Learning record of arouter principle

Preface

The first share after the Spring Festival , The working state is also slowly getting back . The sharing that this article will bring to you is ARouter Introduction to the principle of , By understanding its principle , We can know how it supports calling or page jumping between componentized and non interdependent modules .

Text

ARouter Introduce

ARouter Alibaba open source is a routing framework for componentization , It can help page Jump and service call between components that do not depend on each other .

ARouter Use

Add dependency ：

android {
    
  //...
  defaultConfig {
    
       kapt {
    
            arguments {
    
                arg("AROUTER_MODULE_NAME", project.getName())
            }
        }
  }
  //...
}

dependencies {
    
    api 'com.alibaba:arouter-api:1.5.0'
    kapt 'com.alibaba:arouter-compiler:1.2.2'
}

Define jump Activity Of path：

@Route(path = "/test/router_activity")
class RouterActivity : AppCompatActivity() {
    
    override fun onCreate(savedInstanceState: Bundle?) {
    
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_router)
    }
}

initialization Router frame ：

class RouterDemoApp : Application() {
    
    override fun onCreate() {
    
        super.onCreate()
      // initialization 、 Inject 
        ARouter.init(this)
    }
}

Call jump ：

ARouter.getInstance().build("/test/router_activity").navigation()

Generated code （ Generated routing table ）

When we give Activity Or services, etc., plus Route After the note ,build once ,ARouter The framework will help us generate according to the template java file , And it can be accessed at runtime . The technology used is apt technology . Let's take a look at the code generated by the above example ：

public class ARouter$$Root$$app implements IRouteRoot {
    
  @Override
  public void loadInto(Map<String, Class<? extends IRouteGroup>> routes) {
    
    routes.put("test", ARouter$$Group$$test.class);
  }
}

public class ARouter$$Group$$test implements IRouteGroup {
    
  @Override
  public void loadInto(Map<String, RouteMeta> atlas) {
    
    atlas.put("/test/router_activity", RouteMeta.build(RouteType.ACTIVITY, RouterActivity.class, "/test/router_activity", "test", null, -1, -2147483648));
  }
}

According to the code generated above, we can see , The generated code is a routing table , First, match the group with the group's class correspond , Inside each group is the routing table under the Group .

initialization init()（ Load the group of the routing table ）

Next, let's look at initialization , What is done in the routing framework ：

//#ARouter
public static void init(Application application) {
    
    if (!hasInit) {
    
      //... Omitted code 
        hasInit = _ARouter.init(application);
 			//... Omitted code 
    }
}

//#_ARouter
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;
    }

The core code of initialization looks like LogisticsCenter in ：

public synchronized static void init(Context context, ThreadPoolExecutor tpe) throws HandlerException {
    
    mContext = context;
    executor = tpe;

    try {
    
        //... Omit code 
        if (registerByPlugin) {
    
            //... Omit code 
        } else {
    
            Set<String> routerMap;

            //  If it is debug Package or newer version 
            if (ARouter.debuggable() || PackageUtils.isNewVersion(context)) {
    
               // To get in com.alibaba.android.arouter.routes So class Class name 
                routerMap = ClassUtils.getFileNameByPackageName(mContext, ROUTE_ROOT_PAKCAGE);
              // Update to sp in 
                if (!routerMap.isEmpty()) {
    
                    context.getSharedPreferences(AROUTER_SP_CACHE_KEY, Context.MODE_PRIVATE).edit().putStringSet(AROUTER_SP_KEY_MAP, routerMap).apply();
                }
								// An updated version 
                PackageUtils.updateVersion(context); 
            } else {
    
                // Take out the stored data directly from the cache class
                routerMap = new HashSet<>(context.getSharedPreferences(AROUTER_SP_CACHE_KEY, Context.MODE_PRIVATE).getStringSet(AROUTER_SP_KEY_MAP, new HashSet<String>()));
            }
						
          // Traverse routerMap, take group Class loaded into the cache 
            for (String className : routerMap) {
    
                if (className.startsWith(ROUTE_ROOT_PAKCAGE + DOT + SDK_NAME + SEPARATOR + SUFFIX_ROOT)) {
    
                  // Generated Root、 For example, our example above ARouter$$Root$$app, call loadInto It's equivalent to loading routes.put("test", ARouter$$Group$$test.class)
                    ((IRouteRoot) (Class.forName(className).getConstructor().newInstance())).loadInto(Warehouse.groupsIndex);
                } else if (className.startsWith(ROUTE_ROOT_PAKCAGE + DOT + SDK_NAME + SEPARATOR + SUFFIX_INTERCEPTORS)) {
    
                    // Load interceptors , For example, generated ARouter$$Interceptors$$app
                    ((IInterceptorGroup) (Class.forName(className).getConstructor().newInstance())).loadInto(Warehouse.interceptorsIndex);
                } else if (className.startsWith(ROUTE_ROOT_PAKCAGE + DOT + SDK_NAME + SEPARATOR + SUFFIX_PROVIDERS)) {
    
                    //  load Provider, For example, generated ARouter$$Providers$$app
                    ((IProviderGroup) (Class.forName(className).getConstructor().newInstance())).loadInto(Warehouse.providersIndex);
                }
            }
        }
        //... Omit code 
    } catch (Exception e) {
    
        throw new HandlerException(TAG + "ARouter init logistics center exception! [" + e.getMessage() + "]");
    }
}

The core logic above is if debug Package or newer version , Then go get com.alibaba.android.arouter.routes So class Class name , And then update to sp in , And update the version number . Then load through reflection IRouteRoot, To load the group and its corresponding class object , In addition, interceptors will be loaded ,Provider.

Here we focus on obtaining class File path method getFileNameByPackageName：

public static Set<String> getFileNameByPackageName(Context context, final String packageName) throws NameNotFoundException, IOException, InterruptedException {
    
    final Set<String> classNames = new HashSet();
  // Get dex File path 
    List<String> paths = getSourcePaths(context);
    final CountDownLatch parserCtl = new CountDownLatch(paths.size());
    Iterator var5 = paths.iterator();

    while(var5.hasNext()) {
    
        final String path = (String)var5.next();
        DefaultPoolExecutor.getInstance().execute(new Runnable() {
    
            public void run() {
    
                DexFile dexfile = null;
                try {
    
                  // Load out dexfile file 
                    if (path.endsWith(".zip")) {
    
                        dexfile = DexFile.loadDex(path, path + ".tmp", 0);
                    } else {
    
                        dexfile = new DexFile(path);
                    }

                    Enumeration dexEntries = dexfile.entries();
									//  Traverse dexFile The elements inside , Load out .class file 
                    while(dexEntries.hasMoreElements()) {
    
                        String className = (String)dexEntries.nextElement();
                      // start "com.alibaba.android.arouter.routes"
                        if (className.startsWith(packageName)) {
    
                            classNames.add(className);
                        }
                    }
                } catch (Throwable var12) {
    
                    Log.e("ARouter", "Scan map file in dex files made error.", var12);
                } finally {
    
                    //... Omit code 
                    parserCtl.countDown();
                }
            }
        });
    }

    parserCtl.await();
  	//... Omit code 
    return classNames;
}

The core logic in this method is to load dex Path to file , Then build DexFile, After construction, traverse the elements inside , If it is com.alibaba.android.arouter.routes At the beginning class file , Then save it to the list and wait for it to return .

getSourcePaths：

public static List<String> getSourcePaths(Context context) throws NameNotFoundException, IOException {
    
    ApplicationInfo applicationInfo = context.getPackageManager().getApplicationInfo(context.getPackageName(), 0);
    File sourceApk = new File(applicationInfo.sourceDir);
    List<String> sourcePaths = new ArrayList();
    sourcePaths.add(applicationInfo.sourceDir);
    String extractedFilePrefix = sourceApk.getName() + ".classes";
  // Whether it is turned on multidex, If it's on , You need to get each dex route 
    if (!isVMMultidexCapable()) {
    
        int totalDexNumber = getMultiDexPreferences(context).getInt("dex.number", 1);
        File dexDir = new File(applicationInfo.dataDir, SECONDARY_FOLDER_NAME);
				// Go through each one dex file 
        for(int secondaryNumber = 2; secondaryNumber <= totalDexNumber; ++secondaryNumber) {
    
          //app.classes2.zip、app.classes3.zip ...
            String fileName = extractedFilePrefix + secondaryNumber + ".zip";
            File extractedFile = new File(dexDir, fileName);
            if (!extractedFile.isFile()) {
    
                throw new IOException("Missing extracted secondary dex file '" + extractedFile.getPath() + "'");
            }
            sourcePaths.add(extractedFile.getAbsolutePath());
        }
    }

    if (ARouter.debuggable()) {
    
        sourcePaths.addAll(tryLoadInstantRunDexFile(applicationInfo));
    }

    return sourcePaths;
}

getSourcePaths The function of is to get app All of the dex Path to file , Turn into class File to get class The file path provides data .

Summary ：

• ARouter.init(this) The call is handed over to the internal _ARouter.init(application), Then the real thing is LogisticsCenter.init(mContext, executor)
• If it is debug Package or upgraded version , Then go to load com.alibaba.android.arouter.routes Under bag dex Path to file , And update it to the cache
• Through these dex To get all the corresponding class Path to file
• Finally, according to the prefix of the class name, it is loaded into Warehouse Corresponding map in , Among them group、interceptor and provider

Call and process

ARouter.getInstance().build("/test/router_activity").navigation()

build Will build a Postcard The object comes out ：

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

//#_ARouter
    protected Postcard build(String path) {
    
        if (TextUtils.isEmpty(path)) {
    
            throw new HandlerException(Consts.TAG + "Parameter is invalid!");
        } else {
    
            PathReplaceService pService = ARouter.getInstance().navigation(PathReplaceService.class);
            if (null != pService) {
    
                path = pService.forString(path);
            }
          //extractGroup The way is from path To extract from group, such as "/test/router_activity",test Is extracted group
            return build(path, extractGroup(path));
        }
    }

build(path, group) Method will eventually build a Postcard The object comes out .

Build up PostCard after , Call it the navigation Method can realize our jump or get the corresponding entity .navigation Method will finally call _ARouter Of navigation Method ：

protected Object navigation(final Context context, final Postcard postcard, final int requestCode, final NavigationCallback callback) {
    
    //... Omit code 
    try {
    
      //1. according to postCard Of group Load routing table , And complete postCard Information about 
        LogisticsCenter.completion(postcard);
    } catch (NoRouteFoundException ex) {
    
        //... exception handling 
        return null;
    }
    if (null != callback) {
    
        callback.onFound(postcard);
    }

  // If it's not the green channel , The logic of interceptors is needed , Otherwise, the interceptor will be skipped 
    if (!postcard.isGreenChannel()) {
     
        interceptorService.doInterceptions(postcard, new InterceptorCallback() {
    
            @Override
            public void onContinue(Postcard postcard) {
    
              //2. Truly realize action processing 
                _navigation(context, postcard, requestCode, callback);
            }
            @Override
            public void onInterrupt(Throwable exception) {
    
                if (null != callback) {
    
                    callback.onInterrupt(postcard);
                }
								//... Omit code 
            }
        });
    } else {
    
      //2. Truly realize action processing 
        return _navigation(context, postcard, requestCode, callback);
    }
    return null;
}

navigation The core logic of the method is ： Load routing table , And complete postCard Information about , Then really deal with jump or request logic .

LogisticsCenter.completion(postcard) The core source code is as follows ：

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) {
    
      //groupsIndex stay init It has been loaded by , You can go through here group Get the corresponding group Of class object 
        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 {
    
                //... Omit code 
                IRouteGroup iGroupInstance = groupMeta.getConstructor().newInstance();
              // take group The routing table inside is loaded into memory , Our first example is to implement ：atlas.put("/test/router_activity", RouteMeta.build(RouteType.ACTIVITY, RouterActivity.class, "/test/router_activity", "test", null, -1, -2147483648));
                iGroupInstance.loadInto(Warehouse.routes);
              // Because the routing table is loaded , So you can group Remove... From memory , Save memory 
                Warehouse.groupsIndex.remove(postcard.getGroup());
								//... Omit code 
            } catch (Exception e) {
    
                throw new HandlerException(TAG + "Fatal exception when loading group meta. [" + e.getMessage() + "]");
            }
						// Have already put group The routing table in is loaded , Execute the function again .
            completion(postcard);   // Reload
        }
    } else {
    
      	//  The second time , to postCard Fill in the information 
        postcard.setDestination(routeMeta.getDestination());
        postcard.setType(routeMeta.getType());
        postcard.setPriority(routeMeta.getPriority());
        postcard.setExtra(routeMeta.getExtra());
			//... Omit code , Mainly parsing uri Then the assignment of parameters 

      // According to different types of route acquisition , Continue to add some information to postCard
        switch (routeMeta.getType()) {
    
            case PROVIDER:  
            		//... Omit code , It is mainly to add some other parameters 
                postcard.greenChannel();    // Provider should skip all of interceptors
                break;
            case FRAGMENT:
                postcard.greenChannel();    // Fragment needn't interceptors
            default:
                break;
        }
    }
}

End of supplement postCard After the message , Now let's see _navigation Method ：

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:
            // structure Intent, Then switch to the main thread , And jump to the specified Activity
            break;
        case PROVIDER:
            return postcard.getProvider();
        case BOARDCAST:
        case CONTENT_PROVIDER:
        case FRAGMENT:
        	// Reflection constructs an instance and returns 
        case METHOD:
        default:
            return null;
    }

    return null;
}

You can see , Eventually, according to different type, To respond differently , for example ACTIVITY Words , Will be carried out in activity The jump , Other operations such as instance return will be constructed through reflection .

Summary ：

• The beginning of the call , Will build a PostCard object , initialization path and group
• navigation Method will eventually call _ARouter Of navigation Method , And then through LogisticsCenter.completion(postcard) To load the group The routing table inside , And complete postcard Information .
• If there is a green channel , The interceptor is not executed , Just skip , Otherwise, you need to execute the interceptor .
• Finally, perform corresponding operations through different types .

Conclusion

The sharing of this article ends here , Believe that after reading , Can be right ARouter Have a certain understanding of the principle of , So that if we use it later , Can better use , Or provide a good idea reference for customizing the routing framework for the project . meanwhile , Such an excellent framework is also worth learning some of its design ideas .