WebViewJSBridge源碼很簡(jiǎn)單，只有一個(gè)類跪腹，下面是這個(gè)類的類圖（去除了OSX平臺(tái)的代碼）。
WebViewJSBridge類.png
JS和Native的交互主要通過(guò)發(fā)送WVJBMessage消息來(lái)完成，它是一個(gè)字典栅迄，有五個(gè)字段：
- data，交互數(shù)據(jù)
- callbackId皆怕，是一個(gè)字符串毅舆，結(jié)構(gòu)為objc_cb_(_uniqueid),_uniqueId是一個(gè)全局自增的整型變量
- handlerName西篓，回調(diào)名稱
- responseId,js調(diào)用native時(shí)使用，對(duì)應(yīng)callbackId憋活，標(biāo)示是否是針對(duì)請(qǐng)求的回復(fù)
- responseData,js調(diào)用native時(shí)使用
JS調(diào)用Native
JS調(diào)用Native的技巧是：定義了一個(gè)專用scheme和host岂津，在webView的- (BOOL)webView:(UIWebView *)webView shouldStartLoadWithRequest:(NSURLRequest *)request navigationType:(UIWebViewNavigationType)navigationType代理中判斷是否是這個(gè)scheme來(lái)判斷請(qǐng)求是否來(lái)自jsBridge，通過(guò)host判斷是否有新消息悦即，如果有吮成，則主動(dòng)調(diào)用協(xié)議定義的js方法來(lái)獲取消息。
- (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 ([[url scheme] isEqualToString:kCustomProtocolScheme]) {
if ([[url host] isEqualToString:kQueueHasMessage]) {
[self _flushMessageQueue];//確認(rèn)js想調(diào)用native
} else {
NSLog(@"WebViewJavascriptBridge: WARNING: Received unknown WebViewJavascriptBridge command %@://%@", kCustomProtocolScheme, [url path]);
}
return NO;//來(lái)自jsbridge的請(qǐng)求不會(huì)加載
} else if (strongDelegate && [strongDelegate respondsToSelector:@selector(webView:shouldStartLoadWithRequest:navigationType:)]) {
return [strongDelegate webView:webView shouldStartLoadWithRequest:request navigationType:navigationType];
} else {
return YES;
}
}
_flushMessage主要分為下面幾個(gè)步驟：
1.主動(dòng)調(diào)用WebViewJavascriptBridge._fetchQueue()獲取消息隊(duì)列辜梳；
2.循環(huán)遍歷消息隊(duì)列
3.解析message粱甫，針對(duì)不同情況進(jìn)行不同的處理
- (void)_flushMessageQueue {
//調(diào)用jsBridge協(xié)議的方法來(lái)獲取js端想發(fā)送的信息
NSString *messageQueueString = [_webView stringByEvaluatingJavaScriptFromString:@"WebViewJavascriptBridge._fetchQueue();"];
id messages = [self _deserializeMessageJSON:messageQueueString];
if (![messages isKindOfClass:[NSArray class]]) {
NSLog(@"WebViewJavascriptBridge: WARNING: Invalid %@ received: %@", [messages class], messages);
return;
}
for (WVJBMessage* message in messages) {
if (![message isKindOfClass:[WVJBMessage class]]) {
NSLog(@"WebViewJavascriptBridge: WARNING: Invalid %@ received: %@", [message class], message);
continue;
}
[self _log:@"RCVD" json:message];
//取出responseId
NSString* responseId = message[@"responseId"];
if (responseId) {
/*
*這個(gè)分支說(shuō)明這個(gè)消息是針對(duì)native調(diào)用js的響應(yīng)
*取出這個(gè)responseId的回調(diào)，并且執(zhí)行完畢后從字典中移除
*/
WVJBResponseCallback responseCallback = _responseCallbacks[responseId];
responseCallback(message[@"responseData"]);
[_responseCallbacks removeObjectForKey:responseId];
} else {
//這個(gè)分支說(shuō)明是js主動(dòng)想調(diào)用native
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];//執(zhí)行完畢后作瞄，發(fā)送消息給js茶宵，通知調(diào)用已經(jīng)完畢
};
} else {
responseCallback = ^(id ignoreResponseData) {
// Do nothing
};
}//設(shè)置調(diào)用native后的處理回調(diào)
WVJBHandler handler;
if (message[@"handlerName"]) {
handler = _messageHandlers[message[@"handlerName"]];
} else {
handler = _messageHandler;
}
if (!handler) {
[NSException raise:@"WVJBNoHandlerException" format:@"No handler for message from JS: %@", message];
}
//執(zhí)行調(diào)用
handler(message[@"data"], responseCallback);
}
}
}
Native調(diào)用JS
這個(gè)過(guò)程是比較簡(jiǎn)單的，直接調(diào)用stringByEvaluatingJavaScriptFromString即可宗挥。主要分為兩步步：
- 調(diào)用提供的send接口
- 構(gòu)建一個(gè)message乌庶，如果隊(duì)列存在塞入隊(duì)列，如果不存在直接dispatch
下面是主要的源碼：
-(void)_sendData:(id)data responseCallback:(WVJBResponseCallback)responseCallback handlerName:(NSString*)handlerName {
NSMutableDictionary* message = [NSMutableDictionary dictionary];
if (data) {
message[@"data"] = data;
}
if (responseCallback) {
//將回調(diào)注冊(cè)到_responseCallbacks中
NSString* callbackId = [NSString stringWithFormat:@"objc_cb_%ld", ++_uniqueId];
_responseCallbacks[callbackId] = [responseCallback copy];
message[@"callbackId"] = callbackId;
}
if (handlerName) {
message[@"handlerName"] = handlerName;
}
[self _queueMessage:message];
}
- (void)_queueMessage:(WVJBMessage*)message {
//如果queue存在契耿，則加入到queue中安拟，否則直接調(diào)用dispatchMessage
if (_startupMessageQueue) {
[_startupMessageQueue addObject:message];
} else {
[self _dispatchMessage:message];
}
}
//將Message字典序列化成JSON，主線程調(diào)用JS方法宵喂。
- (void)_dispatchMessage:(WVJBMessage*)message {
NSString *messageJSON = [self _serializeMessage:message];
[self _log:@"SEND" json:messageJSON];
NSLog(@"%@ %@", message ,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"];
NSLog(@"%@ %@", message ,messageJSON);
NSString* javascriptCommand = [NSString stringWithFormat:@"WebViewJavascriptBridge._handleMessageFromObjC('%@');", messageJSON];
if ([[NSThread currentThread] isMainThread]) {
[_webView stringByEvaluatingJavaScriptFromString:javascriptCommand];
} else {
__strong WVJB_WEBVIEW_TYPE* strongWebView = _webView;
dispatch_sync(dispatch_get_main_queue(), ^{
[strongWebView stringByEvaluatingJavaScriptFromString:javascriptCommand];
});
}
}
