ARouter源码解析（一）
前言
之前对 ActivityRouter 的源码做了一次分析，相信大家对路由框架已经有一个大概的理解了。
而今天给大家分析一下 ARouter 。大家在项目组件化的过程中，可能绝大多数的开发者都会使用 ARouter 来作为项目的路由框架。毕竟 ARouter 是阿里出品，优点自然不必多说了。
所以在平常使用的过程中，不仅仅要做到会用，还要深入了解一下 ARouter 的内部原理。
本次 ARouter 的解析分为三部分：
- 对 IRouteRoot 页面跳转进行源码解析；
- 对 IInterceptorGroup 拦截器进行源码解析；
- 对 IProviderGroup 服务组件进行源码解析；
本篇是 ARouter 系列的第一篇，下面就对 IRouteRoot 页面跳转进行详细解析。
ARouter 源码
使用 ARouter 的时候，都需要初始化
if (isDebug()) {
ARouter.openLog();
ARouter.openDebug();
}
ARouter.init(mApplication);
源码分析的入口，就在 ARouter.init 里
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.");
}
}
源码上可以看到，ARouter 的内部其实是 _ARouter 在起作用，ARouter 只是把 _ARouter 再做了一层包装。那么我们就跟进 _ARouter 的 init 方法。
protected static synchronized boolean init(Application application) {
mContext = application;
LogisticsCenter.init(mContext, executor);
logger.info(Consts.TAG, "ARouter init success!");
hasInit = true;
mHandler = new Handler(Looper.getMainLooper());
return true;
}
最重要的一句代码还是 LogisticsCenter.init(mContext, executor) ，其中 executor 是线程池。
那么问题来了， LogisticsCenter 是干什么的呢？
* LogisticsCenter contains all of the map.
*
* 1. Creates instance when it is first used.
* 2. Handler Multi-Module relationship map(*)
* 3. Complex logic to solve duplicate group definition
根据官方的注释，LogisticsCenter 是包含了所有的映射，处理跨模块的映射关系以及匹配路由等。
所以根据之前 ActivityRouter 的经验猜测得到，LogisticsCenter 的 init 方法里面，肯定会去加载路由，并建立关系。
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 routerMap;
// 如果是debug或者新版本的话，会去重新加载路由映射
if (ARouter.debuggable() || PackageUtils.isNewVersion(context)) {
logger.info(TAG, "Run with debug mode or new install, rebuild router map.");
// 加载路由映射
routerMap = ClassUtils.getFileNameByPackageName(mContext, ROUTE_ROOT_PAKCAGE);
// 保存所有的路由映射到 SharedPreferences
if (!routerMap.isEmpty()) {
context.getSharedPreferences(AROUTER_SP_CACHE_KEY, Context.MODE_PRIVATE).edit().putStringSet(AROUTER_SP_KEY_MAP, routerMap).apply();
}
// 保存新版本号到 sharedpreference
PackageUtils.updateVersion(context); // Save new version name when router map update finishes.
} else {
// 否则就从 SharedPreferences 中读取之前保存的所有路由映射
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()));
}
logger.info(TAG, "Find router map finished, map size = " + routerMap.size() + ", cost " + (System.currentTimeMillis() - startInit) + " ms.");
startInit = System.currentTimeMillis();
// 把上面加载得到的路由映射根据ClassName分为三种，分别进行注册
// IRouteRoot 页面跳转
// IInterceptorGroup 拦截器
// IProviderGroup 服务组件
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() + "]");
}
}
LogisticsCenter 的 init 方法的代码基本上都可以看得懂，其中 ClassUtils.getFileNameByPackageName 是我们值得探究的地方。这句代码主要做的事情就是从 dex 中遍历 class 找到 arouter-compiler 生成的类集合。具体的分析我们到最后面再讲，这里先埋个伏笔。
接着往下看，我们知道，routerMap 中的 className 都是 arouter-compiler 在编译期生成的，那我们先来看看生成的类长什么样
/**
* DO NOT EDIT THIS FILE!!! IT WAS GENERATED BY AROUTER. */
public class ARouter$$Root$$app implements IRouteRoot {
@Override
public void loadInto(Map> routes) {
routes.put("test", ARouter$$Group$$test.class);
routes.put("yourservicegroupname", ARouter$$Group$$yourservicegroupname.class);
}
}
ARouter 的路由会分组加载，比如当前有 /test/abc 和 /test/def 两个路由，那他们同属于 /test 这个组。所以在 Warehouse.groupsIndex 中存放的 key 是路由组名，value 是对应组路由类。查找路由的时候也是根据组名 key ，再找到组路由类 value 中查找匹配的路由。
/**
* DO NOT EDIT THIS FILE!!! IT WAS GENERATED BY AROUTER. */
public class ARouter$$Group$$test implements IRouteGroup {
@Override
public void loadInto(Map atlas) {
atlas.put("/test/activity1", RouteMeta.build(RouteType.ACTIVITY, Test1Activity.class, "/test/activity1", "test", new java.util.HashMap(){{put("ser", 9); put("ch", 5); put("fl", 6); put("dou", 7); put("boy", 0); put("url", 8); put("pac", 10); put("obj", 11); put("name", 8); put("objList", 11); put("map", 11); put("age", 3); put("height", 3); }}, -1, -2147483648));
atlas.put("/test/activity2", RouteMeta.build(RouteType.ACTIVITY, Test2Activity.class, "/test/activity2", "test", new java.util.HashMap(){{put("key1", 8); }}, -1, -2147483648));
atlas.put("/test/activity3", RouteMeta.build(RouteType.ACTIVITY, Test3Activity.class, "/test/activity3", "test", new java.util.HashMap(){{put("name", 8); put("boy", 0); put("age", 3); }}, -1, -2147483648));
atlas.put("/test/activity4", RouteMeta.build(RouteType.ACTIVITY, Test4Activity.class, "/test/activity4", "test", null, -1, -2147483648));
atlas.put("/test/fragment", RouteMeta.build(RouteType.FRAGMENT, BlankFragment.class, "/test/fragment", "test", null, -1, -2147483648));
atlas.put("/test/webview", RouteMeta.build(RouteType.ACTIVITY, TestWebview.class, "/test/webview", "test", null, -1, -2147483648));
}
}
可以看到路由相关的参数配置被构造成了一个 RouteMeta 对象。RouteMeta 类如下所示：
public class RouteMeta {
private RouteType type; // Type of route
private Element rawType; // Raw type of route
private Class destination; // Destination
private String path; // Path of route
private String group; // Group of route
private int priority = -1; // The smaller the number, the higher the priority
private int extra; // Extra data
private Map paramsType; // Param type
private String name;
private Map injectConfig; // Cache inject config.
...
}
到这里，加载路由的部分就完成了，剩下的就是跳转路由了。
跳转路由的通常操作：
ARouter.getInstance().build("/test/abc").navigation();
那先看一下 ARouter 的 build 方法
public Postcard build(String path) {
return _ARouter.getInstance().build(path);
}
里面调用的是 _ARouter 的 build 方法。
protected Postcard build(String path) {
if (TextUtils.isEmpty(path)) {
throw new HandlerException(Consts.TAG + "Parameter is invalid!");
} else {
// 获取 PathReplaceService 实例，如果不为空，就处理 path
PathReplaceService pService = ARouter.getInstance().navigation(PathReplaceService.class);
if (null != pService) {
path = pService.forString(path);
}
return build(path, extractGroup(path));
}
}
/**
* 截取跳转路径中的第一段作为分组名
*/
private String extractGroup(String path) {
if (TextUtils.isEmpty(path) || !path.startsWith("/")) {
throw new HandlerException(Consts.TAG + "Extract the default group failed, the path must be start with '/' and contain more than 2 '/'!");
}
try {
String defaultGroup = path.substring(1, path.indexOf("/", 1));
if (TextUtils.isEmpty(defaultGroup)) {
throw new HandlerException(Consts.TAG + "Extract the default group failed! There's nothing between 2 '/'!");
} else {
return defaultGroup;
}
} catch (Exception e) {
logger.warning(Consts.TAG, "Failed to extract default group! " + e.getMessage());
return null;
}
}
PathReplaceService 是官方给我们预留的口子，用来对 path 做预处理。如果你有需求来对 path 做统一的预处理，那么直接实现 PathReplaceService 即可。
我们接着跟进，看下 _ARouter.build(String path, String group) 方法
protected Postcard build(String path, String group) {
if (TextUtils.isEmpty(path) || TextUtils.isEmpty(group)) {
throw new HandlerException(Consts.TAG + "Parameter is invalid!");
} else {
PathReplaceService pService = ARouter.getInstance().navigation(PathReplaceService.class);
if (null != pService) {
path = pService.forString(path);
}
return new Postcard(path, group);
}
}
发现在 build(String path, String group) 中直接创建了一个 Postcard 对象并返回。Postcard 类是继承了 RouteMeta ，额外添加了一些其他的信息。
有了 Postcard 之后，直接调用 navigation 进行跳转。
public Object navigation(Context context, NavigationCallback callback) {
return ARouter.getInstance().navigation(context, this, -1, callback);
}
public void navigation(Activity mContext, int requestCode, NavigationCallback callback) {
ARouter.getInstance().navigation(mContext, this, requestCode, callback);
}
Postcard 的所有 navigation 方法最后都会调用 ARouter 的 navigation 这个方法。
public Object navigation(Context mContext, Postcard postcard, int requestCode, NavigationCallback callback) {
return _ARouter.getInstance().navigation(mContext, postcard, requestCode, callback);
}
最后还是调用了 _ARouter.navigation
protected Object navigation(final Context context, final Postcard postcard, final int requestCode, final NavigationCallback callback) {
try {
// 将 postcard 与路由表中进行匹配，并且填充 postcard 的数据
LogisticsCenter.completion(postcard);
} catch (NoRouteFoundException ex) {
logger.warning(Consts.TAG, ex.getMessage());
// 如果 debug ，就显示匹配错误
if (debuggable()) {
// Show friendly tips for user.
runInMainThread(new Runnable() {
@Override
public void run() {
Toast.makeText(mContext, "There's no route matched!\n" +
" Path = [" + postcard.getPath() + "]\n" +
" Group = [" + postcard.getGroup() + "]", Toast.LENGTH_LONG).show();
}
});
}
// 回调路由匹配失败
if (null != callback) {
callback.onLost(postcard);
} else {
// No callback for this invoke, then we use the global degrade service.
// 如果没有回调，就调用全局降级的策略
DegradeService degradeService = ARouter.getInstance().navigation(DegradeService.class);
if (null != degradeService) {
degradeService.onLost(context, postcard);
}
}
return null;
}
// 回调路由匹配成功
if (null != callback) {
callback.onFound(postcard);
}
// 如果不是绿色通道，就调用拦截器，拦截器这部分后面单独出来讲，这里就不讲了
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 {
// 否则调用 _navigation 进行跳转
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: // 如果是 activity 的，执行跳转
// 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);
}
// Set Actions
String action = postcard.getAction();
if (!TextUtils.isEmpty(action)) {
intent.setAction(action);
}
// Navigation in main looper.
runInMainThread(new Runnable() {
@Override
public void run() {
startActivity(requestCode, currentContext, intent, postcard, callback);
}
});
break;
case PROVIDER: // 如果是服务组件，那么直接返回该组件
return postcard.getProvider();
case BOARDCAST:
case CONTENT_PROVIDER:
case FRAGMENT: // 如果是 fragment 的话，返回该 fragment 的实例
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;
}
上面的代码基本上都写了注释，大家应该都能看懂。
我们重点来关注下 LogisticsCenter.completion(postcard);
public synchronized static void completion(Postcard postcard) {
if (null == postcard) {
throw new NoRouteFoundException(TAG + "No postcard!");
}
// 先根据 path 去获取 RouteMeta
RouteMeta routeMeta = Warehouse.routes.get(postcard.getPath());
if (null == routeMeta) { // 如果 routeMeta 为空，可能是不存在或者是未加载
Class groupMeta = Warehouse.groupsIndex.get(postcard.getGroup()); // 加载分组下的路由映射
// 如果不存在，就报错
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()));
}
// 实现按需加载
IRouteGroup iGroupInstance = groupMeta.getConstructor().newInstance();
iGroupInstance.loadInto(Warehouse.routes);
// 移除 groupsIndex , 否则会造成死循环
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() + "]");
}
// 重新加载一遍
completion(postcard); // Reload
}
} else {
// 找到对应的 routeMeta， 填充 postcard 数据
postcard.setDestination(routeMeta.getDestination());
postcard.setType(routeMeta.getType());
postcard.setPriority(routeMeta.getPriority());
postcard.setExtra(routeMeta.getExtra());
Uri rawUri = postcard.getUri();
// 如果 rawUri 不为空，则是 uri 跳转。就解析 rawUri 中的参数，放入 bundle 中
if (null != rawUri) { // Try to set params into bundle.
Map resultMap = TextUtils.splitQueryParameters(rawUri);
Map paramsType = routeMeta.getParamsType();
if (MapUtils.isNotEmpty(paramsType)) {
// Set value by its type, just for params which annotation by @Param
for (Map.Entry 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());
}
// 如果是 PROVIDER 和 FRAGMENT 类型的，开启绿色通道
switch (routeMeta.getType()) {
case PROVIDER: // if the route is provider, should find its instance
// Its provider, so it must implement IProvider
Class providerMeta = (Class) 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;
}
}
}
至此，整个路由跳转的流程就讲完了，大致的流程可以分为
- 加载路由映射
- 根据 path 构造出 Postcard 对象
- 区分 Postcard 的 type 来实现跳转
番外
前面说过，ARouter 会在 dex 中寻找 arouter-compiler 生成的类。那我们最后来看看是怎么实现的。
public static Set getFileNameByPackageName(Context context, final String packageName) throws PackageManager.NameNotFoundException, IOException, InterruptedException {
final Set classNames = new HashSet<>();
// 获取 dex 文件存放的路径
List paths = getSourcePaths(context);
final CountDownLatch parserCtl = new CountDownLatch(paths.size());
// 遍历所有 dex 文件的路径
for (final String path : paths) {
DefaultPoolExecutor.getInstance().execute(new Runnable() {
@Override
public void run() {
DexFile dexfile = null;
try {
// 根据路径加载 dex 文件
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);
}
// 遍历 dexfile 的中所有 className 如果是 arouter 报名开头的，就加入到 classNames 中
Enumeration 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;
}
我们再来看下 getSourcePaths 方法，看看它是怎么找 dex 文件路径的
public static List getSourcePaths(Context context) throws PackageManager.NameNotFoundException, IOException {
ApplicationInfo applicationInfo = context.getPackageManager().getApplicationInfo(context.getPackageName(), 0);
File sourceApk = new File(applicationInfo.sourceDir);
List sourcePaths = new ArrayList<>();
sourcePaths.add(applicationInfo.sourceDir); //add the default apk path
//the prefix of extracted file, ie: test.classes
String extractedFilePrefix = sourceApk.getName() + EXTRACTED_NAME_EXT;
// 如果VM已经支持了MultiDex，就不要去Secondary Folder加载 Classesx.zip了，那里已经么有了
// 通过是否存在sp中的multidex.version是不准确的，因为从低版本升级上来的用户，是包含这个sp配置的
if (!isVMMultidexCapable()) {
//the total dex numbers
int totalDexNumber = getMultiDexPreferences(context).getInt(KEY_DEX_NUMBER, 1);
File dexDir = new File(applicationInfo.dataDir, SECONDARY_FOLDER_NAME);
for (int secondaryNumber = 2; secondaryNumber <= totalDexNumber; secondaryNumber++) {
//for each dex file, ie: test.classes2.zip, test.classes3.zip...
String fileName = extractedFilePrefix + secondaryNumber + EXTRACTED_SUFFIX;
File extractedFile = new File(dexDir, fileName);
if (extractedFile.isFile()) {
sourcePaths.add(extractedFile.getAbsolutePath());
//we ignore the verify zip part
} else {
throw new IOException("Missing extracted secondary dex file '" + extractedFile.getPath() + "'");
}
}
}
// 如果是debug的，那么额外去加载下 instant run 中的dex文件路径
if (ARouter.debuggable()) { // Search instant run support only debuggable
sourcePaths.addAll(tryLoadInstantRunDexFile(applicationInfo));
}
return sourcePaths;
}
更多的细节有兴趣的同学可以自己回去看，这里因为篇幅的原因就不过多讲这些了。
那么今天就到这里结束了，关于 ARouter 系列的更多源码解析，可以看接下来的两篇博客。
bye
