Java ActionListeners 到独立类

Question

有没有办法将 actionListener 类移动到独立类？

我使用 Java 和 MVC 设计模式做了一个例子。我有 3 个更改背景颜色的按钮。

这是模型

public class ChangeFontColorApplicationModel {
    public ChangeFontColorApplicationModel(){}
}

查看

import java.awt.event.*;
import javax.swing.*;

public class ChangeFontColorApplicationView extends JFrame{
private JButton changeToYellowButton = new JButton("Yellow font");
private JButton changeToBlackButton = new JButton("Black font");
private JButton changeToBlueButton = new JButton("Blue font");

public ChangeFontColorApplicationView(){
    super("Change font");
    JPanel buttonPanel = new JPanel();

    buttonPanel.add(changeToYellowButton);
    buttonPanel.add(changeToBlackButton);
    buttonPanel.add(changeToBlueButton);

    this.add(buttonPanel);
}

public void addButtonActionListener(){
    changeToYellowButton.addActionListener(new yellowBackgroundHandler());
    changeToBlackButton.addActionListener(new yellowBackgroundHandler());
    changeToBlueButton.addActionListener(new yellowBackgroundHandler());
}
}

控制器

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

public class ChangeFontColorApplicationController {
private ChangeFontColorApplicationView changeFontColorApplicationViewObject;
backgroundHandler yellowBackgroundHandlerObject = new yellowBackgroundHandler();
backgroundHandler blackBackgroundHandlerObject = new blackBackgroundHandler();
backgroundHandler blueBackgroundHandlerObject = new blueBackgroundHandler();

public ChangeFontColorApplicationController(ChangeFontColorApplicationView changeFontColorApplicationViewObject){
    this.changeFontColorApplicationViewObject = changeFontColorApplicationViewObject;

    yellowBackgroundHandlerObject.setNextHandlerInChain(blackBackgroundHandlerObject);
    blackBackgroundHandlerObject.setNextHandlerInChain(blueBackgroundHandlerObject);

    this.changeFontColorApplicationViewObject.addButtonActionListener();
}
}

现在我创建了一个处理按钮事件的接口

public interface backgroundHandler extends ActionListener{
public void setNextHandlerInChain(backgroundHandler nextInChain);
public void handleCommand(String getActionCommandString);
public void actionPerformed(ActionEvent event);
}

每个实现接口的类都处理 ActionEvent。如果不能，则传递给下一个类（作为责任链）

黄色字体处理程序

import java.awt.Color;
import java.awt.event.ActionEvent;

public class yellowBackgroundHandler implements backgroundHandler{
private backgroundHandler nextInChain;
private ChangeFontColorApplicationView ChangeFontColorApplicationViewObject = new ChangeFontColorApplicationView();

public yellowBackgroundHandler(){}

@Override
public void setNextHandlerInChain(backgroundHandler nextInChain) {
    this.nextInChain = nextInChain;
}

@Override
public void handleCommand(String getActionCommandString) {
    if(getActionCommandString.equalsIgnoreCase("Yellow font")){
        ChangeFontColorApplicationViewObject.setBackground(Color.yellow);
    }
    else {
        nextInChain.handleCommand(getActionCommandString);
    }
}

@Override
public void actionPerformed(ActionEvent event) {
    try{
        handleCommand(event.getActionCommand());
    }
    catch (Exception exeption){
        ChangeFontColorApplicationViewObject.setTitle(exeption.toString());            
    }
}
}

黑色字体处理程序

import java.awt.Color;
import java.awt.event.ActionEvent;

public class blackBackgroundHandler implements backgroundHandler{
private backgroundHandler nextInChain;
private ChangeFontColorApplicationView ChangeFontColorApplicationViewObject = new ChangeFontColorApplicationView();

public blackBackgroundHandler(){}

@Override
public void setNextHandlerInChain(backgroundHandler nextInChain) {
    this.nextInChain = nextInChain;
}

@Override
public void handleCommand(String getActionCommandString) {
    if(getActionCommandString.equalsIgnoreCase("Black font")){
        ChangeFontColorApplicationViewObject.setBackground(Color.BLACK);
    }
    else {
        nextInChain.handleCommand(getActionCommandString);
    }
}

@Override
public void actionPerformed(ActionEvent event) {
    try{
        handleCommand(event.getActionCommand());
    }
    catch (Exception exeption){
        ChangeFontColorApplicationViewObject.setTitle(exeption.toString());            
    }
}
}

蓝色字体处理程序

import java.awt.Color;
import java.awt.event.ActionEvent;

public class blueBackgroundHandler implements backgroundHandler{
private backgroundHandler nextInChain;
private ChangeFontColorApplicationView ChangeFontColorApplicationViewObject = new ChangeFontColorApplicationView();

public blueBackgroundHandler(){}

@Override
public void setNextHandlerInChain(backgroundHandler nextInChain) {
    this.nextInChain = nextInChain;
}

@Override
public void handleCommand(String getActionCommandString) {
    if(getActionCommandString.equalsIgnoreCase("Μπλε φόντο")){
        ChangeFontColorApplicationViewObject.setBackground(Color.BLUE);
    }
    else {
        ChangeFontColorApplicationViewObject.setTitle("This is the back end of COR");
    }
}

@Override
public void actionPerformed(ActionEvent event) {
    try{
        handleCommand(event.getActionCommand());
    }
    catch (Exception exeption){
        ChangeFontColorApplicationViewObject.setTitle(exeption.toString());            
    }
}
}

最后我用main方法创建了类

public class ChangeFontColorApp {
public static void main(String[] args){
    ChangeFontColorApplicationView changeFontColorApplicationViewObject = new ChangeFontColorApplicationView();
    ChangeFontColorApplicationController changeFontColorApplicationControllerObject = new ChangeFontColorApplicationController(changeFontColorApplicationViewObject);

    changeFontColorApplicationViewObject.setVisible(true);
    changeFontColorApplicationViewObject.setSize(600, 600);
       changeFontColorApplicationViewObject.setDefaultCloseOperation(ChangeFontColorApplicationView.EXIT_ON_CLOSE);
}
}

有什么办法可以做到这一点吗？我不想有一个用于事件处理的内部类，其中包含多个 if blick。任何建议将不胜感激。

Answer 1

那是行不通的。但是，问题不是因为你有独立的类（使用独立的类很好）。相反，问题是：

在视图类中，您有：

public void addButtonActionListener(){
    changeToYellowButton.addActionListener(new yellowBackgroundHandler());
    changeToBlackButton.addActionListener(new yellowBackgroundHandler());
    changeToBlueButton.addActionListener(new yellowBackgroundHandler());
}

这意味着所有按钮的点击都由 YellowBackgroundHandler 处理。但是，yellowBackgroundHandler 只接受来自 changeToYellowButton 的点击。除此之外，yellowBackgroundHandler 没有配置下一个处理程序。

要解决此问题，请在视图类中更改：

public void addButtonActionListener(){
    changeToYellowButton.addActionListener(new yellowBackgroundHandler());
    changeToBlackButton.addActionListener(new yellowBackgroundHandler());
    changeToBlueButton.addActionListener(new yellowBackgroundHandler());
}

到

public void addButtonActionListener(backgroundHandler handler){
    changeToYellowButton.addActionListener(handler);
    changeToBlackButton.addActionListener(handler);
    changeToBlueButton.addActionListener(handler);
}

在控制器类中，改变这个：

this.changeFontColorApplicationViewObject.addButtonActionListener();

到

this.changeFontColorApplicationViewObject.addButtonActionListener(yellowBackgroundHandlerObject);

我看到的另一个问题是，yellowBackgroundHandler、blackBackgroundHandler 和 blueBackgroundHandler 有私有变量 ChangeFontColorApplicationViewObject，它指向自己的 ChangeFontColorApplicationView 实例。我们需要这个变量指向在 main 方法中创建的实例。为此，请更改：

private ChangeFontColorApplicationView ChangeFontColorApplicationViewObject = new ChangeFontColorApplicationView();
public blueBackgroundHandler(){}

到：

private ChangeFontColorApplicationView ChangeFontColorApplicationViewObject;
public blueBackgroundHandler(ChangeFontColorApplicationView ChangeFontColorApplicationViewObject){
  this.ChangeFontColorApplicationViewObject = ChangeFontColorApplicationViewObject;
}

并改变这个：

private ChangeFontColorApplicationView ChangeFontColorApplicationViewObject = new ChangeFontColorApplicationView();
public blackBackgroundHandler(){}

到：

private ChangeFontColorApplicationView ChangeFontColorApplicationViewObject;
public blackBackgroundHandler(ChangeFontColorApplicationView ChangeFontColorApplicationViewObject){
  this.ChangeFontColorApplicationViewObject = ChangeFontColorApplicationViewObject;
}

并改变这个：

private ChangeFontColorApplicationView ChangeFontColorApplicationViewObject = new ChangeFontColorApplicationView();
public blueBackgroundHandler(){}

到：

private ChangeFontColorApplicationView ChangeFontColorApplicationViewObject;
public blueBackgroundHandler(ChangeFontColorApplicationView ChangeFontColorApplicationViewObject){
  this.ChangeFontColorApplicationViewObject = ChangeFontColorApplicationViewObject;
}

最后，改变这个：

backgroundHandler yellowBackgroundHandlerObject = new yellowBackgroundHandler();
backgroundHandler blackBackgroundHandlerObject = new blackBackgroundHandler();
backgroundHandler blueBackgroundHandlerObject = new blueBackgroundHandler();

public ChangeFontColorApplicationController(ChangeFontColorApplicationView changeFontColorApplicationViewObject){
    this.changeFontColorApplicationViewObject = changeFontColorApplicationViewObject;

    yellowBackgroundHandlerObject.setNextHandlerInChain(blackBackgroundHandlerObject);
    blackBackgroundHandlerObject.setNextHandlerInChain(blueBackgroundHandlerObject);

    this.changeFontColorApplicationViewObject.addButtonActionListener();
}

到

backgroundHandler yellowBackgroundHandlerObject = new yellowBackgroundHandler();
backgroundHandler blackBackgroundHandlerObject = new blackBackgroundHandler();
backgroundHandler blueBackgroundHandlerObject = new blueBackgroundHandler();

public ChangeFontColorApplicationController(ChangeFontColorApplicationView changeFontColorApplicationViewObject){
    this.changeFontColorApplicationViewObject = changeFontColorApplicationViewObject;
    this.yellowBackgroundHandlerObject = new yellowBackgroundHandler(this.changeFontColorApplicationViewObject);
    this.blackBackgroundHandlerObject = new blackBackgroundHandler(this.changeFontColorApplicationViewObject);
    this.blueBackgroundHandlerObject = new blueBackgroundHandler(this.changeFontColorApplicationViewObject);

    yellowBackgroundHandlerObject.setNextHandlerInChain(blackBackgroundHandlerObject);
    blackBackgroundHandlerObject.setNextHandlerInChain(blueBackgroundHandlerObject);

    this.changeFontColorApplicationViewObject.addButtonActionListener(this.changeFontColorApplicationViewObject);
}