使用 JS 代码获取内容高度

web 加载完成之后。注：由于图片的原因可能还是不一定准。

- (void)webViewDidFinishLoad:(UIWebView *)webView {
    CGFloat height = [[self.webView stringByEvaluatingJavaScriptFromString:@"document.body.scrollHeight"] floatValue];
}

KVO

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

- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary<NSString *,id> *)change context:(void *)context {
    CGSize size = [[change objectForKey:NSKeyValueChangeNewKey] CGSizeValue];
}

RAC

    [[self.webView.scrollView rac_valuesAndChangesForKeyPath:@"contentSize"
                                                 options:NSKeyValueObservingOptionNew
                                                observer:nil]
     subscribeNext:^(RACTuple *x) {
         @strongify_self
         CGSize size = [[[[x allObjects] lastObject] objectForKey:NSKeyValueChangeNewKey] CGSizeValue];
     }];

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