如何绘制图形数组

Question

好的，所以我正在做一个学校项目(小动画(，我目前正在尝试下雨。我不确定我将如何使用 JPanel 绘制单个"水滴"。到目前为止我的代码：

主类：

public class RainPanel extends JPanel {
private static final long serialVersionUID = 1L;
public static void main(String[] args) {
    new RainPanel();
}
private final int WIDTH = 800, HEIGHT = 800;
Drop drop;
public RainPanel() {
    init();
}
public void init() {
    JFrame frame = new JFrame("Rain");
    JPanel drop = new Drop();
    frame.setVisible(true);
    frame.setSize(WIDTH, HEIGHT);
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.setLocationRelativeTo(null);
    frame.add(drop);
}
public void paintComponent(Graphics g) {
    super.paintComponent(g);
        drop.paint(g);
}

掉落类：

public class Drop extends JPanel implements ActionListener{
private static final long serialVersionUID = 1L;
int x,y;
int yVel = 2;
Timer t = new Timer(5, this);
Random r = new Random();
ArrayList<Drop> DropArray;
public Drop() {
    x = r.nextInt(800);
    y = r.nextInt(800);
    t.start();
}
public void paint(Graphics g) {
    super.paintComponent(g);
    DropArray = new ArrayList<>(100); 
    for (int i = 0; i < DropArray.size(); i++) {
        DropArray.add(new Drop());
    }
    g.setColor(Color.BLUE);
    g.fillRect(x, y, 3, 15);
}
public void update() {
    y += yVel;
    if (y > 800) 
        y = r.nextInt(800);
}
@Override
public void actionPerformed(ActionEvent e) {
        update();
        repaint();
}

我理解你现在是否可能畏缩不前(我对图形编码相当陌生，并且主要熟悉 Java 本身(。我目前得到的只是一滴雨滴。任何建议不胜感激。

Answer 1

• 不要从paint内部打电话给super.paintComponent，你正在破坏油漆链，这可能会导致无休止的问题。 直接覆盖paintComponent
• 您不应该从任何绘制方法中修改组件的状态或组件所依赖的任何内容，可以快速连续多次调用 paint，这可能会导致无休止的问题
• 基于组件的动画不是一个简单的任务，除非你真的需要它，否则你应该尽量避免它。 相反，编写一个"可涂漆"的类，您可以从paintComponent方法调用它

例如。。

import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.geom.Rectangle2D;
import java.util.ArrayList;
import java.util.List;
import java.util.Random;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.Timer;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
public class RainDropsKeepFalling {
    public static void main(String[] args) {
        new RainDropsKeepFalling();
    }
    public RainDropsKeepFalling() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                    ex.printStackTrace();
                }
                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.add(new RainPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }
    public class RainPane extends JPanel {
        private List<Drop> drops = new ArrayList<>(100);
        public RainPane() {
            for (int index = 0; index < 100; index++) {
                drops.add(new Drop(getPreferredSize()));
            }
            Timer timer = new Timer(5, new ActionListener() {
                @Override
                public void actionPerformed(ActionEvent e) {
                    for (Drop drop : drops) {
                        drop.update(getSize());
                        repaint();
                    }
                }
            });
            timer.start();
        }
        @Override
        public Dimension getPreferredSize() {
            return new Dimension(200, 200);
        }
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            for (Drop drop : drops) {
                Graphics2D g2d = (Graphics2D) g.create();
                drop.paint(g2d);
                g2d.dispose();
            }
        }
    }
    protected static final Random random = new Random();
    public static class Drop {
        private double vDelta = random.nextDouble() + 0.5;
        private int height = 15;
        private int width = 3;
        private double x;
        private double y = -height;
        private Rectangle2D shape;
        public Drop(Dimension size) {
            x = random.nextInt(size.width - width) + width;
            y = random.nextInt(size.height - height) + height;
            shape = new Rectangle2D.Double(x, y, width, height);
        }
        public void paint(Graphics2D g2d) {
            g2d.setColor(Color.BLUE);
            g2d.fill(shape);
        }
        public void update(Dimension size) {
            y += vDelta;
            if (y > size.height) {
                y = -height;
                x = random.nextInt(size.width - width) + width;
            }
            shape.setRect(x, y, width, height);
        }
    }
}