典型调用

arouter的源码：https://github.com/alibaba/ARouter/tree/1.5.0

implementation'com.alibaba:arouter-api:1.3.1'
annotationProcessor'com.alibaba:arouter-compiler:1.1.4'

public class MyApplication extends  Application() {

    public void onCreate() {
        super.onCreate()
        ARouter.init(mApplication);
    }
}

ARouter.getInstance().build("/app/MainActivity").navigation();

@Router(path = "/app/MainActivity")
public class MainActivity extends Activity{
  protected void onCreate(){
    ...
      //注入
      ARouter.getInstance().inject(this)
  }
}

注解处理器

1、注解处理是在编译期，这个时候会调用arouter-compiler这个工程，里面的注解处理器遍历所有的使用Arouter的工程，生成相应的文件给arouter api调用
annotationProcessor编译库中的代码没有直接使用的意义，也没有提供开放的api调用，最终的目的是得到编译库中生成的文件，供我们调用
https://github.com/alibaba/ARouter/blob/1.5.0/arouter-compiler/src/main/java/com/alibaba/android/arouter/compiler/processor/RouteProcessor.java

• 使用了javapoet生成java辅助类，就是 implementation'com.squareup:javapoet:1.8.0'

annotationProcessor project(':Compiler')

public class RouteProcessor extends BaseProcessor {

   @Override
    public synchronized void init(ProcessingEnvironment processingEnv) {
        super.init(processingEnv);
    }

    public boolean process(Set<? extends TypeElement> annotations, RoundEnvironment roundEnv) {
       Set<? extends Element> routeElements = roundEnv.getElementsAnnotatedWith(Route.class);
        this.parseRoutes(routeElements);
        return true;
    }

    private void parseRoutes(Set<? extends Element> routeElements) throws IOException {
        if (CollectionUtils.isNotEmpty(routeElements)) {
            // prepare the type an so on.

            logger.info(">>> Found routes, size is " + routeElements.size() + " <<<");

            rootMap.clear();

            TypeMirror type_Activity = elementUtils.getTypeElement(ACTIVITY).asType();
            TypeMirror type_Service = elementUtils.getTypeElement(SERVICE).asType();
            TypeMirror fragmentTm = elementUtils.getTypeElement(FRAGMENT).asType();
            TypeMirror fragmentTmV4 = elementUtils.getTypeElement(Consts.FRAGMENT_V4).asType();

            // Interface of ARouter
            TypeElement type_IRouteGroup = elementUtils.getTypeElement(IROUTE_GROUP);
            TypeElement type_IProviderGroup = elementUtils.getTypeElement(IPROVIDER_GROUP);
            ClassName routeMetaCn = ClassName.get(RouteMeta.class);
            ClassName routeTypeCn = ClassName.get(RouteType.class);

            /*
               Build input type, format as :
               ```Map<String, Class<? extends IRouteGroup>>```
             */
            ParameterizedTypeName inputMapTypeOfRoot = ParameterizedTypeName.get(
                    ClassName.get(Map.class),
                    ClassName.get(String.class),
                    ParameterizedTypeName.get(
                            ClassName.get(Class.class),
                            WildcardTypeName.subtypeOf(ClassName.get(type_IRouteGroup))
                    )
            );

            /*
              ```Map<String, RouteMeta>```
             */
            ParameterizedTypeName inputMapTypeOfGroup = ParameterizedTypeName.get(
                    ClassName.get(Map.class),
                    ClassName.get(String.class),
                    ClassName.get(RouteMeta.class)
            );

            /*
              Build input param name.
             */
            ParameterSpec rootParamSpec = ParameterSpec.builder(inputMapTypeOfRoot, "routes").build();
            ParameterSpec groupParamSpec = ParameterSpec.builder(inputMapTypeOfGroup, "atlas").build();
            ParameterSpec providerParamSpec = ParameterSpec.builder(inputMapTypeOfGroup, "providers").build();  // Ps. its param type same as groupParamSpec!

            /*
              Build method : 'loadInto'
             */
            MethodSpec.Builder loadIntoMethodOfRootBuilder = MethodSpec.methodBuilder(METHOD_LOAD_INTO)
                    .addAnnotation(Override.class)
                    .addModifiers(PUBLIC)
                    .addParameter(rootParamSpec);

            //  Follow a sequence, find out metas of group first, generate java file, then statistics them as root.
            for (Element element : routeElements) {
                TypeMirror tm = element.asType();
                Route route = element.getAnnotation(Route.class);
                RouteMeta routeMeta;

                if (types.isSubtype(tm, type_Activity)) {                 // Activity
                    logger.info(">>> Found activity route: " + tm.toString() + " <<<");

                    // Get all fields annotation by @Autowired
                    Map<String, Integer> paramsType = new HashMap<>();
                    Map<String, Autowired> injectConfig = new HashMap<>();
                    for (Element field : element.getEnclosedElements()) {
                        if (field.getKind().isField() && field.getAnnotation(Autowired.class) != null && !types.isSubtype(field.asType(), iProvider)) {
                            // It must be field, then it has annotation, but it not be provider.
                            Autowired paramConfig = field.getAnnotation(Autowired.class);
                            String injectName = StringUtils.isEmpty(paramConfig.name()) ? field.getSimpleName().toString() : paramConfig.name();
                            paramsType.put(injectName, typeUtils.typeExchange(field));
                            injectConfig.put(injectName, paramConfig);
                        }
                    }
                    routeMeta = new RouteMeta(route, element, RouteType.ACTIVITY, paramsType);
                    routeMeta.setInjectConfig(injectConfig);
                } else if (types.isSubtype(tm, iProvider)) {         // IProvider
                    logger.info(">>> Found provider route: " + tm.toString() + " <<<");
                    routeMeta = new RouteMeta(route, element, RouteType.PROVIDER, null);
                } else if (types.isSubtype(tm, type_Service)) {           // Service
                    logger.info(">>> Found service route: " + tm.toString() + " <<<");
                    routeMeta = new RouteMeta(route, element, RouteType.parse(SERVICE), null);
                } else if (types.isSubtype(tm, fragmentTm) || types.isSubtype(tm, fragmentTmV4)) {
                    logger.info(">>> Found fragment route: " + tm.toString() + " <<<");
                    routeMeta = new RouteMeta(route, element, RouteType.parse(FRAGMENT), null);
                } else {
                    throw new RuntimeException("ARouter::Compiler >>> Found unsupported class type, type = [" + types.toString() + "].");
                }

                categories(routeMeta);
            }

            MethodSpec.Builder loadIntoMethodOfProviderBuilder = MethodSpec.methodBuilder(METHOD_LOAD_INTO)
                    .addAnnotation(Override.class)
                    .addModifiers(PUBLIC)
                    .addParameter(providerParamSpec);

            Map<String, List<RouteDoc>> docSource = new HashMap<>();

            // Start generate java source, structure is divided into upper and lower levels, used for demand initialization.
            for (Map.Entry<String, Set<RouteMeta>> entry : groupMap.entrySet()) {
                String groupName = entry.getKey();

                MethodSpec.Builder loadIntoMethodOfGroupBuilder = MethodSpec.methodBuilder(METHOD_LOAD_INTO)
                        .addAnnotation(Override.class)
                        .addModifiers(PUBLIC)
                        .addParameter(groupParamSpec);

                List<RouteDoc> routeDocList = new ArrayList<>();

                // Build group method body
                Set<RouteMeta> groupData = entry.getValue();
                for (RouteMeta routeMeta : groupData) {
                    RouteDoc routeDoc = extractDocInfo(routeMeta);

                    ClassName className = ClassName.get((TypeElement) routeMeta.getRawType());

                    switch (routeMeta.getType()) {
                        case PROVIDER:  // Need cache provider's super class
                            List<? extends TypeMirror> interfaces = ((TypeElement) routeMeta.getRawType()).getInterfaces();
                            for (TypeMirror tm : interfaces) {
                                routeDoc.addPrototype(tm.toString());

                                if (types.isSameType(tm, iProvider)) {   // Its implements iProvider interface himself.
                                    // This interface extend the IProvider, so it can be used for mark provider
                                    loadIntoMethodOfProviderBuilder.addStatement(
                                            "providers.put($S, $T.build($T." + routeMeta.getType() + ", $T.class, $S, $S, null, " + routeMeta.getPriority() + ", " + routeMeta.getExtra() + "))",
                                            (routeMeta.getRawType()).toString(),
                                            routeMetaCn,
                                            routeTypeCn,
                                            className,
                                            routeMeta.getPath(),
                                            routeMeta.getGroup());
                                } else if (types.isSubtype(tm, iProvider)) {
                                    // This interface extend the IProvider, so it can be used for mark provider
                                    loadIntoMethodOfProviderBuilder.addStatement(
                                            "providers.put($S, $T.build($T." + routeMeta.getType() + ", $T.class, $S, $S, null, " + routeMeta.getPriority() + ", " + routeMeta.getExtra() + "))",
                                            tm.toString(),    // So stupid, will duplicate only save class name.
                                            routeMetaCn,
                                            routeTypeCn,
                                            className,
                                            routeMeta.getPath(),
                                            routeMeta.getGroup());
                                }
                            }
                            break;
                        default:
                            break;
                    }

                    // Make map body for paramsType
                    StringBuilder mapBodyBuilder = new StringBuilder();
                    Map<String, Integer> paramsType = routeMeta.getParamsType();
                    Map<String, Autowired> injectConfigs = routeMeta.getInjectConfig();
                    if (MapUtils.isNotEmpty(paramsType)) {
                        List<RouteDoc.Param> paramList = new ArrayList<>();

                        for (Map.Entry<String, Integer> types : paramsType.entrySet()) {
                            mapBodyBuilder.append("put(\"").append(types.getKey()).append("\", ").append(types.getValue()).append("); ");

                            RouteDoc.Param param = new RouteDoc.Param();
                            Autowired injectConfig = injectConfigs.get(types.getKey());
                            param.setKey(types.getKey());
                            param.setType(TypeKind.values()[types.getValue()].name().toLowerCase());
                            param.setDescription(injectConfig.desc());
                            param.setRequired(injectConfig.required());

                            paramList.add(param);
                        }

                        routeDoc.setParams(paramList);
                    }
                    String mapBody = mapBodyBuilder.toString();

                    loadIntoMethodOfGroupBuilder.addStatement(
                            "atlas.put($S, $T.build($T." + routeMeta.getType() + ", $T.class, $S, $S, " + (StringUtils.isEmpty(mapBody) ? null : ("new java.util.HashMap<String, Integer>(){{" + mapBodyBuilder.toString() + "}}")) + ", " + routeMeta.getPriority() + ", " + routeMeta.getExtra() + "))",
                            routeMeta.getPath(),
                            routeMetaCn,
                            routeTypeCn,
                            className,
                            routeMeta.getPath().toLowerCase(),
                            routeMeta.getGroup().toLowerCase());

                    routeDoc.setClassName(className.toString());
                    routeDocList.add(routeDoc);
                }

                // Generate groups
                String groupFileName = NAME_OF_GROUP + groupName;
                JavaFile.builder(PACKAGE_OF_GENERATE_FILE,
                        TypeSpec.classBuilder(groupFileName)
                                .addJavadoc(WARNING_TIPS)
                                .addSuperinterface(ClassName.get(type_IRouteGroup))
                                .addModifiers(PUBLIC)
                                .addMethod(loadIntoMethodOfGroupBuilder.build())
                                .build()
                ).build().writeTo(mFiler);

                logger.info(">>> Generated group: " + groupName + "<<<");
                rootMap.put(groupName, groupFileName);
                docSource.put(groupName, routeDocList);
            }

            if (MapUtils.isNotEmpty(rootMap)) {
                // Generate root meta by group name, it must be generated before root, then I can find out the class of group.
                for (Map.Entry<String, String> entry : rootMap.entrySet()) {
                    loadIntoMethodOfRootBuilder.addStatement("routes.put($S, $T.class)", entry.getKey(), ClassName.get(PACKAGE_OF_GENERATE_FILE, entry.getValue()));
                }
            }

            // Output route doc
            if (generateDoc) {
                docWriter.append(JSON.toJSONString(docSource, SerializerFeature.PrettyFormat));
                docWriter.flush();
                docWriter.close();
            }

            // Write provider into disk
            String providerMapFileName = NAME_OF_PROVIDER + SEPARATOR + moduleName;
            JavaFile.builder(PACKAGE_OF_GENERATE_FILE,
                    TypeSpec.classBuilder(providerMapFileName)
                            .addJavadoc(WARNING_TIPS)
                            .addSuperinterface(ClassName.get(type_IProviderGroup))
                            .addModifiers(PUBLIC)
                            .addMethod(loadIntoMethodOfProviderBuilder.build())
                            .build()
            ).build().writeTo(mFiler);

            logger.info(">>> Generated provider map, name is " + providerMapFileName + " <<<");

            // Write root meta into disk.
            String rootFileName = NAME_OF_ROOT + SEPARATOR + moduleName;
            JavaFile.builder(PACKAGE_OF_GENERATE_FILE,
                    TypeSpec.classBuilder(rootFileName)
                            .addJavadoc(WARNING_TIPS)
                            .addSuperinterface(ClassName.get(elementUtils.getTypeElement(ITROUTE_ROOT)))
                            .addModifiers(PUBLIC)
                            .addMethod(loadIntoMethodOfRootBuilder.build())
                            .build()
            ).build().writeTo(mFiler);

            logger.info(">>> Generated root, name is " + rootFileName + " <<<");
        }
    }
}

• 这个方法做了一个重要的事情：归类所有Aroute注解的类，然后生成3个java文件

public class ARouter$$Group$$arouter implements IRouteGroup {
    public ARouter$$Group$$arouter() {
    }

    public void loadInto(Map<String, RouteMeta> atlas) {
        atlas.put("/arouter/service/autowired", RouteMeta.build(RouteType.PROVIDER, AutowiredServiceImpl.class, "/arouter/service/autowired", "arouter", (Map)null, -1, -2147483648));
        atlas.put("/arouter/service/interceptor", RouteMeta.build(RouteType.PROVIDER, InterceptorServiceImpl.class, "/arouter/service/interceptor", "arouter", (Map)null, -1, -2147483648));
    }
}

public class ARouter$$Providers$$arouterapi implements IProviderGroup {
    public ARouter$$Providers$$arouterapi() {
    }

    public void loadInto(Map<String, RouteMeta> providers) {
        providers.put("com.alibaba.android.arouter.facade.service.AutowiredService", RouteMeta.build(RouteType.PROVIDER, AutowiredServiceImpl.class, "/arouter/service/autowired", "arouter", (Map)null, -1, -2147483648));
        providers.put("com.alibaba.android.arouter.facade.service.InterceptorService", RouteMeta.build(RouteType.PROVIDER, InterceptorServiceImpl.class, "/arouter/service/interceptor", "arouter", (Map)null, -1, -2147483648));
    }
}

public class ARouter$$Root$$arouterapi implements IRouteRoot {
    public ARouter$$Root$$arouterapi() {
    }

    public void loadInto(Map<String, Class<? extends IRouteGroup>> routes) {
        routes.put("arouter", arouter.class);
    }
}

• 生成辅助类的常量
  public static final String KEY_MODULE_NAME = "AROUTER_MODULE_NAME";就是我们项目名

这个就是我们在build.gradle中的配置
annotationProcessorOptions{
    arguments = [AROUTER_MODULE_NAME:project.getName()]
    includeCompileClasspath =true
}

https://github.com/alibaba/ARouter/blob/1.5.0/arouter-compiler/src/main/java/com/alibaba/android/arouter/compiler/utils/Consts.java

public class Consts {
    // Generate
    public static final String SEPARATOR = "$$";
    public static final String PROJECT = "ARouter";
    public static final String TAG = PROJECT + "::";
    public static final String WARNING_TIPS = "DO NOT EDIT THIS FILE!!! IT WAS GENERATED BY AROUTER.";
    public static final String METHOD_LOAD_INTO = "loadInto";
    public static final String METHOD_INJECT = "inject";
    public static final String NAME_OF_ROOT = PROJECT + SEPARATOR + "Root";
    public static final String NAME_OF_PROVIDER = PROJECT + SEPARATOR + "Providers";
    public static final String NAME_OF_GROUP = PROJECT + SEPARATOR + "Group" + SEPARATOR;
    public static final String NAME_OF_INTERCEPTOR = PROJECT + SEPARATOR + "Interceptors";
    public static final String NAME_OF_AUTOWIRED = SEPARATOR + PROJECT + SEPARATOR + "Autowired";
    public static final String PACKAGE_OF_GENERATE_FILE = "com.alibaba.android.arouter.routes";
    public static final String PACKAGE_OF_GENERATE_DOCS = "com.alibaba.android.arouter.docs";

    // System interface
    public static final String ACTIVITY = "android.app.Activity";
    public static final String FRAGMENT = "android.app.Fragment";
    public static final String FRAGMENT_V4 = "android.support.v4.app.Fragment";
    public static final String SERVICE = "android.app.Service";
    public static final String PARCELABLE = "android.os.Parcelable";

    // Java type
    private static final String LANG = "java.lang";
    public static final String BYTE = LANG + ".Byte";
    public static final String SHORT = LANG + ".Short";
    public static final String INTEGER = LANG + ".Integer";
    public static final String LONG = LANG + ".Long";
    public static final String FLOAT = LANG + ".Float";
    public static final String DOUBEL = LANG + ".Double";
    public static final String BOOLEAN = LANG + ".Boolean";
    public static final String CHAR = LANG + ".Character";
    public static final String STRING = LANG + ".String";
    public static final String SERIALIZABLE = "java.io.Serializable";

    // Custom interface
    private static final String FACADE_PACKAGE = "com.alibaba.android.arouter.facade";
    private static final String TEMPLATE_PACKAGE = ".template";
    private static final String SERVICE_PACKAGE = ".service";
    private static final String MODEL_PACKAGE = ".model";
    public static final String IPROVIDER = FACADE_PACKAGE + TEMPLATE_PACKAGE + ".IProvider";
    public static final String IPROVIDER_GROUP = FACADE_PACKAGE + TEMPLATE_PACKAGE + ".IProviderGroup";
    public static final String IINTERCEPTOR = FACADE_PACKAGE + TEMPLATE_PACKAGE + ".IInterceptor";
    public static final String IINTERCEPTOR_GROUP = FACADE_PACKAGE + TEMPLATE_PACKAGE + ".IInterceptorGroup";
    public static final String ITROUTE_ROOT = FACADE_PACKAGE + TEMPLATE_PACKAGE + ".IRouteRoot";
    public static final String IROUTE_GROUP = FACADE_PACKAGE + TEMPLATE_PACKAGE + ".IRouteGroup";
    public static final String ISYRINGE = FACADE_PACKAGE + TEMPLATE_PACKAGE + ".ISyringe";
    public static final String JSON_SERVICE = FACADE_PACKAGE + SERVICE_PACKAGE + ".SerializationService";
    public static final String TYPE_WRAPPER = FACADE_PACKAGE + MODEL_PACKAGE + ".TypeWrapper";

    // Log
    static final String PREFIX_OF_LOGGER = PROJECT + "::Compiler ";
    public static final String NO_MODULE_NAME_TIPS = "These no module name, at 'build.gradle', like :\n" +
            "android {\n" +
            "    defaultConfig {\n" +
            "        ...\n" +
            "        javaCompileOptions {\n" +
            "            annotationProcessorOptions {\n" +
            "                arguments = [AROUTER_MODULE_NAME: project.getName()]\n" +
            "            }\n" +
            "        }\n" +
            "    }\n" +
            "}\n";

    // Options of processor
    public static final String KEY_MODULE_NAME = "AROUTER_MODULE_NAME";
    public static final String KEY_GENERATE_DOC_NAME = "AROUTER_GENERATE_DOC";

    public static final String VALUE_ENABLE = "enable";

    // Annotation type
    public static final String ANNOTATION_TYPE_INTECEPTOR = FACADE_PACKAGE + ".annotation.Interceptor";
    public static final String ANNOTATION_TYPE_ROUTE = FACADE_PACKAGE + ".annotation.Route";
    public static final String ANNOTATION_TYPE_AUTOWIRED = FACADE_PACKAGE + ".annotation.Autowired";
}

流程分析

1、在application初始化arouter，ARouter.init(this)

ARouter.init(this)

public static void init(Application application) {
        if (!hasInit) {
            hasInit = _ARouter.init(application);
            if (hasInit) {
                _ARouter.afterInit();
            }
        }
    }

final class _ARouter {
    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;
    }
}

2、 加载动态生成的java文件的内容

public class LogisticsCenter {
  /**
     * LogisticsCenter init, load all metas in memory. Demand initialization
     */
    public synchronized static void init(Context context, ThreadPoolExecutor tpe) throws HandlerException {
        mContext = context;
        executor = tpe;

        try {
            long startInit = System.currentTimeMillis();
            //billy.qi modified at 2017-12-06
            //load by plugin first
            loadRouterMap();
            if (registerByPlugin) {
                logger.info(TAG, "Load router map by arouter-auto-register plugin.");
            } else {
                Set<String> routerMap;

                // It will rebuild router map every times when debuggable.
                if (ARouter.debuggable() || PackageUtils.isNewVersion(context)) {
                    logger.info(TAG, "Run with debug mode or new install, rebuild router map.");
                    // These class was generate by arouter-compiler.
                    routerMap = ClassUtils.getFileNameByPackageName(mContext, ROUTE_ROOT_PAKCAGE);
                    if (!routerMap.isEmpty()) {
                        context.getSharedPreferences(AROUTER_SP_CACHE_KEY, Context.MODE_PRIVATE).edit().putStringSet(AROUTER_SP_KEY_MAP, routerMap).apply();
                    }

                    PackageUtils.updateVersion(context);    // Save new version name when router map update finish.
                } else {
                    logger.info(TAG, "Load router map from cache.");
                    routerMap = new HashSet<>(context.getSharedPreferences(AROUTER_SP_CACHE_KEY, Context.MODE_PRIVATE).getStringSet(AROUTER_SP_KEY_MAP, new HashSet<String>()));
                }

                logger.info(TAG, "Find router map finished, map size = " + routerMap.size() + ", cost " + (System.currentTimeMillis() - startInit) + " ms.");
                startInit = System.currentTimeMillis();

                for (String className : routerMap) {
                    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);
                    }
                }
            }
           ...            
        } catch (Exception e) {
            throw new HandlerException(TAG + "ARouter init logistics center exception! [" + e.getMessage() + "]");
        }
    }

3、 ClassUtils.getFileNameByPackageName(mContext, ROUTE_ROOT_PAKCAGE)，开启线程池加载apt生成的数据

public static Set<String> getFileNameByPackageName(Context context, final String packageName) throws PackageManager.NameNotFoundException, IOException, InterruptedException {
        final Set<String> classNames = new HashSet<>();

        List<String> paths = getSourcePaths(context);
        final CountDownLatch parserCtl = new CountDownLatch(paths.size());

        for (final String path : paths) {
            DefaultPoolExecutor.getInstance().execute(new Runnable() {
                @Override
                public void run() {
                    DexFile dexfile = null;

                    try {
                        if (path.endsWith(EXTRACTED_SUFFIX)) {
                            //NOT use new DexFile(path), because it will throw "permission error in /data/dalvik-cache"
                            dexfile = DexFile.loadDex(path, path + ".tmp", 0);
                        } else {
                            dexfile = new DexFile(path);
                        }

                        Enumeration<String> dexEntries = dexfile.entries();
                        while (dexEntries.hasMoreElements()) {
                            String className = dexEntries.nextElement();
                            if (className.startsWith(packageName)) {
                                classNames.add(className);
                            }
                        }
                    } catch (Throwable ignore) {
                        Log.e("ARouter", "Scan map file in dex files made error.", ignore);
                    } finally {
                        if (null != dexfile) {
                            try {
                                dexfile.close();
                            } catch (Throwable ignore) {
                            }
                        }

                        parserCtl.countDown();
                    }
                }
            });
        }

        parserCtl.await();

        Log.d(Consts.TAG, "Filter " + classNames.size() + " classes by packageName <" + packageName + ">");
        return classNames;
    }

跳转

1、初始化单例ARouter类

public final class ARouter {
 public static ARouter getInstance() {
        if (!hasInit) {
            throw new InitException("ARouter::Init::Invoke init(context) first!");
        } else {
            if (instance == null) {
                synchronized (ARouter.class) {
                    if (instance == null) {
                        instance = new ARouter();
                    }
                }
            }
            return instance;
        }
    }

    public Postcard build(String path) {
        return _ARouter.getInstance().build(path);
    }
   
}

2、实际调用的是Postcard类的navigation()方法

public final class Postcard extends RouteMeta {
    public Object navigation() {
        return navigation(null);
    }

    public Object navigation(Context context) {
        return navigation(context, null);
    }

    public Object navigation(Context context, NavigationCallback callback) {
        return ARouter.getInstance().navigation(context, this, -1, callback);
    }
}

public final class ARouter {    
    public Object navigation(Context mContext, Postcard postcard, int requestCode, NavigationCallback callback) {
        return _ARouter.getInstance().navigation(mContext, postcard, requestCode, callback);
    }
}

3、LogisticsCenter.completion(postcard);是将postcard放到路由表中去填充数据

final class _ARouter {
    protected Object navigation(final Context context, final Postcard postcard, final int requestCode, final NavigationCallback callback) {
        try {
            LogisticsCenter.completion(postcard);
        } catch (NoRouteFoundException ex) {
            logger.warning(Consts.TAG, ex.getMessage());

            if (debuggable()) { // Show friendly tips for user.
                Toast.makeText(mContext, "There's no route matched!\n" +
                        " Path = [" + postcard.getPath() + "]\n" +
                        " Group = [" + postcard.getGroup() + "]", Toast.LENGTH_LONG).show();
            }

            if (null != callback) {
                callback.onLost(postcard);
            } else {    // No callback for this invoke, then we use the global degrade service.
                DegradeService degradeService = ARouter.getInstance().navigation(DegradeService.class);
                if (null != degradeService) {
                    degradeService.onLost(context, postcard);
                }
            }

            return null;
        }

        if (null != callback) {
            callback.onFound(postcard);
        }

        if (!postcard.isGreenChannel()) {   // It must be run in async thread, maybe interceptor cost too mush time made ANR.
            interceptorService.doInterceptions(postcard, new InterceptorCallback() {
                /**
                 * Continue process
                 *
                 * @param postcard route meta
                 */
                @Override
                public void onContinue(Postcard postcard) {
                    _navigation(context, postcard, requestCode, callback);
                }

                /**
                 * Interrupt process, pipeline will be destory when this method called.
                 *
                 * @param exception Reson of interrupt.
                 */
                @Override
                public void onInterrupt(Throwable exception) {
                    if (null != callback) {
                        callback.onInterrupt(postcard);
                    }

                    logger.info(Consts.TAG, "Navigation failed, termination by interceptor : " + exception.getMessage());
                }
            });
        } else {
            return _navigation(context, postcard, requestCode, callback);
        }

        return null;
    }

    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;
            ...
        }

        return null;
    }

4、LogisticsCenter类的completion()方法

• 递归调用completion(postcard)，直到找到postcard
• 填充数据到postcard

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()));
                    }
                    将路由表的数据填充到map(Warehouse.routes)
                    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 auto inject.
                    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;
            }
        }
    }

总结

1、加载路由映射
2、根据 path 构造出 Postcard 对象
3、区分 Postcard 的 type 来实现跳转

其他

1、通过指定包名，扫描包下面包含的所有的ClassName(用了线程池和aqs锁处理)

public class LogisticsCenter {
    public synchronized static void init(Context context, ThreadPoolExecutor tpe) throws HandlerException {
             // These class was generate by arouter-compiler.
           routerMap = ClassUtils.getFileNameByPackageName(mContext, ROUTE_ROOT_PAKCAGE);
           ...     
    }
}

 public static Set<String> getFileNameByPackageName(Context context, final String packageName) throws PackageManager.NameNotFoundException, IOException, InterruptedException {
        final Set<String> classNames = new HashSet<>();

        List<String> paths = getSourcePaths(context);
        final CountDownLatch parserCtl = new CountDownLatch(paths.size());

        for (final String path : paths) {
            DefaultPoolExecutor.getInstance().execute(new Runnable() {
                @Override
                public void run() {
                    DexFile dexfile = null;

                    try {
                        if (path.endsWith(EXTRACTED_SUFFIX)) {
                            //NOT use new DexFile(path), because it will throw "permission error in /data/dalvik-cache"
                            dexfile = DexFile.loadDex(path, path + ".tmp", 0);
                        } else {
                            dexfile = new DexFile(path);
                        }

                        Enumeration<String> dexEntries = dexfile.entries();
                        while (dexEntries.hasMoreElements()) {
                            String className = dexEntries.nextElement();
                           // packageName ：”"com.alibaba.android.arouter.routes"
                            if (className.startsWith(packageName)) {
                                classNames.add(className);
                            }
                        }
                    } catch (Throwable ignore) {
                        Log.e("ARouter", "Scan map file in dex files made error.", ignore);
                    } finally {
                        if (null != dexfile) {
                            try {
                                dexfile.close();
                            } catch (Throwable ignore) {
                            }
                        }

                        parserCtl.countDown();
                    }
                }
            });
        }

        parserCtl.await();

        Log.d(Consts.TAG, "Filter " + classNames.size() + " classes by packageName <" + packageName + ">");
        return classNames;
    }