防止uiscrollview进一步滚动到特定点 [英] Prevent uiscrollview from scrolling further then certain point

问题描述

我有一个UIScrollView，该UIScrollView的子视图创建的内容的宽度约为7000. 现在，我希望UIScrollView不会再滚动到2000.

I have a UIScrollView which has subviews that create a content with a width of about 7000. Now I want the UIScrollView to not scroll any further then 2000.

我尝试过:

[scrollView setContentSize:CGSizeMake(768.0, 2000.0)];  
[scrollView setClipsToBounds:YES];

但是我仍然可以滚动到末尾，如何防止这种情况发生?

But I can still scroll to the end, how do I prevent this?

推荐答案

页面加载后，似乎webView正在更改其scrollView contentSize.

It's seems that webView is changing its scrollView contentSize after page loading.

在您的init中将self设置为WebView的委托:

In your init set self as a delegate of WebView:

[webView setDelegate: self];

并添加此方法:

- (void)webViewDidFinishLoad: (UIWebView *)webView {
    [webView.scrollView setContentSize: CGSizeMake(768.0, 2000.0)]; 
}

在我的测试用例中，它工作正常.

In my test case it's working fine.

已更新:

调用javascript方法有时不会触发webViewDidFinishLoad.因此，最通用的技术将是键值观察.

Calling javascript methods sometimes does not trigger webViewDidFinishLoad. So the most universal technique will be Key-Value Observing.

初始化:

[webView.scrollView addObserver:self forKeyPath:@"contentSize" options:NSKeyValueObservingOptionNew context:nil];

在此方法的某个地方:

- (void)observeValueForKeyPath:(NSString *)keyPath
                      ofObject:(id)object
                        change:(NSDictionary *)change
                       context:(void *)context
{
    UIScrollView * scrlView = (UIScrollView *) object;
    if ([keyPath isEqual:@"contentSize"]) {
        NSLog(@"New contentSize: %f x %f",scrlView.contentSize.width,scrlView.contentSize.height);
        if(scrlView.contentSize.width!=768.0||scrlView.contentSize.height!=2000.0)
        [scrlView setContentSize:CGSizeMake(768.0, 2000.0)]; 
    }
}

别忘了在取消分配的情况下删除观察者:

Do not forget to remove observer in case of dealloc:

[webView.scrollView removeObserver:self forKeyPath:@"contentSize"];

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