3. Android 一步步手写ARouter

CountDownLatch的使用！系统里面经常用到！

跳转遇到的问题？Arounter需要解决的问题

不能拿到对方的类。你只能通过找到类的路径去反射拿到这个class，那么有没有一种更好的解决办法呢？

Arounter的原理：产生路由表，通过key去找到value

分析：

首先第一步，定义注解：

Target:ElementType.Type

<pre style="margin: 8px 0px; background-color: rgb(43, 43, 43); color: rgb(169, 183, 198); font-family: "JetBrains Mono", monospace; font-size: 0.817rem;">@Target(ElementType.TYPE)
@Retention(RetentionPolicy.CLASS)
public @interface Route {

/**

• 路由的路径 * * @return
  /
  String path(); /*
• 将路由节点进行分组，可以实现动态加载 * * @return
  */
  String group() default ""; }
  </pre>

为什么需要分组？

Route注解里有path和group，这便是仿照ARouter对路由进行分组。因为当项目变得越来越庞大的时候，为了便于管理和减小首次加载路由表过于耗时的问题

第二步：定义基本的接口

**[图片上传失败...(image-c9e97f-1640330005823)]

IRouteGroup：自定义加载接口。不是自动生成的，自定义的

<pre style="margin: 8px 0px; background-color: rgb(43, 43, 43); color: rgb(169, 183, 198); font-family: "JetBrains Mono", monospace; font-size: 0.817rem;">public interface IRouteGroup {
void loadInto(Map<String, RouteMeta> atlas); }</pre>**

第三步，编写注解处理器。

需要生成的.java文件

[图片上传失败...(image-11f849-1640330005863)]

EaseRouter_Root_app.java: 里面需要是代表有几个模块，组。有2组

EaseRouter_Group_main.java :包含了Main模块里面的跳转

EaseRouter_Group_show.java :包含了show模块里面的跳转

<pre style="margin: 8px 0px; background-color: rgb(43, 43, 43); color: rgb(169, 183, 198); font-family: "JetBrains Mono", monospace; font-size: 0.817rem;">public class EaseRouter_Root_app implements IRouteRoot {
@Override
public void loadInto(Map<String, Class<? extends IRouteGroup>> routes) {
routes.put("main", EaseRouter_Group_main.class);
routes.put("show", EaseRouter_Group_show.class);
}
}
</pre>

EaseRouter_Group_main.java文件

<pre style="margin: 8px 0px; background-color: rgb(43, 43, 43); color: rgb(169, 183, 198); font-family: "JetBrains Mono", monospace; font-size: 0.817rem;">public class EaseRouter_Group_main implements IRouteGroup {
@Override
public void loadInto(Map<String, RouteMeta> atlas) {
atlas.put("/main/main",RouteMeta.build(RouteMeta.Type.ACTIVITY,MainActivity.class,"/main/main","main"));
atlas.put("/main/main2",RouteMeta.build(RouteMeta.Type.ACTIVITY,Main2Activity.class,"/main/main2","main"));
}
}</pre>

EaseRouter_Group_show

<pre style="margin: 8px 0px; background-color: rgb(43, 43, 43); color: rgb(169, 183, 198); font-family: "JetBrains Mono", monospace; font-size: 0.817rem;">public class EaseRouter_Group_show implements IRouteGroup {
@Override
public void loadInto(Map<String, RouteMeta> atlas) {
atlas.put("/show/info",RouteMeta.build(RouteMeta.Type.ACTIVITY,ShowActivity.class,"/show/info","show"));
}
}</pre>

通过注解的形式重写几个方法，比butterknife的又强了点！

@AutoService(Processor.class)
/**
  处理器接收的参数 替代 {@link AbstractProcessor#getSupportedOptions()} 函数
 */
@SupportedOptions(Constant.ARGUMENTS_NAME)
/**
 * 注册给哪些注解的  替代 {@link AbstractProcessor#getSupportedAnnotationTypes()} 函数
 */
@SupportedAnnotationTypes(Constant.ANNOTATION_TYPE_ROUTE)

生成文件的方法：

<pre style="margin: 8px 0px; background-color: rgb(43, 43, 43); color: rgb(169, 183, 198); font-family: "JetBrains Mono", monospace; font-size: 0.817rem;">/**

• • @param set 使用了支持处理注解的节点集合
• @param roundEnvironment 表示当前或是之前的运行环境,可以通过该对象查找找到的注解。
• @return true 表示后续处理器不会再处理(已经处理)
  */ @Override public boolean process(Set<? extends TypeElement> set, RoundEnvironment roundEnvironment) {
  if (!Utils.isEmpty(set)) {
  //被Route注解的节点集合
  Set<? extends Element> rootElements = roundEnvironment.getElementsAnnotatedWith(Route.class);
  if (!Utils.isEmpty(rootElements)) {
  processorRoute(rootElements);
  }
  return true;
  }
  return false; }

private void processorRoute(Set<? extends Element> rootElements) {
//获得Activity这个类的节点信息
TypeElement activity = elementUtils.getTypeElement(Constant.ACTIVITY);
TypeElement service = elementUtils.getTypeElement(Constant.ISERVICE);
for (Element element : rootElements) {
RouteMeta routeMeta;
//类信息
TypeMirror typeMirror = element.asType();
log.i("Route class:" + typeMirror.toString());
Route route = element.getAnnotation(Route.class);
if (typeUtils.isSubtype(typeMirror, activity.asType())) {
routeMeta = new RouteMeta(RouteMeta.Type.ACTIVITY, route, element);
} else if (typeUtils.isSubtype(typeMirror, service.asType())) {
routeMeta = new RouteMeta(RouteMeta.Type.ISERVICE, route, element);
} else {
throw new RuntimeException("Just support Activity or IService Route: " + element);
}
categories(routeMeta);
}
TypeElement iRouteGroup = elementUtils.getTypeElement(Constant.IROUTE_GROUP);
TypeElement iRouteRoot = elementUtils.getTypeElement(Constant.IROUTE_ROOT); //生成Group记录分组表
generatedGroup(iRouteGroup); //生成Root类 作用：记录<分组，对应的Group类>
generatedRoot(iRouteRoot, iRouteGroup); }</pre>

用2个Map保存信息！

<pre style="margin: 8px 0px; background-color: rgb(43, 43, 43); color: rgb(169, 183, 198); font-family: "JetBrains Mono", monospace; font-size: 0.817rem;">/**

• key:组名 value:类名 / private Map<String, String> rootMap = new TreeMap<>(); /*
• 分组 key:组名 value:对应组的路由信息 */ private Map<String, List<RouteMeta>> groupMap = new HashMap<>();</pre>

生成Group的java文件

<pre style="margin: 8px 0px; background-color: rgb(43, 43, 43); color: rgb(169, 183, 198); font-family: "JetBrains Mono", monospace; font-size: 0.817rem;">private void generatedGroup(TypeElement iRouteGroup) {
//创建参数类型 Map<String, RouteMeta>
ParameterizedTypeName parameterizedTypeName = ParameterizedTypeName.get(
ClassName.get(Map.class),
ClassName.get(String.class),
ClassName.get(RouteMeta.class));
ParameterSpec altas = ParameterSpec.builder(parameterizedTypeName, "atlas").build(); for (Map.Entry<String, List<RouteMeta>> entry : groupMap.entrySet()) {
MethodSpec.Builder methodBuilder = MethodSpec.methodBuilder(Constant.METHOD_LOAD_INTO)
.addModifiers(Modifier.PUBLIC)
.addAnnotation(Override.class)
.addParameter(altas); String groupName = entry.getKey();
List<RouteMeta> groupData = entry.getValue();
for (RouteMeta routeMeta : groupData) {
//函数体的添加
methodBuilder.addStatement("atlas.put(T.build(L,S,$S))",
routeMeta.getPath(),
ClassName.get(RouteMeta.class),
ClassName.get(RouteMeta.Type.class),
routeMeta.getType(),
ClassName.get(((TypeElement) routeMeta.getElement())),
routeMeta.getPath(),
routeMeta.getGroup());
}
String groupClassName = Constant.NAME_OF_GROUP + groupName;
TypeSpec typeSpec = TypeSpec.classBuilder(groupClassName)
.addSuperinterface(ClassName.get(iRouteGroup))
.addModifiers(Modifier.PUBLIC)
.addMethod(methodBuilder.build())
.build();
JavaFile javaFile = JavaFile.builder(Constant.PACKAGE_OF_GENERATE_FILE, typeSpec).build();
try {
javaFile.writeTo(filerUtils);
} catch (IOException e) {
e.printStackTrace();
}
rootMap.put(groupName, groupClassName); }
}</pre>

几个类：

TypeElement：元素类型，比如activty,Service

TypeMirror： 类信息

注解处理器的源码：

<pre style="margin: 8px 0px; background-color: rgb(43, 43, 43); color: rgb(169, 183, 198); font-family: "JetBrains Mono", monospace; font-size: 0.817rem;">@AutoService(Processor.class)
/**
处理器接收的参数 替代 {@link AbstractProcessor#getSupportedOptions()} 函数
/ @SupportedOptions(Constant.ARGUMENTS_NAME)
/*

• 指定使用的Java版本 替代 {@link AbstractProcessor#getSupportedSourceVersion()} 函数
  / @SupportedSourceVersion(SourceVersion.RELEASE_7)
  /*
• 注册给哪些注解的 替代 {@link AbstractProcessor#getSupportedAnnotationTypes()} 函数
  */ @SupportedAnnotationTypes(Constant.ANNOTATION_TYPE_ROUTE)

public class RouterProcessor extends AbstractProcessor {
/**

• key:组名 value:类名 / private Map<String, String> rootMap = new TreeMap<>();
  /*

• 分组 key:组名 value:对应组的路由信息 / private Map<String, List<RouteMeta>> groupMap = new HashMap<>(); /*

• 节点工具类 (类、函数、属性都是节点) / private Elements elementUtils; /*

• type(类信息)工具类 / private Types typeUtils; /*

• 文件生成器 类/资源 */ private Filer filerUtils; private String moduleName; private Log log; @Override
  public synchronized void init(ProcessingEnvironment processingEnvironment) {
  super.init(processingEnvironment);
  //获得apt的日志输出
  log = Log.newLog(processingEnvironment.getMessager());
  elementUtils = processingEnvironment.getElementUtils();
  typeUtils = processingEnvironment.getTypeUtils();
  filerUtils = processingEnvironment.getFiler(); //参数是模块名 为了防止多模块/组件化开发的时候 生成相同的 xx文件
  Map<String, String> options = processingEnvironment.getOptions();
  if (!Utils.isEmpty(options)) {
  moduleName = options.get(Constant.ARGUMENTS_NAME);
  }
  if (Utils.isEmpty(moduleName)) {
  throw new RuntimeException("Not set processor moudleName option !");
  }
  log.i("init RouterProcessor " + moduleName + " success !");
  }

  /**

• • @param set 使用了支持处理注解的节点集合

• @param roundEnvironment 表示当前或是之前的运行环境,可以通过该对象查找找到的注解。

• @return true 表示后续处理器不会再处理(已经处理)
  */ @Override
  public boolean process(Set<? extends TypeElement> set, RoundEnvironment roundEnvironment) {
  if (!Utils.isEmpty(set)) {
  //被Route注解的节点集合
  Set<? extends Element> rootElements = roundEnvironment.getElementsAnnotatedWith(Route.class);
  if (!Utils.isEmpty(rootElements)) {
  processorRoute(rootElements);
  }
  return true;
  }
  return false;
  }

  private void processorRoute(Set<? extends Element> rootElements) {
  //获得Activity这个类的节点信息
  TypeElement activity = elementUtils.getTypeElement(Constant.ACTIVITY);
  TypeElement service = elementUtils.getTypeElement(Constant.ISERVICE);
  for (Element element : rootElements) {
  RouteMeta routeMeta;
  //类信息
  TypeMirror typeMirror = element.asType();
  log.i("Route class:" + typeMirror.toString());
  Route route = element.getAnnotation(Route.class);
  if (typeUtils.isSubtype(typeMirror, activity.asType())) {
  routeMeta = new RouteMeta(RouteMeta.Type.ACTIVITY, route, element);
  } else if (typeUtils.isSubtype(typeMirror, service.asType())) {
  routeMeta = new RouteMeta(RouteMeta.Type.ISERVICE, route, element);
  } else {
  throw new RuntimeException("Just support Activity or IService Route: " + element);
  }
  categories(routeMeta);
  }
  TypeElement iRouteGroup = elementUtils.getTypeElement(Constant.IROUTE_GROUP);
  TypeElement iRouteRoot = elementUtils.getTypeElement(Constant.IROUTE_ROOT); //生成Group记录分组表
  generatedGroup(iRouteGroup); //生成Root类 作用：记录<分组，对应的Group类>
  generatedRoot(iRouteRoot, iRouteGroup);
  }

  /**

• 生成Root类 作用：记录<分组，对应的Group类>

• @param iRouteRoot

• @param iRouteGroup
  */
  private void generatedRoot(TypeElement iRouteRoot, TypeElement iRouteGroup) {
  //创建参数类型 Map<String,Class<? extends IRouteGroup>> routes>
  //Wildcard 通配符 ParameterizedTypeName parameterizedTypeName = ParameterizedTypeName.get(
  ClassName.get(Map.class),
  ClassName.get(String.class),
  ParameterizedTypeName.get(
  ClassName.get(Class.class),
  WildcardTypeName.subtypeOf(ClassName.get(iRouteGroup))
  ));
  //参数 Map<String,Class<? extends IRouteGroup>> routes> routes
  ParameterSpec parameter = ParameterSpec.builder(parameterizedTypeName, "routes").build();
  //函数 public void loadInfo(Map<String,Class<? extends IRouteGroup>> routes> routes)
  MethodSpec.Builder methodBuilder = MethodSpec.methodBuilder(Constant.METHOD_LOAD_INTO)
  .addModifiers(Modifier.PUBLIC)
  .addAnnotation(Override.class)
  .addParameter(parameter);
  //函数体
  for (Map.Entry<String, String> entry : rootMap.entrySet()) {
  methodBuilder.addStatement("routes.put(T.class)", entry.getKey(), ClassName.get(Constant.PACKAGE_OF_GENERATE_FILE, entry.getValue()));
  }
  //生成类
  String className = Constant.NAME_OF_ROOT + moduleName;
  TypeSpec typeSpec = TypeSpec.classBuilder(className)
  .addSuperinterface(ClassName.get(iRouteRoot))
  .addModifiers(Modifier.PUBLIC)
  .addMethod(methodBuilder.build())
  .build();
  try {
  JavaFile.builder(Constant.PACKAGE_OF_GENERATE_FILE, typeSpec).build().writeTo(filerUtils);
  log.i("Generated RouteRoot：" + Constant.PACKAGE_OF_GENERATE_FILE + "." + className);
  } catch (IOException e) {
  e.printStackTrace();
  }
  }

  private void generatedGroup(TypeElement iRouteGroup) {
  //创建参数类型 Map<String, RouteMeta>
  ParameterizedTypeName parameterizedTypeName = ParameterizedTypeName.get(
  ClassName.get(Map.class),
  ClassName.get(String.class),
  ClassName.get(RouteMeta.class));
  ParameterSpec altas = ParameterSpec.builder(parameterizedTypeName, "atlas").build(); for (Map.Entry<String, List<RouteMeta>> entry : groupMap.entrySet()) {
  MethodSpec.Builder methodBuilder = MethodSpec.methodBuilder(Constant.METHOD_LOAD_INTO)
  .addModifiers(Modifier.PUBLIC)
  .addAnnotation(Override.class)
  .addParameter(altas); String groupName = entry.getKey();
  List<RouteMeta> groupData = entry.getValue();
  for (RouteMeta routeMeta : groupData) {
  //函数体的添加
  methodBuilder.addStatement("atlas.put(T.build(L,S,$S))",
  routeMeta.getPath(),
  ClassName.get(RouteMeta.class),
  ClassName.get(RouteMeta.Type.class),
  routeMeta.getType(),
  ClassName.get(((TypeElement) routeMeta.getElement())),
  routeMeta.getPath(),
  routeMeta.getGroup());
  }
  String groupClassName = Constant.NAME_OF_GROUP + groupName;
  TypeSpec typeSpec = TypeSpec.classBuilder(groupClassName)
  .addSuperinterface(ClassName.get(iRouteGroup))
  .addModifiers(Modifier.PUBLIC)
  .addMethod(methodBuilder.build())
  .build();
  JavaFile javaFile = JavaFile.builder(Constant.PACKAGE_OF_GENERATE_FILE, typeSpec).build();
  try {
  javaFile.writeTo(filerUtils);
  } catch (IOException e) {
  e.printStackTrace();
  }
  rootMap.put(groupName, groupClassName); }
  }

  /**

• 检查是否配置 group 如果没有配置 则从path截取出组名 * @param routeMeta
  */
  private void categories(RouteMeta routeMeta) {
  if (routeVerify(routeMeta)) {
  log.i("Group : " + routeMeta.getGroup() + " path=" + routeMeta.getPath());
  //分组与组中的路由信息
  List<RouteMeta> routeMetas = groupMap.get(routeMeta.getGroup());
  if (Utils.isEmpty(routeMetas)) {
  routeMetas = new ArrayList<>();
  routeMetas.add(routeMeta);
  groupMap.put(routeMeta.getGroup(), routeMetas);
  } else {
  routeMetas.add(routeMeta);
  }
  } else {
  log.i("Group info error:" + routeMeta.getPath());
  }
  }

  /**

• 验证path路由地址的合法性 * @param routeMeta

• @return
  */
  private boolean routeVerify(RouteMeta routeMeta) {
  String path = routeMeta.getPath();
  String group = routeMeta.getGroup();
  // 必须以 / 开头来指定路由地址
  if (!path.startsWith("/")) {
  return false;
  }
  //如果group没有设置 我们从path中获得group
  if (Utils.isEmpty(group)) {
  String defaultGroup = path.substring(1, path.indexOf("/", 1));
  //截取出的group还是空
  if (Utils.isEmpty(defaultGroup)) {
  return false;
  }
  routeMeta.setGroup(defaultGroup);
  }
  return true;
  }

}
</pre>

第四步： 文件生成后，需要调用，通过反射，需要反射去创建实例！

先模拟调用的代码！

需要2个Map去装载组和类

public void test() {
    EaseRouter_Root_app rootApp = new EaseRouter_Root_app();
    HashMap<String, Class<? extends IRouteGroup>> rootMap = new HashMap<>();
    rootApp.loadInto(rootMap);

    //得到/main分组
    Class<? extends IRouteGroup> aClass = rootMap.get("main");
    try {
        HashMap<String, RouteMeta> groupMap = new HashMap<>();
        aClass.newInstance().loadInto(groupMap);
        //得到MainActivity
        RouteMeta main = groupMap.get("/main/main");
        Class<?> mainActivityClass = main.getDestination();

        Intent intent = new Intent(this, mainActivityClass);
        startActivity(intent);
    } catch (InstantiationException e) {
        e.printStackTrace();
    } catch (IllegalAccessException e) {
        e.printStackTrace();
    }

}

具体：在application的时候去填充map

<pre style="margin: 8px 0px; background-color: rgb(43, 43, 43); color: rgb(169, 183, 198); font-family: "JetBrains Mono", monospace; font-size: 0.817rem;">public class Warehouse {

// root 映射表 保存分组信息

static Map<String, Class<? extends IRouteGroup>> groupsIndex = new HashMap<>(); // group 映射表 保存组中的所有数据
static Map<String, RouteMeta> routes = new HashMap<>(); // group 映射表 保存组中的所有数据
static Map<Class, IService> services = new HashMap<>();
// TestServiceImpl.class , TestServiceImpl 没有再反射 /**

• 以键值对优先级的方式保存拦截器对象 / public static Map<Integer, Class<? extends IInterceptor>> interceptorsIndex = new UniqueKeyTreeMap<>();
  /*
• 以集合的方式保存所有拦截器对象 */ public static List<IInterceptor> interceptors = new ArrayList<>(); }
  </pre>

<pre style="margin: 8px 0px; background-color: rgb(43, 43, 43); color: rgb(169, 183, 198); font-family: "JetBrains Mono", monospace; font-size: 0.817rem;">/**

• 分组表制作 */ private static void loadInfo() throws PackageManager.NameNotFoundException, InterruptedException, ClassNotFoundException, NoSuchMethodException, IllegalAccessException, InvocationTargetException, InstantiationException {
  //获得所有 apt生成的路由类的全类名 (路由表)
  Set<String> routerMap = ClassUtils.getFileNameByPackageName(mContext, ROUTE_ROOT_PAKCAGE);
  for (String className : routerMap) {
  if (className.startsWith(ROUTE_ROOT_PAKCAGE + "." + SDK_NAME + SEPARATOR + SUFFIX_ROOT)) {
  //root中注册的是分组信息 将分组信息加入仓库中
  ((IRouteRoot) Class.forName(className).getConstructor().newInstance()).loadInto(Warehouse.groupsIndex);
  } else if (className.startsWith(ROUTE_ROOT_PAKCAGE + "." + SDK_NAME + SEPARATOR + SUFFIX_INTERCEPTOR)) {

       ((IInterceptorGroup) Class.forName(className).getConstructor().newInstance()).loadInto(Warehouse.interceptorsIndex);
  

}
}
for (Map.Entry<String, Class<? extends IRouteGroup>> stringClassEntry : Warehouse.groupsIndex.entrySet()) {
Log.d(TAG, "Root映射表[ " + stringClassEntry.getKey() + " : " + stringClassEntry.getValue() + "]");
}

}</pre>

这里用到了CountDownLatch类，会分path一个文件一个文件的检索，等到所有的类文件都找到后便会返回这个Set<String>集合。

注意，Warehouse就是专门用来存放路由映射关系的类，里面保存着存路由信息的map，这在ARouter里面也是一样的。这段代码Warehouse.routes.get(card.getPath())通过path拿到对应的RouteMeta，这个RouteMeta里面保存了activityClass等信息。继续往下看，如果判断拿到的RouteMeta是空，说明这个路由地址还没有加载到map里面(初始化时为了节省性能，只会加载所有的分组信息，而每个分组下的路由映射关系，会使用懒加载，在首次用到的时候去加载)

下面就是用到了反射！！

<pre style="margin: 8px 0px; background-color: rgb(43, 43, 43); color: rgb(169, 183, 198); font-family: "JetBrains Mono", monospace; font-size: 0.817rem;">/**

• 准备卡片 * * @param card
  */ private void prepareCard(Postcard card) {
  RouteMeta routeMeta = Warehouse.routes.get(card.getPath());
  if (null == routeMeta) {
  Class<? extends IRouteGroup> groupMeta = Warehouse.groupsIndex.get(card.getGroup());
  if (null == groupMeta) {
  throw new NoRouteFoundException("没找到对应路由：分组=" + card.getGroup() + " 路径=" + card.getPath());
  }
  IRouteGroup iGroupInstance;
  try {
  iGroupInstance = groupMeta.getConstructor().newInstance();
  } catch (Exception e) {
  throw new RuntimeException("路由分组映射表记录失败.", e);
  }
  iGroupInstance.loadInto(Warehouse.routes);
  //已经准备过了就可以移除了 (不会一直存在内存中)
  Warehouse.groupsIndex.remove(card.getGroup());
  //再次进入 else
  prepareCard(card);
  } else {
  //类 要跳转的activity 或IService实现类
  card.setDestination(routeMeta.getDestination());
  card.setType(routeMeta.getType());
  switch (routeMeta.getType()) {
  case ISERVICE:
  Class<?> destination = routeMeta.getDestination();
  IService service = Warehouse.services.get(destination);
  if (null == service) {
  try {
  service = (IService) destination.getConstructor().newInstance();
  Warehouse.services.put(destination, service);
  } catch (Exception e) {
  e.printStackTrace();
  }
  }
  card.setService(service);
  break; default:
  break;
  }
  }
  }</pre>

最好的实现

https://www.jianshu.com/p/857aea5b54a8