Question

我有一个简单的应用程序，我将UIPinchGestureRecognizer和UIPanGestureRecognizer附加到imageView，以便我可以拖动和缩放它。我已经做到了这一点，因此可以将imageView部分地从屏幕上移开并最小化显示器，但是图像的一小部分75像素仍保留在显示器上，因此可以将图像拖回到它上面。因此，例如，如果我尝试将imageView拖离显示器的右侧部分，它将在图像视图的75个像素剩余时停止，留下足够的空间让我将其拖回。与缩放相同的概念，我创建的边界框架可以防止imageView在显示屏上最小化。

无论如何，我的UIPinchGestureRecognizer委托方法中的边界代码存在这个问题。我正在做边界的方式是我创建一个框架，它是imageViews超级视图的复制品 - 除了它在每侧以及顶部和底部以75像素推动。我检查imageView是否与此框架相交，然后我知道它已到达右侧/左侧或顶部/底部的边界之一。它大部分都适用，但是当我将图像放大到相当大（通常在1000以上1000）时，边界不起作用 - 如果我进行超快速最小化缩放，则imageView被完全推离屏幕所以我不能拖回来。

我只是想知道为什么会这样。是否与图像尺寸过大有关？或者这是我的代码中的缺陷？（我在下面列出）。如果有人可以提供帮助，我们将不胜感激。

- (void)scale:(UIPinchGestureRecognizer *)sender 
{
    if([sender state] == UIGestureRecognizerStateBegan) 
    {
        lastScale = [sender scale];
    }

    if ([sender state] == UIGestureRecognizerStateBegan || 
        [sender state] == UIGestureRecognizerStateChanged) 
    {
        CGFloat currentScale = [[[sender view].layer valueForKeyPath:@"transform.scale"] floatValue];
        CGFloat newScale = 1 -  (lastScale - [sender scale]);// * (CropThePhotoViewControllerPinchSpeed);    
        newScale = MAX(newScale, CropThePhotoViewControllerMinScale / currentScale);

        CGFloat scaledWidth = newScale * sender.view.frame.size.width;
        CGFloat scaledHeight = newScale * sender.view.frame.size.height;

        CGRect translatedRect = CGRectMake(sender.view.frame.origin.x, sender.view.frame.origin.y, scaledWidth, scaledHeight);
        CGRect boundaryRect = CGRectMake(sender.view.superview.frame.origin.x + CropThePhotoViewControllerBoundaryBuffer, sender.view.superview.frame.origin.y + CropThePhotoViewControllerBoundaryBuffer, sender.view.superview.frame.size.width - (CropThePhotoViewControllerBoundaryBuffer * 2), sender.view.superview.frame.size.height - (CropThePhotoViewControllerBoundaryBuffer * 2));

        if (!(!CGRectIntersectsRect(boundaryRect,translatedRect) && newScale < 1))
        {
            CGAffineTransform transform = CGAffineTransformScale([[sender view] transform], newScale, newScale);
            [[sender view] setTransform: transform];
            lastScale = [sender scale];;
        }
    } 
}

Answer 1

我注意到我必须检查缩放后的NaN（不是数字）结果，然后单独处理它们。使用isnan（）来检查。

Answer 2

我发现了什么问题。对于这行代码，我错误地设置了x和y值：

CGRect translatedRect = CGRectMake(sender.view.frame.origin.x, sender.view.frame.origin.y, scaledWidth, scaledHeight);

应该是：

CGRect translatedRect = CGRectMake(sender.view.frame.origin.x + (((sender.view.frame.size.width - scaledWidth) / 2)), sender.view.frame.origin.y + (((sender.view.frame.size.height - scaledHeight) / 2)), scaledWidth, scaledHeight);

我没有考虑到当imageview缩小时原点会移动的事实。

我做了这个改变，实际上更新了要改进的方法。现在，如果用户尝试最小化超出边界，而不是仅执行缩放，而是将imageView右移到边框。这是更顺畅，最终更好的imo。经过测试，它运行良好，但如果有人发现任何错误，请告诉我：

- (void)scale:(UIPinchGestureRecognizer *)sender 
{
    if([sender state] == UIGestureRecognizerStateBegan) 
    {
        previousScale = [sender scale];
    }


    if ([sender state] == UIGestureRecognizerStateBegan || 
        [sender state] == UIGestureRecognizerStateChanged) 
    {
        CGFloat nextScale = 1 -  (previousScale - [sender scale]);// * (CropThePhotoViewControllerPinchSpeed); 

        nextScale = MAX(nextScale, CropThePhotoViewControllerMinScale / [[[sender view].layer valueForKeyPath:@"transform.scale"] floatValue]);

        CGFloat scaledWidth = nextScale * sender.view.frame.size.width;
        CGFloat scaledHeight = nextScale * sender.view.frame.size.height;
        CGFloat currentScale = [sender scale];

        CGRect translatedRect = CGRectMake(sender.view.frame.origin.x + (((sender.view.frame.size.width - scaledWidth) / 2)), sender.view.frame.origin.y + (((sender.view.frame.size.height - scaledHeight) / 2)), scaledWidth, scaledHeight);
        CGRect boundaryRect = CGRectMake(sender.view.superview.frame.origin.x + CropThePhotoViewControllerBoundaryBuffer, sender.view.superview.frame.origin.y + CropThePhotoViewControllerBoundaryBuffer, sender.view.superview.frame.size.width - (CropThePhotoViewControllerBoundaryBuffer * 2), sender.view.superview.frame.size.height - (CropThePhotoViewControllerBoundaryBuffer * 2));

        if ((!CGRectIntersectsRect(boundaryRect,translatedRect)) && (nextScale < 1))        
        {
            CGFloat leftScaledEdge, rightScaledEdge, topScaledEdge, bottomScaledEdge;
            CGFloat leftBoundary, rightBoundary, topBoundary, bottomBoundary;
            CGFloat nextXScale, nextYScale;

            nextXScale = CGFLOAT_MIN;
            nextYScale = CGFLOAT_MIN;

            rightScaledEdge = translatedRect.origin.x + translatedRect.size.width;
            leftScaledEdge = translatedRect.origin.x;
            bottomScaledEdge = translatedRect.origin.y + translatedRect.size.height;
            topScaledEdge = translatedRect.origin.y;

            leftBoundary = boundaryRect.origin.x;
            rightBoundary = boundaryRect.origin.x + boundaryRect.size.width; 
            topBoundary = boundaryRect.origin.y;
            bottomBoundary = boundaryRect.origin.y + boundaryRect.size.height;  

            if (rightScaledEdge < leftBoundary || leftScaledEdge > rightBoundary)
            {
                if (rightScaledEdge < leftBoundary)
                {
                    CGFloat adjustedWidth = sender.view.frame.size.width - fabsf((leftBoundary - (sender.view.frame.origin.x + sender.view.frame.size.width)));
                    nextXScale = (nextScale * (adjustedWidth)) / scaledWidth;
                }
                else
                {
                    CGFloat adjustedWidth = sender.view.frame.size.width - fabsf((rightBoundary - sender.view.frame.origin.x));
                    nextXScale = (nextScale * (adjustedWidth)) / scaledWidth;
                }
            }

            if (bottomScaledEdge < topBoundary || topScaledEdge > bottomBoundary)
            {
                if (bottomScaledEdge < topBoundary)
                {
                    CGFloat adjustedHeight = sender.view.frame.size.height - fabsf((topBoundary - (sender.view.frame.origin.y + sender.view.frame.size.height)));
                    nextYScale = (nextScale * (adjustedHeight)) / scaledHeight;
                }
                else
                {
                    CGFloat adjustedHeight = sender.view.frame.size.height - fabsf((bottomBoundary - sender.view.frame.origin.y));
                    nextYScale = (nextScale * (adjustedHeight)) / scaledHeight;

                }
            }

            if (nextXScale >= nextYScale)
            {
                nextScale = nextXScale;
            }
            else 
            {
                nextScale = nextYScale;
            }

            currentScale = nextScale - 1 + previousScale;
        }

        CGAffineTransform transform = CGAffineTransformScale([[sender view] transform], nextScale, nextScale);
        [[sender view] setTransform: transform];
        previousScale = currentScale;
    }

当图像变得太大时，UIPinchGestureRecognizer表现得很有趣

2 个答案: