创建自定义的UIGestureRecognizer

Question

我已经创建了几个自定义的UIGestureRecognizers，并且没有任何问题。我决定想要一个自定义版本的单击手势，于是开始子类化UIGestureRecognizer。一切都很好，除了一个问题。在我的操作处理程序中，[gestureRecognizer locationInView:self]始终返回x和y都为零。当我回到UITapGestureRecognizer时，操作处理程序正常工作。这一定与子类化的手势识别器有关，下面是我的代码：

#import "gr_TapSingle.h"

#define tap_Timeout 0.25

@implementation gr_TapSingle


- (id)init
{
    self = [super init];
    if ( self )
    {
    }
    return self;
}

- (void)reset
{
}

-(void)gesture_Fail
{
    self.state = UIGestureRecognizerStateFailed;
}

-(void)touchesBegan:(NSSet*)touches withEvent:(UIEvent*)event
{
    [super touchesBegan:touches withEvent:event];

    if ( [self numberOfTouches] > 1 )
    {
        self.state = UIGestureRecognizerStateFailed;
        return;
    }

    originLocation = [[[event allTouches] anyObject] locationInView:self.view];

    [self performSelector:@selector(gesture_Fail) withObject:nil afterDelay:tap_Timeout];
}

-(void)touchesMoved:(NSSet*)touches withEvent:(UIEvent*)event
{
    [super touchesMoved:touches withEvent:event];

    if ( self.state == UIGestureRecognizerStatePossible )
    {
        CGPoint l_Location = [[[event allTouches] anyObject] locationInView:self.view];
        CGPoint l_Location_Delta = CGPointMake( l_Location.x - originLocation.x, l_Location.y - originLocation.y );
        CGFloat l_Distance_Delta = sqrt( l_Location_Delta.x * l_Location_Delta.x + l_Location_Delta.y * l_Location_Delta.y );
        if ( l_Distance_Delta > 15 )
            self.state = UIGestureRecognizerStateFailed;
        return;
    }
}

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

    if ( self.state == UIGestureRecognizerStatePossible )
        [[self class] cancelPreviousPerformRequestsWithTarget:self selector:@selector(gesture_Fail) object:nil];

    if ( self.state != UIGestureRecognizerStateFailed )
        self.state = UIGestureRecognizerStateEnded;
}

-(void)touchesCancelled:(NSSet*)touches withEvent:(UIEvent*)event
{
    [super touchesCancelled:touches withEvent:event];
    if ( self.state == UIGestureRecognizerStatePossible )
        [[self class] cancelPreviousPerformRequestsWithTarget:self selector:@selector(gesture_Fail) object:nil];
    self.state = UIGestureRecognizerStateFailed;
}

@end

- user1178361

Answer 1

苹果文档中说：

返回值是UIKit框架计算的通用单点手势位置。它通常是涉及手势的触摸点的质心。对于UISwipeGestureRecognizer和UITapGestureRecognizer类的对象，此方法返回的位置具有与手势相关的特殊意义。这些特殊意义在这些类的参考文献中有所记录。

因此，我认为每个子类都有自己特殊的实现方式，以适应其各自的特点。因此，如果要创建UIGestureRecognizer的子类，则必须自己实现此方法。

编辑：

类似以下内容：

- (CGPoint)locationInView:(UIView *)view
{
   if(view == self.view)
   {
      return originLocation;
   }
   else
   {
     //you decide
   }
}

- Kai Huppmann