需求：一個底部UIScrollView，上面是一個UIImageView，下面是一個UIWebView，要求加載完UIWebView，禁止UIWebView滾動，UIWebView全部顯示，如果大于屏幕高度，UIScrollView滾動，否則不滾動

根據(jù)需求需要獲取UIWebView的實際高度，以便設(shè)置UIScrollView的contentSize

1加載webView

@property (nonatomic,strong) UIWebView *webView;

-(UIWebView *)webView {
    if (!_webView) {
        _webView = [[UIWebView alloc]initWithFrame:CGRectZero];
        _webView.delegate = self;
        _webView.scalesPageToFit = YES;
        _webView.autoresizingMask = UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight;
        [_webView.scrollView addObserver:self forKeyPath:@"contentSize" options:NSKeyValueObservingOptionNew context:nil];
    }
    return _webView;
}

2 當WebView加載完成后，禁止WebView滾動

#pragma mark - UIWebViewDelegate
- (void)webViewDidFinishLoad:(UIWebView *)webView
{
    webView.scrollView.scrollEnabled = NO;
}

3 KVO監(jiān)聽webView的contentSize變化，拿到實際高度，重置約束，設(shè)置UIScrollView的contentSize

#pragma mark - KVO
- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context
{
    if ([keyPath isEqualToString:@"contentSize"]) {
        
        CGPoint point = [change[@"new"] CGPointValue];
        
        CGFloat height = point.y;
        NSLog(@"point.y---%f",height);
        
        CGSize fittingSize = [_webView sizeThatFits:CGSizeZero];
        
        CGFloat webHeight = fittingSize.height;

        [self.webView mas_remakeConstraints:^(MASConstraintMaker *make) {
            make.top.equalTo(self.topView.mas_bottom);
            make.left.right.equalTo(self.view);
            make.height.mas_equalTo(webHeight);
        }];
        self.bgScrollView.contentSize = CGSizeMake(self.view.ssWidth, self.topView.ssHeight+webHeight);
    }
}

大功告成，另外說一下為什么不在webViewDidFinishLoad中直接獲取webView高度，因為如果webView中加載的有圖片，如果圖片顯示慢了，就可能在webViewDidFinishLoad中拿不到圖片高度，這樣拿到的高度有可能偏低，所以我這里通過KVO拿webView高度，而不是在webViewDidFinishLoad中直接獲取