WKWebView 是 iOS 8 引入的一個 WebKit API,替換 iOS 的 UIWebView 和 OSX 的 WebView,WKWebView 使用 Nitro JavaScript 引擎,運行 JavaScript 和 Safari 一樣快。WKWebView 和 UIWebView 使用上有很多區別,這篇主要介紹代理、標題、進度條展示的區別。
代理
UIWebView 是 delegate: 'UIWebViewDelegate',WKWebView 使用以下兩個代理
navigationDelegate: ' WKNavigationDelegate'
UIDelegate: ' WKUIDelegate'
其中 navigationDelegate 代替 UIWebView 中的 delegate,下表是這兩個代理方法的對比:
比如,如果要攔截網頁請求,UIWebView 使用以下代碼:
- (BOOL)webView:(UIWebView *)webView shouldStartLoadWithRequest:(NSURLRequest *)request navigationType:(UIWebViewNavigationType)navigationType {
NSURL *url = request.URL;
NSString *host = [url host];
if ([url.scheme isEqualToString:@"inapp"]) {
/*
* 做一些處理
*/
return NO;
}
return YES;
}
在 WKWebView 中則用以下代碼:
- (void)webView:(WKWebView *)webView decidePolicyForNavigationAction:(WKNavigationAction *)navigationAction decisionHandler:(void (^)(WKNavigationActionPolicy))decisionHandler {
NSURL *url = navigationAction.request.URL;
NSString *host = [url host];
if ([url.scheme isEqualToString:@"inapp"]) {
/*
* 做一些處理
*/
decisionHandler(WKNavigationActionPolicyCancel);
} else {
decisionHandler(WKNavigationActionPolicyAllow);
}
}
獲取 title
在 UIWebView 中
self.title = [webView stringByEvaluatingJavaScriptFromString:@"document.title"];
而 WKWebView 有 title 屬性可直接獲取網頁標題,可通過 KVO 方式獲取網頁標題的動態變化。
self.title = webView.title;
estimatedProgress
WKWebView 增加了 estimatedProgress,獲取網頁加載進度,輕鬆顯示進度條。可通過 KVO 的方式獲取 estimatedProgress 的變化。首先在 viewDidLoad 中添加觀察者
[self.webView addObserver:self forKeyPath:NSStringFromSelector(@selector(estimatedProgress)) options:NSKeyValueObservingOptionNew context:NULL];
[self.webView addObserver:self forKeyPath:NSStringFromSelector(@selector(title)) options:NSKeyValueObservingOptionNew context:NULL];
KVO 的實現:
- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context {
if ([keyPath isEqualToString:NSStringFromSelector(@selector(estimatedProgress))] && object == self.webView) {
NSLog(@"%f", self.webView.estimatedProgress);
// estimatedProgress is a value from 0.0 to 1.0
// Update your UI here accordingly
[self.progressView setAlpha:1.0f];
[self.progressView setProgress:self.webView.estimatedProgress animated:YES];
if(self.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 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];
}
}
最後,在 dealloc 中移除觀察者
- (void)dealloc {
if ([self isViewLoaded]) {
[self.webView removeObserver:self forKeyPath:NSStringFromSelector(@selector(estimatedProgress))];
[self.webView removeObserver:self forKeyPath:NSStringFromSelector(@selector(title))];
}
[self.webView setNavigationDelegate:nil];
}
WKWebView 還增加了 Message Handlers,用於和網頁的JS交互,不需要處理複雜的evaluateJavaScript。例如:
class NotificationScriptMessageHandler: NSObject, WKScriptMessageHandler {
func userContentController(userContentController: WKUserContentController, didReceiveScriptMessage message: WKScriptMessage!) {
print(message.body)
}
}
let userContentController = WKUserContentController()
let handler = NotificationScriptMessageHandler()
userContentController.addScriptMessageHandler(handler, name: "notification")
則 JavaScript 端可通過以下代碼即可調用原生的代碼:
window.webkit.messageHandlers.notification.postMessage({body: "..."});
轉自:簡書作者蝦米233
詳情參考 NSHipster 這篇 WKWebView