从其他类调用时的类层次结构方法

First off this is a pretty basic problem, but i just cant seem to get it, ok so here is a general overview of my program

首先这是一个非常基本的问题，但我似乎无法得到它，好吧所以这里是我的程序的一般概述

       |class A |
       |new B();|
       |new C();|
      /         \
     /           \
|Class B |     |Class C     |
|new D();|     |method E(){}|
    |
|Class D         |
|Invokes method E|

This is my programs hierarchy and I want to invoke the non static method E from class D, without creating a new instance of class C, is there a way to do this or do i have to restructure my class hierarchy.

这是我的程序层次结构，我想从类D调用非静态方法E，而不创建类C的新实例，有没有办法做到这一点，或者我必须重构我的类层次结构。

**EDIT:**Here is real code to display my problem(without a class B though):

**编辑：**这是显示我的问题的真实代码（虽然没有B类）：

import javax.swing.JFrame;
import javax.swing.JSplitPane;

public class TheFrame extends JFrame{
public TheFrame(){
    setTitle("Suduku Solver");
    add(new JSplitPane(JSplitPane.HORIZONTAL_SPLIT,
            new TextLabel(),  new ChangeButton()));
    setVisible(true);
    setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
    setSize(300,300);
    setLocationRelativeTo(null);
}
public static void main(String[] args) {
    new TheFrame();
}
}


import javax.swing.JLabel;
public class TextLabel extends JLabel{
public TextLabel(){
    setText("This is the Label");
}
public void ChangeLabel(){
    setText("Changed Label");
}
}

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
public class ChangeButton extends JButton {
public ChangeButton(){
    setText("Click to change Label");
    addActionListener(new ActionListener(){
        @Override
        public void actionPerformed(ActionEvent e) {
            //Invoke TextLabel changeText method here
        }
    });
}
}

i would like to invoke the changeText method by clicking the button

我想通过单击按钮调用changeText方法

2 个解决方案

#1

You can't invoke a non-static method without an instance. That's "non negotiable".

没有实例，您无法调用非静态方法。这是“不可谈判的”。

You'll have to rework your class structure.

你必须重写你的班级结构。

#2

You could inject C class to D using constructor or setters. This is an example with constructor injection.

您可以使用构造函数或setter将C类注入到D中。这是构造函数注入的示例。

class A {
 A() {
   C c = new C();
   B b = new B(c);
 }
}

class B {
 B(C c) {
   D d = new D(C c);
 }
}

class D {
 private C c;

 D(C c) {
   this.c = c;
 }

 public void methodThatCallsE() {
  c.E();
 }
}

This way you can call method E without having to create an object of C in D.

这样您就可以调用方法E而无需在D中创建C的对象。

You could modify your ChangeButton class to receive any JLabel object.

您可以修改ChangeButton类以接收任何JLabel对象。

public class ChangeButton extends JButton {
       private JLabel jlabel;
       public ChangeButton(JLabel jlabel){
          this.jlabel = jlabel;
          setText("Click to change Label");
          addActionListener(new ActionListener(){
              @Override
              public void actionPerformed(ActionEvent e) {
                  jlabel.setText("new Text");
              }
          });
      }
  }

And then, TheFrame class would look like this.

然后，TheFrame类看起来像这样。

public class TheFrame extends JFrame{
public TheFrame(){
    setTitle("Suduku Solver");
    JLabel jlabel = new TextLabel();
    add(new JSplitPane(JSplitPane.HORIZONTAL_SPLIT,
            jlabel,  new ChangeButton(jlabel)));
...

#1