结合向下滑动和长按

Question

我试图在我的 ViewController（它有一个 tableView）中实现两个手势识别器，它们必须一个接一个地工作。第一个是向下滑动手势，第二个是长按手势。

这是我使用@sergio 建议修改的代码

    - (void)viewDidLoad
    {
        [super viewDidLoad];

        swipeDown = [[[UISwipeGestureRecognizer alloc]initWithTarget:self action:@selector(swipeDownAction)] autorelease];

        longPress = [[[CustomLongPress alloc]initWithTarget:self action:@selector(longPressAction)] autorelease];


        longPress.minimumPressDuration = 2;

        swipeDown.numberOfTouchesRequired = 1;

        swipeDown.direction = UISwipeGestureRecognizerDirectionDown;


       swipeDown.delegate = self ;

        longPress.delegate = self ;

        [myTableView addGestureRecognizer:swipeDown];

        [myTableView addGestureRecognizer:longPress];





  }


    -(void)swipeDownAction {

        _methodHasBeenCalled = YES;    // bool @property declared in .h

        NSLog(@"Swipe down detected");


    }



    -(void)longPressAction {

        NSLog(@"long press detected");
    }

    - (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer
    {
        return YES;
    }

还有我的 UILongPressGestureRecognizer 子类：

#import "CustomLongPress.h"
#import "ViewController.h"


@interface CustomLongPress()
{

    ViewController *vc;
}

@end


@implementation CustomLongPress
-(id)initWithTarget:(id)target action:(SEL)action controller:(ViewController *)viewCon
{
    self = [super initWithTarget:target action:action];

    if (self) {

        vc = viewCon;

    }

    return self;
}


-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
     NSLog(vc.methodHasBeenCalled ? @"Yes" : @"No");

    if (vc.methodHasBeenCalled) {

        [super touchesBegan:touches withEvent:event];
    }
}

不幸的是，我仍然只能从 swipeDown 获得日志，但在 longPress 时没有日志

Answer 1

为此，您需要创建自己的自定义手势识别器。最好的方法是让您继承 UILongPressGestureRecognizer 并使其仅在滑动结束后“接受”长按。例如，在touchesBegan 方法中

- (void)touchesBegan:(NSSet*)touches withEvent:(UIEvent*)event {
   <if swipe recognizer action method has been called>
       [super touchesBegan:touches withEvent:event];
   }
}

这样，两个手势识别器都会尝试识别手势：滑动识别器会立即这样做；而自定义识别器会“等待”滑动识别器触发。

实现条件<if swipe recognizer action method has been called> 的一种简单方法是在您的滑动操作中设置一个全局标志（您在执行滑动操作时设置它；然后自定义识别器读取它的值）。这简单，目前还不是你能找到的最好的实现。

另一种方法是依靠 requiresGestureRecognizerToFail 链接 3 个标准手势识别器，我们称它们为 A、B 和 C，其中：

1. A 是UISwipeGestureRecognizer;
2. C 是UILongPressGestureRecognizer;
3. B 是任何手势识别器。

您可以这样配置它们：

C --> B --> A

其中x --> y 表示x 要求y 失败。因此，您将拥有C（您的长按手势识别器）将要求B GR 失败，而B 需要A（您的滑动识别器）失败；只要A 识别到滑动，B 就会失败；一旦B 失败，C 将被允许识别长按。

编辑：

阅读您的评论后，您是否介意尝试一下，看看是否有帮助：

1. 删除您覆盖的 touchesBegan 并将其替换为：

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

2. 然后定义：

   - (void)touchesMoved:(NSSet*)touches withEvent:(UIEvent*)event {
   
     if (vc.methodHasBeenCalled) {
       [super touchesBegan:touches withEvent:event];
     } else {
        return;
     }
   }
   

如果这不起作用，则让您的自定义手势识别器继承自通用手势识别器并

1. 将touchesBegan: 留在原处并将touchesMoved 替换为：

   - (void)touchesMoved:(NSSet*)touches withEvent:(UIEvent*)event {
   
     self.lastTouch = [touches anyObject];
     if (vc.methodHasBeenCalled && self.gestureNotBegunYet == YES) {
       self.gestureNotBegunYet = NO;
       [self performSelector:@selector(recognizeLongPress) withObject:nil afterDelay:1.0];
   
     } else {
        return;
     }
   }
   

并添加：

- (float)travelledDistance {
  CGPoint currentLocation = [self.lastTouch locationInView:self.view.superview];
  return sqrt(pow((currentLocation.x - self.initialLocation.x), 2.0) +
            pow((currentLocation.y - self.initialLocation.y), 2.0));
}

- (void)fail {
  self.gestureNotBegunYet = YES;
  [NSObject cancelPreviousPerformRequestsWithTarget:self];

}

- (void)recognizeLongPress {

  if ([self travelledDistance] < kTapDragThreshold) {
    self.longPressed = YES;
    self.state = UIGestureRecognizerStateChanged;
  } else {
        [self fail];
        self.state = UIGestureRecognizerStateFailed;
  }
}

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

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

您需要在.h中定义

@property(nonatomic) CGPoint initialLocation;
@property(nonatomic, retain) UITouch* lastTouch;
@property(nonatomic) BOOL gestureNotBegunYet;

Answer 2

如果我没记错的话，一旦系统检测到特定类型的手势（点击、滑动、平移、长按等），它就不能再为该触摸动作发送不同类型的手势。

这并不妨碍您实现您想要的结果。也许结合重载以下UIResponder 方法：

– touchesBegan:withEvent:
– touchesMoved:withEvent:
– touchesEnded:withEvent:
– touchesCancelled:withEvent:

并且使用手势识别器（不确定输入是否会被一个人使用而另一个人会忽略），您可以确定它是“长滑动”