前言
相信絕大多數公司項目都做了組件化。為了解耦,組件化勢必要解決
組件間的通信。其中阿里巴巴開源的Arouter很好的解決了組件間的通信,一直受到開發者的青睞。今天,我們來一步步揭開它的神秘面紗。首先下載源代碼,項目地址:
https://github.com/alibaba/ARouter
來講一下項目結構
- app:項目主工程,演示代碼
- module-java:java演示代碼
- module-kotlin:kotlin演示代碼
- arouter-annotation:所有註解以及註解涉及到的類
- arouter-compiler:註解處理器,APT
- arouter-gradle-plugin:路由表自動註冊插件
- arouter-idea-plugin:路由跳轉插件,搜索ARouter Helper插件安裝即可。
- arouter-api:所有的api
第一步就是要生成註解類
@Route @Autowired Interceptor Provider都會生成如下面所示的對應註解類,java生成的註解類的位置在build-generated-sourse-apt中,kotlin生成的註解類的位置在build-generated-sourse-kapt
public class ARouter$$Group$$app implements IRouteGroup { @Override public void loadInto(Map atlas) { atlas.put("/app/degrade1", RouteMeta.build(RouteType.PROVIDER, DegradeServiceImpl.class, "/app/degrade1", "app", null, -1, -2147483648)); atlas.put("/app/main", RouteMeta.build(RouteType.ACTIVITY, MainActivity.class, "/app/main", "app", null, -1, -2147483648)); atlas.put("/app/path", RouteMeta.build(RouteType.PROVIDER, PathReplaceServiceImpl.class, "/app/path", "app", null, -1, -2147483648)); } }
這裡需要重點關注一下RouteMeta這個類,這個類存儲了目標對象的所有信息。包括路由類型、目標對象類、path、group、參數、優先級、額外參數。
涉及到的知識點:
- apt
- javapoet
- auto-service
這裡是我寫的一個AptDemo,僅供參考:
https://github.com/liulingfeng/APT
關於AbstractProcessor的process多次執行可以通過下面方法處理
@Override public boolean process(Set extends TypeElement> annotations, RoundEnvironment roundEnvironment) { if (annotations != null && annotations.size() > 0) { } }
下面正式講解api
先整體感受一下整個流程
根據官方說明,首先在Application中調用如下api
if(BuildConfig.DEBUG){ ARouter.openLog();//打開日誌 ARouter.openDebug();//打開路由調試 } ARouter.init(this);
進入Arouter.init(this)
public static void init(Application application) { if (!hasInit) { logger = _ARouter.logger; hasInit = _ARouter.init(application); if (hasInit) { _ARouter.afterInit(); } } }
hasInit保證只初始化一次,內部調用了_ARouter.init(application),Arouter是門面, _Arouter是具體實現,有一點裝飾模式的感覺。初始化之後調用 _ARouter.afterInit實例化攔截器(這個後面細講)。繼續跟進 _ARouter.init
protected static synchronized boolean init(Application application) { mContext = application; LogisticsCenter.init(mContext, executor); logger.info(Consts.TAG, "ARouter init success!"); hasInit = true; return true; }
一眼就看到關鍵代碼在LogisticsCenter.init中,executor是一個自定義的線程池(實現了一種拋出錯誤的方式)。
public synchronized static void init(Context context, ThreadPoolExecutor tpe) throws HandlerException { try { if (registerByPlugin) { logger.info(TAG, "Load router map by arouter-auto-register plugin."); } else { Set routerMap; if (ARouter.debuggable() || PackageUtils.isNewVersion(context)) { 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); } else { 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); } } } } catch (Exception e) { throw new HandlerException(TAG + "ARouter init logistics center exception! [" + e.getMessage() + "]"); } }
代碼比較長,我把它分解一下
- 1.判斷是不是用插件自動註冊路由表,插件註冊的方式另說
- 2.從dex中加載指定路徑(com.alibaba.android.arouter.routes)下的所有類名,其實就是註解生成類,然後根據版本號升級版本。非debuggable環境下從SharedPreferences緩存中讀取(做的一個優化點)
- 3.反射調用loadInto把Group、Interceptor、Provider的映射關係添加到集合中
看一下各種類型的註解生成類
Root(這裡做了優化先加載各個group,用到的時候再加載各個group下的路由)
public class ARouter$$Root$$app implements IRouteRoot { @Override public void loadInto(Map> routes) { routes.put("app", ARouter$$Group$$app.class); } }
Interceptor
public class ARouter$$Interceptors$$app implements IInterceptorGroup { @Override public void loadInto(Map> interceptors) { interceptors.put(9, TestInterceptor2.class); interceptors.put(10, TestInterceptor.class); } }
Provider
public class ARouter$$Providers$$app implements IProviderGroup { @Override public void loadInto(Map providers) { providers.put("com.xls.HelloService", RouteMeta.build(RouteType.PROVIDER, HelloServiceImpl.class, "/yourservicegroupname/hello", "yourservicegroupname", null, -1, -2147483648)); } }
init工作總結及知識點
- 1.把Group、Interceptor、Provider註解類的映射添加到Warehouse.groupsIndex、Warehouse.interceptorsIndex、Warehouse.providersIndex集合中
- 2.實例化所有的Interceptor添加到Warehouse.interceptors中
- 3.dex分析-多dex怎麼查找-熱修復的根本原理是什麼
- 4.線程池-線程池各個參數-線程池拋出錯誤的方法-如何保證線程池線程名字唯一性-原子類
順便補充一下插件自動註冊路由表
首先目光移到PluginLaunch,這是自定義插件的入口。
public class PluginLaunch implements Plugin { @Override public void apply(Project project) { def android = project.extensions.getByType(AppExtension) def transformImpl = new RegisterTransform(project) ArrayList list = new ArrayList <>(3) list.add(new ScanSetting('IRouteRoot')) list.add(new ScanSetting('IInterceptorGroup')) list.add(new ScanSetting('IProviderGroup')) RegisterTransform.registerList = list android.registerTransform(transformImpl) } } }
這裡完成了自定義Transform的註冊以及添加需要過濾的接口到ScanSetting,最主要的代碼自然是在RegisterTransform中。直奔RegisterTransform的transform方法,首先遍歷jar。
inputs.each { TransformInput input -> input.jarInputs.each { if (ScanUtil.shouldProcessPreDexJar(src.absolutePath)) { ScanUtil.scanJar(src, dest) } FileUtils.copyFile(src, dest) }
static void scanJar(File jarFile, File destFile) { if (jarFile) { def file = new JarFile(jarFile) Enumeration enumeration = file.entries() while (enumeration.hasMoreElements()) { JarEntry jarEntry = (JarEntry) enumeration.nextElement() String entryName = jarEntry.getName() if (entryName.startsWith("com/alibaba/android/arouter/routes/")) { InputStream inputStream = file.getInputStream(jarEntry) scanClass(inputStream) inputStream.close() } else if ("com/alibaba/android/arouter/core/LogisticsCenter.class" == entryName) { RegisterTransform.fileContainsInitClass = destFile } } file.close() } }
做到兩步工作:1.把com/alibaba/android/arouter/routes包名下的交給scanClass處理(這個稍後會分析到) 2.找到LogisticsCenter.class類,對於這個類想必很熟悉吧。
接下來遍歷directory
input.directoryInputs.each { DirectoryInput directoryInput -> directoryInput.file.eachFileRecurse { File file -> if(file.isFile() && ScanUtil.shouldProcessClass(path)){ ScanUtil.scanClass(file) } } }
static void scanClass(InputStream inputStream) { ClassReader cr = new ClassReader(inputStream) ClassWriter cw = new ClassWriter(cr, 0) ScanClassVisitor cv = new ScanClassVisitor(Opcodes.ASM5, cw) cr.accept(cv, ClassReader.EXPAND_FRAMES) inputStream.close() }
把文件流丟給ScanClassVisitor
static class ScanClassVisitor extends ClassVisitor { ScanClassVisitor(int api, ClassVisitor cv) { super(api, cv) } void visit(int version, int access, String name, String signature, String superName, String[] interfaces) { super.visit(version, access, name, signature, superName, interfaces) RegisterTransform.registerList.each { ext -> if (ext.interfaceName && interfaces != null) { interfaces.each { itName -> if (itName == ext.interfaceName) { ext.classList.add(name) } } } } } }
一看就明白,就是把所有實現了IRouteRoot、IInterceptorGroup、IProviderGroup接口的類存到集合中。
接著看最後一步做了什麼
if (fileContainsInitClass) { registerList.each { ext -> if (ext.classList.isEmpty()) { Logger.e("No class implements found for interface:" + ext.interfaceName) } else { RegisterCodeGenerator.insertInitCodeTo(ext) } } }
關鍵代碼都在RegisterCodeGenerator這個類中,我只列關鍵代碼。
private byte[] referHackWhenInit(InputStream inputStream) { ClassReader cr = new ClassReader(inputStream) ClassWriter cw = new ClassWriter(cr, 0) ClassVisitor cv = new MyClassVisitor(Opcodes.ASM5, cw) cr.accept(cv, ClassReader.EXPAND_FRAMES) return cw.toByteArray() } MethodVisitor visitMethod(int access, String name, String desc, String signature, String[] exceptions) { MethodVisitor mv = super.visitMethod(access, name, desc, signature, exceptions) if (name == "loadRouterMap") { mv = new RouteMethodVisitor(Opcodes.ASM5, mv) } return mv }
找到hook點loadRouterMap。hook點的設計特別巧妙,增強了代碼的可讀性。
void visitInsn(int opcode) { if ((opcode >= Opcodes.IRETURN && opcode <= Opcodes.RETURN)) { extension.classList.each { name -> mv.visitMethodInsn(Opcodes.INVOKESTATIC , "com/alibaba/android/arouter/core/LogisticsCenter" , "register" , "(Ljava/lang/String;)V" , false) } } super.visitInsn(opcode) }
調用LogisticsCenter的register方法,我們來看一下register方法做了什麼。
private static void register(String className) { if (!TextUtils.isEmpty(className)) { try { Class> clazz = Class.forName(className); Object obj = clazz.getConstructor().newInstance(); if (obj instanceof IRouteRoot) { registerRouteRoot((IRouteRoot) obj); } else if (obj instanceof IProviderGroup) { registerProvider((IProviderGroup) obj); } else if (obj instanceof IInterceptorGroup) { registerInterceptor((IInterceptorGroup) obj); } else { logger.info(TAG, "register failed, class name: " + className + " should implements one of IRouteRoot/IProviderGroup/IInterceptorGroup."); } } catch (Exception e) { logger.error(TAG,"register class error:" + className); } } }
所有實現了IRouteRoot、IInterceptorGroup、IProviderGroup接口的類都加入了Warehouse相對應的集合中。至此自動註冊工作完成。
路由跳轉
ARouter.getInstance().build("/home/test").withString("key3", "888") .withLong("key1", 666L) .navigation(this)
先看build,new一個Postcard對象並給Postcard設置path和group。Postcard構造方法中new了一個bundler對象。PathReplaceService提供了動態改path的方式,後面細講。
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); } }
.withString("key3", "888").withLong("key1", 666L)把參數設置給當前Postcard的bundle中。
再看navigation方法
protected Object navigation(final Context context, final Postcard postcard, final int requestCode, final NavigationCallback callback) { try { LogisticsCenter.completion(postcard); } catch (NoRouteFoundException ex) { if (debuggable()) { Toast.makeText(mContext, "There's no route matched!\n" + " Path = [" + postcard.getPath() + "]\n" + " Group = [" + postcard.getGroup() + "]", Toast.LENGTH_LONG).show(); } if (null != callback) { callback.onLost(postcard); } else { DegradeService degradeService = ARouter.getInstance().navigation(DegradeService.class); if (null != degradeService) { degradeService.onLost(context, postcard); } } return null; } return null; }
先看第一部分,重點落在LogisticsCenter.completion(postcard)。內部主要做的是實例化當前group下的具體Route添加到Warehouse.routes,如果沒找到就降級處理,兩種方式(1.設置NavigationCallback 2.實現DegradeService)
public synchronized static void completion(Postcard postcard) { RouteMeta routeMeta = Warehouse.routes.get(postcard.getPath()); if (null == routeMeta) { Class extends IRouteGroup> groupMeta = Warehouse.groupsIndex.get(postcard.getGroup()); if (null == groupMeta) { throw new NoRouteFoundException(TAG + "There is no route match the path [" + postcard.getPath() + "], in group [" + postcard.getGroup() + "]"); } else { try { IRouteGroup iGroupInstance = groupMeta.getConstructor().newInstance(); iGroupInstance.loadInto(Warehouse.routes); Warehouse.groupsIndex.remove(postcard.getGroup()); } catch (Exception e) { throw new HandlerException(TAG + "Fatal exception when loading group meta. [" + e.getMessage() + "]"); } completion(postcard); } } else { postcard.setDestination(routeMeta.getDestination()); postcard.setType(routeMeta.getType()); postcard.setPriority(routeMeta.getPriority()); postcard.setExtra(routeMeta.getExtra()); Uri rawUri = postcard.getUri(); if (null != rawUri) { Map resultMap = TextUtils.splitQueryParameters(rawUri); Map paramsType = routeMeta.getParamsType(); if (MapUtils.isNotEmpty(paramsType)) { for (Map.Entry params : paramsType.entrySet()) { setValue(postcard, params.getValue(), params.getKey(), resultMap.get(params.getKey())); } postcard.getExtras().putStringArray(ARouter.AUTO_INJECT, paramsType.keySet().toArray(new String[]{})); } postcard.withString(ARouter.RAW_URI, rawUri.toString()); } switch (routeMeta.getType()) { case PROVIDER: Class extends IProvider> providerMeta = (Class extends IProvider>) routeMeta.getDestination(); IProvider instance = Warehouse.providers.get(providerMeta); if (null == instance) { 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(); break; case FRAGMENT: postcard.greenChannel(); default: break; } } }
分析一下這段代碼
- 1.判斷Warehouse的routes中對應path的RouteMeta是否為空,看過註解生成類其實我們知道RouteMeta保存了類的具體信息
- 2.在集合中找到對應的group分組,然後實例化對應分組下的具體Route添加到集合中
- 3.把RouteMeta的各種信息設置給當前postcard對象
- 4.uri跳轉的處理,uri跳轉和普通跳轉唯一的區別就是參數的剝離,普通跳轉是直接設置的而uri是通過在鏈接中剝離的,其中參數的數據類型是在Routemeta的paramsType中設置的
- 5.根據跳轉的類型不同做不同處理。如果是服務,直接實例化當前服務調用init方法並設置給postcard。設置綠色通道;如果是fragment,設置綠色通道。所謂綠色通道就是不被攔截器攔截。
第二個部分是處理攔截。我們稍後再講
先看第三部分
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: final Intent intent = new Intent(currentContext, postcard.getDestination()); intent.putExtras(postcard.getExtras()); int flags = postcard.getFlags(); if (-1 != flags) { intent.setFlags(flags); } else if (!(currentContext instanceof Activity)) { intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK); } String action = postcard.getAction(); if (!TextUtils.isEmpty(action)) { intent.setAction(action); } 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; }
看到這裡是不是很親切,這不就是我們平時常寫的startActivity(intent,class)嗎?如果是fragment的話反射調用Fragment構造方法返回fragment對象。provider也是返回 Provider對象。至此跳轉這一塊基本上都搞清楚了。
分析一下攔截器怎麼實現的
之前講了Aroute.init之後會將所有的攔截器實例化。我們看看_ARouter.afterInit()做了什麼
static void afterInit() { interceptorService = (InterceptorService) ARouter.getInstance().build("/arouter/service/interceptor").navigation(); }
使用自己的路由方法初始化interceptorService服務,沒毛病。該服務的實現類是InterceptorServiceImpl,從前面的分析可以知道navigation會調用服務的init方法。看看init裡面做了什麼
@Override public void init(final Context context) { LogisticsCenter.executor.execute(new Runnable() { @Override public void run() { if (MapUtils.isNotEmpty(Warehouse.interceptorsIndex)) { for (Map.Entry> entry : Warehouse.interceptorsIndex.entrySet()) { Class extends IInterceptor> interceptorClass = entry.getValue(); try { IInterceptor iInterceptor = interceptorClass.getConstructor().newInstance(); iInterceptor.init(context); Warehouse.interceptors.add(iInterceptor); } catch (Exception ex) { throw new HandlerException(TAG + "ARouter init interceptor error! name = [" + interceptorClass.getName() + "], reason = [" + ex.getMessage() + "]"); } } interceptorHasInit = true; } } }); }
反射調用所有攔截器的構造函數實例化對象添加到Warehouse.interceptors並調用init方法,這裡使用了object.wait和object.notifyAll保證子線程中的所有攔截器實例化完成。攔截的時機在前面已經提到過了,我們來看看具體的代碼。
if (!postcard.isGreenChannel()) { interceptorService.doInterceptions(postcard, new InterceptorCallback() { @Override public void onContinue(Postcard postcard) { _navigation(context, postcard, requestCode, callback); } @Override public void onInterrupt(Throwable exception) { if (null != callback) { callback.onInterrupt(postcard); } } });
@Override public void doInterceptions(final Postcard postcard, final InterceptorCallback callback) { if (null != Warehouse.interceptors && Warehouse.interceptors.size() > 0) { 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); if (interceptorCounter.getCount() > 0) { callback.onInterrupt(new HandlerException("The interceptor processing timed out.")); } else if (null != postcard.getTag()) { callback.onInterrupt(new HandlerException(postcard.getTag().toString())); } else { callback.onContinue(postcard); } } catch (Exception e) { callback.onInterrupt(e); } } }); } else { callback.onContinue(postcard); } }
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) { counter.countDown(); _excute(index + 1, counter, postcard); } @Override public void onInterrupt(Throwable exception) { postcard.setTag(null == exception ? new HandlerException("No message.") : exception.getMessage()); // save the exception message for backup. counter.cancel(); } }); } }
使用CountDownLatch.await使得代碼阻塞直到所有攔截器執行完成或者超時。攔截器process方法中需要調用callback.onContinue才能調用到counter.countDown()移交到下一個攔截器,這就解釋了自定義的攔截器為什麼一定要調用counter.countDown()
涉及知識點
- 1.線程間通信
- 2.CountDownLatch
- 3.Object.wait/Object.notify
降級處理
兩種方式:1.navigation的時候添加NavigationCallback回調 2.寫一個類實現DegradeService別忘了添加@Route path可以隨意 第一種比較簡單我麼不講,講一下第二種方式
@Route(path = "/app/degrade1") class DegradeServiceImpl : DegradeService { override fun onLost(context: Context?, postcard: Postcard?) { Log.e("降級處理","自定義降級處理") } override fun init(context: Context?) { } }
生成的註解類在ARouter$$Providers$$app中,也是init的時候就把映射關係添加到集合中。調用的地方是在navigation中,這段代碼也間接的說明了NavigationCallback的優先級高於全局降級處理。
if (null != callback) { callback.onLost(postcard); } else { DegradeService degradeService = ARouter.getInstance().navigation(DegradeService.class); if (null != degradeService) { degradeService.onLost(context, postcard); } }
關鍵代碼是下面一段代碼,詮釋了服務的navigation是如何運行的
protected T navigation(Class extends T> service) { try { Postcard postcard = LogisticsCenter.buildProvider(service.getName()); if (null == postcard) { postcard = LogisticsCenter.buildProvider(service.getSimpleName()); } LogisticsCenter.completion(postcard); return (T) postcard.getProvider(); } catch (NoRouteFoundException ex) { logger.warning(Consts.TAG, ex.getMessage()); return null; } }
buildProvider是根據service的名字從集合中找到對應的RouteMeta並把path和group設置給postcard,接下來也是給postcard設置其他各種參數,和上面分析的大同小異。
path動態改變
調用的方式和降級處理一模一樣,時機是在build的時候。
參數自動獲取
@Autowired @JvmField var key3: String? = null @Autowired @JvmField var key1: Long = 0L ARouter.getInstance().inject(this)
從文檔中可以知道,按照上面的方式就可以自動獲取各個參數。關鍵代碼肯定是在inject方法中,調用的還是服務。
static void inject(Object thiz) { AutowiredService autowiredService = ((AutowiredService) ARouter.getInstance().build("/arouter/service/autowired").navigation()); if (null != autowiredService) { autowiredService.autowire(thiz); } }
看看AutowiredService的autowire方法
@Override public void autowire(Object instance) { String className = instance.getClass().getName(); try { if (!blackList.contains(className)) { ISyringe autowiredHelper = classCache.get(className); if (null == autowiredHelper) { autowiredHelper = (ISyringe) Class.forName(instance.getClass().getName() + SUFFIX_AUTOWIRED).getConstructor().newInstance(); } autowiredHelper.inject(instance); classCache.put(className, autowiredHelper); } } catch (Exception ex) { blackList.add(className); } }
最關鍵的方法是XXclass_$$ARouter$$Autowired.inject,其實這個類還是在註解生成類中
public class TestOneActivity$$ARouter$$Autowired implements ISyringe { private SerializationService serializationService; @Override public void inject(Object target) { serializationService = ARouter.getInstance().navigation(SerializationService.class); TestOneActivity substitute = (TestOneActivity)target; substitute.key3 = substitute.getIntent().getStringExtra("girl"); substitute.key1 = substitute.getIntent().getLongExtra("key1", substitute.key1); } }
還是通過getIntent().getExtra方法獲取的參數,然後把獲取的參數設置給當前類。