Java MouseListener 不工作

Question

I am trying to get the console to print when the mouse is pressed within an object of class RenderCanvas which extends JPanel . However, I am getting no feedback when I press the mouse down in the window. Any suggestions as to what I might be able to change to make the MouseListener work?

Here is my code:

RenderCanvas Class:

import java.awt.event.MouseEvent;
import java.util.ArrayList;
import java.util.List;
import java.awt.Color;
import java.awt.Graphics;
import javax.swing.JPanel;
import java.awt.event.MouseAdapter;


public class RenderCanvas extends JPanel {
    private List<Rect> rectangles = new ArrayList<Rect>();
    private List<Line> lines = new ArrayList<Line>();

    public void renderCanvas() {
        addMouseListener(new MouseAdapter() {
            public void mousePressed(MouseEvent e) {
                addRect(0, 0, 200, 200, Color.ORANGE);
                System.out.println(e);
            }
        });
    }

    public void paintComponent(Graphics g) {
        for (Rect rectangle : rectangles) {
            rectangle.draw(g);
        }
        for (Line line : lines) {
            line.draw(g);
        }
    }

    public void addRect(int x, int y, int width, int height, Color color) {
        Rect rectangle = new Rect(x, y, width, height, color);
        this.rectangles.add(rectangle);
    }

    public void addLine(int y, int width, Color color) {
        Line line = new Line(y, width, color);
        this.lines.add(line);
    }
}

Main Class:

import javax.swing.*;
import java.awt.*;
import java.util.Random;

public class Main {
    public static void main(String[] args) {
        JFrame window = new JFrame("Window");
        RenderCanvas canvas = new RenderCanvas();
        window.setContentPane(canvas);
        window.setSize(640, 360);
        window.setLocation(640, 360);
        window.setVisible(true);
    }
}

Thanks in advance for any help!

Answer 1

public void renderCanvas() is NOT a constructor. Change

public void renderCanvas()

to

public RenderCanvas()

Notice the upper-case "R" and the absence of the "void" return type

Answer 2

void RenderCanvas() is not being called. I believe you mean just public RenderCanvas() instead of public void RenderCanvas , since you're only using the ctor in the main method.

Answer 3

I think you're intending this method:

public void renderCanvas() {

to be a constructor for the RenderCanvas class; it's not, though, for two reasons: it's not capitalized the same way (small r vs capital R) and also it has a return type. Constructors have no return type; the line should look like

public RenderCanvas() {

Because this isn't a constructor, it's a method, and nobody's calling it, so your event handler is never being added.