WKWebView

An object that displays interactive web content, such as for an in-app browser.

WKWebView屬於WebKit.framework框架，Apple在WWDC 2014中隨iOS 8和OS X 10.10提出來的，爲了解決UIWebView加載速度慢、佔用內存大的問題。 使用UIWebView加載網頁的時候，內存會無限增加，還有內存泄漏的問題存在。 WebKit中更新的WKWebView控件的新特性與使用方法，很好的解決了UIWebView存在的內存、加載速度等諸多問題。支持到iOS8，相對於UIWebView，WKWebView有不少明顯優點：

• 佔用更少的內存
• Safari相同的JavaScript引擎
• 擁有高達60FPS滾動刷新率及內置手勢
• html頁面和WKWebView交互更方便
• 提供經常使用的屬性，如加載網頁進度的屬性estimatedProgress
• 支持了更多的HTML5特性

UIWebView

WKWebView

因此，使用WkWebview替換UIWebView仍是頗有必要的。

基本使用

1、導入WebKit.framework框架，而且引入頭文件

#import <WebKit/WebKit.h>

2、初始化

// 初始化1
- (instancetype)initWithFrame:(CGRect)frame;

// 初始化2，WKWebViewConfiguration能夠用來設置與js交互的相關配置
- (instancetype)initWithFrame:(CGRect)frame configuration:(WKWebViewConfiguration *)configuration;

3、WKWebView的使用

1.WKWebView簡單使用，直接加載url地址

WKWebView *webView = [[WKWebView alloc] initWithFrame:self.view.bounds];
[webView loadRequest:[NSURLRequest requestWithURL:[NSURL URLWithString:@"https://developer.apple.com/reference/webkit"]]];    
[self.view addSubview:webView];

2.自定義配置，WKWebView裏面註冊供JS調用的方法

//建立配置
WKWebViewConfiguration *config = [[WKWebViewConfiguration alloc] init];
//建立UserContentController（提供JavaScript向webView發送消息的方法）
WKUserContentController *userContent = [[WKUserContentController alloc] init];
//添加消息處理，self指代的對象須要遵照WKScriptMessageHandler協議，結束時須要移除
[userContent addScriptMessageHandler:self name:@"NativeMethod"];
//將UserConttentController設置到配置文件
config.userContentController = userContent;
//自定義配置建立WKWebView
WKWebView *webView = [[WKWebView alloc] initWithFrame:[UIScreen mainScreen].bounds configuration:config];
//設置訪問的URL
NSURL *url = [NSURL URLWithString:@"https://developer.apple.com/reference/webkit"];
NSURLRequest *request = [NSURLRequest requestWithURL:url];
[webView loadRequest:request];
[self.view addSubview:webView];


//實現WKScriptMessageHandler協議方法
- (void)userContentController:(WKUserContentController *)userContentController didReceiveScriptMessage:(WKScriptMessage *)message {
　　// 判斷是不是調用原生的
   if ([@"NativeMethod" isEqualToString:message.name]) {
  　　 // 判斷message的內容，而後作相應的操做
    　　if ([@"close" isEqualToString:message.body]) {

    　　}
   }
}
//將當前ViewController設置爲MessageHandler以後須要在當前ViewController銷燬前將其移除，不然會形成內存泄漏
- (void)dealloc{
    //WKUserContentController *userContentController
    [userContentController removeScriptMessageHandlerForName:@"NativeMethod"];
}

4、WKWebView主要屬性

/*! @abstract A copy of the configuration with which the web view was initialized. */
//只讀的配置屬性
@property (nonatomic, readonly, copy) WKWebViewConfiguration *configuration;

/*! @abstract The web view's navigation delegate. */
//導航代理
@property (nullable, nonatomic, weak) id <WKNavigationDelegate> navigationDelegate;

/*! @abstract The web view's user interface delegate. */
//用戶交互代理
@property (nullable, nonatomic, weak) id <WKUIDelegate> UIDelegate;

/*! @abstract The web view's back-forward list. */
//前進後退列表
@property (nonatomic, readonly, strong) WKBackForwardList *backForwardList;

/*! @abstract The page title.
 @discussion @link WKWebView @/link is key-value observing (KVO) compliant
 for this property.
 */
//網頁標題,能夠用kvo監聽
@property (nullable, nonatomic, readonly, copy) NSString *title;

/*! @abstract The active URL.
 @discussion This is the URL that should be reflected in the user
 interface.
 @link WKWebView @/link is key-value observing (KVO) compliant for this
 property.
 */
//請求的url，可用kvo監聽
@property (nullable, nonatomic, readonly, copy) NSURL *URL;

/*! @abstract A Boolean value indicating whether the view is currently
 loading content.
 @discussion @link WKWebView @/link is key-value observing (KVO) compliant
 for this property.
 */
//當前是否正在加載網頁,可用kvo監聽
@property (nonatomic, readonly, getter=isLoading) BOOL loading;

/*! @abstract An estimate of what fraction of the current navigation has been completed.
 @discussion This value ranges from 0.0 to 1.0 based on the total number of
 bytes expected to be received, including the main document and all of its
 potential subresources. After a navigation completes, the value remains at 1.0
 until a new navigation starts, at which point it is reset to 0.0.
 @link WKWebView @/link is key-value observing (KVO) compliant for this
 property.
 */
//加載進度範圍0~1,可用kvo監聽
@property (nonatomic, readonly) double estimatedProgress;

/*! @abstract A Boolean value indicating whether all resources on the page
 have been loaded over securely encrypted connections.
 @discussion @link WKWebView @/link is key-value observing (KVO) compliant
 for this property.
 */
//標識頁面中的全部資源是否經過安全加密鏈接來加載，可用kvo監聽
@property (nonatomic, readonly) BOOL hasOnlySecureContent;

/*! @abstract A Boolean value indicating whether horizontal swipe gestures
 will trigger back-forward list navigations.
 @discussion The default value is NO.
 */
//是否支持左右的swipe手勢是否能夠前進、後退
@property (nonatomic) BOOL allowsBackForwardNavigationGestures;

/*! @abstract The custom user agent string or nil if no custom user agent string has been set.
*/
//用戶自定義的user agent 沒有則爲nil
@property (nullable, nonatomic, copy) NSString *customUserAgent API_AVAILABLE(macosx(10.11), ios(9.0));

/*! @abstract A Boolean value indicating whether link preview is allowed for any
 links inside this WKWebView.
 @discussion The default value is YES on Mac and iOS.
 */
//標識不容許連接預覽,在iOS上默認爲NO
@property (nonatomic) BOOL allowsLinkPreview API_AVAILABLE(macosx(10.11), ios(9.0));

#if TARGET_OS_IPHONE
/*! @abstract The scroll view associated with the web view.
 */
//展現網頁內容的scrollview
@property (nonatomic, readonly, strong) UIScrollView *scrollView;
#endif

#if !TARGET_OS_IPHONE
/* @abstract A Boolean value indicating whether magnify gestures will
 change the web view's magnification.
 @discussion It is possible to set the magnification property even if
 allowsMagnification is set to NO.
 The default value is NO.
 */
//是否能夠放大,默認爲no
@property (nonatomic) BOOL allowsMagnification;

/* @abstract The factor by which the page content is currently scaled.
 @discussion The default value is 1.0.
 */
//放大因子,默認1
@property (nonatomic) CGFloat magnification;

5、WKWebView主要方法

/*! @abstract Navigates to the back item in the back-forward list.
 @result A new navigation to the requested item, or nil if there is no back
 item in the back-forward list.
 */
//返回上一頁，若是不能返回則什麼都不作
- (nullable WKNavigation *)goBack;

/*! @abstract Navigates to the forward item in the back-forward list.
 @result A new navigation to the requested item, or nil if there is no
 forward item in the back-forward list.
 */
//前進一頁 若是不能前進則什麼都不作
- (nullable WKNavigation *)goForward;

/*! @abstract Reloads the current page.
 @result A new navigation representing the reload.
 */
//從新加載頁面
- (nullable WKNavigation *)reload;

/*! @abstract Reloads the current page, performing end-to-end revalidation
 using cache-validating conditionals if possible.
 @result A new navigation representing the reload.
 */
//從新加載原始URL
- (nullable WKNavigation *)reloadFromOrigin;

/*! @abstract Stops loading all resources on the current page.
 */
//中止加載
- (void)stopLoading;

/* @abstract Evaluates the given JavaScript string.
 @param javaScriptString The JavaScript string to evaluate.
 @param completionHandler A block to invoke when script evaluation completes or fails.
 @discussion The completionHandler is passed the result of the script evaluation or an error.
*/
//執行JS代碼
- (void)evaluateJavaScript:(NSString *)javaScriptString completionHandler:(void (^ _Nullable)(_Nullable id, NSError * _Nullable error))completionHandler;

/* @abstract Scales the page content by a specified factor and centers the
 result on a specified point.
 * @param magnification The factor by which to scale the content.
 * @param point The point (in view space) on which to center magnification.
 */
//根據設置的縮放因子來縮放頁面，並居中顯示結果在指定的點
- (void)setMagnification:(CGFloat)magnification centeredAtPoint:(CGPoint)point;

6、代理方法

1.WKNavigationDelegate

WKNavigationDelegate主要處理一些跳轉、加載處理操做,因此WKNavigationDelegate 更加經常使用。若是實現了代理方法，必定要在decidePolicyForNavigationAction和decidePolicyForNavigationResponse方法中的回調設置容許跳轉。

//1.在發送請求以前，決定是否跳轉
//WKNavigationActionPolicyCancel 取消跳轉
//WKNavigationActionPolicyAllow  容許跳轉
- (void)webView:(WKWebView *)webView decidePolicyForNavigationAction:(WKNavigationAction *)navigationAction decisionHandler:(void (^)(WKNavigationActionPolicy))decisionHandler {
    NSLog(@"1-------在發送請求以前，決定是否跳轉  -->%@",navigationAction.request);
    decisionHandler(WKNavigationActionPolicyAllow);
}
//2.頁面開始加載時調用
- (void)webView:(WKWebView *)webView didStartProvisionalNavigation:(WKNavigation *)navigation {
    NSLog(@"2----頁面開始加載時調用");
}
//3.收到響應後，決定是否跳轉
- (void)webView:(WKWebView *)webView decidePolicyForNavigationResponse:(WKNavigationResponse *)navigationResponse decisionHandler:(void (^)(WKNavigationResponsePolicy))decisionHandler {
    //在收到服務器的響應頭，根據response相關信息，決定是否跳轉。decisionHandler必須調用，來決定是否跳轉，參數WKNavigationActionPolicyCancel取消跳轉，WKNavigationActionPolicyAllow容許跳轉
    NSLog(@"3-------在收到響應後，決定是否跳轉");
    decisionHandler(WKNavigationResponsePolicyAllow);
}
//4.當內容開始返回時調用
- (void)webView:(WKWebView *)webView didCommitNavigation:(WKNavigation *)navigation {
    NSLog(@"4-------當內容開始返回時調用");
}
//5.頁面加載完成以後調用
- (void)webView:(WKWebView *)webView didFinishNavigation:(WKNavigation *)navigation {
    NSLog(@"5-------頁面加載完成以後調用");
}

//6.頁面加載失敗時調用
- (void)webView:(WKWebView *)webView didFailProvisionalNavigation:(WKNavigation *)navigation {
    NSLog(@"6-------頁面加載失敗時調用");
}
//接收到服務器跳轉請求以後調用
- (void)webView:(WKWebView *)webView didReceiveServerRedirectForProvisionalNavigation:(WKNavigation *)navigation {
    NSLog(@"-------接收到服務器跳轉請求以後調用");
}
//數據加載發生錯誤時調用
- (void)webView:(WKWebView *)webView didFailNavigation:(null_unspecified WKNavigation *)navigation withError:(NSError *)error {
    NSLog(@"----數據加載發生錯誤時調用");
}
// 須要響應身份驗證時調用 一樣在block中須要傳入用戶身份憑證
- (void)webView:(WKWebView *)webView didReceiveAuthenticationChallenge:(NSURLAuthenticationChallenge *)challenge completionHandler:(void (^)(NSURLSessionAuthChallengeDisposition disposition, NSURLCredential * _Nullable credential))completionHandler {
    //用戶身份信息
    NSLog(@"----須要響應身份驗證時調用 一樣在block中須要傳入用戶身份憑證");
    NSURLCredential *newCred = [NSURLCredential credentialWithUser:@"" password:@"" persistence:NSURLCredentialPersistenceNone];
    // 爲 challenge 的發送方提供 credential
    [[challenge sender] useCredential:newCred forAuthenticationChallenge:challenge];
    completionHandler(NSURLSessionAuthChallengeUseCredential,newCred);
}
// 進程被終止時調用
- (void)webViewWebContentProcessDidTerminate:(WKWebView *)webView {
    NSLog(@"----------進程被終止時調用");
}

2.WKUIDelegate

WKUIDelegate主要處理JS腳本，確認框，警告框等。

/**
 *  web界面中有彈出警告框時調用
 *  @param webView           實現該代理的webview
 *  @param message           警告框中的內容
 *  @param completionHandler 警告框消失調用
 */
- (void)webView:(WKWebView *)webView runJavaScriptAlertPanelWithMessage:(NSString *)message initiatedByFrame:(void (^)())completionHandler {
    NSLog(@"web界面中有彈出警告框時調用");
}

//建立新的webView時調用的方法
- (nullable WKWebView *)webView:(WKWebView *)webView createWebViewWithConfiguration:(WKWebViewConfiguration *)configuration forNavigationAction:(WKNavigationAction *)navigationAction windowFeatures:(WKWindowFeatures *)windowFeatures {
    NSLog(@"建立新的webView時調用的方法");
    return webView;
}
//關閉webView時調用的方法
- (void)webViewDidClose:(WKWebView *)webView {
    NSLog(@"關閉webView時調用的方法");
}
//下面這些方法是交互JavaScript的方法
//JavaScript調用confirm方法後回調的方法 confirm是js中的肯定框，須要在block中把用戶選擇的狀況傳遞進去
-(void)webView:(WKWebView *)webView runJavaScriptConfirmPanelWithMessage:(NSString *)message initiatedByFrame:(WKFrameInfo *)frame completionHandler:(void (^)(BOOL))completionHandler {
    NSLog(@"%@",message);
    completionHandler(YES);
}
//JavaScript調用prompt方法後回調的方法 prompt是js中的輸入框 須要在block中把用戶輸入的信息傳入
-(void)webView:(WKWebView *)webView runJavaScriptTextInputPanelWithPrompt:(NSString *)prompt defaultText:(NSString *)defaultText initiatedByFrame:(WKFrameInfo *)frame completionHandler:(void (^)(NSString * _Nullable))completionHandler{
    NSLog(@"%@",prompt);
    completionHandler(@"123");
}
//默認預覽元素調用
- (BOOL)webView:(WKWebView *)webView shouldPreviewElement:(WKPreviewElementInfo *)elementInfo {
    NSLog(@"默認預覽元素調用");
    return YES;
}
//返回一個視圖控制器將致使視圖控制器被顯示爲一個預覽。返回nil將WebKit的默認預覽的行爲。
- (nullable UIViewController *)webView:(WKWebView *)webView previewingViewControllerForElement:(WKPreviewElementInfo *)elementInfo defaultActions:(NSArray<id <WKPreviewActionItem>> *)previewActions {
    NSLog(@"返回一個視圖控制器將致使視圖控制器被顯示爲一個預覽。返回nil將WebKit的默認預覽的行爲。");
    return self;
}
//容許應用程序向它建立的視圖控制器彈出
- (void)webView:(WKWebView *)webView commitPreviewingViewController:(UIViewController *)previewingViewController {
    NSLog(@"容許應用程序向它建立的視圖控制器彈出");
}
// 顯示一個文件上傳面板。completionhandler完成處理程序調用後打開面板已被撤銷。經過選擇的網址，若是用戶選擇肯定，不然爲零。若是不實現此方法，Web視圖將表現爲若是用戶選擇了取消按鈕。
- (void)webView:(WKWebView *)webView runOpenPanelWithParameters:(WKOpenPanelParameters *)parameters initiatedByFrame:(WKFrameInfo *)frame completionHandler:(void (^)(NSArray<NSURL *> * _Nullable URLs))completionHandler {
    NSLog(@"顯示一個文件上傳面板");
}