将这个添加到UIWebView委托:

(经过编辑以检查导航类型。你也可以通过file:// requests传递相对链接)

- (BOOL)webView:(UIWebView *)webView shouldStartLoadWithRequest:(NSURLRequest *)request navigationType:(UIWebViewNavigationType)navigationType {
    if (navigationType == UIWebViewNavigationTypeLinkClicked ) {
        [[UIApplication sharedApplication] openURL:[request URL]];
        return NO;
    }

    return YES;
}

斯威夫特版本:

func webView(webView: UIWebView, shouldStartLoadWithRequest request: NSURLRequest, navigationType: UIWebViewNavigationType) -> Bool {
        if navigationType == UIWebViewNavigationType.LinkClicked {
            UIApplication.sharedApplication().openURL(request.URL!)
            return false
        }
        return true
    }

Swift 3版本:

func webView(_ webView: UIWebView, shouldStartLoadWith request: URLRequest, navigationType: UIWebViewNavigationType) -> Bool {
    if navigationType == UIWebViewNavigationType.linkClicked {
        UIApplication.shared.openURL(request.url!)
        return false
    }
    return true
}

Swift 4版本:

func webView(_ webView: UIWebView, shouldStartLoadWith request: URLRequest, navigationType: UIWebView.NavigationType) -> Bool {
    guard let url = request.url, navigationType == .linkClicked else { return true }
    UIApplication.shared.open(url, options: [:], completionHandler: nil)
    return false
}

更新

由于openURL在iOS 10中已弃用:

- (BOOL)webView:(UIWebView *)webView shouldStartLoadWithRequest:(NSURLRequest *)request navigationType:(UIWebViewNavigationType)navigationType {
        if (navigationType == UIWebViewNavigationTypeLinkClicked ) {
            UIApplication *application = [UIApplication sharedApplication];
            [application openURL:[request URL] options:@{} completionHandler:nil];
            return NO;
        }

        return YES;
}

不建议使用UIWebView和UIWebViewDelegate。你将不被允许将更新推送到Appstore。参考

使用WKWebView和WKNavigationDelegate

示例代码:

class YourClass: WKNavigationDelegate {

    override public func viewDidLoad() {
        super.viewDidLoad()
        let webView = WKWebView()
        webView.navigationDelegate = self
        self.view.addaddSubview(webView)
    }
    
    public func webView(_ webView: WKWebView,
                    didReceive challenge: URLAuthenticationChallenge,
                    completionHandler: @escaping (URLSession.AuthChallengeDisposition, URLCredential?) -> Void) {
        let cred = URLCredential(trust: challenge.protectionSpace.serverTrust!)
        completionHandler(.useCredential, cred)
    }

    public func webView(_ webView: WKWebView,
                    decidePolicyFor navigationAction: WKNavigationAction,
                    decisionHandler: @escaping (WKNavigationActionPolicy) -> Swift.Void) {
    
        self.webView.load(navigationAction.request)
        decisionHandler(.allow)
    }
}

将这个添加到UIWebView委托:

(经过编辑以检查导航类型。你也可以通过file:// requests传递相对链接)

- (BOOL)webView:(UIWebView *)webView shouldStartLoadWithRequest:(NSURLRequest *)request navigationType:(UIWebViewNavigationType)navigationType {
    if (navigationType == UIWebViewNavigationTypeLinkClicked ) {
        [[UIApplication sharedApplication] openURL:[request URL]];
        return NO;
    }

    return YES;
}

斯威夫特版本:

func webView(webView: UIWebView, shouldStartLoadWithRequest request: NSURLRequest, navigationType: UIWebViewNavigationType) -> Bool {
        if navigationType == UIWebViewNavigationType.LinkClicked {
            UIApplication.sharedApplication().openURL(request.URL!)
            return false
        }
        return true
    }

Swift 3版本:

func webView(_ webView: UIWebView, shouldStartLoadWith request: URLRequest, navigationType: UIWebViewNavigationType) -> Bool {
    if navigationType == UIWebViewNavigationType.linkClicked {
        UIApplication.shared.openURL(request.url!)
        return false
    }
    return true
}

Swift 4版本:

func webView(_ webView: UIWebView, shouldStartLoadWith request: URLRequest, navigationType: UIWebView.NavigationType) -> Bool {
    guard let url = request.url, navigationType == .linkClicked else { return true }
    UIApplication.shared.open(url, options: [:], completionHandler: nil)
    return false
}

更新

由于openURL在iOS 10中已弃用:

- (BOOL)webView:(UIWebView *)webView shouldStartLoadWithRequest:(NSURLRequest *)request navigationType:(UIWebViewNavigationType)navigationType {
        if (navigationType == UIWebViewNavigationTypeLinkClicked ) {
            UIApplication *application = [UIApplication sharedApplication];
            [application openURL:[request URL] options:@{} completionHandler:nil];
            return NO;
        }

        return YES;
}

在Swift中，你可以使用以下代码:

extension YourViewController: UIWebViewDelegate {
    func webView(_ webView: UIWebView, shouldStartLoadWith request: URLRequest, navigationType: UIWebView.NavigationType) -> Bool {
        if let url = request.url, navigationType == UIWebView.NavigationType.linkClicked {
            UIApplication.shared.open(url, options: [:], completionHandler: nil)
            return false
        }
        return true
    }

}

确保检查了URL值和navigationType。

对user306253的回答的一个快速评论:小心，当你自己尝试在UIWebView中加载一些东西时(即即使从代码中加载)，这个方法将防止它发生。

你能做什么来防止这种情况(感谢韦德):

if (inType == UIWebViewNavigationTypeLinkClicked) {
    [[UIApplication sharedApplication] openURL:[inRequest URL]];
    return NO;
}

return YES;

你可能还想处理UIWebViewNavigationTypeFormSubmitted和UIWebViewNavigationTypeFormResubmitted类型。

公认的答案行不通。

如果你的页面通过Javascript加载url, navigationType将是UIWebViewNavigationTypeOther。不幸的是，这也包括后台页面加载，如分析。

要检测页面导航，需要比较[request URL]和[request mainDocumentURL]。

这个解决方案将在所有情况下工作:

- (BOOL)webView:(UIWebView *)view shouldStartLoadWithRequest:(NSURLRequest *)request navigationType:(UIWebViewNavigationType)type
{
    if ([[request URL] isEqual:[request mainDocumentURL]])
    {
        [[UIApplication sharedApplication] openURL:[request URL]];
        return NO;
    }
    else
    {       
        return YES;
    }
}