2019-11-16发表Android23 分钟读完 (大约3425个字)

Android ARouter 路由解析

01.原生跳转实现

Google提供的原声路由主要是通过intent，可以分成显示和隐式两种。显示的方案会导致类之间的直接依赖问题，耦合严重；隐式intent需要的配置清单中统一声明，首先有个暴露的问题，另外在多模块开发中协作也比较困难。只要调用startActivity后面的环节我们就无法控制了，在出现错误时无能为力。

02.实现组件跳转方式

2.1 传统跳转方式

第一种，通过intent跳转
第二种，通过aidl跳转
第三种，通过scheme协议跳转

2.2 为何需要路由

显示Intent：项目庞大以后，类依赖耦合太大，不适合组件化拆分
隐式Intent：协作困难，调用时候不知道调什么参数
每个注册了Scheme的Activity都可以直接打开，有安全风险
AndroidMainfest集中式管理比较臃肿
无法动态修改路由，如果页面出错，无法动态降级
无法动态拦截跳转，譬如未登录的情况下，打开登录页面，登录成功后接着打开刚才想打开的页面
H5、Android、iOS地址不一样，不利于统一跳转

03.ARouter配置与优势

3.1 ARouter的优势

如下所示
- 直接解析URL路由，解析参数并赋值
- 支持多模块项目
- 支持InstantRun
- 允许自定义拦截器
- ARouter可以提供IoC容器
- 映射关系自动注册
- 灵活的降级策略

3.2 至于配置和使用

直接看https://www.jianshu.com/p/fed5d5b95bae

04.跨进程组件通信

4.1 URLScheme【例如：ActivityRouter、ARouter等】

优势有：
- 基因中自带支持从webview中调用
- 不用互相注册（不用知道需要调用的app的进程名称等信息）
劣势有:
- 只能单向地给组件发送信息，适用于启动Activity和发送指令，不适用于获取数据(例如：获取用户组件的当前用户登录信息)
- 需要有个额外的中转Activity来统一处理URLScheme
- 如果设备上安装了多个使用相同URLScheme的app，会弹出选择框（多个组件作为app同时安装到设备上时会出现这个问题）
- 无法进行权限设置，无法进行开关设置，存在安全性风险

4.2 AIDL

优势有：
- 可以传递Parcelable类型的对象
- 效率高
- 可以设置跨app调用的开关
劣势有：
- 调用组件之前需要提前知道该组件在那个进程，否则无法建立ServiceConnection
- 组件在作为独立app和作为lib打包到主app时，进程名称不同，维护成本高

4.3 BroadcastReceiver

BroadcastReceiver + Service + LocalSocket。该方案是参考cc路由框架！
跨组件间通信实现的同时，应该满足以下条件：
- 每个app都能给其它app调用
- app可以设置是否对外提供跨进程组件调用的支持
- 组件调用的请求发出去之后，能自动探测当前设备上是否有支持此次调用的app
- 支持超时、取消

4.4 路由通信注意要点

05.ARouter的结构

ARouter主要由三部分组成，包括对外提供的api调用模块、注解模块以及编译时通过注解生产相关的类模块。
- arouter-annotation注解的声明和信息存储类的模块
- arouter-compiler编译期解析注解信息并生成相应类以便进行注入的模块
- arouter-api核心调用Api功能的模块
annotation模块
- Route、Interceptor、Autowired都是在开发是需要的注解。
compiler模块
- AutoWiredProcessor、InterceptorProcessor、RouteProcessor分别为annotation模块对应的Autowired、Interceptor、Route在项目编译时产生相关的类文件。
api模块
- 主要是ARouter具体实现和对外暴露使用的api。

06.ARouter的工作流程

6.1 初始化流程

初始化代码如下所示

/**
 * Init, it must be call before used router.
 */
public static void init(Application application) {
    //如果没有初始化，则
    if (!hasInit) {
        logger = _ARouter.logger;
        _ARouter.logger.info(Consts.TAG, "ARouter init start.");
        
        //做初始化工作
        hasInit = _ARouter.init(application);

        if (hasInit) {
            _ARouter.afterInit();
        }

        _ARouter.logger.info(Consts.TAG, "ARouter init over.");
    }
}

之后接着看_ARouter.init(application)这行代码，点击去查看

protected static synchronized boolean init(Application application) {
    //赋值上下文
    mContext = application;
    //初始化LogisticsCenter
    LogisticsCenter.init(mContext, executor);
    logger.info(Consts.TAG, "ARouter init success!");
    hasInit = true;
    mHandler = new Handler(Looper.getMainLooper());
    return true;
}

接下来看看LogisticsCenter里面做了什么

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();
            Set<String> routerMap;
            //debug或者版本更新的时候每次都重新加载router信息
            // 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.
                //加载alibaba.android.arouter.routes包下载的类
                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. 
                    //导入ARouter$$Root$$app.java,初始化Warehouse.groupsIndex集合
                    ((IRouteRoot) (Class.forName(className).getConstructor().newInstance())).loadInto(Warehouse.groupsIndex);
                } else if (className.startsWith(ROUTE_ROOT_PAKCAGE + DOT + SDK_NAME + SEPARATOR + SUFFIX_INTERCEPTORS)) {
                    // Load interceptorMeta
                    //导入ARouter$$Interceptors$$app.java，初始化Warehouse.interceptorsIndex集合
                    ((IInterceptorGroup) (Class.forName(className).getConstructor().newInstance())).loadInto(Warehouse.interceptorsIndex);
                } else if (className.startsWith(ROUTE_ROOT_PAKCAGE + DOT + SDK_NAME + SEPARATOR + SUFFIX_PROVIDERS)) {
                    // Load providerIndex
                    //导入ARouter$$Providers$$app.java，初始化Warehouse.providersIndex集合
                    ((IProviderGroup) (Class.forName(className).getConstructor().newInstance())).loadInto(Warehouse.providersIndex);
                }
            }

            /*******部分代码省略********/
        } catch (Exception e) {
            throw new HandlerException(TAG + "ARouter init logistics center exception! [" + e.getMessage() + "]");
        }
    }
}

综上所述，整个初始化的流程大概就是：
- 初始化运行时的上下文环境
- 初始化日志logger
- 寻找router相关的类
- 解析并且缓存路由相关信息
- 初始化拦截服务

6.2 跳转页面流程

07.ARouter调用api

7.1 最简单调用

最简单的调用方式

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ARouter.getInstance()
                .build("/user/UserFragment")
                .navigation();

7.2 build源码分析

这个主要是添加跳转的路径

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

然后把这个路径添加到默认的组中

/**
 * Build postcard by path and default group
 */
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);
        }
        return build(path, extractGroup(path));
    }
}

如下所示

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) {
            /**************部分代码省略***************/
            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);
        }
        //是否为绿色通道，是否进过拦截器处理
        if (!postcard.isGreenChannel()) {   // It must be run in async thread, maybe interceptor cost too mush time made ANR.
            interceptorService.doInterceptions(postcard, new InterceptorCallback() {
                @Override
                public void onContinue(Postcard postcard) {
                    _navigation(context, postcard, requestCode, callback);
                }
                @Override
                public void onInterrupt(Throwable exception) {
                    //中断处理
                    if (null != callback) {
                        callback.onInterrupt(postcard);
                    }
                }
            });
        } else {
            return _navigation(context, postcard, requestCode, callback);
        }

        return null;
    }

    private Object _navigation(final Context context, final Postcard postcard, final int requestCode, final NavigationCallback callback) {
        //没有上下文环境，就用Application的上下文环境
        final Context currentContext = null == context ? mContext : context;
        switch (postcard.getType()) {
            case ACTIVITY:
                // Build intent 构建跳转的intent
                final Intent intent = new Intent(currentContext, postcard.getDestination());
                intent.putExtras(postcard.getExtras());
                // Set flags. 设置flag
                int flags = postcard.getFlags();
                if (-1 != flags) {
                    intent.setFlags(flags);
                } else if (!(currentContext instanceof Activity)) {    // Non activity, need less one flag.
                    //如果上下文不是Activity，则添加FLAG_ACTIVITY_NEW_TASK的flag
                    intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
                }
                // Navigation in main looper.  切换到主线程中
                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;
            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;
    }
}

08.Postcard信息携带

Postcard主要为信息的携带者，内容是在构造一次路由信息的时候生产的，其继承于RouteMeta。RouteMeta是在代码编译时生成的内容，主要在初始化WareHouse时对跳转信息做了缓存。

看看代码如下所示

//Postcard继承于RouteMeta
public final class Postcard extends RouteMeta


//然后看看编译生成的文件
/**
 * DO NOT EDIT THIS FILE!!! IT WAS GENERATED BY AROUTER. */
public class ARouter$$Group$$me implements IRouteGroup {
  @Override
  public void loadInto(Map<String, RouteMeta> atlas) {
    atlas.put("/me/ExperienceCouponActivity", RouteMeta.build(RouteType.ACTIVITY, ExperienceCouponActivity.class, "/me/experiencecouponactivity", "me", null, -1, -2147483648));
    atlas.put("/me/ServiceActivity", RouteMeta.build(RouteType.ACTIVITY, ServiceActivity.class, "/me/serviceactivity", "me", null, -1, -2147483648));
    atlas.put("/me/SettingActivity", RouteMeta.build(RouteType.ACTIVITY, SettingActivity.class, "/me/settingactivity", "me", null, -1, -2147483648));
    atlas.put("/me/UdeskServiceActivity", RouteMeta.build(RouteType.ACTIVITY, UdeskServiceActivity.class, "/me/udeskserviceactivity", "me", null, -1, -2147483648));
  }
}

10.DegradeService降级容错服务

首先，自定义一个类，需要继承DegradeService类，如下所示

/**
 * ARouter路由降级处理
 */
@Route(path = DegradeServiceImpl.PATH)
public class DegradeServiceImpl implements DegradeService {

    static final String PATH = "/service/DegradeServiceImpl";

    @Override
    public void onLost(Context context, Postcard postcard) {
        if (context != null && postcard.getGroup().equals("activity")) {
            Intent intent = new Intent(context, WebViewActivity.class);
            intent.putExtra(Constant.URL, Constant.GITHUB);
            intent.putExtra(Constant.TITLE, "github地址");
            ActivityCompat.startActivity(context, intent, null);
        }
    }

    @Override
    public void init(Context context) {

    }
}

如何使用该降级方案，十分简单。

NavigationCallback callback = new NavCallback() {
    @Override
    public void onArrival(Postcard postcard) {
        LogUtils.i("ARouterUtils"+"---跳转完了");
    }

    @Override
    public void onFound(Postcard postcard) {
        super.onFound(postcard);
        LogUtils.i("ARouterUtils"+"---找到了");
    }

    @Override
    public void onInterrupt(Postcard postcard) {
        super.onInterrupt(postcard);
        LogUtils.i("ARouterUtils"+"---被拦截了");
    }

    @Override
    public void onLost(Postcard postcard) {
        super.onLost(postcard);
        LogUtils.i("ARouterUtils"+"---找不到了");
        DegradeServiceImpl degradeService = new DegradeServiceImpl();
        degradeService.onLost(Utils.getApp(),postcard);
    }
};

11.Interceptor拦截器

在ARouter模块的时候讲述Interceptor的使用，如果本次路由跳转不是走的绿色通道那么则会触发拦截器进行过滤。

final class _ARouter {
    protected Object navigation(final Context context, final Postcard postcard, final int requestCode, final NavigationCallback callback) {
        /************部分代码省略************/

        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;
    }
}

拦截器的初始化

在刚开始初始化的时候，就已经做了这个操作。

final class _ARouter {
    static void afterInit() {
        // Trigger interceptor init, use byName.
        interceptorService = (InterceptorService) ARouter.getInstance().build("/arouter/service/interceptor").navigation();
    }
}

InterceptorServiceImpl的init方法：

@Route(path = "/arouter/service/interceptor")
public class InterceptorServiceImpl implements InterceptorService {
    @Override
    public void init(final Context context) {
        LogisticsCenter.executor.execute(new Runnable() {
            @Override
            public void run() {
                if (MapUtils.isNotEmpty(Warehouse.interceptorsIndex)) {
                    //循环遍历仓库中的拦截器
                    for (Map.Entry<Integer, Class<? extends IInterceptor>> entry : Warehouse.interceptorsIndex.entrySet()) {
                        Class<? extends IInterceptor> interceptorClass = entry.getValue();
                        try {
                            //反射机制构造自定义的每一个拦截器实例
                            IInterceptor iInterceptor = interceptorClass.getConstructor().newInstance();
                            iInterceptor.init(context);
                            //并将其添加在缓存中
                            Warehouse.interceptors.add(iInterceptor);
                        } catch (Exception ex) {
                            throw new HandlerException(TAG + "ARouter init interceptor error! name = [" + interceptorClass.getName() + "], reason = [" + ex.getMessage() + "]");
                        }
                    }
                    interceptorHasInit = true;
                    logger.info(TAG, "ARouter interceptors init over.");
                    synchronized (interceptorInitLock) {
                        interceptorInitLock.notifyAll();
                    }
                }
            }
        });
    }
}

拦截器的工作过程

@Route(path = "/arouter/service/interceptor")
public class InterceptorServiceImpl implements InterceptorService {
    @Override
    public void doInterceptions(final Postcard postcard, final InterceptorCallback callback) {
        if (null != Warehouse.interceptors && Warehouse.interceptors.size() > 0) {
            //检测是否初始化完所有的烂机器
            checkInterceptorsInitStatus();
            //没有完成正常的初始化，抛异常
            if (!interceptorHasInit) {
                callback.onInterrupt(new HandlerException("Interceptors initialization takes too much time."));
                return;
            }
            //顺序遍历每一个拦截器，
            LogisticsCenter.executor.execute(new Runnable() {
                @Override
                public void run() {
                    CancelableCountDownLatch interceptorCounter = new CancelableCountDownLatch(Warehouse.interceptors.size());
                    try {
                        _excute(0, interceptorCounter, postcard);
                        interceptorCounter.await(postcard.getTimeout(), TimeUnit.SECONDS);
                        //拦截器的遍历终止之后，如果有还有没有遍历的拦截器，则表示路由事件被拦截
                        if (interceptorCounter.getCount() > 0) {    // Cancel the navigation this time, if it hasn't return anythings.
                            callback.onInterrupt(new HandlerException("The interceptor processing timed out."));
                        } else if (null != postcard.getTag()) {    // Maybe some exception in the tag.
                            callback.onInterrupt(new HandlerException(postcard.getTag().toString()));
                        } else {
                            callback.onContinue(postcard);
                        }
                    } catch (Exception e) {
                        callback.onInterrupt(e);
                    }
                }
            });
        } else {
            callback.onContinue(postcard);
        }
    }

    //执行拦截器的过滤事件
    private static void _excute(final int index, final CancelableCountDownLatch counter, final Postcard postcard) {
        if (index < Warehouse.interceptors.size()) {
            IInterceptor iInterceptor = Warehouse.interceptors.get(index);
            iInterceptor.process(postcard, new InterceptorCallback() {
                @Override
                public void onContinue(Postcard postcard) {
                    // Last interceptor excute over with no exception.
                    counter.countDown();
                    //如果当前没有拦截过滤，那么使用下一个拦截器
                    _excute(index + 1, counter, postcard);  // When counter is down, it will be execute continue ,but index bigger than interceptors size, then U know.
                }

                @Override
                public void onInterrupt(Throwable exception) {
                    // Last interceptor excute over with fatal exception.
                    postcard.setTag(null == exception ? new HandlerException("No message.") : exception.getMessage());    // save the exception message for backup.
                    counter.cancel();
                }
            });
        }
    }
}

12.数据传输和自动注入

13.多dex的支持

可查看multidex源码：

public class ClassUtils {  
  /**
     * Identifies if the current VM has a native support for multidex, meaning there is no need for
     * additional installation by this library.
     *
     * @return true if the VM handles multidex
     */
    private static boolean isVMMultidexCapable() {
        boolean isMultidexCapable = false;
        String vmName = null;

        try {
            if (isYunOS()) {    // YunOS需要特殊判断
                vmName = "'YunOS'";
                isMultidexCapable = Integer.valueOf(System.getProperty("ro.build.version.sdk")) >= 21;
            } else {    // 非YunOS原生Android
                vmName = "'Android'";
                String versionString = System.getProperty("java.vm.version");
                if (versionString != null) {
                    Matcher matcher = Pattern.compile("(\\d+)\\.(\\d+)(\\.\\d+)?").matcher(versionString);
                    if (matcher.matches()) {
                        try {
                            int major = Integer.parseInt(matcher.group(1));
                            int minor = Integer.parseInt(matcher.group(2));
                            isMultidexCapable = (major > VM_WITH_MULTIDEX_VERSION_MAJOR)
                                    || ((major == VM_WITH_MULTIDEX_VERSION_MAJOR)
                                    && (minor >= VM_WITH_MULTIDEX_VERSION_MINOR));
                        } catch (NumberFormatException ignore) {
                            // let isMultidexCapable be false
                        }
                    }
                }
            }
        } catch (Exception ignore) {

        }

        Log.i(Consts.TAG, "VM with name " + vmName + (isMultidexCapable ? " has multidex support" : " does not have multidex support"));
        return isMultidexCapable;
    }
}

14.InstantRun支持

什么是InstantRun支持？
- Android Studio 2.0 中引入的 Instant Run 是 Run 和 Debug 命令的行为，可以大幅缩短应用更新的时间。尽管首次构建可能需要花费较长的时间，Instant Run 在向应用推送后续更新时则无需构建新的 APK，因此，这样可以更快地看到更改。

15.生成的编译代码

如下所示

#基础