Why doesn't observeValueForKeyPath trigger in my webView?

Question

Since webviewdidfinishload has been deprecated and the webKit delegates don't seem to trigger when navigating to another url (from what I can see), I looked into using observer forKeyPath, like here:

How can I detect when url of amp page changed with WKWebview

And while this seems like a valid approach, I can't get the observeValue to trigger. At times it works, but most often it doesn't, and there doesn't seem to be any consistency.

- (void)setUpWebView {
    NSString * urlString = [NSString stringWithFormat:@"www.thisisnottherealurl.com"];

    NSURL *url = [NSURL URLWithString: urlString];

    NSURLRequest *request = [NSURLRequest requestWithURL:url];

    WKWebViewConfiguration *webViewConfig = [WKWebViewConfiguration new];

    _webView = [[WKWebView alloc] initWithFrame:CGRectZero configuration:webViewConfig];
    _webView.navigationDelegate = self;
    _webView.translatesAutoresizingMaskIntoConstraints = NO;
    _webView.alpha = 0.0f;
//    _webView.alpha = 1;

    [_webViewContainer addSubview:_webView];

    [self startLoadingAnimation];

    [_webView.topAnchor constraintEqualToAnchor:_webViewContainer.topAnchor].active = YES;
    [_webView.bottomAnchor constraintEqualToAnchor:_webViewContainer.bottomAnchor].active = YES;
    [_webView.rightAnchor constraintEqualToAnchor:_webViewContainer.rightAnchor].active = YES;
    [_webView.leftAnchor constraintEqualToAnchor:_webViewContainer.leftAnchor].active = YES;
    [_webView.heightAnchor constraintEqualToAnchor:_webViewContainer.heightAnchor].active = YES;

    [_webView loadRequest:request];

    //IMPORTANT PART
    [_webView addObserver:self forKeyPath:@"url" options: NSKeyValueObservingOptionNew | NSKeyValueObservingOptionOld | NSKeyValueObservingOptionPrior context:nil];
}

And then the observeValue part:

- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary<NSKeyValueChangeKey,id> *)change context:(void *)context {
     NSLog(@"OBSERVED");
}

Now, this doesn't trigger. Instead of observing _webView I have also tried _webView.URL.absoluteString. But still, it doesn't trigger. I have added alternative options like so: NSKeyValueObservingOptionNew | NSKeyValueObservingOptionOld | NSKeyValueObservingOptionPrior but still nothing.

What am I doing wrong?

Is there a better approach to this? Is there a delegate that actually trigger when navigating to another url link?

score 0 · Answer 1 · answered Feb 10 '20 at 14:39

0

You can use this method from WKNavigationDelegate of WKWebView.

- (void)webView:(WKWebView *)webView decidePolicyForNavigationAction:(WKNavigationAction *)navigationAction decisionHandler:(void (^)(WKNavigationActionPolicy))decisionHandler
{
 NSURLRequest* request = navigationAction.request;
 if ([request.URL.urlString hasPrefix:@<Do ur checking here>])
{
 decisionHandler(WKNavigationActionPolicyCancel); // Cancel the request
}
else 
{
decisionHandler(WKNavigationActionPolicyAllow); // Allow the request.
}

answered Feb 10 '20 at 14:39

Megha Srinivasan

23
6

Thanks, but that doesn't trigger when I click around. It only when the weView is loaded. – screenMonkey MonkeyMan Feb 10 '20 at 15:44
Can you tell us how are you navigating to another url? Try webViewConfiguration.dataDetectorTypes = WKDataDetectorTypeAll and navigate. This should call the delegate method. The documentation itself says so. "Decides whether to allow or cancel a navigation." – Megha Srinivasan Feb 11 '20 at 07:37
Well, it's just a web page like any else, so pressing different links and buttons takes the user to different sub urls. I added webViewConfiguration.dataDetectorTypes = WKDataDetectorTypeAll but nothing happens. The delegate just trigger (a lot of times) when the webView start, but then nothing. – screenMonkey MonkeyMan Feb 11 '20 at 07:55

Why doesn't observeValueForKeyPath trigger in my webView?

1 Answers1