Java的。抽象类儿童计数器听众

Question

我从Parent继承了n个子类。我需要计算所有子对象，并在完成所有操作后触发侦听器。不幸的是，我收到了错误：＆＃34;静态成员＆＃39; childCountListener＆＃39;通过实例引用访问＆＃34;和＆＃34;＆＃39;这个＆＃39;不能从静态上下文中引用＆＃34;。我知道我不能使用＆＃34;这个＆＃34;因为我没有这个班级的对象，但我不知道如何实现这个目标。

父：

public abstract class Parent {

protected static int childCount = 0;
private static ChildCountListener childCountListener;

public Parent() {
    // (...)
    incrementChildCount();
}

public void doSomething() {
    // (...)
    decrementChildCount();
}

public static int getChildCount() {
    return childCount;
}

private void incrementChildCount() {
    childCount++;
}

private void decrementChildCount() {
    childCount--;

    if (childCount < 1) {
        childCountListener.allDone();
    }
}

public static void addChildCountListener(ChildCountListener childCountListener) {
    this.childCountListener = childCountListener;
    // Static member 'childCountListener' accessed via instance reference
    // 'this' cannot be referenced form a static context
}

public interface ChildCountListener {
    void allDone();
}
}

Answer 1

从this

中删除addChildCountListener

public static void addChildCountListener(ChildCountListener childCountListener) {
    Parent.childCountListener = childCountListener;
}

或

public static void addChildCountListener(ChildCountListener aChildCountListener) {
    childCountListener = aChildCountListener;
}