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:

1 - (void)reset;
2 
3 - (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event;
4 - (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event;
5 - (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event;
6 - (void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event;
7 //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,他是 UITapGestureRecognizer。
  离散型手势的特点是:一旦识别无法取消,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:

1 typedef NS_ENUM(NSInteger, UIGestureRecognizerState) {
2     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
3     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
4     UIGestureRecognizerStateChanged,    // 手势状态发生转变
5     UIGestureRecognizerStateEnded,      // 手势识别操作完成(此时已经松开手指)
6     UIGestureRecognizerStateCancelled,  // 手势被取消,恢复到默认状态
7     UIGestureRecognizerStateFailed,     // 手势识别失败,恢复到默认状态
8     UIGestureRecognizerStateRecognized = UIGestureRecognizerStateEnded // 手势识别完成,同UIGestureRecognizerStateEnded
9 };

  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,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:
  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。
  设置手势识别器对象实例的相关属性(可选部分)
  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。
  拖动:进行当前图片视图位置移动
  捏合:进行当前图片视图缩放
  旋转:进行当前图片视图角度旋转
  点按:双击恢复当前图片视图的缩放、角度旋转、不透明度
  长按:设置当前图片视图的不透明度为0.7
  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
  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

 1 #import <UIKit/UIKit.h>
 2 
 3 typedef NS_ENUM(NSUInteger, Direction) {
 4     DirectionUnknown,
 5     DirectionLeft,
 6     DirectionRight
 7 };
 8 
 9 @interface KMGestureRecognizer : UIGestureRecognizer
10 @property (assign, nonatomic) NSUInteger tickleCount; //挠痒次数
11 @property (assign, nonatomic) CGPoint currentTickleStart; //当前挠痒开始坐标位置
12 @property (assign, nonatomic) Direction lastDirection; //后一次挠痒方向
13 
14 @end

  KMGestureRecognizer.m

 1 #import "KMGestureRecognizer.h"
 2 #import <UIKit/UIGestureRecognizerSubclass.h>
 3 
 4 @implementation KMGestureRecognizer
 5 #define kMinTickleSpacing 20.0
 6 #define kMaxTickleCount 3
 7 
 8 - (void)reset {
 9     _tickleCount = 0;
10     _currentTickleStart = CGPointZero;
11     _lastDirection = DirectionUnknown;
12     
13     if (self.state == UIGestureRecognizerStatePossible) {
14         self.state = UIGestureRecognizerStateFailed;
15     }
16 }
17 
18 - (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
19     UITouch *touch = [touches anyObject];
20     _currentTickleStart = [touch locationInView:self.view]; //设置当前挠痒开始坐标位置
21 }
22 
23 - (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
24     //『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
25     UITouch *touch = [touches anyObject];
26     CGPoint tickleEnd = [touch locationInView:self.view];
27     CGFloat tickleSpacing = tickleEnd.x - _currentTickleStart.x;
28     Direction currentDirection = tickleSpacing < 0 ? DirectionLeft : DirectionRight;
29     
30     //移动的 X 轴间距值是否符合要求,足够大
31     if (ABS(tickleSpacing) >= kMinTickleSpacing) {
32         //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
33         if (_lastDirection == DirectionUnknown ||
34             (_lastDirection == DirectionLeft && currentDirection == DirectionRight) ||
35             (_lastDirection == DirectionRight && currentDirection == DirectionLeft)) {
36             _tickleCount++;
37             _currentTickleStart = tickleEnd;
38             _lastDirection = currentDirection;
39             
40             if (_tickleCount >= kMaxTickleCount && self.state == UIGestureRecognizerStatePossible) {
41                 self.state = UIGestureRecognizerStateEnded;
42                 //NSLog(@"自定义手势成功,将执行回调方法");
43             }
44         }
45     }
46 }
47 
48 - (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {
49     [self reset];
50 }
51 
52 - (void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event {
53     [self reset];
54 }
55 
56 @end

 

  ViewController.h

 

1 #import <UIKit/UIKit.h>
2 #import "KMGestureRecognizer.h"
3 
4 @interface ViewController : UIViewController
5 @property (strong, nonatomic) UIImageView *imgV;
6 @property (strong, nonatomic) UIImageView *imgV2;
7 @property (strong, nonatomic) KMGestureRecognizer *customGestureRecognizer;
8 
9 @end

  ViewController.m
 

  1 #import "ViewController.h"
  2 
  3 @interface ViewController ()
  4 - (void)handlePan:(UIPanGestureRecognizer *)recognizer;
  5 - (void)handlePinch:(UIPinchGestureRecognizer *)recognizer;
  6 - (void)handleRotation:(UIRotationGestureRecognizer *)recognizer;
  7 - (void)handleTap:(UITapGestureRecognizer *)recognizer;
  8 - (void)handleLongPress:(UILongPressGestureRecognizer *)recognizer;
  9 - (void)handleSwipe:(UISwipeGestureRecognizer *)recognizer;
 10 - (void)handleCustomGestureRecognizer:(KMGestureRecognizer *)recognizer;
 11 
 12 - (void)bindPan:(UIImageView *)imgVCustom;
 13 - (void)bindPinch:(UIImageView *)imgVCustom;
 14 - (void)bindRotation:(UIImageView *)imgVCustom;
 15 - (void)bindTap:(UIImageView *)imgVCustom;
 16 - (void)bindLongPress:(UIImageView *)imgVCustom;
 17 - (void)bindSwipe;
 18 - (void)bingCustomGestureRecognizer;
 19 - (void)layoutUI;
 20 @end
 21 
 22 @implementation ViewController
 23 
 24 - (void)viewDidLoad {
 25     [super viewDidLoad];
 26     
 27     [self layoutUI];
 28 }
 29 
 30 - (void)didReceiveMemoryWarning {
 31     [super didReceiveMemoryWarning];
 32     // Dispose of any resources that can be recreated.
 33 }
 34 
 35 #pragma mark - 处理手势操作
 36 /**
 37  *  处理拖动手势
 38  *
 39  *  @param recognizer 拖动手势识别器对象实例
 40  */
 41 - (void)handlePan:(UIPanGestureRecognizer *)recognizer {
 42     //视图前置操作
 43     [recognizer.view.superview bringSubviewToFront:recognizer.view];
 44     
 45     CGPoint center = recognizer.view.center;
 46     CGFloat cornerRadius = recognizer.view.frame.size.width / 2;
 47     CGPoint translation = [recognizer translationInView:self.view];
 48     //NSLog(@"%@", NSStringFromCGPoint(translation));
 49     recognizer.view.center = CGPointMake(center.x + translation.x, center.y + translation.y);
 50     [recognizer setTranslation:CGPointZero inView:self.view];
 51     
 52     if (recognizer.state == UIGestureRecognizerStateEnded) {
 53         //计算速度向量的长度,当他小于200时,滑行会很短
 54         CGPoint velocity = [recognizer velocityInView:self.view];
 55         CGFloat magnitude = sqrtf((velocity.x * velocity.x) + (velocity.y * velocity.y));
 56         CGFloat slideMult = magnitude / 200;
 57         //NSLog(@"magnitude: %f, slideMult: %f", magnitude, slideMult); //e.g. 397.973175, slideMult: 1.989866
 58         
 59         //基于速度和速度因素计算一个终点
 60         float slideFactor = 0.1 * slideMult;
 61         CGPoint finalPoint = CGPointMake(center.x + (velocity.x * slideFactor),
 62                                          center.y + (velocity.y * slideFactor));
 63         //限制小[cornerRadius]和大边界值[self.view.bounds.size.width - cornerRadius],以免拖动出屏幕界限
 64         finalPoint.x = MIN(MAX(finalPoint.x, cornerRadius),
 65                            self.view.bounds.size.width - cornerRadius);
 66         finalPoint.y = MIN(MAX(finalPoint.y, cornerRadius),
 67                            self.view.bounds.size.height - cornerRadius);
 68