iphone UIScrollView逆序定位

Question

我正在根据苹果提供的“滚动”示例代码构建一个应用程序。 一切都运转良好。 我想要显示的图像的性质，如果图像的顺序相反，并且第一个可见图像是最右边的，而不是最左边的，那么它会是理想的。 基本上，用户应该从右到左向后滚动，而不是从左到右。 但现在：我不明白苹果使用的语法，我希望有人可以向我解释发生了什么。 以下是示例应用程序的相关部分：

- (void)viewDidLoad
{
    self.view.backgroundColor = [UIColor whiteColor];

    // load all the images from our bundle and add them to the scroll view
    NSUInteger i;
    for (i = 1; i <= kNumImages; i++)
    {
        NSString *imageName = [NSString stringWithFormat:@"image%d.jpg", i];
        UIImage *image = [UIImage imageNamed:imageName];
        UIImageView *imageView = [[UIImageView alloc] initWithImage:image];

        // setup each frame to a default height and width, it will be properly placed when we call "updateScrollList"
        CGRect rect = imageView.frame;
        rect.size.height = kScrollObjHeight;
        rect.size.width = kScrollObjWidth;
        imageView.frame = rect;
        imageView.tag = i;  // tag our images for later use when we place them in serial fashion
        [scrollView1 addSubview:imageView];
        [imageView release];
    }

    [self layoutScrollImages];  // now place the photos in serial layout within the scrollview

}

- (void)layoutScrollImages
{
    UIImageView *view = nil;
    NSArray *subviews = [scrollView1 subviews];

    // reposition all image subviews in a horizontal serial fashion
    CGFloat curXLoc = 0;
    for (view in subviews)
    {
        if ([view isKindOfClass:[UIImageView class]] && view.tag > 0)
        {
            CGRect frame = view.frame;
            frame.origin = CGPointMake(curXLoc, 0);
            view.frame = frame;

            curXLoc += (kScrollObjWidth);
        }
    }

    // set the content size so it can be scrollable
    [scrollView1 setContentSize:CGSizeMake((kNumImages * kScrollObjWidth), [scrollView1 bounds].size.height)];
}

Answer 1

这就是我最终所做的：
我首先颠倒了子视图的顺序，然后通过添加以下行使滚动视图跳转到最后一个“帧”：

CGPoint lastFrame = CGPointMake(((kNumImages -1) * kScrollObjWidth), 0.0f);
[scrollview setContentOffset:lastFrame];

我希望这对某人有用......

Answer 2

看来你需要修改layoutScrollImages。 将 curXLoc 初始化为所需的最大数量，并在循环中递减它。

- (void)layoutScrollImages
{
    UIImageView *view = nil;
    NSArray *subviews = [scrollView1 subviews];

    // reposition all image subviews in a horizontal serial fashion
    CGFloat curXLoc = kNumImages * kScrollObjWidth;
    for (view in subviews)
    {
        if ([view isKindOfClass:[UIImageView class]] && view.tag > 0)
        {
                CGRect frame = view.frame;
                frame.origin = CGPointMake(curXLoc, 0);
                view.frame = frame;

                curXLoc -= (kScrollObjWidth);
        }
    }

    // set the content size so it can be scrollable
    [scrollView1 setContentSize:CGSizeMake((kNumImages * kScrollObjWidth), [scrollView1 bounds].size.height)];
}