滚动视图中的内容偏移答案

【问题标题】：contentoffset in scrollview滚动视图中的内容偏移
【发布时间】：2012-10-10 09:56:29
【问题描述】：

我如何设置图像的内容偏移量以跟踪用户在哪个图像上并选择将其保存到相册。

 UIScrollView *imageScrollView = [[UIScrollView alloc] initWithFrame:CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height)];

imageScrollView.pagingEnabled = YES;

NSInteger numberOfViews = 61;

for (int i = 0; i < numberOfViews; i++) {

CGFloat xOrigin = i * self.view.frame.size.width;

NSString *imageName = [NSString stringWithFormat:@"image%d.png", i];

_image = [UIImage imageNamed:imageName];

_imageView = [[UIImageView alloc] initWithImage:_image];

_imageView.frame = CGRectMake(xOrigin, 0, self.view.frame.size.width, self.view.frame.size.height);

UILongPressGestureRecognizer *gestureRecognizer = [[UILongPressGestureRecognizer alloc]
                                                   initWithTarget:self
                                                   action:@selector(handleLongPress:)];

imageScrollView.userInteractionEnabled = YES;
[imageScrollView addGestureRecognizer:gestureRecognizer];
gestureRecognizer.delegate = self;
[gestureRecognizer release];

[imageScrollView addSubview:_imageView];

imageScrollView.contentSize = CGSizeMake(self.view.frame.size.width * numberOfViews, self.view.frame.size.height);

编辑：

imageScrollView.contentOffset = CGPointMake(CGFloat x, CGFloat y);

在 contentoffset 中不确定要放置什么，以便可以跟踪用户所在的图像并选择保存到相册

- (void)handleLongPress:(UILongPressGestureRecognizer*)gestureRecognizer{
if (gestureRecognizer.state == UIGestureRecognizerStateBegan){
UIActionSheet *actionSheet = [[UIActionSheet alloc] initWithTitle:nil delegate:self cancelButtonTitle:@"Cancel" destructiveButtonTitle:nil otherButtonTitles:@"Save Photo", nil];
actionSheet.actionSheetStyle = UIActionSheetStyleBlackTranslucent;
[actionSheet showInView:self.view];
[actionSheet release];

 }}

-(void)actionSheet:(UIActionSheet *)actionSheet clickedButtonAtIndex:(NSInteger)buttonIndex {

switch (buttonIndex) {
case 0:
    [self savePhoto];

   break;

default:
    break;

}

 -(void)savePhoto{

CGPoint location = [gesture locationInView:_imageView];

if  (CGRectContainsPoint(_imageView.bounds, location)){

UIImageWriteToSavedPhotosAlbum(_image, self, @selector(image: didFinishSavingWithError:contextInfo:), nil);
  }}}

任何想法都会受到赞赏。

【问题讨论】：

标签： iphone uiscrollview ios6 contentoffset

【解决方案1】：

您可以使用此代码（来自用于滚动视图的苹果示例项目之一）来确定滚动视图中当前可见的“页面”是什么。

// Calculate which page is visible
CGFloat pageWidth = self.scrollView.frame.size.width;
int page = floor((self.scrollView.contentOffset.x - pageWidth / 2) / pageWidth) + 1;

一旦你知道这个索引号，你就可以使用它来确定要保存的图像

【讨论】：