最近抽时间看了一遍WebViewJavascriptBridge这个开源框架，把看到的内容记录下来
源码地址：https://github.com/marcuswestin/WebViewJavascriptBridge
1、对外接口
初始化OC
初始化JS
**[WebViewJavascriptBridge bridgeForWebView:(UIWebView/WebView*)webview handler:(WVJBHandler)handler]**
** **
**[WebViewJavascriptBridge bridgeForWebView:(UIWebView/WebView*)webview webViewDelegate:(UIWebViewDelegate*)webViewDelegate handler:(WVJBHandler)handler]**
**document.addEventListener('WebViewJavascriptBridgeReady', function onBridgeReady(event) { ... }, false)**
** **
**bridge.init(function messageHandler(data, response) { ... })**
OC发送消息to JS
JS发送消息to OC
**[bridge send:(id)data]**
**[bridge send:(id)data responseCallback:(WVJBResponseCallback)responseCallback]**
**bridge.send("Hi there!")**
**bridge.send({ Foo:"Bar" })**
**bridge.send(data, function responseCallback(responseData) { ... })**
OC注册事件（先）
JS调用事件（后）
**[bridge registerHandler:(NSString*)handlerName handler:(WVJBHandler)handler]**
WebViewJavascriptBridge.callHandler("handlerName")
OC调用事件（后）
JS注册事件（先）
**[bridge callHandler:(NSString*)handlerName data:(id)data]**
**[bridge callHandler:(NSString*)handlerName data:(id)data responseCallback:(WVJBResponseCallback)callback]**
**bridge.registerHandler("handlerName", function(responseData) { ... })**
三类API接口用于OC与JS之间交互：初始化接口；发送消息接口，并且可以添加发送消息完成的回调函数；事件注册和调用接口，需要先在一端注册事件，另一端可以根据事件名称调用函数
除了上述提到的外部方法：还有两个方法十分重要，**JS部分最重要的内部方法：**_handleMessageFromObjC；OC部分重要的内部方法：**flushMessageQueue******
2、类结构图
WebViewJavascriptBridge目前既支持原有的UIWebView，也支持iOS8+之后新的WKWebView，使用时可以二选其一；
WebViewjavascriptBridgeBase是通用类，用于处理从Native到JS的消息注入，消息队列处理和分发，JSON数据的序列化和反序列化，LOG输出；
3、源码分析
3.1 消息发送JS－》Native
**[bridge send:(id)data]**
**[bridge send:(id)data responseCallback:(WVJBResponseCallback)responseCallback]**
这两个函数最后都是调用_doSend({ data:data }, responseCallback)
function _doSend(message, responseCallback) { if (responseCallback) { var callbackId = 'cb_'+(uniqueId++)+'_'+new Date().getTime() responseCallbacks[callbackId] = responseCallback message['callbackId'] = callbackId } sendMessageQueue.push(message) messagingIframe.src = CUSTOM_PROTOCOL_SCHEME + '://' + QUEUE_HAS_MESSAGE}
首先生成callbackId，由不断加1的唯一需要和时间戳构成，如果有responseCallback函数，使用callbackId作为索引，存入responseCallbacks对象，等到从OC侧返回的信息中对应的callbackId与当前responseCallbacks中callbackId相同时，调用回调函数responseCallback；sendMessageQueue是个消息数组，每次的新消息放入其中，messagingIframe是iframe对象，当设置src产生一次请求，在OC端的
- (BOOL)webView:(UIWebView *)webView shouldStartLoadWithRequest:(NSURLRequest *)request navigationType:(UIWebViewNavigationType)navigationType 会拦截请求内容
代码：
- (BOOL)webView:(UIWebView *)webView shouldStartLoadWithRequest:(NSURLRequest *)request navigationType:(UIWebViewNavigationType)navigationType { if (webView != _webView) { return YES; } NSURL *url = [request URL]; __strong WVJB_WEBVIEW_DELEGATE_TYPE* strongDelegate = _webViewDelegate; if ([_baseisCorrectProcotocolScheme:url]) { if ([_baseisCorrectHost:url]) { NSString *messageQueueString = [self_evaluateJavascript:[_basewebViewJavascriptFetchQueyCommand]]; [_base flushMessageQueue:messageQueueString]; } else { [_base logUnkownMessage:url]; } return NO; } else if (strongDelegate && [strongDelegate respondsToSelector:@selector(webView:shouldStartLoadWithRequest:navigationType:)]) { return [strongDelegate webView:webView shouldStartLoadWithRequest:requestnavigationType:navigationType]; } else { return YES; }
}
重点部分：执行注入_evaluateJavascript，
OC
-(NSString *)webViewJavascriptFetchQueyCommand { return @"WebViewJavascriptBridge._fetchQueue();";
}
JS
function _fetchQueue() {
var messageQueueString = JSON.stringify(sendMessageQueue)
sendMessageQueue = []
return messageQueueString
}
这个函数从JS的sendMessageQueue消息队列获取内容返回，这个sendMessageQueue是在之前的_doSend函数中传入的消息内容，也就是NSString*messageQueueString = [self_evaluateJavascript:[_basewebViewJavascriptFetchQueyCommand]];这句代码获得从JS侧拿到的数据内容，然后调用[_baseflushMessageQueue:messageQueueString];对消息分发处理
- (void)flushMessageQueue:(NSString *)messageQueueString{ id messages = [self_deserializeMessageJSON:messageQueueString]; if (![messages isKindOfClass:[NSArray class]]) { NSLog(@"WebViewJavascriptBridge: WARNING: Invalid %@ received: %@", [messagesclass], messages); return; } for (WVJBMessage* messagein messages) { if (![message isKindOfClass:[WVJBMessage class]]) { NSLog(@"WebViewJavascriptBridge: WARNING: Invalid %@ received: %@", [messageclass], message); continue; } [self _log:@"RCVD" json:message]; NSString* responseId = message[@"responseId"]; if (responseId) { WVJBResponseCallback responseCallback =_responseCallbacks[responseId]; responseCallback(message[@"responseData"]); [self.responseCallbacksremoveObjectForKey:responseId]; } else { WVJBResponseCallback responseCallback =NULL; NSString* callbackId = message[@"callbackId"]; if (callbackId) { responseCallback = ^(id responseData) { if (responseData == nil) { responseData = [NSNullnull]; } WVJBMessage* msg = @{@"responseId":callbackId, @"responseData":responseData }; [self _queueMessage:msg]; }; } else { responseCallback = ^(id ignoreResponseData) { // Do nothing }; } WVJBHandler handler; if (message[@"handlerName"]) { handler = self.messageHandlers[message[@"handlerName"]]; } else { handler = self.messageHandler; } if (!handler) { [NSException raise:@"WVJBNoHandlerException" format:@"No handler for message from JS: %@", message]; } handler(message[@"data"], responseCallback); } }
}
这个是整个框架中OC侧重要的函数，但是目前首先分析消息发送JS－》Native涉及到的部分内容，返回的消息包含callbackId，数据拼接后调用[self_queueMessage:msg];发送回JS侧的数据改为responseId为关键字key，具体如下：
- (void)_queueMessage:(WVJBMessage*)message { if (self.startupMessageQueue) { [self.startupMessageQueueaddObject:message]; } else { [self _dispatchMessage:message]; }
}
self.startupMessageQueue只有首次启动时有效，之后为nil，所以都是走[self_dispatchMessage:message];
- (void)_dispatchMessage:(WVJBMessage*)message { NSString *messageJSON = [self_serializeMessage:message]; [self _log:@"SEND" json:messageJSON]; messageJSON = [messageJSON stringByReplacingOccurrencesOfString:@"\\"withString:@"\\\\"]; messageJSON = [messageJSON stringByReplacingOccurrencesOfString:@"\""withString:@"\\\""]; messageJSON = [messageJSON stringByReplacingOccurrencesOfString:@"\'"withString:@"\\\'"]; messageJSON = [messageJSON stringByReplacingOccurrencesOfString:@"\n"withString:@"\\n"]; messageJSON = [messageJSON stringByReplacingOccurrencesOfString:@"\r"withString:@"\\r"]; messageJSON = [messageJSON stringByReplacingOccurrencesOfString:@"\f"withString:@"\\f"]; messageJSON = [messageJSON stringByReplacingOccurrencesOfString:@"\u2028"withString:@"\\u2028"]; messageJSON = [messageJSON stringByReplacingOccurrencesOfString:@"\u2029"withString:@"\\u2029"]; NSString* javascriptCommand = [NSStringstringWithFormat:@"WebViewJavascriptBridge._handleMessageFromObjC('%@');", messageJSON]; if ([[NSThreadcurrentThread] isMainThread]) { [self _evaluateJavascript:javascriptCommand]; } else { dispatch_sync(dispatch_get_main_queue(), ^{ [self _evaluateJavascript:javascriptCommand]; }); }
}
此函数对message特殊字符进行转义处理，然后执行JS注入语句，WebViewJavascriptBridge._handleMessageFromObjC执行到JS侧
这个是整个框架中JS侧重要的函数，用于处理从OC侧返回的消息
function _dispatchMessageFromObjC(messageJSON) { setTimeout(function _timeoutDispatchMessageFromObjC() { var message = JSON.parse(messageJSON) var messageHandler var responseCallback if (message.responseId) { responseCallback = responseCallbacks[message.responseId] if (!responseCallback) { return; } responseCallback(message.responseData) delete responseCallbacks[message.responseId] } else { if (message.callbackId) { var callbackResponseId = message.callbackId responseCallback = function(responseData) { _doSend({ responseId:callbackResponseId, responseData:responseData }) } } var handler = WebViewJavascriptBridge._messageHandler if (message.handlerName) { handler = messageHandlers[message.handlerName] } try { handler(message.data, responseCallback) } catch(exception) { if (typeof console != 'undefined') { console.log("WebViewJavascriptBridge: WARNING: javascript handler threw.", message, exception) } } } }) }
执行JS侧本地回调函数
3.2 消息发送 OC--》JS
**bridge.send("Hi there!")**
**bridge.send({ Foo:"Bar" })**
**bridge.send(data, function responseCallback(responseData) { ... })**
****
调用
[_base sendData:dataresponseCallback:responseCallback handlerName:nil];
执行 _queueMessage
3.3 OC注册事件和JS调用
OC侧注册
- (void)registerHandler:(NSString *)handlerName handler:(WVJBHandler)handler {
_base.messageHandlers[handlerName] = [handlercopy];
}
JS调用
function callHandler(handlerName, data, responseCallback) {
_doSend({ handlerName:handlerName, data:data }, responseCallback)
}
加入handlerName和data数据传给OC侧，JS侧记录responseCallback，最后也会走到- (void)flushMessageQueue:(NSString )messageQueueString函数中，由于既没有callbackId也没有responseId，所以只处理handlerName及相关数据，最后走到 - (void)flushMessageQueue:(NSString)messageQueueString解析，OC侧执行之前注册的handler并传入data数据
3.4 JS注册事件和OC调用
JS注册
function registerHandler(handlerName, handler) {
messageHandlers[handlerName] = handler
}
本地记录
OC调用
- (void)callHandler:(NSString *)handlerName data:(id)data { [self callHandler:handlerName data:dataresponseCallback:nil];
}
- (void)callHandler:(NSString *)handlerName data:(id)data responseCallback:(WVJBResponseCallback)responseCallback { [_base sendData:data responseCallback:responseCallbackhandlerName:handlerName];
}
handlerName和data 在
- (void)sendData:(id)data responseCallback:(WVJBResponseCallback)responseCallback handlerName:(NSString*)handlerName
中处理
**4 、总结**
****
1、与其它框架相比，此框架没有采用url拦截解析参数方式，而是多次JS注入参数获取，API接口暴露的操作在底层需要多次OC与JS之间交互完成
2、WKwebview部分没有使用新的delgate方法，而是沿用iframe方式，个人觉得采用新接口可能效率更高