UIGestureRecognizer学习笔记

The concrete subclasses of UIGestureRecognizer
are the following:
UITapGestureRecognizer

UIPinchGestureRecognizer

UIRotationGestureRecognizer

UISwipeGestureRecognizer

UIPanGestureRecognizer

UILongPressGestureRecognizer

UITapGestureRecognizer

         switch (gestureRecognizer.state)
 {  
    case UIGestureRecognizerStateEnded:{ // UIGestureRecognizerStateRecognized = UIGestureRecognizerStateEnded  
        NSLog(@"======UIGestureRecognizerStateEnded || UIGestureRecognizerStateRecognized");  
        break;  
    }  
    case UIGestureRecognizerStateBegan:{ //   
        NSLog(@"======UIGestureRecognizerStateBegan");  
        break;  
    }  
    case UIGestureRecognizerStateChanged:{ //   
        NSLog(@"======UIGestureRecognizerStateChanged");  
          
        gestureRecognizer.view.transform = CGAffineTransformScale(gestureRecognizer.view.transform, gestureRecognizer.scale, gestureRecognizer.scale);  
        gestureRecognizer.scale = 1; // 重置，很重要！！！  
          
        break;  
    }  
    case UIGestureRecognizerStateCancelled:{ //   
        NSLog(@"======UIGestureRecognizerStateCancelled");  
        break;  
    }  
    case UIGestureRecognizerStateFailed:{ //   
        NSLog(@"======UIGestureRecognizerStateFailed");  
        break;  
    }  
    case UIGestureRecognizerStatePossible:{ //   
        NSLog(@"======UIGestureRecognizerStatePossible");  
        break;  
    }  
    default:{  
        NSLog(@"======Unknow gestureRecognizer");  
        break;  
    }  
}    

UIPanGestureRecognizer

    // 拖拽手势  
- (void)handleGesture:(UIPanGestureRecognizer *)gestureRecognizer  
{  
  UIView *view = [gestureRecognizer view]; // 这个view是手势所属的view，也就是增加手势的那个view switch (gestureRecognizer.state) {  
    case UIGestureRecognizerStateBegan:{   
        NSLog(@"======UIGestureRecognizerStateBegan");  
        break;  
    }  
    case UIGestureRecognizerStateChanged:{   
        NSLog(@"======UIGestureRecognizerStateChanged");  
          
        /* 
         让view跟着手指移动 
          
         1.获取每次系统捕获到的手指移动的偏移量translation 
         2.根据偏移量translation算出当前view应该出现的位置 
         3.设置view的新frame 
         4.将translation重置为0（十分重要。否则translation每次都会叠加，很快你的view就会移除屏幕！） 
         */  
          
        CGPoint translation = [gestureRecognizer translationInView:self.view];  
        view.center = CGPointMake(gestureRecognizer.view.center.x + translation.x, gestureRecognizer.view.center.y + translation.y);  
        [gestureRecognizer setTranslation:CGPointMake(0, 0) inView:self.view];//  注意一旦你完成上述的移动，将translation重置为0十分重要。否则translation每次都会叠加，很快你的view就会移除屏幕！  
        break;  
    }  
    case UIGestureRecognizerStateCancelled:{   
        NSLog(@"======UIGestureRecognizerStateCancelled");  
        break;  
    }  
    case UIGestureRecognizerStateFailed:{   
        NSLog(@"======UIGestureRecognizerStateFailed");  
        break;  
    }  
    case UIGestureRecognizerStatePossible:{   
        NSLog(@"======UIGestureRecognizerStatePossible");  
        break;  
    }  
    case UIGestureRecognizerStateEnded:{ // UIGestureRecognizerStateRecognized = UIGestureRecognizerStateEnded  
          
        /* 
         当手势结束后，view的减速缓冲效果 
          
         模拟减速写的一个很简单的方法。它遵循如下策略： 
         计算速度向量的长度（i.e. magnitude） 
         如果长度小于200，则减少基本速度，否则增加它。 
         基于速度和滑动因子计算终点 
         确定终点在视图边界内 
         让视图使用动画到达最终的静止点 
         使用“Ease out“动画参数，使运动速度随着时间降低 
         */  
          
        NSLog(@"======UIGestureRecognizerStateEnded || UIGestureRecognizerStateRecognized");  
          
        CGPoint velocity = [gestureRecognizer velocityInView:self.view];// 分别得出x，y轴方向的速度向量长度（velocity代表按照当前速度，每秒可移动的像素个数，分xy轴两个方向）  
        CGFloat magnitude = sqrtf((velocity.x * velocity.x) + (velocity.y * velocity.y));// 根据直角三角形的算法算出综合速度向量长度  
          
        // 如果长度小于200，则减少基本速度，否则增加它。  
        CGFloat slideMult = magnitude / 200;  
          
        NSLog(@"magnitude: %f, slideMult: %f", magnitude, slideMult);  
        float slideFactor = 0.1 * slideMult; // Increase for more of a slide  
          
        // 基于速度和滑动因子计算终点  
        CGPoint finalPoint = CGPointMake(view.center.x + (velocity.x * slideFactor),  
                                         view.center.y + (velocity.y * slideFactor));  
          
        // 确定终点在视图边界内  
        finalPoint.x = MIN(MAX(finalPoint.x, 0), self.view.bounds.size.width);  
        finalPoint.y = MIN(MAX(finalPoint.y, 0), self.view.bounds.size.height);  
          
        [UIView animateWithDuration:slideFactor*2 delay:0 options:UIViewAnimationOptionCurveEaseOut animations:^{  
            view.center = finalPoint;    
        } completion:nil];  
          
        break;  
    }  
    default:{  
        NSLog(@"======Unknow gestureRecognizer");  
        break;  
    }  
}    

}

原文链接