frame = CGRectMake(20.0, 40.0 + _imgV.frame.size.height,
                               cornerRadius * , cornerRadius * );
     _imgV2.userInteractionEnabled = YES;
     _imgV2.layer.masksToBounds = YES;
     _imgV2.layer.cornerRadius = cornerRadius;
     _imgV2.layer.borderWidth = 2.0;
     _imgV2.layer.borderColor = [UIColor orangeColor].CGColor;
     [self.view addSubview:_imgV2];

     [self bindPan:_imgV];
     [self bindPinch:_imgV];
     [self bindRotation:_imgV];
     [self bindTap:_imgV];
     [self bindLongPress:_imgV];

     [self bindPan:_imgV2];
     [self bindPinch:_imgV2];
     [self bindRotation:_imgV2];
     [self bindTap:_imgV2];
     [self bindLongPress:_imgV2];

     //为了处理手势识别优先级的问题，这里需先绑定自定义挠痒手势
     [self bingCustomGestureRecognizer];
     [self bindSwipe];
 }

 @end