如何在 iPhone 中检测到网页视图页面结束

Question

我是 iPhone 开发人员的新手，

我制作了 epub 阅读器并在我的 webview 中加载了 epub 的每一页，当我在 portrait mode 中看到我的应用程序时，滚动不存在，因为我用过，

webview.scalesPageToFit=TRUE;

但是当我看到我的应用程序在横向模式页面适合但它发生滚动时，所以我想在滚动结束时添加swiperight gesture，以便用户可以导航到下一页，执行rightswipe。

是否有任何方法可以告诉 webview 已完成滚动？

_简而言之如何检测UIWebView到达顶部或底部？_

提前致谢！

编辑 写在确实加载：

    swipeRight = [[UISwipeGestureRecognizer alloc] initWithTarget:self  action:@selector(swipeRightAction:)];
    swipeRight.direction = UISwipeGestureRecognizerDirectionRight;
    swipeRight.delegate = (id<UIGestureRecognizerDelegate>)self;
    [_webview addGestureRecognizer:swipeRight];

    swipeLeft = [[UISwipeGestureRecognizer alloc] initWithTarget:self action:@selector(swipeLeftAction:)];
    swipeLeft.direction = UISwipeGestureRecognizerDirectionLeft;
    swipeLeft.delegate = (id<UIGestureRecognizerDelegate>)self;
    [_webview addGestureRecognizer:swipeLeft];

然后在加载每个页面时，我会检查方向，如果它是纵向的，然后再添加两个向上和向下的手势，如果是横向的，然后移除向上和向下的手势。

if([UIApplication sharedApplication].statusBarOrientation==UIInterfaceOrientationPortrait || [UIApplication sharedApplication].statusBarOrientation==UIInterfaceOrientationPortraitUpsideDown) {

        swipeUp = [[UISwipeGestureRecognizer alloc] initWithTarget:self  action:@selector(swipeLeftAction:)];
        swipeUp.direction = UISwipeGestureRecognizerDirectionUp;
        swipeUp.delegate = (id<UIGestureRecognizerDelegate>)self;
        [_webview addGestureRecognizer:swipeUp];

        swipeDown = [[UISwipeGestureRecognizer alloc] initWithTarget:self  action:@selector(swipeRightAction:)];
        swipeDown.direction = UISwipeGestureRecognizerDirectionDown;
        swipeDown.delegate = (id<UIGestureRecognizerDelegate>)self;
        [_webview addGestureRecognizer:swipeDown];

        counterPort++;
        counterLand=0;
      }
    }

    if (counterLand==0) {

        if([UIApplication sharedApplication].statusBarOrientation==UIInterfaceOrientationLandscapeLeft || [UIApplication sharedApplication].statusBarOrientation==UIInterfaceOrientationLandscapeRight) {

            [_webview removeGestureRecognizer:swipeDown];
            [swipeDown release];
            swipeDown=nil;

            [_webview removeGestureRecognizer:swipeUp]; 
            [swipeUp release];
            swipeUp=nil;

            counterPort=0;
            counterLand++;
        }

根据您的建议：

-(void)scrollViewDidScroll:(UIScrollView *)scrollView{
    float scrollViewHeight = scrollView.frame.size.height;
    float scrollContentSizeHeight = scrollView.contentSize.height;
    float scrollOffset = scrollView.contentOffset.y;

    if (scrollOffset == 0)
    {
        swipeUp = [[UISwipeGestureRecognizer alloc] initWithTarget:self  action:@selector(swipeLeftAction:)];
        swipeUp.direction = UISwipeGestureRecognizerDirectionUp;
        swipeUp.delegate = (id<UIGestureRecognizerDelegate>)self;
        [_webview addGestureRecognizer:swipeUp];  
    }
    else if (scrollOffset + scrollViewHeight == scrollContentSizeHeight)
    {
        swipeDown = [[UISwipeGestureRecognizer alloc] initWithTarget:self  action:@selector(swipeRightAction:)];
        swipeDown.direction = UISwipeGestureRecognizerDirectionDown;
        swipeDown.delegate = (id<UIGestureRecognizerDelegate>)self;
        [_webview addGestureRecognizer:swipeDown];
    }
}

Answer 1

在 ios 5.0 及更高版本中，您可以访问 UIWebView's scrollView 属性。如果您将该滚动视图的委托设置为您的对象，您可以找出它何时到达顶部或底部。只需确保在更改之前持有对先前滚动视图委托的引用。

 _defaultDelegate=[webview.scrollView.delegate retain];
 webview.scrollView.delegate=myController;

您的_defaultDelegate 声明将是

id <UIScrollViewDelegate> _defaultDelegate;

现在，在 myController 的 scrollViewDidScroll: 实现中，您可以确定滚动到了页面的末尾还是开头。

棘手的是你必须实现其他 UIScrollViewDelegate 方法并传递给默认委托，以便 webview 不会失去其默认行为。所以，你像这样实现

- (void)scrollViewDidScrollToTop:(UIScrollView *)scrollView {
    [_defaultDelegate scrollViewDidScrollToTop:scrollView];
}

请参阅此答案以了解 scrollView 是滚动到顶部还是底部： iPhone - knowing if a UIScrollView reached the top or bottom

编辑：阅读您的代码后，我认为您不应该像那样添加和删除手势识别器。创建 4 个手势识别器，涵盖所有可能的滑动方向，并将其添加到 viewDidLoad 的 web 视图中。您可以通过实现该方法来控制手势识别器是否应响应：

- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldReceiveTouch:(UITouch *)touch

不要忘记为每个手势识别器设置委托，并检查其他 UIGestureRecognizerDelegate 方法。视图控制器具有您也可以访问的属性 interfaceOrientation。

要解决滚动问题，请尝试使用 BOOL iVar 来指示您是否位于代码的底部。

-(void)scrollViewDidScroll:(UIScrollView *)scrollView{
    float scrollViewHeight = scrollView.frame.size.height;
    float scrollContentSizeHeight = scrollView.contentSize.height;
    float scrollOffset = scrollView.contentOffset.y;
    _atBottom=NO;
    if (scrollOffset == 0)
    {
        swipeUp = [[UISwipeGestureRecognizer alloc] initWithTarget:self  action:@selector(swipeLeftAction:)];
        swipeUp.direction = UISwipeGestureRecognizerDirectionUp;
        swipeUp.delegate = (id<UIGestureRecognizerDelegate>)self;
        [_webview addGestureRecognizer:swipeUp];  
    }
    else if (scrollOffset + scrollViewHeight == scrollContentSizeHeight)
    {
        swipeDown = [[UISwipeGestureRecognizer alloc] initWithTarget:self  action:@selector(swipeRightAction:)];
        swipeDown.direction = UISwipeGestureRecognizerDirectionDown;
        swipeDown.delegate = (id<UIGestureRecognizerDelegate>)self;
        [_webview addGestureRecognizer:swipeDown];
        _atBottom=YES;
    }
}

并实现 UIGestureRecognizerDelegate 方法

- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldReceiveTouch:(UITouch *)touch {
    return _atBottom;
}