Java 编译器给出错误 - 没有类型的封闭实例

Question

我设计了一个类:

public class CustomEvent< P, T >
{
  /** Facade interface used for adopting user interfaces to our generic class. */
  public interface ICaller< P, T >
  {
    /** callback facade method. */
    void call( P parent, T callback, Object... objects );
  }

  /** Abstract class for simplifying naming in constructor.  */
  public abstract class Caller implements ICaller< P, T >{}

  /** Constructor. */
  public CustomEvent( final String name, final P parent, final Caller caller ){}
}

现在我想创建一个此类的实例:

  public class TestClass
  {
    private final TestEvent mEventOnLoad;

    public TestClass()
    {   
      // ERROR here: No enclosing instance of type CustomEvent<P,T> is accessible. 
      // Must qualify the allocation with an enclosing instance of type 
      // CustomEvent<P,T> (e.g. x.new A() where x is an instance of CustomEvent<P,T>).
      mEventOnLoad = new TestEvent( "onLoad", this, new TestEvent.Caller() {
        public void call( TestClass parent, ITestCallbacks callback, Object... objects )
        {
          // some code here
        }
      } );
    }

    private class TestEvent extends CustomEvent< TestClass, ITestCallbacks >
    {
      public TestEvent( String name, TestClass parent, TestEvent.Caller caller )
      {
        super( name, parent, caller );
      }
    };
  }

有没有可能以某种方式解决这个问题？我想简化类的命名，而不是长泛型声明，而是使用包含所有需要的类型定义的短抽象类名？

我有一个填充是可能的......但我对 Java 还不太熟悉......

解决方案

    private class TestEvent extends CustomEvent< TestClass, ITestCallbacks >
    { 
      public final static TestEvent Instance = new TestEvent( null, null, null );

      public TestEvent( String name, TestClass parent, TestEvent.Caller caller )
      {
        super( name, parent, caller );
      }
    };

    public TestClass()
    {   
      mEventOnLoad = new TestEvent( "onLoad", this, TestEvent.Instance.new Caller() {
        public void call( TestClass parent, ITestCallbacks callback, Object... objects )
        {
          // some code here
        }
      } );
    }

Answer 1

调用者需要被声明为静态的。现在声明的 Caller 是一个内部类，这意味着它只能从现有父类(super class)的实例创建。例如，如果您有:

class A{
  class B{}
}

然后要创建 B 类的东西，您需要:

A a = new A();
B b = new a.B();

那是因为B是一个内部类；它只能存在于某些 A 的上下文中。您可能不需要它成为内部类，因此将其声明为静态的，使其像普通类一样工作。或者，如果不需要，请将其删除。