组件化框架设计之阿里巴巴开源路由框架——ARouter原理分析(一)

阿里P7移动互联网架构师进阶视频(每日更新中)免费学习请点击:https://space.bilibili.com/474380680

背景

当项目的业务越来越复杂,业务线越来越多的时候,就需要按照业务线去分不同的模块去开发,这样专门的人负责专门的业务模块,最终上线由壳工程去负责进行组合打包各个module,完成业务的快速迭代。整个过程会涉及到各个模块间进行通信,比如订单模块和个人中心模块,可能会需要频繁的传递数据和页面跳转,这个时候怎么去处理呢?我们能想到的方案就是采用类名反射,来动态创建需要跳转和交互的类,这样编译时就不会报错,运行时又可以完成模块间的交互。阿里巴巴推出的开源路由框架——ARouter就是基于反射和注解来解决这个问题的,本文不讲基本使用(基本使用在项目的github主页上已经将的非常详细了),通过分析整个路由过程来讲解它的基本原理。

说在前面

首先在我们需要用到的类的类名加上注解@Route(“/group/name”),注意这里需要至少两层路径(第一个是分组,第二个一般是类名)。这个注解就是代表这个类可以被其他模块找到的一个路径的注解,并且它是一个编译时注解,这就意味着在编译时就已经生成了相应的辅助类。ARouter把路由一共分为以下几类:

ACTIVITY(0, “android.app.Activity”), 
SERVICE(1, “android.app.Service”), 
PROVIDER(2, “com.alibaba.android.arouter.facade.template.IProvider”), 
CONTENT_PROVIDER(-1, “android.app.ContentProvider”), 
BOARDCAST(-1, “”), 
METHOD(-1, “”), 
FRAGMENT(-1, “android.app.Fragment”), 
UNKNOWN(-1, “Unknown route type”);

其中我们常用的就是ACTIVITY,PROVIDER,FRAGMENT这三个了,也基本上满足了我们模块化开发的需求。另外一点就是分组的概念,ARouter是按照组来进行整理的,也就是第一层的路径,所以前面说必须要两层路径,否则不知道归到哪里去,一般一个module按照模块名采用统一的分组标识。我们来看看注解生成的类(这里只包含了Activity,Fragment,Provider):

package com.alibaba.android.arouter.routes;
//。。。import省略
/**
 * DO NOT EDIT THIS FILE!!! IT WAS GENERATED BY AROUTER. */
public class ARouter$$Group$$Personal implements IRouteGroup {
  @Override
  public void loadInto(Map<String, RouteMeta> atlas) {
    atlas.put("/Personal/EARNING", RouteMeta.build(RouteType.ACTIVITY, PerEarningActivity.class, "/personal/earning", "personal", null, -1, -2147483648));
    //...省略Activity,Fragment
    atlas.put("/Personal/main", RouteMeta.build(RouteType.FRAGMENT, PerMainFragment.class, "/personal/main", "personal", null, -1, -2147483648));
    atlas.put("/Personal/service", RouteMeta.build(RouteType.PROVIDER, PerServiceImpl.class, "/personal/service", "personal", null, -1, -2147483648));
  }
}

以上就是所有注解的路径的信息集合,包含了所有的Activity,Fragment,Provider(一般一个module一个Provider就够用了,专门用来跟其他模块交互),并都以路径为key放到这个map中。

package com.alibaba.android.arouter.routes;
//。。。import省略
/**
 * DO NOT EDIT THIS FILE!!! IT WAS GENERATED BY AROUTER. */
public class ARouter$$Providers$$modlue_personal implements IProviderGroup {
  @Override
  public void loadInto(Map<String, RouteMeta> providers) {
    providers.put("com.tb.test.service.ModulePersonalService", RouteMeta.build(RouteType.PROVIDER, PerServiceImpl.class, "/Personal/service", "personal", null, -1, -2147483648));
  }
}

这个类是专门的Provider的索引的集合,所有的provider都被以全类名为索引放到一个map中。

package com.alibaba.android.arouter.routes;
//。。。import省略

/**
 * DO NOT EDIT THIS FILE!!! IT WAS GENERATED BY AROUTER. */
public class ARouter$$Root$$modlue_personal implements IRouteRoot {
  @Override
  public void loadInto(Map<String, Class<? extends IRouteGroup>> routes) {
    routes.put("Personal", ARouter$$Group$$Personal.class);
  }
}

这个类是所有的group的信息收集,全部都以group的名字为key,以注解生成的不同的group的类的class对象为value放入到一个map中。

总共就生成这三种类型的类,当然,如果你有不同的分组还会生成其他的类,不过都是这三种里面的一种。

完成了这些注解信息的收集,下面就会去使用这些信息来完成我们的跨模块交互了。

初始化过程

使用ARouter必须先要进行初始化:

if (isDebug()) { 
// These two lines must be written before init, otherwise these configurations will be invalid in the init process 
ARouter.openLog(); // Print log 
ARouter.openDebug(); // Turn on debugging mode (If you are running in InstantRun mode, you must turn on debug mode! Online version needs to be closed, otherwise there is a security risk) 
} 

ARouter.init(mApplication); // As early as possible, it is recommended to initialize in the Application

上面这段话就是去初始化Arouter,我们来看看init里面到底做了什么事。。。

/**
     * Init, it must be call before used router.
     */
    public static void init(Application application) {
        if (!hasInit) {
            logger = _ARouter.logger;
            _ARouter.logger.info(Consts.TAG, "ARouter init start.");
            hasInit = _ARouter.init(application);

            if (hasInit) {
                _ARouter.afterInit();
            }

            _ARouter.logger.info(Consts.TAG, "ARouter init over.");
        }
    }

可以看到,这里使用了外观模式,最终调用都是在_ARouter这个类里面,跟进去:

protected static synchronized boolean init(Application application) {
        mContext = application;
        LogisticsCenter.init(mContext, executor);
        logger.info(Consts.TAG, "ARouter init success!");
        hasInit = true;

        // It's not a good idea.
        // if (Build.VERSION.SDK_INT > Build.VERSION_CODES.ICE_CREAM_SANDWICH) {
        //     application.registerActivityLifecycleCallbacks(new AutowiredLifecycleCallback());
        // }
        return true;
    }

代码也很简单,核心就是LogisticsCenter.init这句话,跟进去看看,核心代码如下:

List<String> classFileNames = ClassUtils.getFileNameByPackageName(mContext, ROUTE_ROOT_PAKCAGE);

            //
            for (String className : classFileNames) {
                if (className.startsWith(ROUTE_ROOT_PAKCAGE + DOT + SDK_NAME + SEPARATOR + SUFFIX_ROOT)) {
                    // This one of root elements, load root.
                    ((IRouteRoot) (Class.forName(className).getConstructor().newInstance())).loadInto(Warehouse.groupsIndex);
                } else if (className.startsWith(ROUTE_ROOT_PAKCAGE + DOT + SDK_NAME + SEPARATOR + SUFFIX_INTERCEPTORS)) {
                    // Load interceptorMeta
                    ((IInterceptorGroup) (Class.forName(className).getConstructor().newInstance())).loadInto(Warehouse.interceptorsIndex);
                } else if (className.startsWith(ROUTE_ROOT_PAKCAGE + DOT + SDK_NAME + SEPARATOR + SUFFIX_PROVIDERS)) {
                    // Load providerIndex
                    ((IProviderGroup) (Class.forName(className).getConstructor().newInstance())).loadInto(Warehouse.providersIndex);
                }
            }

我们可以看到,首先是去获取到所有的app里的由ARouter注解生成的类的类名,他们的统一特点就是在同一个包下,包名为:com.alibaba.android.arouter.routes
然后就是循环遍历这些类,也就是刚才我们说的那三种类。在这里,有一个Warehouse类,看下代码:

/**
 * Storage of route meta and other data.
 *
 * @author zhilong <a href="mailto:zhilong.lzl@alibaba-inc.com">Contact me.</a>
 * @version 1.0
 * @since 2017/2/23 下午1:39
 */
class Warehouse {
    // Cache route and metas
    static Map<String, Class<? extends IRouteGroup>> groupsIndex = new HashMap<>();
    static Map<String, RouteMeta> routes = new HashMap<>();

    // Cache provider
    static Map<Class, IProvider> providers = new HashMap<>();
    static Map<String, RouteMeta> providersIndex = new HashMap<>();

    // Cache interceptor
    static Map<Integer, Class<? extends IInterceptor>> interceptorsIndex = new UniqueKeyTreeMap<>("More than one interceptors use same priority [%s]");
    static List<IInterceptor> interceptors = new ArrayList<>();

    static void clear() {
        routes.clear();
        groupsIndex.clear();
        providers.clear();
        providersIndex.clear();
        interceptors.clear();
        interceptorsIndex.clear();
    }
}

很简单,定义了几个静态map,在初始化的时候来存放之前的注解生成的那些相关信息。初始化里面存的就是所有group索引的map,所有拦截器(本文不讲)索引的map,所有provider索引的map。至此,之前的那些注解类里面的信息都被存储起来了,这样后续在查找的时候就很方便可以找到对应的类,我们继续看初始化之后的afterInit方法:

static void afterInit() {
        // Trigger interceptor init, use byName.
        interceptorService = (InterceptorService) ARouter.getInstance().build("/arouter/service/interceptor").navigation();
    }

我们跟踪之后,发现最终会调用LogisticsCenter中的completion方法:

/**
     * Completion the postcard by route metas
     *
     * @param postcard Incomplete postcard, should completion by this method.
     */
    public synchronized static void completion(Postcard postcard) {
        if (null == postcard) {
            throw new NoRouteFoundException(TAG + "No postcard!");
        }

        RouteMeta routeMeta = Warehouse.routes.get(postcard.getPath());
        if (null == routeMeta) {    // Maybe its does't exist, or didn't load.
            Class<? extends IRouteGroup> groupMeta = Warehouse.groupsIndex.get(postcard.getGroup());  // Load route meta.
            if (null == groupMeta) {
                throw new NoRouteFoundException(TAG + "There is no route match the path [" + postcard.getPath() + "], in group [" + postcard.getGroup() + "]");
            } else {
                // Load route and cache it into memory, then delete from metas.
                try {
                    if (ARouter.debuggable()) {
                        logger.debug(TAG, String.format(Locale.getDefault(), "The group [%s] starts loading, trigger by [%s]", postcard.getGroup(), postcard.getPath()));
                    }

                    IRouteGroup iGroupInstance = groupMeta.getConstructor().newInstance();
                    iGroupInstance.loadInto(Warehouse.routes);
                    Warehouse.groupsIndex.remove(postcard.getGroup());

                    if (ARouter.debuggable()) {
                        logger.debug(TAG, String.format(Locale.getDefault(), "The group [%s] has already been loaded, trigger by [%s]", postcard.getGroup(), postcard.getPath()));
                    }
                } catch (Exception e) {
                    throw new HandlerException(TAG + "Fatal exception when loading group meta. [" + e.getMessage() + "]");
                }

                completion(postcard);   // Reload
            }
        } else {
            postcard.setDestination(routeMeta.getDestination());
            postcard.setType(routeMeta.getType());
            postcard.setPriority(routeMeta.getPriority());
            postcard.setExtra(routeMeta.getExtra());

            Uri rawUri = postcard.getUri();
            if (null != rawUri) {   // Try to set params into bundle.
                Map<String, String> resultMap = TextUtils.splitQueryParameters(rawUri);
                Map<String, Integer> paramsType = routeMeta.getParamsType();

                if (MapUtils.isNotEmpty(paramsType)) {
                    // Set value by its type, just for params which annotation by @Param
                    for (Map.Entry<String, Integer> params : paramsType.entrySet()) {
                        setValue(postcard,
                                params.getValue(),
                                params.getKey(),
                                resultMap.get(params.getKey()));
                    }

                    // Save params name which need autoinject.
                    postcard.getExtras().putStringArray(ARouter.AUTO_INJECT, paramsType.keySet().toArray(new String[]{}));
                }

                // Save raw uri
                postcard.withString(ARouter.RAW_URI, rawUri.toString());
            }

            switch (routeMeta.getType()) {
                case PROVIDER:  // if the route is provider, should find its instance
                    // Its provider, so it must be implememt IProvider
                    Class<? extends IProvider> providerMeta = (Class<? extends IProvider>) routeMeta.getDestination();
                    IProvider instance = Warehouse.providers.get(providerMeta);
                    if (null == instance) { // There's no instance of this provider
                        IProvider provider;
                        try {
                            provider = providerMeta.getConstructor().newInstance();
                            provider.init(mContext);
                            Warehouse.providers.put(providerMeta, provider);
                            instance = provider;
                        } catch (Exception e) {
                            throw new HandlerException("Init provider failed! " + e.getMessage());
                        }
                    }
                    postcard.setProvider(instance);
                    postcard.greenChannel();    // Provider should skip all of interceptors
                    break;
                case FRAGMENT:
                    postcard.greenChannel();    // Fragment needn't interceptors
                default:
                    break;
            }
        }
    }

这个方法有点长,不过我们可以看到,核心功能就是postcard的信息完善。postcard就是整个路由过程中的信使,类似于生活中的明信片功能,包含了路由所有需要的信息。通过第34行的递归调用,根据groupsIndex和providersIndex保证了Warehouse里面的另外两个静态map(routes,providers)的赋值,这样最终都会走到36行else分支,去保证所有路由信息的完整性,另外swtich…case里面的postcard.greenChannel()其实是activity跳转专用的,目的是用来拦截activity跳转,来对跳转过程进行干预,在之前或者之后做一些自己的处理,所以greenChannel就是绿色通道,不进行拦截。另外代码里面也可以看到,类的生成都是采用getConstructor().newInstance()这种反射来进行的,最终调用:

ModulePersonalService service = (ModulePersonalService) ARouter.getInstance().build("/Personal/service").navigation();

得到这个跨模块服务之后,里面的所有方法都可以去调用来实现功能需求了。

调用过程
Activity的跳转如下:

            ARouter.getInstance().build("/Personal/main").navigation(activity);

最终调用代码则是_ARouter类里面的_navigation方法:

private Object _navigation(final Context context, final Postcard postcard, final int requestCode, final NavigationCallback callback) {
        final Context currentContext = null == context ? mContext : context;

        switch (postcard.getType()) {
            case ACTIVITY:
                // Build intent
                final Intent intent = new Intent(currentContext, postcard.getDestination());
                intent.putExtras(postcard.getExtras());

                // Set flags.
                int flags = postcard.getFlags();
                if (-1 != flags) {
                    intent.setFlags(flags);
                } else if (!(currentContext instanceof Activity)) {    // Non activity, need less one flag.
                    intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
                }

                // Navigation in main looper.
                new Handler(Looper.getMainLooper()).post(new Runnable() {
                    @Override
                    public void run() {
                        if (requestCode > 0) {  // Need start for result
                            ActivityCompat.startActivityForResult((Activity) currentContext, intent, requestCode, postcard.getOptionsBundle());
                        } else {
                            ActivityCompat.startActivity(currentContext, intent, postcard.getOptionsBundle());
                        }

                        if ((0 != postcard.getEnterAnim() || 0 != postcard.getExitAnim()) && currentContext instanceof Activity) {    // Old version.
                            ((Activity) currentContext).overridePendingTransition(postcard.getEnterAnim(), postcard.getExitAnim());
                        }

                        if (null != callback) { // Navigation over.
                            callback.onArrival(postcard);
                        }
                    }
                });

                break;
            case PROVIDER:
                return postcard.getProvider();
            case BOARDCAST:
            case CONTENT_PROVIDER:
            case FRAGMENT:
                Class fragmentMeta = postcard.getDestination();
                try {
                    Object instance = fragmentMeta.getConstructor().newInstance();
                    if (instance instanceof Fragment) {
                        ((Fragment) instance).setArguments(postcard.getExtras());
                    } else if (instance instanceof android.support.v4.app.Fragment) {
                        ((android.support.v4.app.Fragment) instance).setArguments(postcard.getExtras());
                    }

                    return instance;
                } catch (Exception ex) {
                    logger.error(Consts.TAG, "Fetch fragment instance error, " + TextUtils.formatStackTrace(ex.getStackTrace()));
                }
            case METHOD:
            case SERVICE:
            default:
                return null;
        }

        return null;
    }

可以看到对Activity的处理,最终就是调用startActivity方法,对provider就是返回一个类的实例,而BOARDCAST、CONTENT_PROVIDER、FRAGMENT也都是生成一个实例返回,对于METHOD、SERVICE暂时是没有处理的。

拦截器和自动注入的功能,本文没有去分析,一般跳到某一个页面需要判断是否登陆的时候,可以使用拦截器,自动注入可以在页面间传递数据,非常方便。

原文链接:https://blog.csdn.net/binbinqq86/article/details/80927885
阿里P7移动互联网架构师进阶视频(每日更新中)免费学习请点击:https://space.bilibili.com/474380680