一、基本概念与理解：


Cocoa Touch将触摸事件发送到正在处理的视图。触摸传达的信息包括：

  • 触摸发生的位置 (当前位置、最近的历史位置)
  • 触摸的阶段 (按下、移动、弹起) 
  • 轻击数量 (tapCount 单击/双击) 
  • 触摸发生时间 (时间戳)  

每个UITouch对象都代表一个触摸事件。在iPhone中，触摸交互遵循一种原始的设计模式，即在UIView类中而非UIViewController类中编程实现。就是说触摸交互采用视图级编程方式。  

如何触摸的，即所谓的基本手势，包括：

  • Swipe:滑过，快速移动
  • Pinch Open:二指往外拨动
  • Pinch Close:二指往内拨动
  • Tap：轻击
  • Touch and hold:长按

这些手势的具体实现最原始的（相对最新的iOS版本）就是通过4个视图方法自定义编程来实现。

二、 触摸和视图方法——自定义手势编程
       预定义的4个回调方法就是处理屏幕上触摸的开始、移动和结束。

touchesBegan: withEvent:

       处理手指的移动——touchesMoved: withEvent:

touchesEnded: withEvent:

touchesCancelled: withEvent:

这4个方法都是一种UIResponder方法，通常在UIView子类中实现。所有视图继承了这些方法的基本版本。示例：自定义一个Tickle(类似划卡)手势。



//  TickleGestureRecognizer.h
//

#import <UIKit/UIKit.h>

typedef enum {
    DirectionUnknown = 0,
    DirectionLeft,
    DirectionRight
} Direction;

@interface TickleGestureRecognizer : UIGestureRecognizer

@property (assign) int tickleCount;
@property (assign) CGPoint curTickleStart;
@property (assign) Direction lastDirection;

@end



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//
//  TickleGestureRecognizer.m
//

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

#define REQUIRED_TICKLES 2
#define MOVE_AMT_PER_TICKLE 25

@implementation TickleGestureRecognizer
@synthesize tickleCount;
@synthesize curTickleStart;
@synthesize lastDirection;

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
    UITouch *touch = [touches anyObject];
    self.curTickleStart = [touch locationInView:self.view];
}

- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
    UITouch *touch = [touches anyObject];
    CGPoint ticklePoint = [touch locationInView:self.view];
    CGFloat moveAmt = ticklePoint.x - curTickleStart.x;
    Direction curDirection;
if (moveAmt < 0) {
        curDirection = DirectionLeft;
    }else{
        curDirection = DirectionRight;
    }
if (ABS(moveAmt) < MOVE_AMT_PER_TICKLE) return;

// Make sure we've switched directions
    if (self.lastDirection == DirectionUnknown || (self.lastDirection == DirectionLeft && curDirection == DirectionRight) || (self.lastDirection == DirectionRight && curDirection == DirectionRight)) {

        self.tickleCount++;
        self.curTickleStart = ticklePoint;
        self.lastDirection = curDirection;

if (self.state == UIGestureRecognizerStatePossible && self.tickleCount > REQUIRED_TICKLES) {
            [self setState:UIGestureRecognizerStateEnded];
        }
    }
}

- (void)reset {
    self.tickleCount = 0;
    self.curTickleStart = CGPointZero;
    self.lastDirection = DirectionUnknown;
if (self.state == UIGestureRecognizerStatePossible) {
        [self setState:UIGestureRecognizerStateFailed];
    }
}

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

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

@end



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其中方法locationInView:即获取当前Touch点位置。若是获取触摸动作之前的位置则用previousLocationInView:方法。以上定义了一个TickleGestureRecognizer新类实现了Tickle手势。具体使用则是：



// 要用手势的UIView的控制器头文件中添加
- (void)handleTickle:(TickleGestureRecognizer *)recognizer;

// 要用手势的UIView的控制器实现文件
// viewDidLoad添加
TickleGestureRecognizer *recognizer = [[TickleGestureRecognizer alloc] initWithTarget:self action:@selector(handleTickle:)];
        recognizer.delegate = self; // 又见强大的委托
        [view addGestureRecognizer:recognizer]; // 用addGestureRecognizer方法将手势添加到视图上

// 委托的回调方法
- (void)handleTickle:(TickleGestureRecognizer *)recognizer {
// Code.....
}



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三、利用UIGestureRecognizer类给视图添加手势
       iOS3.0后引入了UIGestueRecognizer类帮助我们处理触摸动作下各种手势的添加实现。要点就是在要添加手势的视图的控制器类必须实现UIGestureRecognizerDelegate委托协议。其实从编码角度看，就是苹果公司将所有的基本手势由UIGestureRecognizer类来定义实现了（与自定义编程中的TickleGestureRecognizer异曲同工）并引入的委托机制。

四、iOS5.0中可以在StoryBoard Editor中可视化添加手势