Analysis of arouter

ARouter

ARouter yes ： Alibaba developed its own routing framework , It mainly solves the problems between components 、 Between modules Interface jump problem .

principle

• Use apt Generate code during compilation
• grouping + Load on demand The routing list
• For internal use Intent To jump

Principle analysis

// The first one created uses Router Annotated Activity
@Route(path = "/module_main/two")
public class TwoActivity extends AppCompatActivity {
    

    @Override
    protected void onCreate(Bundle savedInstanceState) {
    
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_two);
        Toast.makeText(this, getLocalClassName(), Toast.LENGTH_SHORT).show();
    }
}


// the second 
@Route(path = "/module_comm/comm")
public class CommActivity extends AppCompatActivity {
    

    @Override
    protected void onCreate(Bundle savedInstanceState) {
    
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_comm);
        Toast.makeText(this, getLocalClassName(), Toast.LENGTH_SHORT).show();
    }
}


// Third 
@Route(path = "/module_second/second")
public class SecondActivity extends AppCompatActivity {
    
    @Autowired
    String data;
    
    @Override
    protected void onCreate(Bundle savedInstanceState) {
    
        super.onCreate(savedInstanceState);
        ARouter.getInstance().inject(this);
        TextView textView = new TextView(this);
        textView.setText(data);
        setContentView(textView);
    }
}

These three classes are in different module Inside

Next, let's compile this project , See what code has been generated

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

public class ARouter$$Providers$$app implements IProviderGroup {
    
  @Override
  public void loadInto(Map<String, RouteMeta> providers) {
    
  }
}

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

// the second module
public class ARouter$$Group$$module_comm implements IRouteGroup {
    
  @Override
  public void loadInto(Map<String, RouteMeta> atlas) {
    
    atlas.put("/module_comm/comm", RouteMeta.build(RouteType.ACTIVITY, CommActivity.class, "/module_comm/comm", "module_comm", null, -1, -2147483648));
  }
}

public class ARouter$$Providers$$module_comm implements IProviderGroup {
    
  @Override
  public void loadInto(Map<String, RouteMeta> providers) {
    
  }
}

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

// Third module
public class ARouter$$Group$$module_second implements IRouteGroup {
    
  @Override
  public void loadInto(Map<String, RouteMeta> atlas) {
    
    atlas.put("/module_second/second", RouteMeta.build(RouteType.ACTIVITY, SecondActivity.class, "/module_second/second", "module_second", new java.util.HashMap<String, Integer>(){
    {
    put("data", 8); }}, -1, -2147483648));
  }
}

public class ARouter$$Providers$$module_second implements IProviderGroup {
    
  @Override
  public void loadInto(Map<String, RouteMeta> providers) {
    
  }
}

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

// Here is for Autowired Annotation variable assignment 
public class SecondActivity$$ARouter$$Autowired implements ISyringe {
    
  private SerializationService serializationService;

  @Override
  public void inject(Object target) {
    
    serializationService = ARouter.getInstance().navigation(SerializationService.class);
    SecondActivity substitute = (SecondActivity)target;
    substitute.data = substitute.getIntent().getStringExtra("data");
  }
}

We can see that basically every module At least three classes will be generated ARouter$$Providers$$*** It is an empty implementation that temporarily ignores it , Let's take a look at ARouter$$Group$$Comm

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

You can see it here loadInto Medium is to be used Router Annotated classes with path The value of is key, Class class by value There is Map in ,ps all @Router annotation path The first class with the same value after the value slash will be managed in the same class

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

There will be Router Annotated path The first value after the slash of is key, take ARouter$$Group$$module_comm.class by value There is map in , In this case, can we think ARouter Will Router annotation path The first class with the same value after the slash is divided into a group , Use apt Generate the management class of this group , That's what we have now ARouter$$Group$$module_comm

Here we learn ARouter How to group , Let's take a look ARouter How to get our classes

ARouter.openLog();     //  Print log 
ARouter.openDebug();   //  Turn on debugging mode ( If in InstantRun Run in mode , Debug mode must be turned on ！ Online version needs to be closed , Otherwise, there is a safety risk )
ARouter.init(getApplication()); //  As early as possible , Recommended in the Application In the initialization 

    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.");
        }
    }

	  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;
	    }
	
	  // Code has been cut 
	  public synchronized static void init(Context context, ThreadPoolExecutor tpe) throws HandlerException {
    
	        tr {
    
	                if (ARouter.debuggable() || PackageUtils.isNewVersion(context)) {
    
	                    logger.info(TAG, "Run with debug mode or new install, rebuild router map.");
	                    // These class was generated 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 finishes.
	                } 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() + "]");
	        }
	    }

routerMap = ClassUtils.getFileNameByPackageName(mContext, ROUTE_ROOT_PAKCAGE); We see this line directly

    public static Set<String> getFileNameByPackageName(Context context, final String packageName) throws PackageManager.NameNotFoundException, IOException, InterruptedException {
    
        final Set<String> classNames = new HashSet<>();
		// Got it apk Path after installation 
        List<String> paths = getSourcePaths(context);
        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();
                        // facilitate dex Next class 
                        while (dexEntries.hasMoreElements()) {
    
                            String className = dexEntries.nextElement();
                            // Find the package name is com.alibaba.android.arouter.routes Initial class 
                            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) {
    
                            }
                        }
                    }
                }
            });
        }
        return classNames;
    }

It's coming in here packgeName = com.alibaba.android.arouter.routes After this function is executed, we can get several classes we saw before . Because the package name of the class generated after compilation happens to be com.alibaba.android.arouter.routes

Next we continue to see LogisticsCenter Class init function

 public synchronized static void init(Context context, ThreadPoolExecutor tpe) throws HandlerException {
    
      ...
    for (String className : routerMap) {
    
        if (className.startsWith(ROUTE_ROOT_PAKCAGE + DOT + SDK_NAME + SEPARATOR + SUFFIX_ROOT)) {
    
        ((IRouteRoot) (Class.forName(className).getConstructor().newInstance())).loadInto(Warehouse.groupsIndex);
         } else if (className.startsWith(ROUTE_ROOT_PAKCAGE + DOT + SDK_NAME + SEPARATOR + SUFFIX_INTERCEPTORS)) {
    
          ((IInterceptorGroup(Class.forName(className).getConstructor().newInstance())).loadInto(Warehouse.interceptorsIndex);
        } else if (className.startsWith(ROUTE_ROOT_PAKCAGE + DOT + SDK_NAME + SEPARATOR + SUFFIX_PROVIDERS)) {
    ((IProviderGroup) (Class.forName(className).getConstructor().newInstance())).loadInto(Warehouse.providersIndex);
      }
      ...
    }

Here is to get apt Generated classes and call their loadInto() Of course, there is no specific group called here loadInto So actually path The mapping with the class has not been loaded into memory , This achieves the effect of saving memory , Here is the management class of each group class Added to the Warehouse.groupsIndex in , It is also quite simple for us to take out the mapping relationship of specific groups later

Come here ARouter Of init() It's done. Let's see where we can get the mapping of specific groups

       ARouter.getInstance()
                .build("/module_second/second")
                .navigation();

We usually jump to the page like this. Let's take a look next navigation() What have you done

    protected Object navigation(final Context context, final Postcard postcard, final int requestCode, final NavigationCallback callback) {
    
      		...
            LogisticsCenter.completion(postcard);
       		...
            return _navigation(context, postcard, requestCode, callback);
        	....
    }


    public synchronized static void completion(Postcard postcard) {
    
        if (null == postcard) {
    
            throw new NoRouteFoundException(TAG + "No postcard!");
        }

        RouteMeta routeMeta = Warehouse.routes.get(postcard.getPath());
    	// Current map There is no corresponding path Of class
        if (null == routeMeta) {
     
        	// Take this out path The management class of the Group 
            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()));
                    }
					// Use reflection to create objects 
                    IRouteGroup iGroupInstance = groupMeta.getConstructor().newInstance();
                    // Add all the data of this group to map
                    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() + "]");
                }
				// Reset this function , Next time else molecular 
                completion(postcard);   // Reload
            }
        } else {
    
        	// fill postcard Subsequent interface jumps require 
            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 implement 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;
            }
        }
    }

From the code above, we can see ARouter On demand loading , We are going to look at ARouter How to jump

    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);
                }

                // 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:
                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;
    }

From here we can see that ARouter Internal jump is still used Intent, Then why can't we use component development to reference anything else module But in ARouter But you can , That's because it's going on apk All classes will be packaged together , So we use ARouter It is not only convenient but also beautiful to achieve the effect of decoupling