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WebViewJavascriptBridge－Obj-C和JavaScript互通消息的桥梁

译者：@coderyi9

本文翻译自Marcus Westin的开源框架WebViewJavascriptBridge的readme,英文原文链接 https://github.com/marcuswestin/WebViewJavascriptBridge .

WebViewJavascriptBridge是Obj-C和JavaScript通过UIWebViews/WebViews互通消息的一个iOS/OSX的桥梁. 如果你喜欢WebViewJavascriptBridge,你可能也想check out WebViewProxy .

Obj-C和JavaScript原理简单说一下，Obj-C调用JavaScript很简单，可以通过webview的stringByEvaluatingJavaScriptFromString:方法调用JavaScript代码；JavaScript调用Obj-C，则是通过web view的代理方法shouldStartLoadWithRequest：来接收JavaScript的网络请求从而实现调用。

正在使用WebViewJavascriptBridge的项目

有很多的公司和项目在使用WebViewJavascriptBridge.这个列表不完整,你可以随意添加.

Facebook Messenger
Facebook Paper
Yardsale
EverTrue
Game Insight
Altralogica
Sush.io
Flutterby Labs
JD Media’s 鼎盛中华
Dojo4’s Imbed
CareZone
Hemlig

安装& 例子 (iOS & OSX)

首先打开Example Apps文件夹.打开iOS或者OSX的工程然后点击运行.

在你自己的工程中用WebViewJavascriptBridge:

1) 拖动 WebViewJavascriptBridge 文件夹到你的工程中.

在出现的对话框中, 取消 (我觉得应该是选中)”Copy items into destination group’s folder” 并且选择 “Create groups for any folders”

2) 引入头文件并且申明一个属性:

#import "WebViewJavascriptBridge.h"  ...  @property WebViewJavascriptBridge* bridge;

3) 实例化WebViewJavascriptBridge并且带上一个UIWebView (iOS)或者WebView (OSX):

self.bridge = [WebViewJavascriptBridge bridgeForWebView:webView handler:^(id data, WVJBResponseCallback responseCallback) { NSLog(@"Received message from javascript: %@", data); responseCallback(@"Right back atcha"); }];

4) 首先从ObjC到javascript发送一些消息:

[self.bridge send:@"Well hello there"]; [self.bridge send:[NSDictionary dictionaryWithObject:@"Foo" forKey:@"Bar"]]; [self.bridge send:@"Give me a response, will you?" responseCallback:^(id responseData) { NSLog(@"ObjC got its response! %@", responseData); }];

5) 然后,看看javascript这边:

function connectWebViewJavascriptBridge(callback) { if (window.WebViewJavascriptBridge) { callback(WebViewJavascriptBridge) } else { document.addEventListener('WebViewJavascriptBridgeReady', function() { callback(WebViewJavascriptBridge) }, false) } } connectWebViewJavascriptBridge(function(bridge) { /* Init your app here */ bridge.init(function(message, responseCallback) { alert('Received message: ' + message)    if (responseCallback) { responseCallback("Right back atcha") } }) bridge.send('Hello from the javascript') bridge.send('Please respond to this', function responseCallback(responseData) { console.log("Javascript got its response", responseData) }) })

Contributors & Forks

Contributors: https://github.com/marcuswestin/WebViewJavascriptBridge/graphs/contributors

Forks: https://github.com/marcuswestin/WebViewJavascriptBridge/network/members

API 参考

ObjC API

[WebViewJavascriptBridge bridgeForWebView: (UIWebView/WebView*)webview handler:(WVJBHandler)handler]

[WebViewJavascriptBridge bridgeForWebView:

(UIWebView/WebView*)webview webViewDelegate:

(UIWebViewDelegate*)webViewDelegate handler:(WVJBHandler)handler]

给web view创建一个javascript的桥梁.

假如javascript需要一个反馈,那么 WVJBResponseCallback 不能为 nil .

当然,通过 webViewDelegate:(UIWebViewDelegate*)webViewDelegate 你可以得到 web view的生命周期事件 .

例子:

[WebViewJavascriptBridge bridgeForWebView:webView handler:^(id data, WVJBResponseCallback responseCallback) { NSLog(@"Received message from javascript: %@", data); if (responseCallback) { responseCallback(@"Right back atcha"); } }] [WebViewJavascriptBridge bridgeForWebView:webView webViewDelegate:self handler:^(id data, WVJBResponseCallback responseCallback) { /* ... */ }];

[bridge send:(id)data]

[bridge send:(id)data responseCallback:(WVJBResponseCallback)responseCallback]

发送一个消息给javascript. 并且在发送消息成功后可以通过 responseCallback block做出一些反应.

例子:

[self.bridge send:@"Hi"]; [self.bridge send:[NSDictionary dictionaryWithObject:@"Foo" forKey:@"Bar"]]; [self.bridge send:@"I expect a response!" responseCallback:^(id responseData) { NSLog(@"Got response! %@", responseData); }];

[bridge registerHandler:(NSString*)handlerName handler: (WVJBHandler)handler]

注册一个叫做 handlerName 的handler. javascript能够通过 WebViewJavascriptBridge.callHandler(“handlerName”) 调起这个handler.

例子:

[self.bridge registerHandler:@"getScreenHeight" handler:^(id data, WVJBResponseCallback responseCallback) { responseCallback([NSNumber numberWithInt:[UIScreen mainScreen].bounds.size.height]); }];

[bridge callHandler:(NSString*)handlerName data:(id)data]

[bridge callHandler:(NSString*)handlerName data:(id)data responseCallback:(WVJBResponseCallback)callback]

调起javascript叫做 handlerName的handler. 在调用 handler成功后可以通过responseCallback block做出反应.

例子:

[self.bridge callHandler:@"showAlert" data:@"Hi from ObjC to JS!"]; [self.bridge callHandler:@"getCurrentPageUrl" data:nil responseCallback:^(id responseData) { NSLog(@"Current UIWebView page URL is: %@", responseData); }];

定义 bundle

WebViewJavascriptBridge 要求 WebViewJavascriptBridge.js.txt 文件嵌入到web view来创建一个在JS这边的桥梁.标准的实现是用 mainBundle 找到这个文件.如果你建立一个静态库并且你把这个文件放在其他地方,你可以用下面的方法找 WebViewJavascriptBridge.js.txt 文件:

[WebViewJavascriptBridge bridgeForWebView:

(UIWebView/WebView*)webView webViewDelegate:

(UIWebViewDelegate*)webViewDelegate handler:(WVJBHandler)handler

resourceBundle:(NSBundle*)bundle

例子:

[WebViewJavascriptBridge bridgeForWebView:_webView                           webViewDelegate:self                                   handler:^(id data, WVJBResponseCallback responseCallback) { NSLog(@"Received message from javascript: %@", data);                                   }                            resourceBundle:[NSBundle bundleWithURL:[[NSBundle mainBundle] URLForResource:@"ResourcesBundle" withExtension:@"bundle"]] ];

Javascript API

document.addEventListener(‘WebViewJavascriptBridgeReady’,

function onBridgeReady(event) { … }, false)

一直等待 WebViewJavascriptBridgeReady DOM 事件.

例子:

document.addEventListener('WebViewJavascriptBridgeReady', function(event) { var bridge = event.bridge // Start using the bridge }, false)

bridge.init(function messageHandler(data, response) { … })

初始化这个桥. 这会调起 ‘WebViewJavascriptBridgeReady’ 的事件handler.

这个 messageHandler 函数会接收通过ObjC的 [bridge send:(id)data] 和 [bridge send:(id)data responseCallback:(WVJBResponseCallback)responseCallback] 方法发送的所有消息.

如果ObjC发送消息时有WVJBResponseCallback block,那么可以通过response对象发送消息.

例子:

bridge.init(function(data, responseCallback) { alert("Got data " + JSON.stringify(data)) if (responseCallback) { responseCallback("Right back atcha!") } })

bridge.send(“Hi there!”)

bridge.send({ Foo:”Bar” })

bridge.send(data, function responseCallback(responseData) { …

})

给ObjC发送消息. 在发送成功后可以通过 responseCallback 函数做出反应.

例子:

bridge.send("Hi there!") bridge.send("Hi there!", function(responseData) { alert("I got a response! "+JSON.stringify(responseData)) })

bridge.registerHandler(“handlerName”, function(responseData) { … })

注册一个叫做 handlerName 的handler. ObjC能够通过 [bridge callHandler:”handlerName” data:@”Foo”] 和 [bridge callHandler:”handlerName” data:@”Foo” responseCallback:^(id responseData) { … }] 两个方法调起这个handler.

例子:

bridge.registerHandler("showAlert", function(data) { alert(data) }) bridge.registerHandler("getCurrentPageUrl", function(data, responseCallback) { responseCallback(document.location.toString()) })