在iOS中检测PAN手势的方向

Question

在我的应用程序中有一个图像视图.我将PAN手势添加到该图像视图.

这工作正常.

图像视图处于横向模式.

我希望在用户向右平移时增加标签中的计数,并在用户向左平移时减少该计数.

我google了很多,但没有找到解决方案.

谁能帮助我如何检测用户平移的方向(左/右)？

Answer 1

在手势识别器的目标选择器中,使用- (CGPoint)velocityInView:(UIView *)view;:

- (void)panRecognized:(UIPanGestureRecognizer *)rec
{
    CGPoint vel = [rec velocityInView:self.view];
    if (vel.x > 0)
    {
        // user dragged towards the right
        counter++;
    }
    else
    {
        // user dragged towards the left
        counter--;
    }
}

Ps:直到约,我才知道这个方法.3分钟前 谷歌的第一个热门歌曲之一就是官方的Apple文档.

Answer 2

像这样的东西:

- (void)pan:(UIPanGestureRecognizer *)sender
{

    typedef NS_ENUM(NSUInteger, UIPanGestureRecognizerDirection) {
        UIPanGestureRecognizerDirectionUndefined,
        UIPanGestureRecognizerDirectionUp,
        UIPanGestureRecognizerDirectionDown,
        UIPanGestureRecognizerDirectionLeft,
        UIPanGestureRecognizerDirectionRight
    };

    static UIPanGestureRecognizerDirection direction = UIPanGestureRecognizerDirectionUndefined;

    switch (sender.state) {

        case UIGestureRecognizerStateBegan: {

            if (direction == UIPanGestureRecognizerDirectionUndefined) {

                CGPoint velocity = [sender velocityInView:recognizer.view];

                BOOL isVerticalGesture = fabs(velocity.y) > fabs(velocity.x);

                if (isVerticalGesture) {
                    if (velocity.y > 0) {
                        direction = UIPanGestureRecognizerDirectionDown;
                    } else {
                        direction = UIPanGestureRecognizerDirectionUp;
                    }
                }

                else {
                    if (velocity.x > 0) {
                        direction = UIPanGestureRecognizerDirectionRight;
                    } else {
                        direction = UIPanGestureRecognizerDirectionLeft;
                    }
                }
            }

            break;
        }

        case UIGestureRecognizerStateChanged: {
            switch (direction) {
                case UIPanGestureRecognizerDirectionUp: {
                    [self handleUpwardsGesture:sender];
                    break;
                }
                case UIPanGestureRecognizerDirectionDown: {
                    [self handleDownwardsGesture:sender];
                    break;
                }
                case UIPanGestureRecognizerDirectionLeft: {
                    [self handleLeftGesture:sender];
                    break;
                }
                case UIPanGestureRecognizerDirectionRight: {
                    [self handleRightGesture:sender];
                    break;
                }
                default: {
                    break;
                }
            }
        }

        case UIGestureRecognizerStateEnded: {
            direction = UIPanGestureRecognizerDirectionUndefined;   
            break;
        }

        default:
            break;
    }

}

- (void)handleUpwardsGesture:(UIPanGestureRecognizer *)sender
{
    NSLog(@"Up");
}

- (void)handleDownwardsGesture:(UIPanGestureRecognizer *)sender
{
    NSLog(@"Down");
}

- (void)handleLeftGesture:(UIPanGestureRecognizer *)sender
{
    NSLog(@"Left");
}

- (void)handleRightGesture:(UIPanGestureRecognizer *)sender
{
    NSLog(@"Right");
}

Answer 3

我之前在Swift的回答

public enum Direction: Int {
    case Up
    case Down
    case Left
    case Right

    public var isX: Bool { return self == .Left || self == .Right }
    public var isY: Bool { return !isX }
}

public extension UIPanGestureRecognizer {

    public var direction: Direction? {
        let velocity = velocityInView(view)
        let vertical = fabs(velocity.y) > fabs(velocity.x)
        switch (vertical, velocity.x, velocity.y) {
        case (true, _, let y) where y < 0: return .Up
        case (true, _, let y) where y > 0: return .Down
        case (false, let x, _) where x > 0: return .Right
        case (false, let x, _) where x < 0: return .Left
        default: return nil
        }
    }
}

Answer 4

这是一个清理过的Swift 3版本,其中包含使用示例:

public enum PanDirection: Int {
    case up, down, left, right
    public var isVertical: Bool { return [.up, .down].contains(self) }
    public var isHorizontal: Bool { return !isVertical }
}

public extension UIPanGestureRecognizer {

   var direction: PanDirection? {
        let velocity = self.velocity(in: view)
        let isVertical = abs(velocity.y) > abs(velocity.x)
        switch (isVertical, velocity.x, velocity.y) {
        case (true, _, let y) where y < 0: return .up
        case (true, _, let y) where y > 0: return .down
        case (false, let x, _) where x > 0: return .right
        case (false, let x, _) where x < 0: return .left
        default: return nil
        }
    }

}

@IBAction func pan(_ recognizer: UIPanGestureRecognizer) {        
    if let direction = recognizer.direction {
        if direction.isVertical {
            //do what you want when pan is vertical
        } else if direction == .left {
            //do what you want when pan is left
        }
    }
}