@Subcomponent可以是parent @Component的子接口吗？

Question

有没有办法让@Subcomponent接口扩展它的父@Component接口？Dagger 2是故意不允许这样做的吗？

我已经成功地创建了一个子组件，它可以注入它的父组件可以注入的任何东西，前提是我给了它这样做的方法：

@Singleton @Component(modules = ParentModule.class)
public interface ParentComponent {
    void inject(SomeObject object);
    ChildComponent plus(ChildModule module);
}

@ChildScope @Subcomponent(modules = ChildModule.class)
public interface ChildComponent {
    void inject(SomeObject object);
    void inject(SomeOtherObject object);
}

但是，子组件接口与父组件接口没有继承关系。我尝试让它扩展父接口，但这不能编译：

@ChildScope @Subcomponent(modules = ChildModule.class)
public interface ChildComponent extends ParentComponent {
    //void inject(SomeObject object);
    void inject(SomeOtherObject object);
}

据我所知，错误消息没有解释原因：

[ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.1:compile (default-compile) on project dagger-test: Compilation failure -> [Help 1]
org.apache.maven.lifecycle.LifecycleExecutionException: Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.1:compile (default-compile) on project dagger-test: Compilation failure
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:213)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:153)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:145)
    at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:84)
    at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:59)
    at org.apache.maven.lifecycle.internal.LifecycleStarter.singleThreadedBuild(LifecycleStarter.java:183)
    at org.apache.maven.lifecycle.internal.LifecycleStarter.execute(LifecycleStarter.java:161)
    at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:320)
    at org.apache.maven.DefaultMaven.execute(DefaultMaven.java:156)
    at org.apache.maven.cli.MavenCli.execute(MavenCli.java:537)
    at org.apache.maven.cli.MavenCli.doMain(MavenCli.java:196)
    at org.apache.maven.cli.MavenCli.main(MavenCli.java:141)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:497)
    at org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced(Launcher.java:289)
    at org.codehaus.plexus.classworlds.launcher.Launcher.launch(Launcher.java:229)
    at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode(Launcher.java:415)
    at org.codehaus.plexus.classworlds.launcher.Launcher.main(Launcher.java:356)
Caused by: org.apache.maven.plugin.compiler.CompilationFailureException: Compilation failure
    at org.apache.maven.plugin.compiler.AbstractCompilerMojo.execute(AbstractCompilerMojo.java:862)
    at org.apache.maven.plugin.compiler.CompilerMojo.execute(CompilerMojo.java:129)
    at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo(DefaultBuildPluginManager.java:101)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:209)
    ... 19 more
[ERROR] 
[ERROR] 
[ERROR] For more information about the errors and possible solutions, please read the following articles:
[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/MojoFailureException

Answer 1

我似乎找到了一个解决方案。@Component和@Subcomponent接口之间不能有直接继承关系，但它们都可以扩展这样的接口。而注入方法可以在这些超接口中：

public interface ParentInjector {
    void inject(Injectable obj);
}

public interface ChildInjector extends ParentInjector {
    void inject(Injectable2 obj);
}

@Singleton @Component(modules = ParentModule.class)
public interface ParentComponent extends ParentInjector {
    ChildComponent childComponent();
}

@ChildScope @Subcomponent(modules = ChildModule.class)
public interface ChildComponent extends ChildInjector {}

Injectable和Injectable2没有继承关系：

public class Injectable {
    @Inject @Named("foo") String mFoo;
}

public class Injectable2 {
    @Inject @Named("foo") String mFoo;
    @Inject @Named("bar") String mBar;
}