我克隆了ROS2 Java示例，并尝试使用Integlij、Gradle 6.3和Java 14用Gradle构建它们。但是，在项目导入过程中会引发以下异常。我已经完成了ROS2的安装，并且可以成功地在cpp和python中运行示例。我复制完整的堆栈。我电脑中的ROS2版本是ROS2-dashing-20200319-windows-amd64。
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异常为：com.intellij.openapi.externalSystem.model.ExternalSystemException：无法在处对null对象调用方法split()org.jetbrains.plugins.gradle.model.ProjectImportAction.addBuildModels(ProjectImportAction.java:272)在org.jetbrains.plugins.gradle.model.ProjectImportAction.execute(ProjectImportAction.java:130)在org.jetbrains.plugins.gradle.model.ProjectImportAction.execute(ProjectImportAction.java:56)在org.gradle.tooling.internal.consumer.connection.InternalBuildActionAdapter.execute(InternalBuildActionAdapter.java:79)在org.gradle.tooling.internal.provider.runner.ClientProviderdPhasedActionRunner$ActionRunningListener.runAction(ClientProviderdPhaseDActionRunner.java:120)在org.gradle.tooling.internal.provider.runner.ClientProviderdPhasedActionRunner$ActionRunningListener.run(ClientProviderdPhaseDActionRunner.java:110)在org.gradle.tooling.internal.provider.runner.ClientProviderdPhasedActionRunner$ActionRunningListener.buildFinished(ClientProviderdPhaseDActionRunner.java:104)位于jdk.internal.reflect.GeneratedMethodAccessor39.invoke(未知来源)java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)在org.gradle.internal.dispatch.ReflectionDispatch.dispatch(反射调度.java:36)在org.gradle.internal.dispatch.ReflectionDispatch.dispatch(反射调度.java:24)在org.gradle.internal.event.DefaultListenerManager$ListenerDetails.dispatch(DefaultListenerManager.java:382)在org.gradle.internal.event.DefaultListenerManager$ListenerDetails.dispatch(DefaultListenerManager.java:364)在org.gradle.internal.event.AbstractBroadcastDispatch.dispatch(AbstractBroadcastDispatch.java:58)在org.gradle.internal.event.DefaultListenerManager$EventBroadcast$ListenerDispatch.dispatch(DefaultListenerManager.java:352)在org.gradle.internal.event.DefaultListenerManager$EventBroadcast$ListenerDispatch.dispatch(DefaultListenerManager.java:339)在org.gradle.internal.event.AbstractBroadcastDispatch.dispatch(AbstractBroadcastDispatch.java:42)在org.gradle.internal.event.BroacastDispatch$SingletonDispatch.dispatch(BroadcastDispatch.java:231)在org.gradle.internal.event.BroacastDispatch$SingletonDispatch.dispatch(BroadcastDispatch.java:150)在org.gradle.internal.event.AbstractBroadcastDispatch.dispatch(AbstractBroadcastDispatch.java:58)在org.gradle.internal.event.BroacastDispatch$CompositeDispatch.dispatch(BroadcastDispatch.java:325)在org.gradle.internal.event.BroacastDispatch$CompositeDispatch.dispatch(BroadcastDispatch.java:235)在org.gradle.internal.event.ListerBroadcast.dispatch(ListenerBroadcast.java:141)在org.gradle.internal.event.ListerBroadcast.dispatch(ListenerBroadcast.java:37)在org.grade.internal.dispatch.ProxyDispatchAdapter$DispatchingInvocationHandler.invoke(ProxyDispatchAdapter.java:94)位于com.sun.proxy.$Proxy18.buildFinished(未知源)org.gradle.sinitialization.DefaultGradleLauncher.finishBuild(DefaultGradleLauncher.java:184)在org.gradle.sinitialization.DefaultGradleLauncher.finishBuild(DefaultGradleLauncher.java:127)在org.gradle.internal.iocation.GradleBuildController$1.create(GradleBuildControll.java:75)在org.gradle.internal.iocation.GradleBuildController$1.create(GradleBuildControll.java:67)在org.gradle.internal.work.DefaultWorkerLeaseService.withLocks(DefaultWorkerLeaceService.java:189)在org.gradle.internal.work.StopShieldingWorkerLeaseService.withLocks(StopShieldingworkerLeaseServices.java:40)在org.gradle.internal.iocation.GradleBuildController.doBuild(GradleBuildControll.java:67)在org.gradle.internal.iocation.GradleBuildController.run(GradleBuildControll.java:56)在org.gradle.tooling.internal.provider.runner.ClientProviderdPhasedActionRunner.run(ClientProviderdPhaseDActionRunner.java:60)在org.gradle.selauncher.exec.ChainingBuildActionRunner.run(ChainingBuildActionRunner.java:35)在org.gradle.selauncher.exec.ChainingBuildActionRunner.run(ChainingBuildActionRunner.java:35)在org.gradle.selauncher.exec.BuildOutcomeReportingBuildActionRunner.run(BuildOutcomeReporting BuildActionRunner.java:63)在org.gradle.tooling.internal.provider.ValidatingBuildActionRunner.run(ValidatingBuildActionRunner.java:32)在org.gradle.selauncher.exec.BuildCompletionNotifyingBuildActionRunner.run(BuildCompletionnotifyingBuildingActionRunner.java:39)在org.gradle.selauncher.exec.RunAsBuildOperationBuildActionRunner$3.call(RunAsBuildOperationBuildingActionRunner.java:51)在org.gradle.selauncher.exec.RunAsBuildOperationBuildActionRunner$3.call(RunAsBuildOperationBuildingActionRunner.java:45)在org.gradle.internal.operations.DefaultBuildOperationExecutor$CallableBuildOperationWorker.execute(DefaultBuildOperationExecutior.java:416)在org.gradle.internal.operations.DefaultBuildOperationExecutor$CallableBuildOperationWorker.execute(DefaultBuildOperationExecutior.java:406)在org.gradle.internal.operations.DefaultBuildOperationExecutor$1.execute(DefaultBuildOperationExecutior.java:165)在org.gradle.internal.operations.DefaultBuildOperationExecution.execute(DefaultBuildOperationExecutior.java:250)在org.gradle.internal.operations.DefaultBuildOperationExecution.execute(DefaultBuildOperationExecutior.java:158)在org.gradle.internal.operations.DefaultBuildOperationExecution.call(DefaultBuildOperationExecutior.java:102)在org.gradle.internal.operations.DelegatingBuildOperationExecutiator.call(DelegatingBuildOperationExecutior.java:36)在org.gradle.selauncher.exec.RunAsBuildOperationBuildActionRunner.run(RunAsBuildOperationBuildingActionRunner.java:45)在org.gradle.selauncher.exec.InProcessBuildActionExecuter$1.transform(InProcessBuildActionExecutor.java:50)在org.gradle.selauncher.exec.InProcessBuildActionExecuter$1.transform(InProcessBuildActionExecutor.java:47)在org.gradle.composite.internal.DefaultRootBuildState.run(DefaultRootBuildState.java:80)在org.gradle.selauncher.exec.InProcessBuildActionExecuter.execute(InProcessBuildActionExecutor.java:47)在org.gradle.selauncher.exec.InProcessBuildActionExecuter.execute(InProcessBuildActionExecutor.java:31)在org.gradle.selauncher.exec.BuildTreeScopeBuildActionExecuter.execute(BuildTreeScopeBuildingActionExecuter.java:42)在org.gradle.selauncher.exec.BuildTreeScopeBuildActionExecuter.execute(BuildTreeScopeBuildingActionExecuter.java:28)在org.gradle.tooling.internal.provider.ContinuousBuildActionExecuter.execute(ContinuousBuildActionExecuter.java:78)在org.gradle.tooling.internal.provider.ContinuousBuildActionExecuter.execute(ContinuousBuildActionExecuter.java:52)在org.gradle.tooling.internal.provider.SubscripteBuildActionExecuter.execute(SubscripteBuildactionExecuter.java:60)在org.gradle.tooling.internal.provider.SubscripteBuildActionExecuter.execute(SubscripteBuildactionExecuter.java:38)在org.gradle.tooling.internal.provider.SessionScopeBuildActionExecuter.execute(SessionScopeBuild ActionExecuteR.java:68)在org.gradle.tooling.internal.provider.SessionScopeBuildActionExecuter.execute(SessionScopeBuild ActionExecuteR.java:38)在org.gradle.tooling.internal.provider.GradleThreadBuildActionExecuter.execute(GradleThreadBuild ActionExecuteR.java:37)在org.gradle.tooling.internal.provider.GradleThreadBuildActionExecuter.execute(GradleThreadBuild ActionExecuteR.java:26)在org.gradle.tooling.internal.provider.ParallelsmConfigurationBuildActionExecuter.execute(ParallelismConfigurationBuildActionExecuter.java:43)在org.gradle.tooling.internal.provider.ParallelsmConfigurationBuildActionExecuter.execute(ParallelismConfigurationBuildActionExecuter.java:29)在org.gradle.tooling.internal.provider.StartParamsValidatingActionExecuter.execute(StartParamsvalidingActionExecutor.java:60)在org.gradle.tooling.internal.provider.StartParamsValidatingActionExecuter.execute(StartParamsvalidingActionExecutor.java:32)在org.gradle.tooling.internal.provider.SessionFailureReportingActionExecuter.execute(SessionFailureReport ingActionExecutor.java:55)在org.gradle.tooling.internal.provider.SessionFailureReportingActionExecuter.execute(SessionFailureReport ingActionExecutor.java:41)在org.gradle.tooling.internal.provider.SetupLoggingActionExecuter.execute(SetupLoggingActionExecuter.java:48)在org.gradle.tooling.internal.provider.SetupLoggingActionExecuter.execute(SetupLoggingActionExecuter.java:32)在org.gradle.selauncher.daemon.server.exec.ExecuteBuild.doBuild(ExecuteBuild.java:68)在org.gradle.selauncher.daemon.server.exec.BuildCommandOnly.exexecute(BuildCommandOnly.java:37)在org.gradle.selauncher.daemon.server.api.DemonCommandExecution.proceed(DaemonCommentExecution.java:104)在org.gradle.selauncher.daemon.server.exec.WatchForDisconnection.execute(WatchForDisconnection.java:39)在org.gradle.selauncher.daemon.server.api.DemonCommandExecution.proceed(DaemonCommentExecution.java:104)在org.gradle.selauncher.daemon.server.exec.ResetDeprecationLogger.execute(ResetDeprecactionLogger.java:29)在org.gradle.selauncher.daemon.server.api.DemonCommandExecution.proceed(DaemonCommentExecution.java:104)在org.gradle.selauncher.daemon.server.exec.RequestStopIfSingleUsedDaemon.execute(RequestStopIfsSingleUsed daemon.java:35)在org.gradle.selauncher.daemon.server.api.DemonCommandExecution.proceed(DaemonCommentExecution.java:104)在org.gradle.selauncher.daemon.server.exec.ForwardClientInput$2.create(ForwardClientInput.java:78)在org.gradle.selauncher.daemon.server.exec.ForwardClientInput$2.create(ForwardClientInput.java:75)网址：org.gradle.util.Swaper.swap(Swapper.java:38)org.gradle.selauncher.daemon.server.exec.ForwardClientInput.exexecute(ForwardClientInput.java:75)在org.gradle.selauncher.daemon.server.api.DemonCommandExecution.proceed(DaemonCommentExecution.java:104)在org.gradle.selauncher.daemon.server.exec.LogAndCheckHealth.exexecute(LogAndCheckHealth.java:55)在org.gradle.selauncher.daemon.server.api.DemonCommandExecution.proceed(DaemonCommentExecution.java:104)在org.gradle.selauncher.daemon.server.exec.LogToClient.doBuild(LogToClient.java:63)在org.gradle.selauncher.daemon.server.exec.BuildCommandOnly.exexecute(BuildCommandOnly.java:37)在org.gradle.selauncher.daemon.server.api.DemonCommandExecution.proceed(DaemonCommentExecution.java:104)在org.gradle.selauncher.daemon.server.exec.EestablishBuildEnvironment.doBuild(EstablishBuildEnvironment.java:82)在org.gradle.selauncher.daemon.server.exec.BuildCommandOnly.exexecute(BuildCommandOnly.java:37)在org.gradle.selauncher.daemon.server.api.DemonCommandExecution.proceed(DaemonCommentExecution.java:104)在org.gradle.selauncher.daemon.server.exec.StartBuildOrRespondWithBusy$1.run(StartBuildOrRespandWithBusy.java:52)在org.gradle.selauncher.daemon.server.DemonStateCoordinator$1.run(DaemonStateCoordinator.java:297)在org.gradle.internal.concurrent.ExecutorPolicy$CatchAndRecordFailures.onExecute(ExecutorPolicy.java:64)在org.gradle.internal.concurrent.ManagedExecutiorImpl$1.run(ManagedExecutiorimpl.java:48)在org.gradle.internal.concurrent.ThreadFactoryImpl$ManagedThreadRunnable.run(ThreadFactoryImpl.java:56)java.lang.NullPointerException：无法对null调用方法split()对象位于org.codehaus.groovy.runtime.NullObject.invokeMethod(NullObject.java:91)在org.codehaus.groovy.runtime.callsite.PogoMetaClassSite.call(PogoMetaClassSite.java:43)在org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCall(CallSiteArray.java:47)在org.codehaus.groovy.runtime.callsite.NullCallSite.call(NullCallSite.java:34)在org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCall(CallSiteArray.java:47)在org.codehaus.groovy.runtime.callsite.PogoMetaClassSite.call(PogoMetaClassSite.java:52)在org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:127)在org.ros2.tools.gradle.JavaAmentPlugin.updateJavaDependencies(JavaAmentplugin.groovy:58)位于jdk.internal.reflect.GeneratedMethodAccessor81.invoke(未知来源)java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)位于java.base/java.lang.reflect.Method.ioke(Method.java:564)org.codehaus.groovy.reflection.CachedMethod.ioke(CachedMethod.java:101)在groovy.lang.MetaMethod.doMethodInvoke(MetaMethod.java:323)groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:1217)org.codehaus.groovy.runtime.ScriptBytecodeAdapter.invokeMethodOnCurrentN(ScriptBytecodeAdapter.java:94)在org.ros2.tools.gradle.JavaAmentPlugin.extension.this$dist$invoke$2(JavaAmentplugin.groovy)在org.ros2.tools.gradle.JavaAmentPluginExtension$1.methodMissing(JavaAmentPluginExtension.groovy)位于jdk.internal.reflect.GeneratedMethodAccessor80.invoke(未知来源)java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)位于java.base/java.lang.reflect.Method.ioke(Method.java:564)org.codehaus.groovy.reflection.CachedMethod.ioke(CachedMethod.java:101)在groovy.lang.MetaClassImpl.invokeMissingMethod(MetaClassImpl.java:958)在groovy.lang.MetaClassImpl.invokePropertyOrMissing(MetaClassImpl.java:1286)在groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:1219)在org.codehaus.groovy.runtime.callsite.PogoMetaClassSite.callCurrent(PogoMetaClassSite.java:64)在org.codehaus.groovy.runtime.callsite.AbstractCallSite.callCurrent(AbstractCallSite.java:160)在org.ros2.tools.gradle.JavaAmentPluginExtension$1.bforeResolve(JavaAmentPlugin.groovy:69)位于jdk.internal.reflect.GeneratedMethodAccessor79.invoke(未知来源)java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)位于java.base/java.lang.reflect.Method.ioke(Method.java:564)org.gradle.internal.dispatch.ReflectionDispatch.dispatch(反射调度.java:36)在org.gradle.internal.dispatch.ReflectionDispatch.dispatch(反射调度.java:24)在org.gradle.internal.event.DefaultListenerManager$ListenerDetails.dispatch(DefaultListenerManager.java:382)在org.gradle.internal.event.DefaultListenerManager$ListenerDetails.dispatch(DefaultListenerManager.java:364)在org.gradle.internal.event.AbstractBroadcastDispatch.dispatch(AbstractBroadcastDispatch.java:58)在org.gradle.internal.event.DefaultListenerManager$EventBroadcast$ListenerDispatch.dispatch(DefaultListenerManager.java:352)在org.gradle.internal.event.DefaultListenerManager$EventBroadcast$ListenerDispatch.dispatch(DefaultListenerManager.java:339)在org.gradle.internal.event.AbstractBroadcastDispatch.dispatch(AbstractBroadcastDispatch.java:42)在org.gradle.internal.event.BroacastDispatch$SingletonDispatch.dispatch(BroadcastDispatch.java:231)在org.gradle.internal.event.BroacastDispatch$SingletonDispatch.dispatch(BroadcastDispatch.java:150)在org.gradle.internal.event.ListerBroadcast.dispatch(ListenerBroadcast.java:141)在org.gradle.internal.event.ListerBroadcast.dispatch(ListenerBroadcast.java:37)在org.grade.internal.dispatch.ProxyDispatchAdapter$DispatchingInvocationHandler.invoke(ProxyDispatchAdapter.java:94)位于com.sun.proxy.$Proxy29.beforeResolve(未知源)org.gradle.api.internal.aartifacts.configurations.DefaultConfiguration.performPreResolveActions(DefaultConfiguration.java:674)在org.gradle.api.internal.aartifacts.configurations.DefaultConfiguration.access$400(DefaultConfiguration.java:141)在org.gradle.api.internal.aartifacts.configurations.DefaultConfiguration$1.run(DefaultConfiguration.java:618)在org.gradle.internal.operations.DefaultBuildOperationExecutior$RunnableBuildOperationWorker.execute(DefaultBuildOperationExecutiator.java:402)在org.gradle.internal.operations.DefaultBuildOperationExecutior$RunnableBuildOperationWorker.execute(DefaultBuildOperationExecutiator.java:394)在org.gradle.internal.operations.DefaultBuildOperationExecutor$1.execute(DefaultBuildOperationExecutior.java:165)在org.gradle.internal.operations.DefaultBuildOperationExecution.execute(DefaultBuildOperationExecutior.java:250)在org.gradle.internal.operations.DefaultBuildOperationExecution.execute(DefaultBuildOperationExecutior.java:158)在org.gradle.internal.operations.DefaultBuildOperationExecution.run(DefaultBuildOperationExecutior.java:92)在org.gradle.internal.operations.DelegatingBuildOperationExecutiator.run(DelegatingBuildOperationExecutior.java:31)在org.gradle.api.internal.aartifacts.configurations.DefaultConfiguration.resolveGraphIfRequired(DefaultConfiguration.java:611)在org.gradle.api.internal.aartifacts.configurations.DefaultConfigurationLambda$resolveExclusivey$4(DefaultConfiguration.java:592)在org.gradle.api.internal.project.DefaultProjectStateRegistry$SafeExclusiveLockImpl.withLock(DefaultProjectStateRegistry.java:289)在org.gradle.api.internal.aartifacts.configurations.DefaultConfiguration.resolveExclusive(DefaultConfiguration.java:590)在org.gradle.api.internal.aartifacts.configurations.DefaultConfiguration.resolveToStateOrLater(DefaultConfiguration.java:576)在org.gradle.api.internal.aartifacts.configurations.DefaultConfiguration.getResolvedConfiguration(DefaultConfiguration.java:554)在org.gradle.api.internal.aartifacts.configurations.DefaultConfiguration_Dcorated.getResolvedConfiguration(未知来源)org.jetbrains.plugins.gradle.tooling.util.resolve.DependencyResolverImpl.resolveDependencies(DependencyResolveImpl.java:153)在org.jetbrains.plugins.gradle.tooling.util.resolve.DependencyResolverImpl.getDependencies(DependencyResolveImpl.java:537)在org.jetbrains.plugins.gradle.tooling.util.resolve.DependencyResolverImpl.resolveDependencies(DependencyResolveImpl.java:131)在org.jetbrains.plugins.gradle.tooling.util.DependencyResolver$resolveDependencies.call(未知来源)org.jetbrains.plugins.gradle.tooling.builder.ExternalProjectBuilderImpl$_getSourceSets_closure1.doCall(ExternalProjectBuilderImpl.groovy:440)在java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native方法)java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)在java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)位于java.base/java.lang.reflect.Method.ioke(Method.java:564)org.codehaus.groovy.reflection.CachedMethod.ioke(CachedMethod.java:101)在groovy.lang.MetaMethod.doMethodInvoke(MetaMethod.java:323)org.codehaus.groovy.runtime.metaclass.ClosureMetaClass.invokeMethod(ClosureMetaClass.java:263)在groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:1041)在groovy.lang.Closure.call(Closure.java:405)groovy.lang.Closure.call(Closure.java:421)org.gradle.util.ClosureBackedAction.execure(ClosureBackedAction.java:71)在org.gradle.util.ConfigureUtil.configureTarget(ConfigureUtil.java:154)位于org.gradle.util.ConfigureUtil.configure(ConfigureUtil.java:105)在org.gradle.util.ConfigureUtil$WrappedConfigureAction.execute(ConfigureUtil.java:166)在org.gradle.api.internal.DefaultDomainObjectCollection.all(DefaultDomainObjectCollection.java:163)在org.gradle.api.internal.DefaultDomainObjectCollection.all(DefaultDomainObjectCollection.java:198)在org.gradle.api.DomainObjectCollection$all$1.call(未知来源)在org.jetbrains.plugins.gradle.tooling.builder.ExternalProjectBuilderImpl.getSourceSets(ExternalProjectBuilderImpl.groovy:240)在org.jetbrains.plugins.gradle.tooling.builder.ExternalProjectBuilderImpl.doBuild(ExternalProjectBuilderImpl.groovy:101)在org.jetbrains.plugins.gradle.tooling.builder.ExternalProjectBuilderImpl.buildAll(ExternalProjectBuilderImpl.groovy:70)在org.jetbrains.plugins.gradle.tooling.internal.ExtraModelBuilder.buildAll(ExtraModelBuildr.java:101)在org.gradle.tooling.provider.model.internal.DefaultToolingModelBuilderRegistry$BuildOperationWrappingToolingModelBuilder$1.create(DefaultToolingModelBuilder Registry.java:104)在org.gradle.api.internal.project.DefaultProjectStateRegistry.withLenientState(DefaultProjectStateRegistry.java:134)在org.gradle.tooling.provider.model.internal.DefaultToolingModelBuilderRegistry$BuildOperationWrappingToolingModelBuilder$1.call(DefaultToolingModeluilderRegistry.java:100)在org.gradle.internal.operations.DefaultBuildOperationExecutor$CallableBuildOperationWorker.execute(DefaultBuildOperationExecutior.java:416)在org.gradle.internal.operations.DefaultBuildOperationExecutor$CallableBuildOperationWorker.execute(DefaultBuildOperationExecutior.java:406)在。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。org.gradle.internal.concurrent.ThreadFactoryImpl$ManagedThreadRunnable.run(ThreadFactoryImpl.java:56)位于java.base/java.lang.Thread.run(Thread.java:832)
从命令行构建ros2_java_examples也会失败，但会出现不同的错误。
ros2_java_examplesrcljava_examples> gradle build
> Task :checkAmentProperties FAILED
FAILURE: Build failed with an exception.
* What went wrong:
Execution failed for task ':checkAmentProperties'.
> Missing Ament Gradle property: ament.build_space
虽然这个问题没有得到解决，但可以通过直接使用命令行来解决它，如注释中所述。
在构建ROS2Java示例之前，需要遵循前面的所有步骤。