iOS:在 UIImageView 之间移动图像

Question

我有一个 View Controller ，其中有一个默认的 UIview 放置在整个屏幕上。我在此 View 中添加了几个 UIImageView(大约 20 个)。我想支持在这些 UIImageView 之间交换图像。我已经使用 UITapGestureRecogniser 来处理这些 UIImageView 上发生的触摸。我可以在 UITapGestureRecogniser 事件本身下处理这些 UIImageView 之间的图像拖放吗？ (或)我需要使用 UIPanGestureRecognizer 或触摸事件吗？实现这些UIImageView之间的图像拖放的最简单、最容易的方法是什么？请建议？

谢谢!

Answer 1

一些想法。

1. 您可以通过点击手势来实现此目的(例如点击第一个 ImageView ，点击目标 ImageView )，但这不是很直观。对于最终用户来说，使用 UIPanGestureRecognizer 进行适当的拖放操作会更加直观。

2. 从技术上讲，您并不是从 ImageView 中拖动图像，而是实际上拖动 ImageView 本身。 (如果没有 ImageView ，图像本身就没有视觉表示。)当您放手时，您将为 ImageView 帧的变化设置动画以完成幻觉。

---

如果您有一个 imageViews 的 NSArray，您可以向其 super View 添加手势:

@property (nonatomic, strong) NSMutableArray *imageViews;

- (void)viewDidLoad
{
    [super viewDidLoad];

    [self createImageViewArray];

    UIPanGestureRecognizer *gesture = [[UIPanGestureRecognizer alloc] initWithTarget:self
                                                                              action:@selector(handlePan:)];
    [self.view addGestureRecognizer:gesture];
}

- (void)createImageViewArray
{
    self.imageViews = [NSMutableArray array];

    // add your imageviews to the array any way you want

    ...
}

- (void)handlePan:(UIPanGestureRecognizer *)gesture
{
    static UIImageView *draggedImage = nil;
    static CGRect draggedImageOriginalFrame;

    CGPoint location = [gesture locationInView:gesture.view];

    if (gesture.state == UIGestureRecognizerStateBegan)
    {
        // see if we grabbed an imageview

        draggedImage = [self determineImageForLocation:location];

        // if so, save its old location for future reference and bring it to the front

        if (draggedImage)
        {
            draggedImageOriginalFrame = draggedImage.frame;
            [draggedImage.superview bringSubviewToFront:draggedImage];
        }
    }
    else if (gesture.state == UIGestureRecognizerStateChanged && draggedImage != nil)
    {
        // if we're dragging it, then update its location 

        CGPoint translation = [gesture translationInView:gesture.view];
        CGRect frame = draggedImageOriginalFrame;
        frame.origin.x += translation.x;
        frame.origin.y += translation.y;
        draggedImage.frame = frame;
    }
    else if (draggedImage != nil && (gesture.state == UIGestureRecognizerStateEnded ||
                                     gesture.state == UIGestureRecognizerStateCancelled ||
                                     gesture.state == UIGestureRecognizerStateFailed))
    {
        // if we let go, let's see if we dropped it over another image view

        UIImageView *droppedOver = nil;

        if (gesture.state == UIGestureRecognizerStateEnded)
            droppedOver = [self draggedImageView:draggedImage toLocation:location];

        if (droppedOver == nil)
        {
            // fail; animate the restoring of the view back to it's original position

            [UIView animateWithDuration:0.25
                             animations:^{
                                 draggedImage.frame = draggedImageOriginalFrame;
                             }];
        }
        else
        {
            // succeed; make sure to bring the view we're about to animate to the front

            [droppedOver.superview bringSubviewToFront:droppedOver];

            // animate the swapping of the views

            [UIView animateWithDuration:0.25
                             animations:^{
                                 draggedImage.frame = droppedOver.frame;
                                 droppedOver.frame = draggedImageOriginalFrame;
                             }];
        }
    }
}

// see if we dragged an imageview over one of our imageviews, returning a point
// to the image view we dropped it over

- (UIImageView *)draggedImageView:(UIImageView *)draggedView toLocation:(CGPoint)location
{
    for (UIImageView *imageview in self.imageViews)
        if (CGRectContainsPoint(imageview.frame, location) && imageview != draggedView)
            return imageview;

    return nil;
}

// see if we started the gesture over an imageview
// (turns out that this is the same as "did we drag an image over another",
// but as we're not dragging an image yet, just pass nil)

- (UIImageView *)determineImageForLocation:(CGPoint)location
{
    return [self draggedImageView:nil toLocation:location];
}