Graphics数组的绘制方法

Question

好的，我正在做一个学校项目（小动画），我目前正在尝试下雨。我不确定如何使用 JPanel 绘制个人 "drops"。到目前为止我的代码：

主要Class：

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 class：

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();
}

我知道你现在是否会畏缩不前（我对图形编码还很陌生，而且对 Java 本身很熟悉）。我目前所画的只是一滴雨。任何建议表示赞赏。

Answer 1

不要从 paint 中调用 super.paintComponent，您会破坏绘制链，这可能会导致无穷无尽的问题。直接覆盖 paintComponent 而不是
您不应该在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，绘制可以快速连续调用多次，这可能会导致无休止的问题
基于组件的动画不是一项简单的任务，除非你真的、真的需要它，否则你应该尽量避免它。相反，写一个 class 即 "paintable"，您可以从 paintComponent 方法

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);
        }

    }

}

Graphics数组的绘制方法

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