Question

当我尝试滚动UIScrollView时，我在main中收到Exc_Bad_Access错误。这个程序很简单。我在AppDelegate中添加了一个UIViewController。然后，这是ViewController中的代码。这适用于滚动但只要我添加tmpScrollView.delegate = self。该程序不会滚动或缩放，并在我尝试缩放时给出Exc_Bad_Access错误。

@interface MainViewController : UIViewController &ltUIScrollViewDelegate>
@property (nonatomic,retain) UIScrollView *tmpScrollView;
@property (nonatomic,retain) UIView *containerView;
@end

- (void)viewDidLoad
{
[super viewDidLoad];

// Do any additional setup after loading the view.
tmpScrollView = [[UIScrollView alloc] initWithFrame:self.view.frame];
tmpScrollView.delegate = self;
[self.view addSubview:tmpScrollView];

// Set up the container view to hold our custom view hierarchy
CGSize containerSize = CGSizeMake(640.0f, 640.0f);
self.containerView = [[UIView alloc] initWithFrame:(CGRect){.origin=CGPointMake(0.0f, 0.0f), .size=containerSize}];
[self.tmpScrollView addSubview:self.containerView];

// Set up custom view hierarchy
UIView *redView = [[UIView alloc] initWithFrame:CGRectMake(0.0f, 0.0f, 640.0f, 80.0f)];
redView.backgroundColor = [UIColor redColor];
[self.containerView addSubview:redView];

UIView *blueView = [[UIView alloc] initWithFrame:CGRectMake(0.0f, 560.0f, 640.0f, 80.0f)];
blueView.backgroundColor = [UIColor blueColor];
[self.containerView addSubview:blueView];

UIView *greenView = [[UIView alloc] initWithFrame:CGRectMake(160.0f, 160.0f, 320.0f, 320.0f)];
greenView.backgroundColor = [UIColor greenColor];
[self.containerView addSubview:greenView];

UIImageView *imageView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"slow.png"]];
imageView.center = CGPointMake(320.0f, 320.0f);
[self.containerView addSubview:imageView];

//Tell the scroll view the size of the contents
self.tmpScrollView.contentSize = containerSize;
}

-(void)viewWillAppear:(BOOL)animated
{
NSLog(@"Will Appear");
[super viewWillAppear:animated];

// Set up the minimum & maximum zoom scales
CGRect scrollViewFrame = self.tmpScrollView.frame;
CGFloat scaleWidth = scrollViewFrame.size.width / self.tmpScrollView.contentSize.width;
CGFloat scaleHeight = scrollViewFrame.size.height / self.tmpScrollView.contentSize.height;
CGFloat minScale = MIN(scaleWidth, scaleHeight);

self.tmpScrollView.minimumZoomScale = minScale;
self.tmpScrollView.maximumZoomScale = 1.0f;
self.tmpScrollView.zoomScale = minScale;

//***** Here is the line for setting the delegate
self.tmpScrollView.delegate = self;

[self centerScrollViewContents];
}


-(void)scrollViewDidEndZooming:(UIScrollView *)scrollView withView:(UIView *)view atScale:(float)scale
{
NSLog(@"End Zoom");
}

-(UIView*)viewForZoomingInScrollView:(UIScrollView *)scrollView {
// Return the view that we want to zoom
return self.containerView;
}

-(void)scrollViewDidZoom:(UIScrollView *)scrollView {
// The scroll view has zoomed, so we need to re-center the contents
[self centerScrollViewContents];
}
@end

感谢您的帮助。这让我疯狂了一天......

编辑：添加centerScrollViewContens：

- (void)centerScrollViewContents {
    CGSize boundsSize = self.tmpScrollView.bounds.size;
    CGRect contentsFrame = self.containerView.frame;

    if (contentsFrame.size.width < boundsSize.width) {
        contentsFrame.origin.x = (boundsSize.width - contentsFrame.size.width) / 2.0f;
    } else {
        contentsFrame.origin.x = 0.0f;
    }

    if (contentsFrame.size.height < boundsSize.height) {
        contentsFrame.origin.y = (boundsSize.height - contentsFrame.size.height) / 2.0f;
    } else {
        contentsFrame.origin.y = 0.0f;
    }

    self.containerView.frame = contentsFrame;
}

Answer 1

无论你提供的代码是什么，我的工作都很好。可能在你的“centerScrollViewContents”方法中存在某种问题。你可以发布这个方法的代码吗？

Answer 2

您需要计算滚动视图的最小缩放比例。缩放比例为1表示内容以正常大小显示。缩放比例低于1表示缩小的内容，而缩放比例大于1表示放大的内容。要获得最小缩放比例，您需要计算缩放所需的距离，以使图像适合放大滚动视图的边界基于其宽度。然后你根据图像的高度做同样的事情。这两个缩放比例的最小值将是滚动视图的最小缩放比例。这为您提供了一个缩放比例，您可以在完全缩小时看到整个图像。

夫特：

let scrollViewFrame = scrollView.frame
let scaleWidth = scrollViewFrame.size.width / scrollView.contentSize.width
let scaleHeight = scrollViewFrame.size.height / scrollView.contentSize.height
let minScale = min(scaleWidth, scaleHeight);
scrollView.minimumZoomScale = minScale;

目标-C

CGFloat scrollViewFrame = scrollView.frame
CGFloat scaleWidth = scrollViewFrame.size.width / scrollView.contentSize.width
CGFloat scaleHeight = scrollViewFrame.size.height / scrollView.contentSize.height
CGFloat minScale = min(scaleWidth, scaleHeight);
scrollView.minimumZoomScale = minScale;

从iOS上的大量GPU（无限滚动，最大位图大小等）的其他项目和个人经验中，我注意到每个设备都有自己的阈值。对于过去的项目，我还将以下值硬编码为minimumZoomScale以防止崩溃：

scale :
        {
                iPad : {
                    min : 0.8
                ,   max : 1.6
            }
            , iPhone : {
                    min : 0.25
                ,   max : 1.6
            }
            , iPhone6 : {
                    min : 0.3333
                ,   max : 1.6
            }
            , iPhoneResizable: {
                    min : 1
                ,   max : 1.6
            }
        }

初学者的优秀教程：http://www.raywenderlich.com/76436/use-uiscrollview-scroll-zoom-content-swift

UIScrollView Zooming使用Exc_Bad_Access崩溃应用程序

2 个答案: