組件化框架設計之阿里巴巴開源路由框架——ARouter原理分析(一)

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背景

當項目的業務越來越複雜,業務線越來越多的時候,就需要按照業務線去分不同的模塊去開發,這樣專門的人負責專門的業務模塊,最終上線由殼工程去負責進行組合打包各個module,完成業務的快速迭代。整個過程會涉及到各個模塊間進行通信,比如訂單模塊和個人中心模塊,可能會需要頻繁的傳遞數據和頁面跳轉,這個時候怎麼去處理呢?我們能想到的方案就是採用類名反射,來動態創建需要跳轉和交互的類,這樣編譯時就不會報錯,運行時又可以完成模塊間的交互。阿里巴巴推出的開源路由框架——ARouter就是基於反射和註解來解決這個問題的,本文不講基本使用(基本使用在項目的github主頁上已經將的非常詳細了),通過分析整個路由過程來講解它的基本原理。

說在前面

首先在我們需要用到的類的類名加上註解@Route(“/group/name”),注意這裏需要至少兩層路徑(第一個是分組,第二個一般是類名)。這個註解就是代表這個類可以被其他模塊找到的一個路徑的註解,並且它是一個編譯時註解,這就意味着在編譯時就已經生成了相應的輔助類。ARouter把路由一共分爲以下幾類:

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”);

其中我們常用的就是ACTIVITY,PROVIDER,FRAGMENT這三個了,也基本上滿足了我們模塊化開發的需求。另外一點就是分組的概念,ARouter是按照組來進行整理的,也就是第一層的路徑,所以前面說必須要兩層路徑,否則不知道歸到哪裏去,一般一個module按照模塊名採用統一的分組標識。我們來看看註解生成的類(這裏只包含了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));
  }
}

以上就是所有註解的路徑的信息集合,包含了所有的Activity,Fragment,Provider(一般一個module一個Provider就夠用了,專門用來跟其他模塊交互),並都以路徑爲key放到這個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));
  }
}

這個類是專門的Provider的索引的集合,所有的provider都被以全類名爲索引放到一個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);
  }
}

這個類是所有的group的信息收集,全部都以group的名字爲key,以註解生成的不同的group的類的class對象爲value放入到一個map中。

總共就生成這三種類型的類,當然,如果你有不同的分組還會生成其他的類,不過都是這三種裏面的一種。

完成了這些註解信息的收集,下面就會去使用這些信息來完成我們的跨模塊交互了。

初始化過程

使用ARouter必須先要進行初始化:

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

上面這段話就是去初始化Arouter,我們來看看init裏面到底做了什麼事。。。

/**
     * 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,這裏使用了外觀模式,最終調用都是在_ARouter這個類裏面,跟進去:

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;
    }

代碼也很簡單,核心就是LogisticsCenter.init這句話,跟進去看看,核心代碼如下:

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);
                }
            }

我們可以看到,首先是去獲取到所有的app裏的由ARouter註解生成的類的類名,他們的統一特點就是在同一個包下,包名爲:com.alibaba.android.arouter.routes
然後就是循環遍歷這些類,也就是剛纔我們說的那三種類。在這裏,有一個Warehouse類,看下代碼:

/**
 * Storage of route meta and other data.
 *
 * @author zhilong <a href="mailto:[email protected]">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();
    }
}

很簡單,定義了幾個靜態map,在初始化的時候來存放之前的註解生成的那些相關信息。初始化裏面存的就是所有group索引的map,所有攔截器(本文不講)索引的map,所有provider索引的map。至此,之前的那些註解類裏面的信息都被存儲起來了,這樣後續在查找的時候就很方便可以找到對應的類,我們繼續看初始化之後的afterInit方法:

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

我們跟蹤之後,發現最終會調用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;
            }
        }
    }

這個方法有點長,不過我們可以看到,核心功能就是postcard的信息完善。postcard就是整個路由過程中的信使,類似於生活中的明信片功能,包含了路由所有需要的信息。通過第34行的遞歸調用,根據groupsIndex和providersIndex保證了Warehouse裏面的另外兩個靜態map(routes,providers)的賦值,這樣最終都會走到36行else分支,去保證所有路由信息的完整性,另外swtich…case裏面的postcard.greenChannel()其實是activity跳轉專用的,目的是用來攔截activity跳轉,來對跳轉過程進行干預,在之前或者之後做一些自己的處理,所以greenChannel就是綠色通道,不進行攔截。另外代碼裏面也可以看到,類的生成都是採用getConstructor().newInstance()這種反射來進行的,最終調用:

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

得到這個跨模塊服務之後,裏面的所有方法都可以去調用來實現功能需求了。

調用過程
Activity的跳轉如下:

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

最終調用代碼則是_ARouter類裏面的_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;
    }

可以看到對Activity的處理,最終就是調用startActivity方法,對provider就是返回一個類的實例,而BOARDCAST、CONTENT_PROVIDER、FRAGMENT也都是生成一個實例返回,對於METHOD、SERVICE暫時是沒有處理的。

攔截器和自動注入的功能,本文沒有去分析,一般跳到某一個頁面需要判斷是否登陸的時候,可以使用攔截器,自動注入可以在頁面間傳遞數據,非常方便。

原文鏈接:https://blog.csdn.net/binbinqq86/article/details/80927885
阿里P7移動互聯網架構師進階視頻(每日更新中)免費學習請點擊:https://space.bilibili.com/474380680

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