补充Cordova流程源码

从js到native的流程源码补充说明：

事件从js触发到native时，通过注入的对象[SystemExposedJsApi &@JavascriptInterface 注解标记的方法 ]
先初始化native，然后再去loadurl
1.注入native端xml文件中声明的 plugin【xml提供了后续扩展解耦plugin添加的入口】，解析xml并用全局map维护，指定onload为true的先行初始化，其他native端plugin 懒加载

... // CordovaActivity 的onCreate
ArrayList<PluginEntry> pluginEntity = (ArrayList<PluginEntry>)getIntent().getSerializableExtra("pluginEntity"); //第一次扩展插件的添加方式
//这里是corodva native插件的懒加载注入入口
        loadConfig(pluginEntity);
...



// 加载xml中的native plugin入口  
@SuppressWarnings("deprecation")
    protected void loadConfig(ArrayList<PluginEntry> list) {
        ConfigXmlParser parser = new ConfigXmlParser();
        if (!CollectionUtils.isEmpty(list)) {
            parser.setDynamicEntity(list);
        }
        parser.parse(this);
        preferences = parser.getPreferences();
        preferences.setPreferencesBundle(getIntent().getExtras());
        launchUrl = parser.getLaunchUrl();
        //xml 解析得到native xml中声明的 plugin 包装对象map 并在下面loadUrl的 init方法中传递到PluginManager中
        pluginEntries = parser.getPluginEntries();
        Config.parser = parser;
    }

2.初始化webview的方法代理CordovaWebviewImpl以及 反射创建了SystemWebViewEngine[作为真正的webview和代理之间的bridge] ，SystemWebViewEngine 是Webview相关属性设置类

public void loadUrl(String url) {
    if (appView == null) {
        init();
    }

    // If keepRunning
    this.keepRunning = preferences.getBoolean("KeepRunning", true);

    appView.loadUrlIntoView(url, true);
}





//init方法调用到engine 的 init方法, 最后调用到 com.xxx.xxx.engine.SystemWebViewEngine#exposeJsInterface
private static void exposeJsInterface(WebView webView, CordovaBridge bridge) {
        if ((Build.VERSION.SDK_INT < Build.VERSION_CODES.JELLY_BEAN_MR1)) {
            LOG.i(TAG, "Disabled addJavascriptInterface() bridge since Android version is old.");
            // Bug being that Java Strings do not get converted to JS strings automatically.
            // This isn't hard to work-around on the JS side, but it's easier to just
            // use the prompt bridge instead.
            return;
        }
        SystemExposedJsApi exposedJsApi = new SystemExposedJsApi(bridge);
        //webview注入native端 SystemExposedJsApi的对象 ，并以 _cordovaNative为名在js端使用
        webView.addJavascriptInterface(exposedJsApi, "_cordovaNative");
    }



// com.xxx.xxx.core.CordovaActivity#init 方法提供了子类重写init方法
protected void init() {
        appView = makeWebView();
        createViews();
        if (!appView.isInitialized()) {
            appView.init(cordovaInterface, pluginEntries, preferences);
        }
        cordovaInterface.onCordovaInit(appView.getPluginManager());

        // Wire the hardware volume controls to control media if desired.
        String volumePref = preferences.getString("DefaultVolumeStream", "");
        if ("media".equals(volumePref.toLowerCase(Locale.ENGLISH))) {
            setVolumeControlStream(AudioManager.STREAM_MUSIC);
        }
    }



// ContainerActivity#makeWebView
@Override
    protected CordovaWebView makeWebView() {

            mSystemWebView = new NormalWebView(this);
            mEngine = new SystemWebViewEngine((NormalWebView)mSystemWebView);
            mFlWeb.addView((NormalWebView)mSystemWebView);

        mCordovaWebView = new CordovaWebViewImpl(mEngine);
        mSystemWebView.resetUserAgent( " " + userAgent);
        //这里抽象了 IWebview 【便于替换X5Webview等其他扩展WebView的实现】
        mSystemWebView.resetWebViewClient(this, mEngine);
        //同理在NormalWebview中注入了重写的WebViewClient和 WebChromeClient
        mSystemWebView.resetWebChromeClient(this, mEngine);
        return mCordovaWebView;
    }



//证书校验调用入口
com.xxx.xxx.impl.RedirectSystemWebViewClient#onReceivedSslError

@Override
            public void onReceivedSslError(WebView webView, SslErrorHandler handler, SslError sslError) {
//                super.onReceivedSslError(webView, handler, sslError); 注释父类实现
            //入口封装传入参数确定是否证书校验
                if (isCheck()) {
                    //检验证书颁发机构以及证书的合法性 证书确实是发给指定域名的且为当前设备的根证书所信任
                        if (SSLChecker.chkMySSLCNCertOCFT(sslError.getCertificate())) {
                            handler.proceed();  // 如果证书一致，忽略错误
                        } else {
                            LogUtil.w("xxx", "onReceivedSslError" + "cancel" + sslError);
                            handler.cancel();
                        }
//                    }
                } else {
                    handler.proceed();
                }
                if (client != null) {
                    client.onReceivedSslError();
                }
                LogUtil.w("xxx", "onReceivedSslError(NormalWebView.java:102)" );
            }
        });

3.初始化完成后，初始化js 部分 ….. 衔接部分

4.js调用native native响应并产生回调部分

// com.xxx.xxx.core.PluginManager#exec    
public void exec(final String service, final String action, final String callbackId, final String rawArgs) {
    //懒加载，根据协定传递指定key为service，初始化对应plugin【已初始化则直接取出】
        CordovaPlugin plugin = getPlugin(service);
        if (plugin == null) {
            LOG.d(TAG, "exec() call to unknown plugin: " + service);
//            PluginResult cr = new PluginResult(PluginResult.Status.CLASS_NOT_FOUND_EXCEPTION);
//            app.sendPluginResult(cr, callbackId);
            return;
        }
    //根据js端生成的callbackId 生成 native端的 CallbackContenxt对象，这个对象是native 回调js端，传递数据的起点
        CallbackContext callbackContext = new CallbackContext(callbackId, app);
        try {
            long pluginStartTime = System.currentTimeMillis();
            // 子plugin实现execute的返回值，action对应事件名,这里通过java多态找到CordovaPlugin的子实现类【即service映射的类】并execute
            boolean wasValidAction = plugin.execute(action, rawArgs, callbackContext);
            long duration = System.currentTimeMillis() - pluginStartTime;
            //提示在主线程执行过长时间，建议使用线程池异步
            if (duration > SLOW_EXEC_WARNING_THRESHOLD) {
                LOG.w(TAG, "THREAD WARNING: exec() call to " + service + "." + action + " blocked the main thread for " + duration + "ms. Plugin should use CordovaInterface.getThreadPool().");
            }//无效行为回调
            if (!wasValidAction) {
                PluginResult cr = new PluginResult(PluginResult.Status.INVALID_ACTION);
                callbackContext.sendPluginResult(cr);
            }
        } catch (JSONException e) {
            //异常回调
            PluginResult cr = new PluginResult(PluginResult.Status.JSON_EXCEPTION);
            callbackContext.sendPluginResult(cr);
        } catch (Exception e) {
            LOG.e(TAG, "Uncaught exception from plugin", e);
            callbackContext.error(e.getMessage());
        }
    }



//任意CordovaPlugin子类完成事件触发即执行execute后，通过方法传递的 CallbackContext回调
...
  public void success(JSONObject message) {
        sendPluginResult(new PluginResult(PluginResult.Status.OK, message));
    }
...//还有很多其他重载的success方法，可以兼容传递不同类型的数据类型，最终都会在PluginResult中完成封装，转换成最终传递到js的 payload string msg



public void sendPluginResult(PluginResult pluginResult) {
        synchronized (this) {
            if (finished) {
                LOG.w(LOG_TAG, "Attempted to send a second callback for ID: " + callbackId + "\nResult was: " + pluginResult.getMessage());
                return;
            } else {
        //如果执行过一次的事件 【finised 为 true】 下次不会再执行，如果keepcallback则可重复调用执行，回执到js端message process后也不会被移除全局的js callback数组【所以保持了两端的同步keepcallback能力】
                finished = !pluginResult.getKeepCallback();
            }
        }
        LogUtil.d("xxx", "sendPluginResult: "+callbackId+"-----"+pluginResult );
        webView.sendPluginResult(pluginResult, callbackId);
    }



//com.xxx.xxx.core.CordovaWebViewImpl#sendPluginResult
 @Override
    public void sendPluginResult(PluginResult cr, String callbackId) {
        // nativeToJsMessageQueue native生成发送到js端的消息维护类
        nativeToJsMessageQueue.addPluginResult(cr, callbackId);
    }

public void addPluginResult(PluginResult result, String callbackId) {
        if (callbackId == null) {
            LogUtil.e(LOG_TAG, "Got plugin result with no callbackId", new Throwable());
            return;
        }
        // Don't send anything if there is no result and there is no need to
        // clear the callbacks.
        boolean noResult = result.getStatus() == PluginResult.Status.NO_RESULT.ordinal();
        boolean keepCallback = result.getKeepCallback();
        if (noResult && keepCallback) {
            return;
        }
     // 将PluginResult 和 callbackId 封装成 JsMessage对象 [ JsMessage 是 NativeToJsMessageQueue 的内部类，JsMessage用于生成协议规则message的类]
        JsMessage message = new JsMessage(result, callbackId);
        if (FORCE_ENCODE_USING_EVAL) {
            StringBuilder sb = new StringBuilder(message.calculateEncodedLength() + 50);
            message.encodeAsJsMessage(sb);
            message = new JsMessage(sb.toString());
        }

        enqueueMessage(message);
    }

 private void enqueueMessage(JsMessage message) {
        synchronized (this) {
            if (activeBridgeMode == null) {
                LOG.d(LOG_TAG, "Dropping Native->JS message due to disabled bridge");
                return;
            }
            queue.add(message);
            if (!paused) {
                activeBridgeMode.onNativeToJsMessageAvailable(this);
            }
        }
    }


        @Override
        public void onNativeToJsMessageAvailable(final NativeToJsMessageQueue queue) {
            cordova.getActivity().runOnUiThread(new Runnable() {
                public void run() {
                    //这里在发送信息到js端前，先处理
                    String js = queue.popAndEncodeAsJs();
                    if (js != null) {
                        //最后调用 webview 的 evaluateJavascript方法，将处理过的带协议规则的信息传递到js端
                        engine.evaluateJavascript(js, null);
                    }
                }
            });
        }
    }

//完成封装的api方法
public String popAndEncodeAsJs() {
        synchronized (this) {
            int length = queue.size();
            if (length == 0) {
                return null;
            }
            int totalPayloadLen = 0;
            int numMessagesToSend = 0;
            for (JsMessage message : queue) {
                //计算长度
                int messageSize = message.calculateEncodedLength() + 50; // overestimate.
                //MAX_PAYLOAD_SIZE最大传递信息长度
                if (numMessagesToSend > 0 && totalPayloadLen + messageSize > MAX_PAYLOAD_SIZE && MAX_PAYLOAD_SIZE > 0) {
                    break;
                }
                totalPayloadLen += messageSize;
                numMessagesToSend += 1;
            }
            boolean willSendAllMessages = numMessagesToSend == queue.size();
            StringBuilder sb = new StringBuilder(totalPayloadLen + (willSendAllMessages ? 0 : 100));
            // Wrap each statement in a try/finally so that if one throws it does
            // not affect the next.
            for (int i = 0; i < numMessagesToSend; ++i) {
                //从队列中取出第一条JsMessage对象并移除
                JsMessage message = queue.removeFirst();
                if (willSendAllMessages && (i + 1 == numMessagesToSend)) {
                    message.encodeAsJsMessage(sb);
                } else {
                    sb.append("try{");
                    message.encodeAsJsMessage(sb);
                    sb.append("}finally{");
                }
            }
            if (!willSendAllMessages) {
                sb.append("window.setTimeout(function(){cordova.require('cordova/plugin/android/polling').pollOnce();},0);");
            }
            for (int i = willSendAllMessages ? 1 : 0; i < numMessagesToSend; ++i) {
                sb.append('}');
            }
            String ret = sb.toString();
            return ret;
        }
    }

// 转换成js能够执行的message【并包装回调js端的信息】
void encodeAsJsMessage(StringBuilder sb) {
            if (pluginResult == null) {
                sb.append(jsPayloadOrCallbackId);
            } else {
                int status = pluginResult.getStatus();
                boolean success = (status == PluginResult.Status.OK.ordinal()) || (status == PluginResult.Status.NO_RESULT.ordinal());
                // js端执行 cordova#callbackFromNative 该方法去处理包装的信息
                sb.append("cordova.callbackFromNative('")
                  .append(jsPayloadOrCallbackId)
                  .append("',")
                  .append(success)
                  .append(",")
                  .append(status)
                  .append(",[");
                switch (pluginResult.getMessageType()) {
                    case PluginResult.MESSAGE_TYPE_BINARYSTRING:
                        sb.append("atob('")
                          .append(pluginResult.getMessage())
                          .append("')");
                        break;
                    case PluginResult.MESSAGE_TYPE_ARRAYBUFFER:
                        sb.append("cordova.require('cordova/base64').toArrayBuffer('")
                          .append(pluginResult.getMessage())
                          .append("')");
                        break;
                    default:
                    sb.append(pluginResult.getMessage());
                }
                sb.append("],")
                  .append(pluginResult.getKeepCallback())
                  .append(");");
            }
        }

// cordova.callbackFromNative('XXXMessagePlugin1365781441',true,1,["{\"latitude\":31.181945,\"longitude\":121.365825}"],false





//com.xxx.xxx.core.CordovaPlugin#execute(java.lang.String, java.lang.String, com.xxx.xxx.core.CallbackContext) 
public boolean execute(String action, String rawArgs, CallbackContext callbackContext) throws JSONException {
        JSONArray args = new JSONArray(rawArgs);
        return execute(action, args, callbackContext);
    }

//com.xxx.xxx.core.CordovaPlugin#execute(java.lang.String, com.xxx.xxx.core.CordovaArgs, com.xxx.xxx.core.CallbackContext)
  public boolean execute(String action, CordovaArgs args, CallbackContext callbackContext) throws JSONException {
        mMCallbackContext = callbackContext;
        return true;
    }











     //额外添加解耦插件添加方式，xml中声明即可，在androidmanifest合并后，sdk启动时通过appinfo读取mete-data信息
         <meta-data
            android:name ="com.xxx.xxx.plugin.ThirdPartPlugin"
            android:value ="ContainerPlugin"/>

        <meta-data
            android:name ="com.xxx.xxx.plugin.ThirdPartPluginAdd"
            android:value ="ContainerPlugin"/>



 /**
     * 映射外置插件的key
     */
    public static final String PLUGIN_MODULE_VALUE = "ContainerPlugin";

    public ArrayList<PluginEntry> parseManifest(Context context) {
        ArrayList<PluginEntry> pluginList = new ArrayList<>();
        try {
            ApplicationInfo appInfo = context.getPackageManager().getApplicationInfo(context.getPackageName(), PackageManager.GET_META_DATA);
            if (appInfo.metaData!=null) {
                for(String key : appInfo.metaData.keySet()) {
                    if(PLUGIN_MODULE_VALUE.equals(appInfo.metaData.get(key))) {
                        String service = key.substring(key.lastIndexOf('.')+1);
                        PluginEntry entry = new PluginEntry(service, key, false);
                        pluginList.add(entry);
                    }
                }
            }
        } catch (PackageManager.NameNotFoundException e) {
            e.printStackTrace();
        }
        return pluginList;
    }