客户端、H5注册
客户端
在BridgeWebView的初始化方法中,添加了自定义的BridgeWebViewClient,在onPageFinished方法中,去加载WebViewJavascriptBridge.js文件(在assets目录下):
@Overridepublic void onPageFinished(WebView view, String url) { super.onPageFinished(view, url); if (BridgeWebView.toLoadJs != null) { BridgeUtil.webViewLoadLocalJs(view, BridgeWebView.toLoadJs); } ... }
BridgeUtil # webViewLoadLocalJs:
public static void webViewLoadLocalJs(WebView view, String path){ String jsContent = assetFile2Str(view.getContext(), path); view.loadUrl("javascript:" + jsContent); }
H5
var doc = document; _createQueueReadyIframe(doc);var readyEvent = doc.createEvent('Events'); readyEvent.initEvent('WebViewJavascriptBridgeReady'); readyEvent.bridge = WebViewJavascriptBridge; doc.dispatchEvent(readyEvent);
H5端在使用的时候需要检测是否初始化完毕:
if(window.WebViewJavascriptBridge) { return callback(WebViewJavascriptBridge); } else { document.addEventListener( 'WebViewJavascriptBridgeReady', function() { return callback(WebViewJavascriptBridge); }, false ); }
Native调用JS
jsBridgeWebview.callHandler(String handlerName, String data, CallBackFunction callBack);public interface CallBackFunction { public void onCallBack(String data); }
callHandler方法中调用doSend方法(参数:方法名; 数据; 回调):
private void doSend(String handlerName, String data, CallBackFunction responseCallback) { Message m = new Message(); if (!TextUtils.isEmpty(data)) { m.setData(data); } if (responseCallback != null) { String callbackStr = String.format(BridgeUtil.CALLBACK_ID_FORMAT, ++uniqueId + (BridgeUtil.UNDERLINE_STR + SystemClock.currentThreadTimeMillis())); responseCallbacks.put(callbackStr, responseCallback); m.setCallbackId(callbackStr); } if (!TextUtils.isEmpty(handlerName)) { m.setHandlerName(handlerName); } queueMessage(m); }
doSend方法中,将参数封装到Message对象中(注意这个Message不是Android SDK中的Message,是该开源库自己封装的Message);
方法名和数据判空后放入Message对象,单独看下回调:
生成每个callBack唯一对应的id(其实就是一个固定格式的字符串,用于存储在Map中的key值):
String callbackStr = String.format(BridgeUtil.CALLBACK_ID_FORMAT, ++uniqueId + (BridgeUtil.UNDERLINE_STR + SystemClock.currentThreadTimeMillis()));
格式:"JAVA_CB_%s" + uniqueId + "_" + 当前时间毫秒值;uniqueId:一个自增的int类型值,默认值为0;
然后将其放入消息队列中(List<Message>):
private void queueMessage(Message m) { if (startupMessage != null) { startupMessage.add(m); } else { dispatchMessage(m); } }
走到这里会看到,startupMessage在直接声明的时候就初始化了,怎么会为空?翻到BridgeWebViewClient类中的onPageFinished方法:
@Overridepublic void onPageFinished(WebView view, String url) { ... if (webView.getStartupMessage() != null) { for (Message m : webView.getStartupMessage()) { webView.dispatchMessage(m); } webView.setStartupMessage(null); } }
这里可以看到,webview内容加载完之后,会遍历这个startupMessage队列,去调用BridgeWebView中的dispatchMessage方法,将Message作为参数,并且将startupMessage队列置为null;
dispatchMessage方法:
void dispatchMessage(Message m) { String messageJson = m.toJson(); //escape special characters for json string messageJson = messageJson.replaceAll("(\\\\)([^utrn])", "\\\\\\\\$1$2"); messageJson = messageJson.replaceAll("(?<=[^\\\\])(\")", "\\\\\""); String javascriptCommand = String.format(BridgeUtil.JS_HANDLE_MESSAGE_FROM_JAVA, messageJson); if (Thread.currentThread() == Looper.getMainLooper().getThread()) { this.loadUrl(javascriptCommand); } }
将Message对象转为Json并做一些处理,最终转为js命令:
"javascript:WebViewJavascriptBridge._handleMessageFromNative('%s');",参数为json;
最终在java主线程中调用loadUrl方法,去执行WebViewJavascriptBridge.js中的方法_handleMessageFromNative;
WebViewJavascriptBridge.js
//提供给native调用,receiveMessageQueue 在会在页面加载完后赋值为null,所以function _handleMessageFromNative(messageJSON) { console.log(messageJSON); if (receiveMessageQueue && receiveMessageQueue.length > 0) { receiveMessageQueue.push(messageJSON); } else { _dispatchMessageFromNative(messageJSON); } }
在webview加载完js,即onPageFinished方法后,receiveMessageQueue被置为null,所以这里直接执行了_dispatchMessageFromNative方法;
//提供给native使用,function _dispatchMessageFromNative(messageJSON) { setTimeout(function() { var message = JSON.parse(messageJSON); var responseCallback; //java call finished, now need to call js callback function if (message.responseId) { responseCallback = responseCallbacks[message.responseId]; if (!responseCallback) { return; } responseCallback(message.responseData); delete responseCallbacks[message.responseId]; } else { //直接发送 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]; } //查找指定handler try { handler(message.data, responseCallback); } catch (exception) { if (typeof console != 'undefined') { console.log("WebViewJavascriptBridge: WARNING: javascript handler threw.", message, exception); } } } }); }
(若responseId不为空,意味着js调用Native并且js有回调,这里表明Native将js回调需要的数据传过来了,从回调函数队列里根据responseId取出回调函数,如果该函数不为空,执行该回调函数,并移除回调函数队列里的该回调函数;)
该方法中,首先将json参数转为Message对象;
Native调用Js时没有responseId,所以直接跳转到else分支,判断callbackId,即Native是否需要js返回数据,如果需要,则初始化一个回调函数,里面调用_doSend方法,将responseId和responseData封装到message中,放入消息队列里;
从messageHandlers中通过handlerName匹配对应的handler(即在Js注册的时候设置的);执行该方法,参数为message中的data,即native中传递的data,以及上面初始化的回调函数;
这里结合H5注册接口说一下:
WebViewJavascriptBridge.registerHandler("functionInJs", function(data, responseCallback) { ... responseCallback(responseData); // 为Native返回数据});
WebViewJavascriptBridge.js #
function registerHandler(handlerName, handler) { messageHandlers[handlerName] = handler; }
可以看到这里在H5页面中注册的供Native调用的方法被添加到messageHandlers队列中,key值为方法名;所以上面取出的handler即为该注册的方法中定义的回调方法;其中data为Java端传来的data,responseCallback为上面初始化的function:
responseCallback = function(responseData) { _doSend({ responseId: callbackResponseId, responseData: responseData }); };
再看一下_doSend方法:
//sendMessage add message, 触发native处理 sendMessagefunction _doSend(message, responseCallback) { ... sendMessageQueue.push(message); messagingIframe.src = CUSTOM_PROTOCOL_SCHEME + '://' + QUEUE_HAS_MESSAGE; }
将message对象存入sendMessageQueue队列,改变iframe的src属性,触发Java端WebViewClient的shouldOverrideUrlLoading方法执行;
src=”yy://__QUEUE_MESSAGE__/”;
其实这里是相当于Js跟Webview定义了一个协议,协议为该src,当webview拦截url时,如果是这个已经定义好的协议,则做相应的处理;
回到BridgeWebViewClient类的shouldOverrideUrlLoading方法中:
@Overridepublic boolean shouldOverrideUrlLoading(WebView view, String url) { ... if (url.startsWith(BridgeUtil.YY_RETURN_DATA)) { // 如果是返回数据 webView.handlerReturnData(url); return true; } else if (url.startsWith(BridgeUtil.YY_OVERRIDE_SCHEMA)) { // webView.flushMessageQueue(); return true; } else { return super.shouldOverrideUrlLoading(view, url); } }
拦截1:url是以"yy://return/"开头的,调用BridgeWebView的handlerReturnData方法,这时是js为Native端返回数据;
拦截2:url是以"yy://"开头的,调用BridgeWebView的flushMessageQueue方法,去刷新消息队列;
这里由于url是满足第二条,所以先看flushMessageQueue方法:
BridgeWebView#flushMessageQueue:
void flushMessageQueue() { if (Thread.currentThread() == Looper.getMainLooper().getThread()) { loadUrl(BridgeUtil.JS_FETCH_QUEUE_FROM_JAVA, new CallBackFunction() { @Override public void onCallBack(String data) { ... } }); } }
该方法要在主线程执行,调用loadUrl方法:
private void loadUrl(String jsUrl, CallBackFunction returnCallback) { this.loadUrl(jsUrl); responseCallbacks.put(BridgeUtil.parseFunctionName(jsUrl), returnCallback); }
JS_FETCH_QUEUE_FROM_JAVA = "javascript:WebViewJavascriptBridge._fetchQueue();"
即调用Js的_fetchQueue方法,将创建的回调对象,以_fetchQueue为key值存入responseCallbacks中;
触发Js的_fetchQueue方法去返回数据,在Native去根据回调解析数据做出相应的处理;
WebViewJavascriptBridge.js # _fetchQueue:
// 提供给native调用,该函数作用:获取sendMessageQueue返回给native,由于android不能直接获取返回的内容,所以使用url shouldOverrideUrlLoading 的方式返回内容function _fetchQueue() { var messageQueueString = JSON.stringify(sendMessageQueue); sendMessageQueue = []; //android can't read directly the return data, so we can reload iframe src to communicate with java messagingIframe.src = CUSTOM_PROTOCOL_SCHEME + '://return/_fetchQueue/' + encodeURIComponent(messageQueueString); }
在该方法中,首先将js需要回传给Native的所有数据sendMessageQueue转为json,然后触发Native拦截url处理消息,url = “yy://return/_fetchQueue/returncontent”;
这里拦截到该url,执行handlerReturnData方法:
BridgeWebView # handlerReturnData:
void handlerReturnData(String url) { String functionName = BridgeUtil.getFunctionFromReturnUrl(url); CallBackFunction f = responseCallbacks.get(functionName); String data = BridgeUtil.getDataFromReturnUrl(url); if (f != null) { f.onCallBack(data); responseCallbacks.remove(functionName); return; } }
从url中获取js传来的方法名以及Js传来的值,从responseCallbacks队列中根据方法名取出回调函数接口对象(该回调对象是在上面存入的key值为_fetchQueue的回调对象),如果回调接口对象不为空,则调用其onCallBack函数将js传来的数据返回给Native端,将该回调函数对象从responseCallbacks队列中移除;
这里的回调即flushMessageQueue方法中在loadUrl中设置的回调函数:
loadUrl(BridgeUtil.JS_FETCH_QUEUE_FROM_JAVA, new CallBackFunction() { @Override public void onCallBack(String data) { // deserializeMessage List<Message> list = null; try { list = Message.toArrayList(data); } catch (Exception e) { ... } ... // 判空 for (int i = 0; i < list.size(); i++) { Message m = list.get(i); String responseId = m.getResponseId(); // 是否是response if (!TextUtils.isEmpty(responseId)) { CallBackFunction function = responseCallbacks.get(responseId); String responseData = m.getResponseData(); function.onCallBack(responseData); responseCallbacks.remove(responseId); } else { ... } } } });
由于这里是在js _fetchQueue方法中将整个消息队列都返回来了,所以需要遍历Message集合,找到对应需要的那一条;取出responseId,我们要取的消息是带有responseId的(Native调用了js并需要回调),这个responseId其实就是一开始java需要回调时生成的callbackId,根据这个callbackId从responseCallbacks取出最开始存入的回调对象 并且执行该回调方法,在Native端拿到数据并做相应的处理;
Js调用Native
Native为Js注册调用接口:
mBridgeWebView.registerHandler("submitFromWeb", new BridgeHandler() { @Override public void handler(String data, final CallBackFunction function) { ... } });
BridgeWebView # registerHandler:
public void registerHandler(String handlerName, BridgeHandler handler) { if (handler != null) { messageHandlers.put(handlerName, handler); } }
注册供Js调用的接口方法,并设置回调,如果回调不为空,将回调方法放入messageHandlers队列中,key值为定义的方法名;
Js调用接口:
WebViewJavascriptBridge.callHandler('submitFromWeb', data, function(responseData) { ... });
WebViewJavascriptBridge.js中:
function callHandler(handlerName, data, responseCallback) { _doSend({ handlerName: handlerName, data: data }, responseCallback); }
返回到WebViewJavascriptBridge # _doSend方法中,将Js端的responseCallback回调函数放入responseCallbacks队列中,key值为生成的唯一标识callbackId,并为message对象设置callbackId,触发Native端去重载url并拦截;
之后的动作与Native中调Js一样,shouldOverrideUrlLoading中拦截,执行flushMessageQueue,loadUrl,Js#_fetchQueue方法,生成回调,保存responseCallbacks中,后面继续执行handlerReturnData,接着看loadUrl中的回调,这次由于js传来的消息没有responseId,直接看else分支,即上文中省略号的地方:
if (!TextUtils.isEmpty(responseId)) { ... } else { CallBackFunction responseFunction = null; // if had callbackId final String callbackId = m.getCallbackId(); if (!TextUtils.isEmpty(callbackId)) { responseFunction = new CallBackFunction() { @Override public void onCallBack(String data) { Message responseMsg = new Message(); responseMsg.setResponseId(callbackId); responseMsg.setResponseData(data); queueMessage(responseMsg); } }; } else { responseFunction = new CallBackFunction() { @Override public void onCallBack(String data) { // do nothing } }; } BridgeHandler handler; if (!TextUtils.isEmpty(m.getHandlerName())) { handler = messageHandlers.get(m.getHandlerName()); } else { handler = defaultHandler; } if (handler != null){ handler.handler(m.getData(), responseFunction); } }
获取callbackId,如果为空,直接默认不做处理;
不为空则说明Js调用了Native,需要Native回调,创建一个回调函数,最后从消息中取出方法名去匹配Native之前注册的方法,如果不为空,则调用该对象的回调方法;
上面Native回调不为空时创建的回调:
responseFunction = new CallBackFunction() { @Override public void onCallBack(String data) { Message responseMsg = new Message(); responseMsg.setResponseId(callbackId); responseMsg.setResponseData(data); queueMessage(responseMsg); } };
作者:丿北纬91度灬
链接:https://www.jianshu.com/p/a31ffedb65a8
共同学习,写下你的评论
评论加载中...
作者其他优质文章