Java Swing-从处理程序类重画

问题描述 投票：0回答：3

因此，我将从将我的代码放到我的两个班级开始。

SquareSimp.java


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

public class SquareSimp
{

    public static void main( String[] args )
    {
        FilledFrame frame = new FilledFrame();

        frame.setVisible( true );
    }
}

class FilledFrame extends JFrame
{
    int size = 400;

    public FilledFrame()
    {
        JButton butSmall   = new JButton("Small");
        JButton butMedium  = new JButton("Medium");
        JButton butLarge   = new JButton("Large");
        JButton butMessage = new JButton("Say Hi!");

        SquarePanel panel = new SquarePanel(this);
        JPanel butPanel = new JPanel();

        butSmall.addActionListener(new ButtonHandler1(this, 200){
            @Override
            public void actionPerformed(ActionEvent actionEvent) {
                size = 200;
                panel.repaint();
            }
        });

        butMedium.addActionListener(new ButtonHandler1(this, this.size){
            @Override
            public void actionPerformed(ActionEvent actionEvent) {
                size = 300;
                panel.repaint();
            }
        });

        butLarge.addActionListener(new ButtonHandler1(this, this.size){
            @Override
            public void actionPerformed(ActionEvent actionEvent) {
                size = 400;
                panel.repaint();
            }
        });



        butPanel.add(butSmall);
        butPanel.add(butMedium);
        butPanel.add(butLarge);
        butPanel.add(butMessage);
        add(butPanel, BorderLayout.NORTH);
        add(panel, BorderLayout.CENTER);

        setSize( size+100, size+100 );
        setDefaultCloseOperation(EXIT_ON_CLOSE);

        // Exercise 2.
        //Anonymous implementations of listeners are very efficient when you do not need to pass parameters to the
        // constructor of the implemented listener.
        butMessage.addActionListener(new ActionListener()
                // An anonymous function. Creates an actionListener that shows a dialog.
        {
            @Override
            public void actionPerformed(ActionEvent e)
            {
                JOptionPane.showMessageDialog(null, "Hiiii");
            }
        });

    }

}

class SquarePanel extends JPanel
{
    FilledFrame theApp;

    SquarePanel(FilledFrame app)
    {
        theApp = app;
    }

    public void paintComponent(Graphics g)
    {
        super.paintComponent(g);
        g.setColor(Color.green);
        g.fillRect(20, 20, theApp.size, theApp.size);
    }
}

ButtonHandler1.java

package Lab2;

import javax.swing.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
// This is a class whose object will handle the event.
public class ButtonHandler1 implements ActionListener{
    private FilledFrame theApp;
    private int theSize;
    ButtonHandler1(FilledFrame app, int size){
        theApp = app;
        theSize = size;
    }

    public void actionPerformed(ActionEvent actionEvent) {
    }

}

到目前为止，所有方法都有效，很棒。但是，根据要求，我被要求为每个类制作一个按钮处理程序。有人可以向我解释一下我的buttonHandler实际上在做什么吗？就像我不想创建匿名函数并覆盖actionPerformed事件一样，我可以做一个更好的方法（在buttonhandler类中创建事件，并根据按下的按钮从那里影响大小）。我不知道该怎么做，所以对解释的任何帮助都很好！

非常感谢！

布兰登

java swing actionlistener actionevent
3个回答
0
投票

*Listener的任何处理程序也用于处理从正在监听的对象生成的events。在主程序中，似乎您有几个按钮可以改变窗口的大小。

对于实现buttonHandler的类，您没有做任何事情，因为您的actionPerformed方法没有做任何事情。

并且anonymous classes是实现侦听器的可接受方法。但是，我更喜欢使用inner classes，因为它们更干净（imho），并且仍然可以访问state的enclosing class。

这是您的处理程序类的外观：

// This is a class whose object will handle the event.
class ButtonHandler1 implements ActionListener {
   private FilledFrame theApp;
   private int         theSize;

   ButtonHandler1(FilledFrame app, int size) {
      theApp = app;
      theSize = size;
   }

   public void actionPerformed(ActionEvent actionEvent) {
      theApp.size = theSize;
      theApp.repaint();
   }
}

这是将处理程序添加到按钮的调用。

      butSmall.addActionListener(new ButtonHandler1(this, 200));
      butMedium.addActionListener(new ButtonHandler1(this, 300));
      butLarge.addActionListener(new ButtonHandler1(this, 400));
0
投票

我不确定我是否理解这个问题，但是有两种方法可以重构您的代码：

  1. 完全删除您的ButtonHandler1类，并实现匿名类中的所有逻辑：
    //FilledFrame.java

    butSmall.addActionListener(new ActionListener(){
                @Override
                public void actionPerformed(ActionEvent actionEvent) {
                    FilledFrame.this.size = 200;
                    panel.repaint();
                }
            });
  1. 您可以在FilledFrame类上添加一些getter和setter方法，并在ButtonHandler1.actionPerformed中调用它们以实现如下所示的逻辑：
    package Lab2;

    import javax.swing.*;
    import java.awt.event.ActionEvent;
    import java.awt.event.ActionListener;
    // This is a class whose object will handle the event.
    public class ButtonHandler1 implements ActionListener{
        private FilledFrame theApp;
        private int theSize;
        ButtonHandler1(FilledFrame app, int size){
            theApp = app;
            theSize = size;
        }

        public void actionPerformed(ActionEvent actionEvent) {
            theApp.setSizeMember(200); //do not use theApp.setSize(), create a method with a different name
            theApp.getSquarePanel().repaint();
        }

    }

我将在FilledFrame上创建吸气剂/设置器留给您。

0
投票

ButtonHandler1并未真正使用，因为从未使用传递给它的参数，并且在构造它时，它的单个方法将被覆盖。所以这个：

     butSmall.addActionListener(new ButtonHandler1(this, 200){
            @Override
            public void actionPerformed(ActionEvent actionEvent) {
                size = 200;
                panel.repaint();
            }
      });

无需编写ButtonHandler1即可编写：

    butSmall.addActionListener(new ActionListener(){
        @Override
        public void actionPerformed(ActionEvent actionEvent) {
            size = 200;
            panel.repaint();
        }
    });

或使用lambda表达式：

    butSmall.addActionListener(actionEvent -> {
        size = 200;
        panel.repaint();
    });

有很多方法可以实现所需的功能。根据您写的内容，您可以像这样定义ButtonHandler1：

class ButtonHandler1 implements ActionListener{
    private final FilledFrame theApp;
    private final int theSize;
    ButtonHandler1(FilledFrame app, int size){
        theApp = app;
        theSize = size;
    }

    @Override
    public void actionPerformed(ActionEvent actionEvent) {
        theApp.size = theSize; //better use a setter in FilledFrame
        theApp.repaint();
    }
}

并像这样使用它：

    butSmall.addActionListener(new ButtonHandler1(this, 200));

    butMedium.addActionListener(new ButtonHandler1(this, 300));

    butLarge.addActionListener(new ButtonHandler1(this, 400));

在ButtonHandler1中使FilledFrame为内部类使事情变得更简单：

class ButtonHandler1 implements ActionListener{
    private final int theSize;
    ButtonHandler1(int size){
        theSize = size;
    }

    @Override
    public void actionPerformed(ActionEvent actionEvent) {
        size = theSize;
        repaint();
    }
}

使用者：

    butSmall.addActionListener(new ButtonHandler1(200));

    butMedium.addActionListener(new ButtonHandler1(300));

    butLarge.addActionListener(new ButtonHandler1(400));
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