前言

Xcode8发布以后，编译器开始不支持IOS7，所以很多应用在适配IOS10之后都不在适配IOS7了，其中包括了很多大公司，网易新闻，滴滴出行等。因此，我们公司的应用也打算淘汰IOS7。

支持到IOS8，第一个要改的自然是用WKWebView替换原来的UIWebView。WKWebView有很多明显优势:

• 更多的支持HTML5的特性

• 官方宣称的高达60fps的滚动刷新率以及内置手势

• 将UIWebViewDelegate与UIWebView拆分成了14类与3个协议,以前很多不方便实现的功能得以实现。文档

• Safari相同的JavaScript引擎

• 占用更少的内存

UIWebView

UIWebView

WKWebView

WKWebView

因此，使用WkWebview替换UIWebView还是很有必要的。

基本使用方法

WKWebView有两个delegate,WKUIDelegate 和 WKNavigationDelegate。WKNavigationDelegate主要处理一些跳转、加载处理操作，WKUIDelegate主要处理JS脚本，确认框，警告框等。因此WKNavigationDelegate更加常用。

比较常用的方法：

#pragma mark - lifeCircle- (void)viewDidLoad {    [super viewDidLoad];    webView = [[WKWebView alloc]init];    [self.view addSubview:webView];    [webView mas_makeConstraints:^(MASConstraintMaker *make) {        make.left.equalTo(self.view);        make.right.equalTo(self.view);        make.top.equalTo(self.view);        make.bottom.equalTo(self.view);    }];    webView.UIDelegate = self;    webView.navigationDelegate = self;    [webView loadRequest:[NSURLRequest requestWithURL:[NSURL URLWithString:@"http://www.baidu.com"]]];}#pragma mark - WKNavigationDelegate// 页面开始加载时调用- (void)webView:(WKWebView *)webView didStartProvisionalNavigation:(WKNavigation *)navigation{}// 当内容开始返回时调用- (void)webView:(WKWebView *)webView didCommitNavigation:(WKNavigation *)navigation{}// 页面加载完成之后调用- (void)webView:(WKWebView *)webView didFinishNavigation:(WKNavigation *)navigation{}// 页面加载失败时调用- (void)webView:(WKWebView *)webView didFailProvisionalNavigation:(WKNavigation *)navigation{}// 接收到服务器跳转请求之后调用- (void)webView:(WKWebView *)webView didReceiveServerRedirectForProvisionalNavigation:(WKNavigation *)navigation{}// 在收到响应后，决定是否跳转- (void)webView:(WKWebView *)webView decidePolicyForNavigationResponse:(WKNavigationResponse *)navigationResponse decisionHandler:(void (^)(WKNavigationResponsePolicy))decisionHandler{    NSLog(@"%@",navigationResponse.response.URL.absoluteString);    //允许跳转    decisionHandler(WKNavigationResponsePolicyAllow);    //不允许跳转    //decisionHandler(WKNavigationResponsePolicyCancel);}// 在发送请求之前，决定是否跳转- (void)webView:(WKWebView *)webView decidePolicyForNavigationAction:(WKNavigationAction *)navigationAction decisionHandler:(void (^)(WKNavigationActionPolicy))decisionHandler{     NSLog(@"%@",navigationAction.request.URL.absoluteString);    //允许跳转    decisionHandler(WKNavigationActionPolicyAllow);    //不允许跳转    //decisionHandler(WKNavigationActionPolicyCancel);}#pragma mark - WKUIDelegate// 创建一个新的WebView- (WKWebView *)webView:(WKWebView *)webView createWebViewWithConfiguration:(WKWebViewConfiguration *)configuration forNavigationAction:(WKNavigationAction *)navigationAction windowFeatures:(WKWindowFeatures *)windowFeatures{    return [[WKWebView alloc]init];}// 输入框- (void)webView:(WKWebView *)webView runJavaScriptTextInputPanelWithPrompt:(NSString *)prompt defaultText:(nullable NSString *)defaultText initiatedByFrame:(WKFrameInfo *)frame completionHandler:(void (^)(NSString * __nullable result))completionHandler{    completionHandler(@"http");}// 确认框- (void)webView:(WKWebView *)webView runJavaScriptConfirmPanelWithMessage:(NSString *)message initiatedByFrame:(WKFrameInfo *)frame completionHandler:(void (^)(BOOL result))completionHandler{    completionHandler(YES);}// 警告框- (void)webView:(WKWebView *)webView runJavaScriptAlertPanelWithMessage:(NSString *)message initiatedByFrame:(WKFrameInfo *)frame completionHandler:(void (^)(void))completionHandler{    NSLog(@"%@",message);    completionHandler();}

OC与JS交互

WKWebview提供了API实现js交互 不需要借助JavaScriptCore或者webJavaScriptBridge。使用WKUserContentController实现js native交互。简单的说就是先注册约定好的方法，然后再调用。

JS调用OC方法

oc代码(有误，内存不释放):

@interface ViewController ()<WKUIDelegate,WKNavigationDelegate,WKScriptMessageHandler>{    WKWebView * webView;    WKUserContentController* userContentController;}@end@implementation ViewController#pragma mark - lifeCircle- (void)viewDidLoad {    [super viewDidLoad];    //配置环境    WKWebViewConfiguration * configuration = [[WKWebViewConfiguration alloc]init];    userContentController =[[WKUserContentController alloc]init];    configuration.userContentController = userContentController;    webView = [[WKWebView alloc]initWithFrame:CGRectMake(0, 0, 100, 100) configuration:configuration];    //注册方法    [userContentController addScriptMessageHandler:self  name:@"sayhello"];//注册一个name为sayhello的js方法    [self.view addSubview:webView];    [webView mas_makeConstraints:^(MASConstraintMaker *make) {        make.left.equalTo(self.view);        make.right.equalTo(self.view);        make.top.equalTo(self.view);        make.bottom.equalTo(self.view);    }];    webView.UIDelegate = self;    webView.navigationDelegate = self;    [webView loadRequest:[NSURLRequest requestWithURL:[NSURL URLWithString:@"http://www.test.com"]]];}- (void)dealloc{    //这里需要注意，前面增加过的方法一定要remove掉。    [userContentController removeScriptMessageHandlerForName:@"sayhello"];}#pragma mark - WKScriptMessageHandler- (void)userContentController:(WKUserContentController *)userContentController didReceiveScriptMessage:(WKScriptMessage *)message{    NSLog(@"name:%@\\\\n body:%@\\\\n frameInfo:%@\\\\n",message.name,message.body,message.frameInfo);}@end

上面的OC代码如果认证测试一下就会发现dealloc并不会执行，这样肯定是不行的，会造成内存泄漏。原因是[userContentController addScriptMessageHandler:self name:@"sayhello"];这句代码造成无法释放内存。（ps:试了下用weak指针还是不能释放，不知道是什么原因。）因此还需要进一步改进，正确的写法是用一个新的controller来处理,新的controller再绕用delegate绕回来。

oc代码(正确写法):

@interface ViewController ()<WKUIDelegate,WKNavigationDelegate,WKScriptMessageHandler>{    WKWebView * webView;    WKUserContentController* userContentController;}@end@implementation ViewController#pragma mark - lifeCircle- (void)viewDidLoad {    [super viewDidLoad];    //配置环境    WKWebViewConfiguration * configuration = [[WKWebViewConfiguration alloc]init];    userContentController =[[WKUserContentController alloc]init];    configuration.userContentController = userContentController;    webView = [[WKWebView alloc]initWithFrame:CGRectMake(0, 0, 100, 100) configuration:configuration];    //注册方法    WKDelegateController * delegateController = [[WKDelegateController alloc]init];    delegateController.delegate = self;    [userContentController addScriptMessageHandler:delegateController  name:@"sayhello"];    [self.view addSubview:webView];    [webView mas_makeConstraints:^(MASConstraintMaker *make) {        make.left.equalTo(self.view);        make.right.equalTo(self.view);        make.top.equalTo(self.view);        make.bottom.equalTo(self.view);    }];    webView.UIDelegate = self;    webView.navigationDelegate = self;    [webView loadRequest:[NSURLRequest requestWithURL:[NSURL URLWithString:@"http://www.test.com"]]];}- (void)dealloc{    //这里需要注意，前面增加过的方法一定要remove掉。    [userContentController removeScriptMessageHandlerForName:@"sayhello"];}#pragma mark - WKScriptMessageHandler- (void)userContentController:(WKUserContentController *)userContentController didReceiveScriptMessage:(WKScriptMessage *)message{    NSLog(@"name:%@\\\\n body:%@\\\\n frameInfo:%@\\\\n",message.name,message.body,message.frameInfo);}@end

WKDelegateController代码：

#import <UIKit/UIKit.h>#import <WebKit/WebKit.h>@protocol WKDelegate <NSObject>- (void)userContentController:(WKUserContentController *)userContentController didReceiveScriptMessage:(WKScriptMessage *)message;@end@interface WKDelegateController : UIViewController <WKScriptMessageHandler>@property (weak , nonatomic) id<WKDelegate> delegate;@end

.m代码：

#import "WKDelegateController.h"@interface WKDelegateController ()@end@implementation WKDelegateController- (void)viewDidLoad {    [super viewDidLoad];}- (void)userContentController:(WKUserContentController *)userContentController didReceiveScriptMessage:(WKScriptMessage *)message{    if ([self.delegate respondsToSelector:@selector(userContentController:didReceiveScriptMessage:)]) {        [self.delegate userContentController:userContentController didReceiveScriptMessage:message];    }}@end

h5代码:

<html><head>    <script>function say(){//前端需要用 window.webkit.messageHandlers.注册的方法名.postMessage({body:传输的数据} 来给native发送消息    window.webkit.messageHandlers.sayhello.postMessage({body: ‘hello world!‘});}</script></head>    <body>        <h1>hello world</h1>        <button onclick="say()">say hello</button>    </body></html>

打印出的log：

 name:sayhello body:{    body = "hello world!";} frameInfo:<WKFrameInfo: 0x7f872060ce20; isMainFrame = YES; request =     <NSMutableURLRequest: 0x618000010a30> { URL: http://www.test.com/ }>

注意点

• addScriptMessageHandler要和removeScriptMessageHandlerForName配套出现，否则会造成内存泄漏。
• h5只能传一个参数，如果需要多个参数就需要用字典或者json组装。

oc调用JS方法

代码如下：

- (void)webView:(WKWebView *)tmpWebView didFinishNavigation:(WKNavigation *)navigation{    //say()是JS方法名，completionHandler是异步回调block    [webView evaluateJavaScript:@"say()" completionHandler:^(id _Nullable result, NSError * _Nullable error) {        NSLog(@"%@",result);    }];}

h5代码同上。

WebViewJavascriptBridge

一般来说，一个好的UI总有一个大神会开发出一个好的第三方封装框架。WebViewJavascriptBridge的作者也做了一套支持WKWebView与JS交互的第三方框架:WKWebViewJavascriptBridge。

• cocoaPods: pod ‘WebViewJavascriptBridge‘, ‘~> 5.0.5‘

• github地址：https://github.com/marcuswestin/WebViewJavascriptBridge

主要方法如下：

//初始化方法+ (instancetype)bridgeForWebView:(WKWebView*)webView;+ (void)enableLogging;//注册函数名- (void)registerHandler:(NSString*)handlerName handler:(WVJBHandler)handler;//调用函数名- (void)callHandler:(NSString*)handlerName;- (void)callHandler:(NSString*)handlerName data:(id)data;- (void)callHandler:(NSString*)handlerName data:(id)data responseCallback:(WVJBResponseCallback)responseCallback;//重置- (void)reset;//设置WKNavigationDelegate- (void)setWebViewDelegate:(id<WKNavigationDelegate>)webViewDelegate;

基本的实现方法和上面写的差不多，就是封装了一下，有兴趣的童鞋可以自己pod下来使用。

IOS进阶之WKWebView