Question

我是Java的新手，但不是编程新手，我无法理解hows paintComponent(Graphics graphics)，mouseDragged(MouseEvent event)和mouseMoved(MouseEvent event)与public static void main(String[] args)方法相关联。请帮我理解这个问题。

package com.company;

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

public class Main {
    public static void main(String[] args) {
        JFrame frame = new JFrame("Leaning Java");
        HelloComponent helloObject = new HelloComponent("Ajay");
        frame.add(helloObject);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(300, 300);
        frame.setVisible(true);
    }
}

class HelloComponent extends JComponent implements MouseMotionListener {
    String theMessage;
    int messageX = 125, messageY = 95;

    public HelloComponent(String string) {
        theMessage = string;
        addMouseMotionListener(this);

    }

    public void paintComponent(Graphics graphics) {
        graphics.drawString(theMessage, messageX, messageY);
    }

    public void mouseDragged(MouseEvent event) {
        messageX = event.getX();
        messageY = event.getY();
        repaint();
    }

    public void mouseMoved(MouseEvent event) {

    }

}

Answer 1

在您的代码中，您无需再执行任何操作来调用这些方法。

paintComponent由JComponent的父级调用。在您的情况下，您要将HelloComponent的实例添加到JFrame。 {} {}会在必要时致电JFrame。

paintComponent和mouseDragged是mouseMoved界面中定义的方法。通过调用MouseMotionListener，您可以在适当的鼠标操作发生时注册您的类以接收这些消息。

如何将paintComponent链接到用户定义的类？

1 个答案: