java - 在屏幕帮助上保留形状，无法弄清楚如何跟踪 X、Y 坐标

Question

我已经尝试了很多次，我查找了很多将形状保留在屏幕上的示例，但似乎无法适应我的代码。在摘要中，左键单击打印正方形，右键单击打印圆形。我想用正方形(矩形)和圆形填充窗口。任何帮助和解释以便我可以学习这个概念都会很棒。我知道我必须跟踪坐标，也许是在循环中，但似乎可以让它工作。再次感谢。

import java.awt.*;
import javax.swing.JFrame;
import java.awt.event.MouseListener;
import java.awt.event.MouseEvent;

public class MouseButtonTester extends JFrame implements MouseListener
{
    private int mouseX, mouseY;
    private int mouseButton;
    private boolean isFirstRun;
    private static final int WIDTH = 640;
    private static final int HEIGHT = 480;
    private static final long serialVersionUID = 0;  //use this if you do not like warnings

    public MouseButtonTester() //constructor
    {
        super("Mouse Button Tester");

        //set up all variables
        mouseX = mouseY = 0;
        mouseButton = 0;
        isFirstRun = true;

        //set up the Frame
        setSize(WIDTH,HEIGHT);
        setBackground(Color.WHITE);
        setVisible(true);

        //start trapping for mouse clicks
        addMouseListener(this);
    }

    public void mouseClicked(MouseEvent e)
    {
        mouseX=e.getX();  //Tracks x coordinates
        mouseY=e.getY();  //Tracker y coordinates

        mouseButton = e.getButton(); //gets button number



           repaint();


    }

    public void paint( Graphics window ) // Draws the Window
    {
        if(isFirstRun)
        {
            window.setColor(Color.WHITE);
            window.fillRect(0,0,WIDTH, HEIGHT);

            //change isFirstRun

        }

        window.setFont(new Font("TAHOMA",Font.BOLD,12));
        window.setColor(Color.BLUE);
        window.drawString("MOUSE BUTTON TESTER", 420,55);

        draw(window);


    }

    public void draw(Graphics window)
    {
        if(mouseButton==MouseEvent.BUTTON1)     //left mouse button pressed
        {
            //window.drawString("BUTTON1", 50,200);  //debug code
            window.setColor(Color.RED);
            window.drawRect(mouseX,mouseY,10,10);



        }
        //right mouse button pressed
        {
            if (mouseButton == MouseEvent.BUTTON2)

                window.setColor(Color.BLUE);
            window.drawOval(mouseX,mouseY,10,10);


        }


        //any other mouse button pressed
        {



        }
    }




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

------ Main Method --------------
public class MouseButtonTesterRunner
 {
     public static void main(String[] args)


     { MouseButtonTester prog = new MouseButtonTester();




     }


 }

Answer 1

首先，从通读开始:

• Performing Custom Painting
• Painting in AWT and Swing

这样您就可以了解 Swing 中的绘画是如何工作的、如何使用它以及这样做时您的责任。

接下来，通读一下:

• How can I set in the midst?
• Java JFrame .setSize(x, y) not working?
• How to get the EXACT middle of a screen, even when re-sized
• Graphics rendering in title bar

为什么您应该避免覆盖顶级容器(例如 JFrame)的 paint

最后...

在 Swing 中绘制是破坏性的，也就是说，每次绘制组件时，您都应该从头开始完全重新绘制组件状态。

为了实现您的目标，您需要维护要绘制的项目的缓存。

这个概念本身非常困难，但过程中可能会遇到一些“陷阱”

import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Font;
import java.awt.FontMetrics;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Point;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.util.ArrayList;
import java.util.List;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;

public class Test {

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

    public Test() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                JFrame frame = new JFrame();
                frame.add(new TestPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class TestPane extends JPanel {

        private List<Point> circles;
        private List<Point> squares;

        public TestPane() {
            circles = new ArrayList<>();
            squares = new ArrayList<>();

            addMouseListener(new MouseAdapter() {
                @Override
                public void mouseReleased(MouseEvent e) {
                    if (SwingUtilities.isLeftMouseButton(e)) {
                        circles.add(e.getPoint());
                    } else if (SwingUtilities.isRightMouseButton(e)) {
                        squares.add(e.getPoint());
                    }
                    repaint();
                }
            });
        }

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(200, 200);
        }

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            // I'm picky
            Graphics2D g2d = (Graphics2D) g.create();
            g2d.setColor(Color.RED);
            for (Point p : circles) {
                g2d.drawOval(p.x, p.y, 10, 10);
            }
            g2d.setColor(Color.BLUE);
            for (Point p : squares) {
                g2d.drawRect(p.x, p.y, 10, 10);
            }

            g2d.setFont(new Font("TAHOMA", Font.BOLD, 12));
            g2d.setColor(Color.BLUE);

            FontMetrics fm = g2d.getFontMetrics();
            String text = "MOUSE BUTTON TESTER";

            int x = getWidth() - fm.stringWidth(text) - 10;
            int y = getHeight() - (fm.getAscent() - fm.getHeight()) - 10;

            g2d.drawString(text, x, y);
            g2d.dispose();
        }

    }
}