java - 如何向一帧添加多个paintComponent()？

Question

这是我的主课:

package testgame;

import java.awt.EventQueue;
import javax.swing.JFrame;

public class Game extends JFrame {

public static JFrame frame = new JFrame("Just a test!");

public static void LoadUI() {
    frame.setDefaultCloseOperation(frame.EXIT_ON_CLOSE);
    frame.setSize(550, 500);
    frame.setLocationRelativeTo(null);
    frame.setVisible(true); }

public static void main(String[] args) {
    LoadUI();
    frame.add(new Circles());
    }
}

这是处理我想要绘制的内容的类:

package testgame;

import java.awt.BasicStroke;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.geom.AffineTransform;
import java.awt.geom.Ellipse2D;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
import javax.swing.Timer;

public class Circles extends JPanel {

@Override
public void paintComponent(Graphics g) {
    super.paintComponent(g);
    drawBubbles(g); }

public void drawBubbles(Graphics g) {
    Graphics2D g2d = (Graphics2D) g;
    RenderingHints rh
            = new RenderingHints(RenderingHints.KEY_ANTIALIASING,
            RenderingHints.VALUE_ANTIALIAS_ON);
    rh.put(RenderingHints.KEY_RENDERING, 
            RenderingHints.VALUE_RENDER_QUALITY);
    g2d.setRenderingHints(rh);
    int x, y, size;
    x = (int) (Math.random() * 500) + 15;
    y = (int) (Math.random() * 450) + 15;
    size = (int) (Math.random() * 50) + 25;
    g2d.setColor(Color.GREEN);
    g2d.drawOval(x, y, size, size);
    g2d.fillOval(x, y, size, size); }
}

如果我添加另一个

 frame.add(new Circles());

什么也没发生。我认为这与框架的布局有关，但气泡的坐标是随机的，所以我不确定如何处理它。

Answer 1

在本例中，我使用的是 5 的固定大小数组，您可以将其更改为更大的固定大小数组或 ArrayList，如 this answer 所示

对于您的特定情况，我将创建一个 Circle 类，其中可能包含每个圆的数据，即坐标和大小

然后创建一个 CirclePane 类，该类将在单个 paintComponent() 方法中绘制所有 Circle。

最后，Main 类将具有一个 JFrame，其中可能包含添加到其中的 CirclePane。

考虑到上述提示，您最终可能会得到如下结果:

import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Point;
import java.awt.geom.Ellipse2D;

import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;

public class CircleDrawer {
    private JFrame frame;
    
    public static void main(String[] args) {
        SwingUtilities.invokeLater(new CircleDrawer()::createAndShowGui); //We place our program on the EDT
    }
    
    private void createAndShowGui() {
        frame = new JFrame(getClass().getSimpleName());
        
        CirclePane circle = new CirclePane(5); //We want to create 5 circles, we may want to add more so we change it to 10, or whatever number we want
        
        frame.add(circle);
        
        frame.pack();
        frame.setVisible(true);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }
    
    //Data class
    class Circle {
        private Point coords;
        private int size;
        
        public Circle(Point coords, int size) {
            this.coords = coords;
            this.size = size;
        }
        
        public Point getCoords() {
            return coords;
        }
        public void setCoords(Point coords) {
            this.coords = coords;
        }
        public int getSize() {
            return size;
        }
        public void setSize(int size) {
            this.size = size;
        }
    }
    
    //The drawing class
    @SuppressWarnings("serial")
    class CirclePane extends JPanel {
        private int numberOfCircles;
        private Circle[] circles;

        public CirclePane(int numberOfCircles) {
            this.numberOfCircles = numberOfCircles;
            
            circles = new Circle[numberOfCircles];
            
            for (int i = 0; i < numberOfCircles; i++) {
                Point coords = new Point((int) (Math.random() * 500) + 15, (int) (Math.random() * 450) + 15); //We generate random coords
                int size = (int) (Math.random() * 50) + 25; //And random sizes
                circles[i] = new Circle(coords, size); //Finally we create a new Circle with these properties
            }
        }
        
        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            Graphics2D g2d = (Graphics2D) g;
            
            for (int i = 0; i < numberOfCircles; i++) {
                g2d.draw(new Ellipse2D.Double(circles[i].getCoords().getX(), circles[i].getCoords().getY(), circles[i].getSize(), circles[i].getSize())); //We iterate over each circle in the array and paint it according to its coords and sizes
            }
        }
        
        @Override
        public Dimension getPreferredSize() { //Never call JFrame.setSize(), instead override this method and call JFrame.pack()
            return new Dimension(500, 500);
        }
    }
}

这会产生与此类似的输出:

我希望这可以帮助您获得更好的想法，请阅读我在这个答案中使用的 MVC 模式。

<小时/>

注意:

在这个答案中，我根据 @MadProgrammer 在 other answer 中的建议使用了 Shapes API。 。我在 g2d.draw(...) 行中使用了它。

要更深入地了解 Swing 中自定义绘制的工作原理，请查看 Oracle 的 Lesson: Performing Custom Painting和 Painting in AWT and Swing教程。