Cordova源碼深入分析-第五講__cordova

上一講將主體流程和架構都已經介紹完了，

再次查看整個代碼的時候，發現我還是有一些細節並沒有列舉出來，

例如之前只是介紹了addJavaScript一種方式實現通訊，實際上還有另一種通訊方式就是prompt方式，本講再次介紹一下。

prompt有幾個優勢：

1.可以避免掉android 4.2以下，js安全問題

2.可以實現同步調用，直接傳回值

下面開始分析代碼邏輯：

重複的位置，不再累述。直接來到cordova.js中

define("cordova/android/nativeapiprovider", function(require, exports, module) {var nativeApi = this._cordovaNative || require('cordova/android/promptbasednativeapi');//這裡其實如果沒有定義_cordovaNative就會走promptvar currentApi = nativeApi;module.exports = {    get: function() { return currentApi; },    setPreferPrompt: function(value) {        currentApi = value ? require('cordova/android/promptbasednativeapi') : nativeApi;    },    // Used only by tests.    set: function(value) {        currentApi = value;    }};});

而在使用prompt方式的時候，方法都是一樣的。

define("cordova/android/promptbasednativeapi", function(require, exports, module) {module.exports = {    exec: function(bridgeSecret, service, action, callbackId, argsJson) {        return prompt(argsJson, 'gap:'+JSON.stringify([bridgeSecret, service, action, callbackId]));//直接進入java端,程式碼片段1    },    setNativeToJsBridgeMode: function(bridgeSecret, value) {        prompt(value, 'gap_bridge_mode:' + bridgeSecret);    },    retrieveJsMessages: function(bridgeSecret, fromOnlineEvent) {        return prompt(+fromOnlineEvent, 'gap_poll:' + bridgeSecret);    }};});

程式碼片段1：SystemWebChromeClient.java

    @Override    public boolean onJsPrompt(WebView view, String origin, String message, String defaultValue, final JsPromptResult result) {        // Unlike the @JavascriptInterface bridge, this method is always called on the UI thread.        String handledRet = parentEngine.bridge.promptOnJsPrompt(origin, message, defaultValue);//程式碼片段2        if (handledRet != null) {            result.confirm(handledRet);        } else {            dialogsHelper.showPrompt(message, defaultValue, new CordovaDialogsHelper.Result() {                @Override                public void gotResult(boolean success, String value) {                    if (success) {                        result.confirm(value);                    } else {                        result.cancel();                    }                }            });        }        return true;    }

程式碼片段2：CordovaBridge.java

    public String promptOnJsPrompt(String origin, String message, String defaultValue) {        if (defaultValue != null && defaultValue.length() > 3 && defaultValue.startsWith("gap:")) {            JSONArray array;            try {                array = new JSONArray(defaultValue.substring(4));                int bridgeSecret = array.getInt(0);                String service = array.getString(1);                String action = array.getString(2);                String callbackId = array.getString(3);                String r = jsExec(bridgeSecret, service, action, callbackId, message);//執行與之前介紹的邏輯一樣的流程中了                return r == null ? "" : r;            } catch (JSONException e) {                e.printStackTrace();            } catch (IllegalAccessException e) {                e.printStackTrace();            }            return "";        }        // Sets the native->JS bridge mode.        else if (defaultValue != null && defaultValue.startsWith("gap_bridge_mode:")) {            try {                int bridgeSecret = Integer.parseInt(defaultValue.substring(16));                jsSetNativeToJsBridgeMode(bridgeSecret, Integer.parseInt(message));            } catch (NumberFormatException e){                e.printStackTrace();            } catch (IllegalAccessException e) {                e.printStackTrace();            }            return "";        }        // Polling for JavaScript messages        else if (defaultValue != null && defaultValue.startsWith("gap_poll:")) {            int bridgeSecret = Integer.parseInt(defaultValue.substring(9));            try {                String r = jsRetrieveJsMessages(bridgeSecret, "1".equals(message));                return r == null ? "" : r;            } catch (IllegalAccessException e) {                e.printStackTrace();            }            return "";        }        else if (defaultValue != null && defaultValue.startsWith("gap_init:")) {            // Protect against random iframes being able to talk through the bridge.            // Trust only pages which the app would have been allowed to navigate to anyway.            if (pluginManager.shouldAllowBridgeAccess(origin)) {                // Enable the bridge                int bridgeMode = Integer.parseInt(defaultValue.substring(9));                jsMessageQueue.setBridgeMode(bridgeMode);                // Tell JS the bridge secret.                int secret = generateBridgeSecret();                return ""+secret;            } else {                LOG.e(LOG_TAG, "gap_init called from restricted origin: " + origin);            }            return "";        }        return null;    }

到這裡整個流程又銜接上了，就不在廢話了