Question

我正在尝试为这样的东西创建一个构造函数。

public <T extends AppCompatActivity & DialogInterface.OnDismissListener> GooglePlayUtils(T activity) {
    this.activity = activity;
}

Android工作室对此没有任何抱怨，但CompileDebugJava上的构建失败

但是如果删除第二个边界，编译工作正常。我做错了还是还有其他因素导致我失踪？

修改将类型参数添加到类本身后而不是构造函数为我解决了问题。但是我仍然保持这个问题是开放的，所以有人可以解释为什么这样做？

编辑2 将类型参数添加到类而不是构造函数

public abstract class GooglePlayUtils<T extends AppCompatActivity & DialogInterface.OnDismissListener> {

private T activity;

public GooglePlayUtils(T activity) {
    this.activity = activity;
}

错误

java.lang.AssertionError： at com.sun.tools.javac.util.Assert.error（Assert.java:133）在com.sun.tools.javac.util.Assert.check（Assert.java:86） at com.sun.tools.javac.comp.Attr.attribBounds（Attr.java:561） at com.sun.tools.javac.comp.Attr.visitMethodDef（Attr.java:723） at com.sun.tools.javac.tree.JCTree $ JCMethodDecl.accept（JCTree.java:669）在com.sun.tools.javac.comp.Attr.attribTree（Attr.java:431）在com.sun.tools.javac.comp.Attr.attribTree（Attr.java:418） at com.sun.tools.javac.comp.Attr.attribStat（Attr.java:480） at com.sun.tools.javac.comp.Attr.attribClassBody（Attr.java:3250） at com.sun.tools.javac.comp.Attr.attribClass（Attr.java:3173） at com.sun.tools.javac.comp.Attr.attribClass（Attr.java:3109） at com.sun.tools.javac.comp.Attr.visitClassDef（Attr.java:708） at com.sun.tools.javac.tree.JCTree $ JCClassDecl.accept（JCTree.java:591）在com.sun.tools.javac.comp.Attr.attribTree（Attr.java:431）在com.sun.tools.javac.comp.Attr.attribTree（Attr.java:418） at com.sun.tools.javac.comp.Attr.attribStat（Attr.java:480） at com.sun.tools.javac.comp.Attr.visitNewClass（Attr.java:1790） at com.sun.tools.javac.tree.JCTree $ JCNewClass.accept（JCTree.java:1372）在com.sun.tools.javac.comp.Attr.attribTree（Attr.java:431）在com.sun.tools.javac.comp.Attr.attribTree（Attr.java:418） at com.sun.tools.javac.comp.Attr.attribExpr（Attr.java:449） at com.sun.tools.javac.comp.Attr.visitAssign（Attr.java:1993） at com.sun.tools.javac.tree.JCTree $ JCAssign.accept（JCTree.java:1466）在com.sun.tools.javac.comp.Attr.attribTree（Attr.java:431）在com.sun.tools.javac.comp.Attr.attribTree（Attr.java:418） at com.sun.tools.javac.comp.Attr.attribExpr（Attr.java:460） at com.sun.tools.javac.comp.Attr.visitExec（Attr.java:1294） at com.sun.tools.javac.tree.JCTree $ JCExpressionStatement.accept（JCTree.java:1167）在com.sun.tools.javac.comp.Attr.attribTree（Attr.java:431）在com.sun.tools.javac.comp.Attr.attribTree（Attr.java:418） at com.sun.tools.javac.comp.Attr.attribStat（Attr.java:480） at com.sun.tools.javac.comp.Attr.attribStats（Attr.java:496） at com.sun.tools.javac.comp.Attr.visitBlock（Attr.java:918） at com.sun.tools.javac.tree.JCTree $ JCBlock.accept（JCTree.java:781）在com.sun.tools.javac.comp.Attr.attribTree（Attr.java:431）在com.sun.tools.javac.comp.Attr.attribTree（Attr.java:418） at com.sun.tools.javac.comp.Attr.attribStat（Attr.java:480） at com.sun.tools.javac.comp.Attr.visitMethodDef（Attr.java:836） at com.sun.tools.javac.tree.JCTree $ JCMethodDecl.accept（JCTree.java:669）在com.sun.tools.javac.comp.Attr.attribTree（Attr.java:431）在com.sun.tools.javac.comp.Attr.attribTree（Attr.java:418） at com.sun.tools.javac.comp.Attr.attribStat（Attr.java:480） at com.sun.tools.javac.comp.Attr.attribClassBody（Attr.java:3250） at com.sun.tools.javac.comp.Attr.attribClass（Attr.java:3173） at com.sun.tools.javac.comp.Attr.attribClass（Attr.java:3109） at com.sun.tools.javac.comp.Attr.attrib（Attr.java:3083） at com.sun.tools.javac.main.JavaCompiler.attribute（JavaCompiler.java:1184） at com.sun.tools.javac.main.JavaCompiler.compile2（JavaCompiler.java:870） at com.sun.tools.javac.main.JavaCompiler.compile（JavaCompiler.java:829）在com.sun.tools.javac.main.Main.compile（Main.java:439）在com.sun.tools.javac.api.JavacTaskImpl.call（JavacTaskImpl.java:132）在org.gradle.api.internal.tasks.compile.JdkJavaCompiler.execute（JdkJavaCompiler.java:45）在org.gradle.api.internal.tasks.compile.JdkJavaCompiler.execute（JdkJavaCompiler.java:33）在org.gradle.api.internal.tasks.compile.NormalizingJavaCompiler.delegateAndHandleErrors（NormalizingJavaCompiler.java:101）在org.gradle.api.internal.tasks.compile.NormalizingJavaCompiler.execute（NormalizingJavaCompiler.java:50）在org.gradle.api.internal.tasks.compile.NormalizingJavaCompiler.execute（NormalizingJavaCompiler.java:36）在org.gradle.api.internal.tasks.compile.CleaningJavaCompilerSupport.execute（CleaningJavaCompilerSupport.java:34）在org.gradle.api.internal.tasks.compile.CleaningJavaCompilerSupport.execute（CleaningJavaCompilerSupport.java:25）在org.gradle.api.tasks.compile.JavaCompile.performCompilation（JavaCompile.java:157）在org.gradle.api.tasks.compile.JavaCompile.compile（JavaCompile.java:137）在org.gradle.api.tasks.compile.JavaCompile.compile（JavaCompile.java:91） at sun.reflect.GeneratedMethodAccessor1481.invoke（Unknown Source） at sun.reflect.DelegatingMethodAccessorImpl.invoke（DelegatingMethodAccessorImpl.java:43） at java.lang.reflect.Method.invoke（Method.java:606）在org.gradle.internal.reflect.JavaMethod.invoke（JavaMethod.java:75） at org.gradle.api.internal.project.taskfactory.AnnotationProcessingTaskFactory $ IncrementalTaskAction.doExecute（AnnotationProcessingTaskFactory.java:243） at org.gradle.api.internal.project.taskfactory.AnnotationProcessingTaskFactory $ StandardTaskAction.execute（AnnotationProcessingTaskFactory.java:219） at org.gradle.api.internal.project.taskfactory.AnnotationProcessingTaskFactory $ IncrementalTaskAction.execute（AnnotationProcessingTaskFactory.java:230）在org.gradle.api.internal.project.taskfactory.AnnotationProcessingTaskFactory $ StandardTaskAction.execute（AnnotationProcessingTaskFactory.java:208） at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.executeAction（ExecuteActionsTaskExecuter.java:80）在org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.executeActions（ExecuteActionsTaskExecuter.java:61）在org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.execute（ExecuteActionsTaskExecuter.java:46）在org.gradle.api.internal.tasks.execution.PostExecutionAnalysisTaskExecuter.execute（PostExecutionAnalysisTaskExecuter.java:35）在org.gradle.api.internal.tasks.execution.SkipUpToDateTaskExecuter.execute（SkipUpToDateTaskExecuter.java:64）在org.gradle.api.internal.tasks.execution.ValidatingTaskExecuter.execute（ValidatingTaskExecuter.java:58）在org.gradle.api.internal.tasks.execution.SkipEmptySourceFilesTaskExecuter.execute（SkipEmptySourceFilesTaskExecuter.java:42）在org.gradle.api.internal.tasks.execution.SkipTaskWithNoActionsExecuter.execute（SkipTaskWithNoActionsExecuter.java:52）在org.gradle.api.internal.tasks.execution.SkipOnlyIfTaskExecuter.execute（SkipOnlyIfTaskExecuter.java:53）在org.gradle.api.internal.tasks.execution.ExecuteAtMostOnceTaskExecuter.execute（ExecuteAtMostOnceTaskExecuter.java:43）在org.gradle.api.internal.AbstractTask.executeWithoutThrowingTaskFailure（AbstractTask.java:310）在org.gradle.execution.taskgraph.AbstractTaskPlanExecutor $ TaskExecutorWorker.executeTask（AbstractTaskPlanExecutor.java:79） at org.gradle.execution.taskgraph.AbstractTaskPlanExecutor $ TaskExecutorWorker.processTask（AbstractTaskPlanExecutor.java:63） at org.gradle.execution.taskgraph.AbstractTaskPlanExecutor $ TaskExecutorWorker.run（AbstractTaskPlanExecutor.java:51）在org.gradle.execution.taskgraph.DefaultTaskPlanExecutor.process（DefaultTaskPlanExecutor.java:23）在org.gradle.execution.taskgraph.DefaultTaskGraphExecuter.execute（DefaultTaskGraphExecuter.java:88）在org.gradle.execution.SelectedTaskExecutionAction.execute（SelectedTaskExecutionAction.java:37）在org.gradle.execution.DefaultBuildExecuter.execute（DefaultBuildExecuter.java:62）在org.gradle.execution.DefaultBuildExecuter.access $ 200（DefaultBuildExecuter.java:23）在org.gradle.execution.DefaultBuildExecuter $ 2.proceed（DefaultBuildExecuter.java:68）在org.gradle.execution.DryRunBuildExecutionAction.execute（DryRunBuildExecutionAction.java:32）在org.gradle.execution.DefaultBuildExecuter.execute（DefaultBuildExecuter.java:62）在org.gradle.execution.DefaultBuildExecuter.execute（DefaultBuildExecuter.java:55）在org.gradle.initialization.DefaultGradleLauncher.doBuildStages（DefaultGradleLauncher.java:149）在org.gradle.initialization.DefaultGradleLauncher.doBuild（DefaultGradleLauncher.java:106）在org.gradle.initialization.DefaultGradleLauncher.run（DefaultGradleLauncher.java:86） at org.gradle.launcher.exec.InProcessBuildActionExecuter $ DefaultBuildController.run（InProcessBuildActionExecuter.java:90）在org.gradle.tooling.internal.provider.runner.BuildModelActionRunner.run（BuildModelActionRunner.java:54）在org.gradle.launcher.exec.ChainingBuildActionRunner.run（ChainingBuildActionRunner.java:35） at org.gradle.launcher.exec.InProcessBuildActionExecuter.execute（InProcessBuildActionExecuter.java:41） at org.gradle.launcher.exec.InProcessBuildActionExecuter.execute（InProcessBuildActionExecuter.java:28）在org.gradle.launcher.daemon.server.exec.ExecuteBuild.doBuild（ExecuteBuild.java:49）在org.gradle.launcher.daemon.server.exec.BuildCommandOnly.execute（BuildCommandOnly.java:36）在org.gradle.launcher.daemon.server.api.DaemonCommandExecution.proceed（DaemonCommandExecution.java:120）在org.gradle.launcher.daemon.server.exec.WatchForDisconnection.execute（WatchForDisconnection.java:37）在org.gradle.launcher.daemon.server.api.DaemonCommandExecution.proceed（DaemonCommandExecution.java:120）在org.gradle.launcher.daemon.server.exec.ResetDeprecationLogger.execute（ResetDeprecationLogger.java:26）在org.gradle.launcher.daemon.server.api.DaemonCommandExecution.proceed（DaemonCommandExecution.java:120）在org.gradle.launcher.daemon.server.exec.RequestStopIfSingleUsedDaemon.execute（RequestStopIfSingleUsedDaemon.java:34）在org.gradle.launcher.daemon.server.api.DaemonCommandExecution.proceed（DaemonCommandExecution.java:120）在org.gradle.launcher.daemon.server.exec.ForwardClientInput $ 2.call（ForwardClientInput.java:74）在org.gradle.launcher.daemon.server.exec.ForwardClientInput $ 2.call（ForwardClientInput.java:72）在org.gradle.util.Swapper.swap（Swapper.java:38）在org.gradle.launcher.daemon.server.exec.ForwardClientInput.execute（ForwardClientInput.java:72）在org.gradle.launcher.daemon.server.api.DaemonCommandExecution.proceed（DaemonCommandExecution.java:120）在org.gradle.launcher.daemon.server.health.DaemonHealthTracker.execute（DaemonHealthTracker.java:47）在org.gradle.launcher.daemon.server.api.DaemonCommandExecution.proceed（DaemonCommandExecution.java:120）在org.gradle.launcher.daemon.server.exec.LogToClient.doBuild（LogToClient.java:66）在org.gradle.launcher.daemon.server.exec.BuildCommandOnly.execute（BuildCommandOnly.java:36）在org.gradle.launcher.daemon.server.api.DaemonCommandExecution.proceed（DaemonCommandExecution.java:120）在org.gradle.launcher.daemon.server.exec.EstablishBuildEnvironment.doBuild（EstablishBuildEnvironment.java:71）在org.gradle.launcher.daemon.server.exec.BuildCommandOnly.execute（BuildCommandOnly.java:36）在org.gradle.launcher.daemon.server.api.DaemonCommandExecution.proceed（DaemonCommandExecution.java:120）在org.gradle.launcher.daemon.server.health.HintGCAfterBuild.execute（HintGCAfterBuild.java:41）在org.gradle.launcher.daemon.server.api.DaemonCommandExecution.proceed（DaemonCommandExecution.java:120）在org.gradle.launcher.daemon.server.exec.StartBuildOrRespondWithBusy $ 1.run（StartBuildOrRespondWithBusy.java:50）在org.gradle.launcher.daemon.server.DaemonStateCoordinator $ 1.run（DaemonStateCoordinator.java:246） at org.gradle.internal.concurrent.ExecutorPolicy $ CatchAndRecordFailures.onExecute（ExecutorPolicy.java:54） at org.gradle.internal.concurrent.StoppableExecutorImpl $ 1.run（StoppableExecutorImpl.java:40）在java.util.concurrent.ThreadPoolExecutor.runWorker（ThreadPoolExecutor.java:1145） at java.util.concurrent.ThreadPoolExecutor $ Worker.run（ThreadPoolExecutor.java:615）在java.lang.Thread.run（Thread.java:745）

Answer 1

您是在尝试创建泛型类，还是构造函数采用泛型参数的具体类？

如果您尝试创建一个泛型类，可以为扩展AppCompatActivity & DialogInterface.OnDismissListener的对象实例化，则需要使该类具有通用性（如编辑中所示）。在泛型类中，类型参数不需要在构造函数定义中重复，它们由隐式编译器承担。

如果您尝试创建一个具体或泛型类的类，其构造函数可以接受扩展AppCompatActivity & DialogInterface.OnDismissListener的对象，则需要一种方法将该参数显式地转换为任何类型this.activity定义为。将通用activity参数分配给this.activity而不进行转换的唯一方法是在类型擦除后它们是相同的类型。

虽然可以创建一个参数是通用的构造函数，但是不能在不进行转换的情况下将泛型参数分配给另一个类型（在类型擦除之后）。

在这种情况下如何在java泛型中使用多个边界

1 个答案: