无法创建gradle插件扩展的实例

我正在尝试使用kotlin编写gradle插件。 它应该这样工作。 同时提供配置

 apply plugin: 'appenv' app { srcLink "" downloadPath "" } 

它应该允许从srcLink下载文件并使用任务downloadAll将其存储在downloadAll

我创建了扩展类

 open class ApplicationEnvironmentExtension { val project: Any? constructor(project: Any?) { this.project = project } var srcLink: String = "" var downloadPath: String = "" } 

创建插件类

 class ApplicationEnvironmentPlugin : Plugin<Project> { override fun apply(project: Project) { project.extensions.create("app", ApplicationEnvironmentExtension::class.java) project.task(mapOf ("type" to Download::class.java), "downloadAll") } } 

在这里他的任务

 class Download : DefaultTask() { @TaskAction fun download() { val extension = this.project.extensions.getByName("app") as ApplicationEnvironmentExtension DownloadUtils.download(extension.srcLink, extension.downloadPath) } } 

我构建它并将其作为jar依赖项添加到我的项目中。 要检查是否添加了任务，我运行gradle tasks 。 但在这期间，我得到了错误

 Could not create an instance of type com.lapots.gradle.plugins.appenv.ApplicationEnvironmentExtension_Decorated. 

在stacktrace我得到

 Caused by: org.gradle.internal.reflect.ObjectInstantiationException: Could not create an instance of type com.lapots.gradle.plugins.appenv.ApplicationEnvironmentExtension_Decorated. at org.gradle.internal.reflect.DirectInstantiator.newInstance(DirectInstantiator.java:53) at org.gradle.api.internal.ClassGeneratorBackedInstantiator.newInstance(ClassGeneratorBackedInstantiator.java:36) at org.gradle.api.internal.plugins.DefaultConvention.create(DefaultConvention.java:106) at com.lapots.gradle.plugins.appenv.ApplicationEnvironmentPlugin.apply(ApplicationEnvironmentPlugin.kt:11) at com.lapots.gradle.plugins.appenv.ApplicationEnvironmentPlugin.apply(ApplicationEnvironmentPlugin.kt:8) at org.gradle.api.internal.plugins.ImperativeOnlyPluginApplicator.applyImperative(ImperativeOnlyPluginApplicator.java:35) at org.gradle.api.internal.plugins.RuleBasedPluginApplicator.applyImperative(RuleBasedPluginApplicator.java:43) at org.gradle.api.internal.plugins.DefaultPluginManager.doApply(DefaultPluginManager.java:144) ... 58 more Caused by: java.lang.IllegalArgumentException: Could not find any public constructor for class com.lapots.gradle.plugins.appenv.ApplicationEnvironmentExtension_Decorated which accepts parameters []. at org.gradle.internal.reflect.DirectInstantiator.newInstance(DirectInstantiator.java:44) ... 65 more 

问题是什么？ 我应该为扩展提供一些附加构造函数吗？

Answer 1

扩展需要一个默认的（无参数）构造函数。 如果你真的需要在你的扩展中为一个值赋值一个字段，你可以使用lateinit var并在插件中创建扩展名后赋值。

在这种情况下，它看起来并不需要你的project领域，所以你可以摆脱那个和构造函数。 否则，如果你确实需要这个字段，仍然会移除这个构造函数，但是你需要使project的默认值为null 。