OC調(diào)用JS過程

與JS端調(diào)用OC基本思想一致
以WKWebView為例
1、JS端注冊

        bridge.registerHandler('testJavascriptHandler', function(data, responseCallback) {
            log('ObjC called testJavascriptHandler with', data)
            var responseData = { 'Javascript Says':'Right back atcha!' }
            log('JS responding with', responseData)
            responseCallback(responseData)
        })
//實際調(diào)用
// 對應(yīng) 原生端JS調(diào)用OC
    function registerHandler(handlerName, handler) {
        messageHandlers[handlerName] = handler;
    }

2、OC端調(diào)用

    [_bridge callHandler:@"testJavascriptHandler" data:data responseCallback:^(id response) {
        NSLog(@"testJavascriptHandler responded: %@", response);
    }];
// 實際調(diào)用 
- (void)sendData:(id)data responseCallback:(WVJBResponseCallback)responseCallback handlerName:(NSString*)handlerName {
    NSMutableDictionary* message = [NSMutableDictionary dictionary];
    
    if (data) {
        message[@"data"] = data;
    }
    // 同理 全局字典保存 
    if (responseCallback) {
        NSString* callbackId = [NSString stringWithFormat:@"objc_cb_%ld", ++_uniqueId];
        self.responseCallbacks[callbackId] = [responseCallback copy];
        message[@"callbackId"] = callbackId;
    }
    
    if (handlerName) {
        message[@"handlerName"] = handlerName;
    }
// message 為@{@"data":data,@"callbackId": callbackId,@"handlerName": handlerName}
    [self _queueMessage:message];
}

3、調(diào)用JS

- (void)_dispatchMessage:(WVJBMessage*)message {
    NSString *messageJSON = [self _serializeMessage:message pretty:NO];
    [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 = [NSString stringWithFormat:@"WebViewJavascriptBridge._handleMessageFromObjC('%@');", messageJSON];
    if ([[NSThread currentThread] isMainThread]) {
        [self _evaluateJavascript:javascriptCommand];

    } else {
        dispatch_sync(dispatch_get_main_queue(), ^{
            [self _evaluateJavascript:javascriptCommand];
        });
    }
}

4、解析

        function _doDispatchMessageFromObjC() {
            var message = JSON.parse(messageJSON);
            var messageHandler;
            var responseCallback;
//不會走下面流程
/*
            if (message.responseId) {
                responseCallback = responseCallbacks[message.responseId];
                if (!responseCallback) {
                    return;
                }
                responseCallback(message.responseData);
                delete responseCallbacks[message.responseId];
            } else */
 {
              //同理 回傳handlerName 和參數(shù)  再次回傳  callbackResponseId 
                if (message.callbackId) {
                    var callbackResponseId = message.callbackId;
                    responseCallback = function(responseData) {
// 進入回調(diào)OC流程
                        _doSend({ handlerName:message.handlerName, responseId:callbackResponseId, responseData:responseData });
                    };
                }
                // 同理 執(zhí)行保存的匿名函數(shù) 調(diào)用js的過程已經(jīng)完結(jié)
                var handler = messageHandlers[message.handlerName];
                if (!handler) {
                    console.log("WebViewJavascriptBridge: WARNING: no handler for message from ObjC:", message);
                } else {
// 執(zhí)行js方法 并且開始回調(diào)
                    handler(message.data, responseCallback);
                }
            }
        }
    }

5、OC端通過代理 處理回調(diào)

function _doSend(message, responseCallback) {
 // responseCallback為空 不走下面流程
/*
    if (responseCallback) {
            var callbackId = 'cb_'+(uniqueId++)+'_'+new Date().getTime();
            responseCallbacks[callbackId] = responseCallback;
            message['callbackId'] = callbackId;
        }
*/
// 此處的 message { handlerName:message.handlerName, responseId:callbackResponseId, responseData:responseData }
        sendMessageQueue.push(message);
        messagingIframe.src = CUSTOM_PROTOCOL_SCHEME + '://' + QUEUE_HAS_MESSAGE;
    }

6、OC端解析

// 同理 取出 JS端保存的  { handlerName:message.handlerName, responseId:callbackResponseId, responseData:responseData }
- (void)WKFlushMessageQueue {
    [_webView evaluateJavaScript:[_base webViewJavascriptFetchQueyCommand] completionHandler:^(NSString* result, NSError* error) {
        if (error != nil) {
            NSLog(@"WebViewJavascriptBridge: WARNING: Error when trying to fetch data from WKWebView: %@", error);
        }
        [_base flushMessageQueue:result];
    }];
}

7、核心方法 執(zhí)行回調(diào)

- (void)flushMessageQueue:(NSString *)messageQueueString{
    if (messageQueueString == nil || messageQueueString.length == 0) {
        NSLog(@"WebViewJavascriptBridge: WARNING: ObjC got nil while fetching the message queue JSON from webview. This can happen if the WebViewJavascriptBridge JS is not currently present in the webview, e.g if the webview just loaded a new page.");
        return;
    }

    id messages = [self _deserializeMessageJSON:messageQueueString];
    for (WVJBMessage* message in messages) {
        if (![message isKindOfClass:[WVJBMessage class]]) {
            NSLog(@"WebViewJavascriptBridge: WARNING: Invalid %@ received: %@", [message class], message);
            continue;
        }
        [self _log:@"RCVD" json:message];
        
        NSString* responseId = message[@"responseId"];
        if (responseId) {
            WVJBResponseCallback responseCallback = _responseCallbacks[responseId];
            responseCallback(message[@"responseData"]);
            [self.responseCallbacks removeObjectForKey:responseId];
        }
//以下流程不會走 回調(diào)完成  整個OC調(diào)用js方法 完成
/* else {
            WVJBResponseCallback responseCallback = NULL;
            NSString* callbackId = message[@"callbackId"];
            if (callbackId) {
                responseCallback = ^(id responseData) {
                    if (responseData == nil) {
                        responseData = [NSNull null];
                    }
                    
                    WVJBMessage* msg = @{ @"responseId":callbackId, @"responseData":responseData };
                    [self _queueMessage:msg];
                };
            } else {
                responseCallback = ^(id ignoreResponseData) {
                    // Do nothing
                };
            }
            
            WVJBHandler handler = self.messageHandlers[message[@"handlerName"]];
            
            if (!handler) {
                NSLog(@"WVJBNoHandlerException, No handler for message from JS: %@", message);
                continue;
            }
            
            handler(message[@"data"], responseCallback);
        }
    }
*/
}