向右滑动，页面控件的当前页面会发生变化，但点不会

Question

我用一些相关的图像创建了一个教程，并在上面添加了一个页面控件。此外，我添加了一个滑动手势，它通过更改图片来响应。在下面的代码中，定义了一个 switch case，以便根据滑动的方向（左/右）决定下一个应该是哪个图像和点。

- (IBAction)handleSwipe:(UISwipeGestureRecognizer *)sender
{
//    NSLog(@"swiped");
    NSArray *images;

    if (self.selectedRow == 0) {
        images = [[NSArray alloc] initWithObjects:@"w8.JPG",@"w7.JPG",@"w6.JPG",@"w5.JPG",@"w4.JPG",@"w3.JPG", @"w2.JPG", @"w1.JPG" ,@"w9.JPG", nil];

        self.pageControl.hidden = NO;
        [self.pageControl setNumberOfPages:9];

        UISwipeGestureRecognizerDirection direction = [(UISwipeGestureRecognizer *) sender direction];

        switch (direction) {
            case UISwipeGestureRecognizerDirectionRight:
                if (pageController == 0 || imageIndex == 8)
                {
                    self.Oops = [[UIAlertView alloc] initWithTitle:@"Oops!" message:@"You cannot swipe to the left, there are not any previous steps." delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil, nil];
                    [self.Oops show];
                }
                else {
                    [self.pageControl setCurrentPage:pageController - 1];
                    pageController = pageController - 1;
                }
                imageIndex++;
                break;
            case UISwipeGestureRecognizerDirectionLeft:
                if (pageController < 8 && pageController >= 0) {
                    [self.pageControl setCurrentPage:pageController];
                    pageController = pageController + 1;
                }
                else {
                    [self.pageControl setCurrentPage: pageController ];
                    pageController = 0;
                }
                imageIndex--;
                break;
            default:
                break;
        }
        NSLog(@"pagecontroller is %li and imageIndex is %li " , pageController, imageIndex);
        imageIndex = (imageIndex < 0) ? ([images count] - 1): imageIndex % [images count];
        self.imageView.image = [UIImage imageNamed:[images objectAtIndex:imageIndex]];
    }

正如您在代码中看到的，有一个 NSLog；当我运行该应用程序时，一切正常，但是当我向右滑动以查看上一张图像时，尽管 NSLog 显示点和图像的所有索引都正确更改并且我们看到了上一张图像，但点并没有改变。再次向右滑动，点会发生变化，但为时已晚，因为必须分类的图像和点的顺序变得无序，例如最后一张图像与第一个点一起显示。 我确信我的算法是正确的，因为我用那个 NSLog 检查了它，而且在向右滑动之前一切正常。 有什么想法吗？

我稍微改了一下代码：

 switch (direction) {
            case UISwipeGestureRecognizerDirectionRight:
                if (pageController != 0 && imageIndex != 9) {
                    [self.pageControl setCurrentPage:(pageController - 1)];
                    pageController --;
                    imageIndex++;
                }
                break;
            case UISwipeGestureRecognizerDirectionLeft:
                if (pageController <= 8 && pageController >= 0) {
                    [self.pageControl setCurrentPage:pageController];
                    pageController = pageController + 1;
                    imageIndex--;
                }
                break;
            default:
                break;
        }

现在唯一的问题是，当我向不同方向滑动时，页面控件会计算当前点两次。

Answer 1

您的 imageIndex++ 和 imageIndex-- 行放错了位置。 （例如，如果 pageController 已经为 0，您可能不想更改图像）。将它们移至：

- (IBAction)handleSwipe:(UISwipeGestureRecognizer *)sender
{
//    NSLog(@"swiped");
    NSArray *images;
    
    if (self.selectedRow == 0) {
        images = [[NSArray alloc] initWithObjects:@"w8.JPG",@"w7.JPG",@"w6.JPG",@"w5.JPG",@"w4.JPG",@"w3.JPG", @"w2.JPG", @"w1.JPG" ,@"w9.JPG", nil];
        
        self.pageControl.hidden = NO;
        [self.pageControl setNumberOfPages:9];
        
        UISwipeGestureRecognizerDirection direction = [(UISwipeGestureRecognizer *) sender direction];
        
        switch (direction) {
            case UISwipeGestureRecognizerDirectionRight:
                if (pageController == 0 || imageIndex == 8)
                {
                    self.Oops = [[UIAlertView alloc] initWithTitle:@"Oops!" message:@"You should turn over to the left." delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil, nil];
                    [self.Oops show];
                }
                else {
                    [self.pageControl setCurrentPage:pageController - 1];
                    pageController = pageController - 1;
                    imageIndex++;
                }
                break;
            case UISwipeGestureRecognizerDirectionLeft:
                if (pageController < 8 && pageController >= 0) {
                    [self.pageControl setCurrentPage:pageController];
                    pageController = pageController + 1;
                    imageIndex--;
                }
                else {
                    [self.pageControl setCurrentPage: pageController ];
                    pageController = 0;
                }
                break;
            default:
                break;
        }
        NSLog(@"pagecontroller is %li and imageIndex is %li " , pageController, imageIndex);
        imageIndex = (imageIndex < 0) ? ([images count] - 1): imageIndex % [images count];
        self.imageView.image = [UIImage imageNamed:[images objectAtIndex:imageIndex]];
    }

在您修改后的代码中，我认为您需要以不同的方式设置页面控件（到 pageController+1）以向左滑动：

switch (direction) {
        case UISwipeGestureRecognizerDirectionRight:
            if (pageController != 0 && imageIndex != 9) {
                [self.pageControl setCurrentPage:(pageController - 1)];
                pageController --;
                imageIndex++;
            }
            break;
        case UISwipeGestureRecognizerDirectionLeft:
            if (pageController <= 8 && pageController >= 0) {
                [self.pageControl setCurrentPage:pageController+1];
                pageController = pageController + 1;
                imageIndex--;
            }
            break;
        default:
            break;
    }