背景

来自我司业务方要求，需开发一款APP。但由于时间限制，只能采取套壳app方式，即原生app内嵌webview展示前端页面。本文主要记述JavaScript与原生app间通信，以及内嵌webview开发时，前端方面可能踩的一些坑。

技术架构

前端：vue+vuex+vue-router+webpack全家桶开发
后端：Node(express框架)简单转发接口至java-真后端接口。

js与原生通信

采用jsBridge技术和原生APP通信
android 传送门 和ios 传送门，因为两个平台初始化方式不同，因此在开发过程中，需针对每个平台做对应操作。 具体做法

1. 按照库要求，声明好初始化函数

//android
function connectWebViewJavascriptBridge{if (window.WebViewJavascriptBridge) {//do your work here} else {document.addEventListener('WebViewJavascriptBridgeReady', function(){//do your work here},false);}
}
//ios
setupWebViewJavascriptBridge(function(bridge){/* Initialize your app here */bridge.registerHandler('JS Echo', function(data, responseCallback){console.log("JS Echo called with:", data)responseCallback(data)})bridge.callHandler('ObjC Echo', {'key':'value'}, function responseCallback(responseData){console.log("JS received response:", responseData)})
})

2. 初始化，得到bride对象。则可调用原生app已定义方法或注册js方法供原生调用

setupWebViewJavascriptBridge(function(bridge){/* Initialize your app here */bridge.registerHandler('JS Echo', function(data, responseCallback){console.log("JS Echo called with:", data)responseCallback(data) //})bridge.callHandler('ObjC Echo', {'key':'value'}, function responseCallback(responseData){console.log("JS received response:", responseData)})
})

Tips:

• Android 与 IOS初化方式不同，需要判断平台后再进行调用。另外Android初始化时，需额外引入一些方法。
• 调用Android定义方法时，返回值只能为字符串。而IOS可为JSON对象。需要在callHandler时，对返回值进行封装处理或统一规定好数据格式。
• 完整业务代码文末给出

踩坑

1. 调用bridge属性方法registerHandler,callHandler，在回调函数内处理页面逻辑时，最好避免使用this
2. vue组件下，在registerHandler，callHandler回调函数内使用vue实例时,无法获取实例对象。正确做法是在回调函数内调用window对象下方法，再通过该方法去使用vue实例对象。

//vue 组件
mounted(){window['handleServicePushMessage'] = (res) => {vm.handleServicePushMessage(res)};bridge.registerHandler("servicePushMessage", function (data, responseCallback){handleServicePushMessage(data)responseCallback(data) //可传值到App})
}

3. 桌面推送消息点击跳转至App内详情情况下，js注册方法供调用时，可能会引起重复调用的问题。故在方法内需做好重复调用判断
4. IOS-12.0版本下，在有输入框的页面，输入时软键盘会顶起webview，当失去焦点时，webview不会自动回弹。需调用APP做处理拉回界面。

//解决ios 12版本 ui不自动回拉问题
document.addEventListener('focusout', function (event){let curTarget = event.target || event.srcElement;let isInput= ['input', 'textarea'];//处理页面连续点击都为输入框的情况let curTargetTagName= curTarget.tagName.toLowerCase();if (isInput.includes(curTargetTagName)) {//事件处理//延迟获取activeElement再进行判断setTimeout(function (){let activeEle = document.activeElement;let activeEleTagName= activeEle.tagName.toLowerCase();if (!isInput.includes(activeEleTagName)) {// console.log(document.activeElement.tagName);//调用app桥拉回webviewperformMethod('scrollTotop', null);}}, 200);}
}, true);

5.当js调用app不存在的桥时，无法捕获异常，页面不会报错
6.导航栏显示问题，由于项目时间紧迫，并且app开发人员不承载太多开发任务，所以路由控制放在前端处理。此时就有导航栏电池时间栏的适配问题。本项目采用顶部下调20PX处理，电池时间栏字体颜色的控制也是通过桥调用来设置；另外iPhone X适配另外处理。
7.当app加载完网页时，js立即调用原生方法桥时，可能出现原生方法桥未注册完情况。故特殊情况需延迟调用桥操作。

完整代码

/*判断平台*/
function (window){window.device = {};var ua = navigator.userAgent;var android = ua.match(/(Android);?[\s\/]+([\d.]+)?/);var ipad = ua.match(/(iPad).*OS\s([\d_]+)/);var ipod = ua.match(/(iPod)(.*OS\s([\d_]+))?/);var iphone = !ipad && ua.match(/(iPhone\sOS)\s([\d_]+)/);device.ios = device.android = device.iphone = device.ipad = device.androidChrome = false;if (android) {device.os = 'android';device.osVersion = android[2];device.android = true;device.androidChrome = ua.toLowerCase().indexOf('chrome') >= 0}if (ipad || iphone || ipod) {device.os = 'ios';device.ios = true}
}(window)
/*引入Android需要的初始化，IOS不执行，如执行IOS端桥调用会受影响*/
(function (){if (window.WebViewJavascriptBridge || device.ios) {return false;}var messagingIframe;var sendMessageQueue = [];var receiveMessageQueue = [];var messageHandlers = {};var CUSTOM_PROTOCOL_SCHEME = 'yy';var QUEUE_HAS_MESSAGE = '__QUEUE_MESSAGE__/';var responseCallbacks = {};var uniqueId = 1;function _createQueueReadyIframe(doc){messagingIframe = doc.createElement('iframe');messagingIframe.style.display = 'none';doc.documentElement.appendChild(messagingIframe);}/*set default messageHandler*/function init(messageHandler){if (WebViewJavascriptBridge._messageHandler) {throw new Error('WebViewJavascriptBridge.init called twice');}WebViewJavascriptBridge._messageHandler = messageHandler;var receivedMessages = receiveMessageQueue;receiveMessageQueue = null;for (var i = 0; i < receivedMessages.length; i++) {_dispatchMessageFromNative(receivedMessages[i]);}}function send(data, responseCallback){_doSend({data: data}, responseCallback);}function registerHandler(handlerName, handler){messageHandlers[handlerName] = handler;}function callHandler(handlerName, data, responseCallback){_doSend({handlerName: handlerName, data: data}, responseCallback);}/*sendMessage add message, 触发native处理 sendMessage*/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;}/* 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);}/*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);}}}});}/*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){if (receiveMessageQueue && receiveMessageQueue.length > 0) {receiveMessageQueue.push(messageJSON);} else {_dispatchMessageFromNative(messageJSON);}}var WebViewJavascriptBridge = window.WebViewJavascriptBridge = {init: init,send: send,registerHandler: registerHandler,callHandler: callHandler,_fetchQueue: _fetchQueue,_handleMessageFromNative: _handleMessageFromNative};var doc = document;_createQueueReadyIframe(doc);var readyEvent = doc.createEvent('Events');readyEvent.initEvent('WebViewJavascriptBridgeReady');readyEvent.bridge = WebViewJavascriptBridge;doc.dispatchEvent(readyEvent);
})();
/*Android端初始化函数*/
function connectWebViewJavascriptBridge(callback){if (window.WebViewJavascriptBridge) {callback(WebViewJavascriptBridge)} else {document.addEventListener('WebViewJavascriptBridgeReady', function (){callback(WebViewJavascriptBridge)}, false);}
}
/*IOS端初始化函数*/
function setupWebViewJavascriptBridge(callback){if (window.WebViewJavascriptBridge) {return callback(WebViewJavascriptBridge)} else {}if (window.WVJBCallbacks) {return window.WVJBCallbacks.push(callback)}window.WVJBCallbacks = [callback];var WVJBIframe = document.createElement('iframe');WVJBIframe.style.display = 'none';WVJBIframe.src = 'wvjbscheme://__BRIDGE_LOADED__';document.documentElement.appendChild(WVJBIframe);setTimeout(function (){document.documentElement.removeChild(WVJBIframe)}, 0)
}
if(device.ios){setupWebViewJavascriptBridge(function(bridge){/*挂载上全局对象*/window.BRIDGE= brige;})
}
if(device.android){connectWebViewJavascriptBridge(function(bridge){/*挂载上全局对象*/window.BRIDGE= brige;})
}