我已经让 UIPanGestureRecognizer 只检测大部分垂直平底锅，我如何让它只检测真正垂直平底锅？

Posted 2023-03-13

【中文标题】我已经让 UIPanGestureRecognizer 只检测大部分垂直平底锅，我如何让它只检测真正垂直平底锅？

【英文标题】：I've made UIPanGestureRecognizer only detect mostly vertical pans, how do I make it only detect REALLY vertical pans?

【发布时间】：2013-04-14 19:52:32

【问题描述】：

我刚刚实现了这个：

- (BOOL)gestureRecognizerShouldBegin:(UIPanGestureRecognizer *)panGestureRecognizer 
    CGPoint translation = [panGestureRecognizer translationInView:someView];
    return fabs(translation.y) > fabs(translation.x);

（如here所述。）

但如果用户在对角线上垂直平移，它将开始。如何使公差对于它认为垂直的内容更加严格？

基本上，下图描述了我所追求的。第一张图是它现在检测到的，该区域内的任何东西，第二张图是我想要它做的。

【参考方案1】：

您可以使用atan2f 给定x 和y 值来计算垂直角度。例如，要在与垂直方向的角度小于 4 度时开始手势，您可以执行以下操作：

- (BOOL)gestureRecognizerShouldBegin:(UIPanGestureRecognizer *)gesture 
    CGPoint translation = [gesture translationInView:gesture.view];
    if (translation.x != 0 || translation.y != 0) 
        CGFloat angle = atan2f(fabs(translation.x), fabs(translation.y));
        return angle < (4.0 * M_PI / 180.0); // four degrees, but in radians
    
    return FALSE;

【参考方案2】：

检测纯垂直手势，我假设 translation.x == 0 然后。

您还应该从您引用的帖子中检查正确答案。他将先前的位置与当前位置进行比较。你可以创造感性。您可以查看我的project，例如查看我使用此敏感性定义的操作何时有效（小于或等于敏感性）或无效（大于敏感性）。检查RPSliderViewController.m内的MOVEMENT_SENSIBILITY。

【讨论】：

这太棒了。当我偶然发现这个问题时，这正是我所需要的。我会将其更改为： if((translation.x > 0) && (translation.x

【参考方案3】：

我曾经为此目的编写了一个UIGestureRecognizer 子类。它只跟踪垂直平移。也许这对你有帮助。您可以将其用作任何其他手势识别器，只需设置阈值并在其目标的操作方法中跟踪翻译。

VerticalPanGestureRecognizer.h

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

@interface VerticalPanGestureRecognizer : UIGestureRecognizer

@property (assign, nonatomic)float translation;
@property (assign, nonatomic)float offsetThreshold;

@end

VerticalPanGestureRecognizer.m

#import "VerticalPanGestureRecognizer.h"

@interface VerticalPanGestureRecognizer ()

    CGPoint _startPoint;

@end

@implementation VerticalPanGestureRecognizer

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event

    if ([touches count] > 1) 
        self.state = UIGestureRecognizerStateFailed;
    
    else
    
        _startPoint = [[touches anyObject] locationInView:self.view];
    


- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event

    if (self.state == UIGestureRecognizerStateFailed || self.state == UIGestureRecognizerStateCancelled) 
        return;
    
    CGPoint currentLocation = [[touches anyObject] locationInView:self.view];
    CGPoint translation;
    translation.x = currentLocation.x - _startPoint.x;
    translation.y = currentLocation.y - _startPoint.y;        

    if (self.state == UIGestureRecognizerStatePossible)
    
        //if the x-translation is above our threshold the gesture fails 
        if (fabsf(translation.x) > self.offsetThreshold)
            self.state = UIGestureRecognizerStateFailed;
        //if the y-translation has reached the threshold the gesture is recognized and the we start sending action methods
        else if (fabsf(translation.y) > self.offsetThreshold)
            self.state = UIGestureRecognizerStateBegan;

        return;                
            
    //if we reached this point the gesture was succesfully recognized so we now enter changed state
    self.state = UIGestureRecognizerStateChanged;

    //we are just insterested in the vertical translation
    self.translation = translation.y;


- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event

    //if at this point the state is still 'possible' the threshold wasn't reached at all so we fail
    if (self.state == UIGestureRecognizerStatePossible)
    
        self.state = UIGestureRecognizerStateFailed;
    
    else
    
        CGPoint currentLocation = [[touches anyObject] locationInView:self.view];
        CGPoint translation;
        translation.x = _startPoint.x - currentLocation.x;
        translation.y = _startPoint.y - currentLocation.y;
        self.translation = translation.y;
        self.state = UIGestureRecognizerStateEnded;
    



- (void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event

    self.state = UIGestureRecognizerStateCancelled;


- (void)reset

    [super reset];
    _startPoint = CGPointZero;


@end