iphone - 如何在 iPhone 中检测网页 View 页面是否已到达

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 的每个页面，当我在纵向模式 下看到我的应用程序时，滚动不存在，因为我已经使用过，

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在滚动时发生时，所以我想在到达滚动结束时添加向右滑动手势，以便用户可以导航到下一页，进行rightswipe。

有没有什么方法可以告诉webview已经完成滚动？

_简而言之如何检测 UIWebView 到达顶部或底部？_

提前致谢!

编辑写在did load中:

    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，我检查方向(如果是纵向)，然后添加两个以上手势向上和向下手势(如果横向)，然后删除向上和向下手势。

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的 scrollView属性。如果您将该 ScrollView 的委托(delegate)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保留对先前 ScrollView 委托(delegate)的引用即可。

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

您的 _defaultDelegate 声明将为

id <UIScrollViewDelegate> _defaultDelegate;

现在，在 myController 的 scrollViewDidScroll: 实现中，您可以确定滚动是否到达页面的末尾或开头。

棘手的是，您必须实现其他 UIScrollViewDelegate 方法并传递给默认委托(delegate)，以便 webview 不会丢失其默认行为。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是否滚动到顶部或底部: iPhone - knowing if a UIScrollView reached the top or bottom

编辑:阅读您的代码后，我认为您不应该像这样添加和删除手势识别器。创建 4 个涵盖所有可能的滑动方向的手势识别器，并将其添加到 viewDidLoad 中的 web View 中。您可以通过实现以下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(delegate)，并检查其他 UIGestureRecognizerDelegate 方法。 View Controller 有一个属性interfaceOrientation，您也可以访问它。

要解决滚动问题，请尝试使用 BOOL iVar 来指示您是否位于代码底部。

-(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;
}