java - 形状消失

Question

好吧，我想出了我得到的一切，但现在我真的被困住了。每次您选择不同的形状时，先前选择的形状都会消失。我该怎么做才能让它们在您退出之前不会消失并一直停留在屏幕上？

import java.awt.*;
import java.awt.event.*;
import java.awt.geom.*;
import java.util.*;
import javax.swing.*;
public class ShapeStamper extends JFrame{
    Random rand = new Random();
    public int x;
    public int y;
    private JPanel panel1, panel2;
    private JButton button1, button2, button3, button4;
    private int option = 0;

public ShapeStamper(){
    super("Shape Stamper!");
    panel1 = new JPanel();
    button1 = new JButton("Circle");
    button2 = new JButton("Square");
    button3 = new JButton("Rectangle");
    button4 = new JButton("Oval");

    button1.addActionListener(
            new ActionListener(){
        public void actionPerformed(ActionEvent ae){
            option = 1;
                }
            }
    );
     button2.addActionListener(
            new ActionListener(){
        public void actionPerformed(ActionEvent ae){
            option = 2;
                }
            }
    );
     button3.addActionListener(
            new ActionListener(){
        public void actionPerformed(ActionEvent ae){
            option = 3;
                }
            }
    );
     button4.addActionListener(
            new ActionListener(){
        public void actionPerformed(ActionEvent ae){
            option = 4;
                }
            }
    );
  panel2 = new JPanel();
  panel2.setBackground(Color.WHITE);
  MouseHandler mouse = new MouseHandler();
  setVisible(true);
  addMouseListener(mouse);
  addMouseMotionListener(mouse);
  add(panel2);
  panel1.add(button1);
  panel1.add(button2);
  panel1.add(button3);
  panel1.add(button4);

  add(panel1, BorderLayout.SOUTH);
  setSize(500,500);
  setVisible(true);
          }
private class MouseHandler extends MouseAdapter implements MouseMotionListener{
        @Override
    public void mousePressed(MouseEvent e){
        x = e.getX();
        y = e.getY();

        repaint();
    }
}
public void paint(Graphics g){
    super.paintComponents(g);
    Graphics2D g2d = (Graphics2D) g;
    if(option == 0){
        g.setFont(new Font("Serif", Font.BOLD, 32));
        g.drawString("Shape Stamper!", 150, 220);
        g.setFont(new Font("Serif", Font.ITALIC, 16));
        g.drawString("Programmed by: Chris", 150, 230);
    }
    if(option == 1){
        Color randColor1 = new Color(rand.nextInt(256), rand.nextInt(256), rand.nextInt(256));
        g2d.setPaint(randColor1);
        g2d.drawOval(50, 50, 100, 100);
            }
    if(option == 2){
        Color randColor2 = new Color(rand.nextInt(256), rand.nextInt(256), rand.nextInt(256));
        g2d.setPaint(randColor2);
        g2d.drawRect(50, 50, 100, 100);
            }
    if(option == 3){
        Color randColor3 = new Color(rand.nextInt(256), rand.nextInt(256), rand.nextInt(256));
        g2d.setPaint(randColor3);
        g2d.draw(new Rectangle2D.Double(75,50,150,100));
            }
    if(option == 4){
        Color randColor4 = new Color(rand.nextInt(256), rand.nextInt(256), rand.nextInt(256));
        g2d.setPaint(randColor4);
        g2d.draw(new Ellipse2D.Double(50, 25, 100, 50));
            }
}
    public static void main(String[] args) {
        ShapeStamper application = new ShapeStamper();
        application.setDefaultCloseOperation(EXIT_ON_CLOSE);
    }
    }

Answer 1

你不应该覆盖 paint顶层容器，然后尝试在您已添加的组件的顶部进行绘制。

您将遇到的基本问题是，绘画系统足够聪明，它可能永远不会调用 paint。框架，而是直接更新子组件。

相反，为自己创建一个自定义组件，从类似于 JPanel 的东西扩展而来并覆盖它的 paintComponent方法并在那里执行您的自定义绘画。然后将此组件添加到您的框架中。

您还会发现油漆更新更干净，更新时不会闪烁。

您还应该确保您调用的是 repaint在此自定义组件上，每当您更改一个组件时，它都会提供选项以确保将更改绘制回组件

看看Performing Custom Painting了解更多详情。

此外，为了清楚起见，您不应该调用 super.paintComponents来自 paint (或者实际上除了当你覆盖 paintComponents 之外的任何地方......确实应该需要做......)