如何从 UICollectionViewCell 将平移手势传递给 UICollectionVIew？

Question

我有一个UICollectionView 实现自定义UICollectionViewCells 的基于网格的布局。为了让单元格响应拖动，我分别为每个单元格添加了UIPanGestureRecognizer。

UICollectionView 在我从单元格之间的点开始向下和向左/向右滑动时仍会滚动（水平），但只要将平移手势识别器添加到单元格，CollectionView 似乎拒绝当我在单元格内开始滑动点击时滚动。

现在，我将水平左/右拖动与垂直向上/向下拖动分开，因此将单元格拖出（垂直滑动）和滚动CollectionView（水平滑动）之间不应该有任何冲突。在这种情况下，如何将滑动传递给集合/滚动视图，以便它知道像正常一样滚动？必须从单元格之间的边界或间距开始，真的很烦人。

从单元格中移除平移手势后，无论我开始在单元格上还是在单元格之间滑动，滚动都会正常工作。

编辑：下面发布为当前代码的所需平移手势行为

// Handle pans by detecting swipes:
-(void) handlePan:(UIPanGestureRecognizer*)recognizer
{
    // Calculate touch location
    CGPoint touchXY = [recognizer locationInView:masterWindowView];

    // Handle touch
    if (recognizer.state == UIGestureRecognizerStateBegan)
    {
        gestureWasHandled = NO;
        pointCount = 1;
        startPoint = touchXY;
    }

    if (recognizer.state == UIGestureRecognizerStateChanged)
    {
        ++pointCount;

        // Calculate whether a swipe has occurred
        float dX = deltaX(touchXY, startPoint);
        float dY = deltaY(touchXY, startPoint);

        BOOL finished = YES;
        if ((dX > kSwipeDragMin) && (ABS(dY) < kDragLimitMax)) {
            touchType = TouchSwipeLeft;
            NSLog(@"LEFT swipe detected");
            [recognizer requireGestureRecognizerToFail:recognizer];
            //[masterScrollView handlePan]
        }
        else if ((dX < -kSwipeDragMin) && (ABS(dY) < kDragLimitMax)) {
            touchType = TouchSwipeRight;
            NSLog(@"RIGHT swipe detected");
            [recognizer requireGestureRecognizerToFail:recognizer];
        }
        else if ((dY > kSwipeDragMin) && (ABS(dX) < kDragLimitMax)) {
            touchType = TouchSwipeUp;
            NSLog(@"UP swipe detected");
        }
        else if ((dY < -kSwipeDragMin) && (ABS(dX) < kDragLimitMax)) {
            touchType = TouchSwipeDown;
            NSLog(@"DOWN swipe detected");
        }
        else
            finished = NO;

        // If unhandled and downward, produce a new draggable view
        if (!gestureWasHandled && finished && (touchType == TouchSwipeDown))
        {

            [self.delegate cellBeingDragged:self];
            dragView.center = touchXY;
            dragView.hidden = NO;
            dragView.backgroundColor = [UIColor clearColor];


            masterScrollView.scrollEnabled = NO; // prevent user from scrolling during
            gestureWasHandled = YES;
        }
        else if (gestureWasHandled)
        {
            // allow continued dragging after detection
            dragView.center = touchXY;
        }
    }

    if (recognizer.state == UIGestureRecognizerStateEnded)
    {
        // ensure that scroll view returns to scrollable
        if (gestureWasHandled) {
            [self.delegate cell:self dragEndedAt:touchXY];
        }
    }
}

// Allow simultaneous recognition
-(BOOL) gestureRecognizer:(UIGestureRecognizer*)gestureRecognizer shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer*)otherGestureRecognizer
{
    return YES;
}

此代码适用于每个单独的单元格。当附加到 UICollectionView 作为其手势识别器时，它不起作用，实际上它会停止所有滚动。

Answer 1

不要将UIPanGestureRecognizer 附加到每个单元格（这会降低性能），而是将UIPanGestureRecognizer 添加到UICollectionView，当平移手势发生时使用locationInView 来获取UICollectionView 中的点，其中pan 启动，然后 indexPathForItemAtPoint 将返回您应该设置动画的单元格的索引路径。

这样，您的整个集合视图将只有一个手势识别器（好！），同时还保持视图控制器中的控制（如您所愿） - 双赢！

使用此解决方案，您将在视图控制器中实现gestureRecognizer:shouldReceiveTouch:，获取给定的gestureRecognizer，确保它是您的UIPanGestureRecognizer，并使用它的translationInView: 方法来确定平移是在X 轴还是Y 轴上.使用该信息来决定是否要返回 YES 或 NO。例如：

- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldReceiveTouch:(UITouch *)touch {
  if([gestureRecognizer isEqual:myTapGesture]) {
    CGPoint point = [gestureRecognizer translationInView:self.collectionView];
    if(point.x != 0) { //adjust this condition if you want some leniency on the X axis
      //The translation was on the X axis, i.e. right/left, 
      //so this gesture recognizer shouldn't do anything about it
      return NO;
    }
  }
  return YES;
}

Answer 2

拥有 -shouldReceiveTouch: 和 -shouldRecognizeSimultaneouslyWithGestureRecognizer: 返回 YES，添加 UIGestureRecognizerDelegate 作为您的类协议列表，并将您的手势委托委托给 -viewDidLoad 中的 self。

yourGesture.delegate = self;