ios - 尝试使 UITableViewCell 可滑动和可点击，同时保持 UITableView 可滚动，为什么我的单元格有时只能滑动？

Question

我有一个 UITableView，它的单元格是 UITableViewCell 的子类，它有一个顶部 UIView 和一个底部 UIView，如果用户拖动他/她的手指，允许顶部 UIView 向右和向左移动。

我通过向每个 UITableViewCell 添加一个平移手势识别器来让它工作。很简单的东西。但我只想要水平平移，但它会在它打算向上滚动时检测到整个单元格的垂直平移，这会导致 UITableView 不移动。

我试图做到这一点，只有当用户水平移动他/她的手指超过 5 像素时才会检测到手势，但它似乎不起作用。滚动效果很好，我可以点击单元格，但我在一个单元格上滑动十次，它可能只工作一次。

我不明白为什么。

相关代码:

- (BOOL)gestureRecognizerShouldBegin:(UIGestureRecognizer *)recognizer {
    if ([recognizer isKindOfClass:[UIPanGestureRecognizer class]]) {
        NSLog(@"hi");
        CGPoint translation = [(UIPanGestureRecognizer *)recognizer translationInView:self];

        if (translation.x > 5 || translation.x < -5) {
            return YES;
        }
        else {
            return NO;
        }
    }
    else {
        return YES;
    }
}

- (void)pannedCell:(UIPanGestureRecognizer *)recognizer {
    if (recognizer.state == UIGestureRecognizerStateBegan) {
        _firstTouchPoint = [recognizer translationInView:self];
    }
    else if (recognizer.state == UIGestureRecognizerStateChanged) {
        CGPoint touchPoint = [recognizer translationInView:self];

        // Holds the value of how far away from the first touch the finger has moved
        CGFloat xPos;

        // If the first touch point is left of the current point, it means the user is moving their finger right and the cell must move right
        if (_firstTouchPoint.x < touchPoint.x) {
            xPos = touchPoint.x - _firstTouchPoint.x;

            if (xPos <= 0) {
                xPos = 0;
            }
        }
        else {
            xPos = -(_firstTouchPoint.x - touchPoint.x);

            if (xPos >= 0) {
                xPos = 0;
            }
        }

        if (xPos > 10 || xPos < -10) {
            // Change our cellFront's origin to the xPos we defined
            CGRect frame = self.cellFront.frame;
            frame.origin = CGPointMake(xPos, 0);
            self.cellFront.frame = frame;
        }
    }
    else if (recognizer.state == UIGestureRecognizerStateEnded) {
        [self springBack];
    }
    else if (recognizer.state == UIGestureRecognizerStateCancelled) {
        [self springBack];
    }
}

我究竟应该怎么做才能使这个实现更好地工作？

Answer 1

一个很好的方法是确定手势识别器在哪个方向平移最多并使用它，而不是在移动某个值时才开始平移。它大大减少了您需要的代码量，并且在我的测试中运行良好。

- (BOOL)gestureRecognizerShouldBegin:(UIGestureRecognizer *)gestureRecognizer {
    if ([gestureRecognizer isKindOfClass:[UIPanGestureRecognizer class]]) {
        CGPoint translation = [(UIPanGestureRecognizer*)gestureRecognizer translationInView:self.superview];
        return fabsf(translation.x) > fabsf(translation.y)
    }

    return YES;
}

现在您的 View 滑动变得更简单了。此代码允许您向任一方向拖动。

- (void)drag:(UIPanGestureRecognizer *)sender {
    CGPoint translation = [sender translationInView:self.superview];
    CGRect frame = self.upperView.frame;

    switch (sender.state) {
        case UIGestureRecognizerStateChanged:
            frame.origin.x = translation.x;
            [self.upperView setFrame:frame];
            break;
        case UIGestureRecognizerStateBegan:
        case UIGestureRecognizerStateEnded:
        case UIGestureRecognizerStateFailed:
        default:
            break;
    }
}

此外，您可能希望让您的手势识别器与其他手势识别器一起工作(例如，处理表格 View 滚动的识别器)，但 gestureRecognizerShouldBegin: 中的代码似乎可以处理此问题没有问题。

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

另请注意，我使用的是 self.superview 而不是您使用的 self。这是因为文档的 translationInView: 部分中的这一行:

The view in whose coordinate system the translation of the pan gesture should be computed. If you want to adjust a view's location to keep it under the user's finger, request the translation in that view's superview's coordinate system.