完美解决Error initializing Cordova:Class not found

今天在测试PhoneGap官方提供的例子，运行到手机上一直弹出Error initializing Cordova:Class not found...网上资料不多，大部分都是说res/xml/config.xml配置有问题，导致找不到类...

然而，细心的查了一遍res/xml/config.xml，并没有发现有错误的地方，那么是什么原因呢？冥思苦想，甚至把cordova.android.js细看了一遍，还是没发现错误，最后，定位到了org.apache.cordova.api.PluginManager这个类，控制台报了这么一段错误：

错误是说config.xml找不到，但是config.xml明明就存在，而且在R文件里面也能找到

这下有意思了，我们来org.apache.cordova.api.PluginManager类里面的loadPlugins()方法的第一行

    /**
     * Load plugins from res/xml/config.xml
     */
    public void loadPlugins() {
        int id = this.ctx.getActivity().getResources().getIdentifier("config", "xml", this.ctx.getActivity().getClass().getPackage().getName()); // 就是这一句，返回的id是0，也就是这样的方式并无法找到config.xml
        //int id = org.apache.cordova.R.xml.config; // 替换成这一句，问题搞定~
    	Log.e(TAG, "。。。。"+id); // 这边id Log输出就知道了...真是个坑
        if (id == 0) {
            this.pluginConfigurationMissing();
            //We have the error, we need to exit without crashing!
            return;
        }
        XmlResourceParser xml = this.ctx.getActivity().getResources().getXml(id);
        int eventType = -1;
        String service = "", pluginClass = "", paramType = "";
        boolean onload = false;
        boolean insideFeature = false;
        while (eventType != XmlResourceParser.END_DOCUMENT) {
            if (eventType == XmlResourceParser.START_TAG) {
                String strNode = xml.getName();
                //This is for the old scheme
                if (strNode.equals("plugin")) {
                    service = xml.getAttributeValue(null, "name");
                    pluginClass = xml.getAttributeValue(null, "value");
                    Log.d(TAG, "<plugin> tags are deprecated, please use <features> instead. <plugin> will no longer work as of Cordova 3.0");
                    onload = "true".equals(xml.getAttributeValue(null, "onload"));
                }
                //What is this?
                else if (strNode.equals("url-filter")) {
                    this.urlMap.put(xml.getAttributeValue(null, "value"), service);
                }
                else if (strNode.equals("feature")) {
                    //Check for supported feature sets  aka. plugins (Accelerometer, Geolocation, etc)
                    //Set the bit for reading params
                    insideFeature = true;
                    service = xml.getAttributeValue(null, "name");
                }
                else if (insideFeature && strNode.equals("param")) {
                    paramType = xml.getAttributeValue(null, "name");
                    if (paramType.equals("service")) // check if it is using the older service param
                        service = xml.getAttributeValue(null, "value");
                    else if (paramType.equals("package") || paramType.equals("android-package"))
                        pluginClass = xml.getAttributeValue(null,"value");
                    else if (paramType.equals("onload"))
                        onload = "true".equals(xml.getAttributeValue(null, "value"));
                }
            }
            else if (eventType == XmlResourceParser.END_TAG)
            {
                String strNode = xml.getName();
                if (strNode.equals("feature") || strNode.equals("plugin"))
                {
                    PluginEntry entry = new PluginEntry(service, pluginClass, onload);
                    this.addService(entry);

                    //Empty the strings to prevent plugin loading bugs
                    service = "";
                    pluginClass = "";
                    insideFeature = false;
                }
            }
            try {
                eventType = xml.next();
            } catch (XmlPullParserException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

所以，把寻找config.xml这句直接替换为 int id = org.apache.cordova.R.xml.config;

那么为什么会找不到config.xml呢？Log输出一下可以发现，this.ctx.getActivity().getClass().getPackage().getName() 这句话返回的包名并不正确，而是我们测试工程里面的一个包名...

为什么会这样呢？因为this.ctx，这个是一个CordovaInterface类型，是一个接口，而最终真正实现它的是org.apache.cordova.test.actions.CordovaActivity这个类，那么我们来看一下他的继承关系：

org.apache.cordova.api.CordovaInterface

-> org.apache.cordova.CordovaActivity

-> org.apache.cordova.DroidGap

-> org.apache.cordova.test.actions.CordovaActivity

这么看来，出现Class not found的问题也就不奇怪了...