如何限制平移手势区域？答案

【问题标题】：How to limit pan gesture area?如何限制平移手势区域？
【发布时间】：2012-08-16 10:11:25
【问题描述】：

我有我的UIImageView，我有另一个UIView 矩形。通过对UIView 矩形应用平移手势，它也会超出UIImageView。我不想被拖出UIImageView

我尝试了下面的代码，但它不是那样工作

-(void)handleMovementView:(UIPanGestureRecognizer *)recognizer
{
    CGPoint movement;

    if(recognizer.state == UIGestureRecognizerStateBegan || recognizer.state == UIGestureRecognizerStateChanged || recognizer.state == UIGestureRecognizerStateEnded)
    {
        CGRect rec = recognizer.view.frame;
        CGRect imgvw = self.imgViewCrop.frame;
        if((rec.origin.x >= imgvw.origin.x && (rec.origin.x + rec.size.width <= imgvw.origin.x + imgvw.size.width)))
        {
            CGPoint translation = [recognizer translationInView:recognizer.view.superview];
            movement = translation;
            recognizer.view.center = CGPointMake(recognizer.view.center.x + translation.x, recognizer.view.center.y + translation.y);
            [recognizer setTranslation:CGPointZero inView:recognizer.view.superview];
            [self handleMovementForHandlers:movement];
        }
    }

}

如果我缓慢应用 Pan，它会应用此条件，但当我快速应用时，它会超出 ImageView

【问题讨论】：

标签： iphone objective-c uiimageview uigesturerecognizer uipangesturerecognizer

【解决方案1】：

不要手动计算点是否在视图的范围内，而是使用CGRectContainsPoint(rect, point)。这对我有用，我喜欢它，因为它更短且更具可读性：

func handlePan(pan: UIPanGestureRecognizer) {
    switch pan.state {
    case .Began:
        if CGRectContainsPoint(self.pannableView.frame, pan.locationInView(self.pannableView)) {
            // Gesture started inside the pannable view. Do your thing.
        }
}

【讨论】：

【解决方案2】：

试试这个

-(void)handleMovementView:(UIPanGestureRecognizer *)recognizer
{
CGPoint movement;

if(recognizer.state == UIGestureRecognizerStateBegan || recognizer.state == UIGestureRecognizerStateChanged || recognizer.state == UIGestureRecognizerStateEnded)
{
    CGRect rec = recognizer.view.frame;
    CGRect imgvw = self.imgViewCrop.frame;
    if((rec.origin.x >= imgvw.origin.x && (rec.origin.x + rec.size.width <= imgvw.origin.x + imgvw.size.width)))
    {
        CGPoint translation = [recognizer translationInView:recognizer.view.superview];
        movement = translation;
        recognizer.view.center = CGPointMake(recognizer.view.center.x + translation.x, recognizer.view.center.y + translation.y);
        rec = recognizer.view.frame;

        if( rec.origin.x < imgvw.origin.x )
            rec.origin.x = imgvw.origin.x;

        if( rec.origin.x + rec.size.width > imgvw.origin.x + imgvw.size.width )
            rec.origin.x = imgvw.origin.x + imgvw.size.width - rec.size.width;

        recognizer.view.frame = rec;

        [recognizer setTranslation:CGPointZero inView:recognizer.view.superview];
        [self handleMovementForHandlers:movement];
    }
}
}

【讨论】：

如果你在移动的时候感觉迟钝，试试min,max函数限制区域。例如： var newCenter = CGPoint(x: x + translation.x, y: y + translation.y) newCenter.x = min(maxXcenter,newCenter.x) newCenter.x = max(minXCenter,newCenter.x) newCenter。 y = min(maxYCenter,newCenter.y) newCenter.y = max(minYCenter,newCenter.y)

【解决方案3】：

扩展 @Matt Quiros 的回答，并在 Swift 3 / 4 中：

func shouldRespondToGesture(_ gesture: UIGestureRecognizer, in frame: CGRect) -> Bool {
    return gesture.state == .began && frame.contains(gesture.location(in: self.view))
}

【讨论】：

【解决方案4】：

先获取识别器（平移手势识别器）的坐标（CGRect），再获取ImageView（Your ImageView）的坐标（CGRect）。

然后根据你的要求比较这个坐标。

如果您仍然遇到任何问题，请记录图像视图和识别器的 x 和 y 值。

【讨论】：

请不要乞求“喜欢”的答案。