如何将 MouseListener 添加到框架 [英] How To Add A MouseListener To A Frame

问题描述

I want to add a mouselistener to mt JFrame frame but when i do frame.addMouseListener(this) i get an error that i cannot use this in a static method

I am making an application that detects a click of the mouse then displays it in int clicks

code

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.FlowLayout;
import java.awt.Font;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import javax.swing.BorderFactory;
import javax.swing.JFrame;
import javax.swing.JTextField;

public class numberOfClicks implements MouseListener{

    static int clicks = 0;

    @Override
    public void mouseClicked(MouseEvent e) {
        clicks++;
    }

    static JTextField text = new JTextField();
    static String string = clicks+" Clicks";

    static JFrame frame = new JFrame("Click Counter");
    public static void frame(){
        Font f = new Font("Engravers MT", Font.BOLD, 23);
        text.setEditable(false);
        text.setBackground(Color.BLUE);
        text.setFont(f);
        text.setForeground(Color.GREEN);
        text.setBorder(BorderFactory.createLineBorder(Color.BLUE));
        text.setText(string);

        frame.add(text, BorderLayout.SOUTH);
        frame.setResizable(false);
        frame.setSize(300, 300);
        frame.getContentPane().setBackground(Color.BLUE);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true);
        frame.addMouseListener(this);
    }

    public static void main(String[] args){
        frame();
    }

    @Override
    public void mousePressed(MouseEvent e) {}
    @Override
    public void mouseEntered(MouseEvent e) {}
    @Override
    public void mouseExited(MouseEvent e) {}
    @Override
    public void mouseReleased(MouseEvent e) {}
}

解决方案

this doesn't exist in a static method since a static method is a method of the class, not of the object (the owner of this). Solution: get rid of all statics from your code above. None of your fields or methods above should be static other than the main method.

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Edit
And as Andrew Thompson correctly states, add the MouseListener to a JPanel that is added to the JFrame's contentPane.

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Edit 2

• You will want to learn and use Java naming conventions. Class names (i.e., NumberOfClicks) should start with an upper case letter. Method and variable names with a lower-case letter.
• You are better off using the mousePressed(...) method rather than the mouseClicked(...) since the former is less persnickety about accepting presses.
• You will also want to set your JTextField's text in your mousePressed(...) method since just changing the clicks value isn't enough to change the display.
• I try to avoid having my GUI (or "view") classes implement my listeners. I prefer to use anonymous inner classes or stand-alone classes where possible.

e.g.,

  JPanel mainPanel = new JPanel();
  mainPanel.addMouseListener(new MouseAdapter() {
     @Override
     public void mousePressed(MouseEvent e) {
        clicks++;
        text.setText(clicks + " Clicks");
     }
  });
  // add mainPanel to the JFrame...

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