最近專案中新增活動，有一個需求，要載入HTML頁面，並且顯示HTML頁面的title；

WKWebView 的estimatedProgress和title 都是KVO模式，所以可以新增監聽：

[webView addObserver:self forKeyPath:@"estimatedProgress" options:NSKeyValueObservingOptionNew context:NULL];
[webView addObserver:self forKeyPath:@"title" options:NSKeyValueObservingOptionNew context:NULL];
 

- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context {

    if ([keyPath isEqualToString:@"estimatedProgress"]) {

        if (object == webView) {
            [self.progressView setAlpha:1.0f];
            [self.progressView setProgress:self.currentSubView.webView.estimatedProgress animated:YES];

            if(self.currentSubView.webView.estimatedProgress >= 1.0f) {

                [UIView animateWithDuration:0.3 delay:0.3 options:UIViewAnimationOptionCurveEaseOut animations:^{
                    [self.progressView setAlpha:0.0f];
                } completion:^(BOOL finished) {
                    [self.progressView setProgress:0.0f animated:NO];
                }];

            }
        }
        else
        {
            [super observeValueForKeyPath:keyPath ofObject:object change:change context:context];
        }

    }
    else if ([keyPath isEqualToString:@"title"])
    {
        if (object == self.webView) {
            self.title = self.webView.title;

        }
        else
        {
            [super observeValueForKeyPath:keyPath ofObject:object change:change context:context];

        }
    }
    else {

        [super observeValueForKeyPath:keyPath ofObject:object change:change context:context];
    }
}
 

進度條增加了動畫，類似safari的進度效果

注意銷燬時一定要移除監聽

[webView removeObserver:self forKeyPath:@"estimatedProgress"];
[webView removeObserver:self forKeyPath:@"title"];