graphics2D列表

Question

下面的代码怎么会起作用呢？我想每隔200毫秒向ArrayList添加新的卵形，并逐一显示并运行它们。当我运行一个粒子s.runner()时，它工作得很好；但是它似乎并不能运行我的所有粒子。

主要：

import java.awt.EventQueue;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.ArrayList;
import javax.swing.JFrame;
import javax.swing.Timer;

public class ExempelGraphics extends JFrame implements ActionListener {
    Timer t;
    private int inc = 0;
    ArrayList<Surface> particle = new ArrayList<>();
    Surface s;

    public ExempelGraphics() {
        t = new Timer(10, this);
        t.start();
        s = new Surface(10, 10);
        initUI();
    }

    private void initUI() {
        add(s);
        setSize(350, 250);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }

    public void actionPerformed(ActionEvent e) {
//        s.runner();
        // add
        if (inc++ % 20 == 0) {
            particle.add(new Surface(10, 10));
        }

        // display
        for (int i = 0; i < particle.size(); i++) {
            Surface p = particle.get(i);
            p.runner();
        }
    }

    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {

            @Override
            public void run() {
                ExempelGraphics ex = new ExempelGraphics();
                ex.setVisible(true);
            }
        });
    }
}

图形：

import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import javax.swing.JPanel;

public class Surface extends JPanel {
    private int locX = 0;
    private int locY = 0;

    public Surface(int locX, int locY) {
        this.locX = locX;
        this.locY = locY;
    }

    public void runner() {
        locX = locX + 1;
        repaint();
    }

    @Override
    public void paintComponent(Graphics g) {
        super.paintComponent(g);
        Graphics2D g2d = (Graphics2D) g;
        g2d.setColor(Color.RED);
        g2d.fillOval(locX, locY, 10, 10);
    }
}

Answer 1

我觉得你的程序结构坏了。这里应该只有一个JPanel进行绘图，它的paintComponent被重写，而您的JPanel类应该是一个逻辑类，而不是一个组件类--换句话说，不要让它扩展JPanel，并给它一个绘制椭圆的public void draw(Graphics g)方法。然后让绘图JPanel保存这些曲面的ArrayList，并在主JPanel的paintComponent方法中迭代这些曲面，调用每个曲面的绘图方法。

此外，您的计时器的延迟是不现实的，太小。15将更加现实。

另外，不要从表面调用repaint()，因为这会产生太多不必要的重绘调用。相反，在调用所有Surface对象上的runner方法之后，从计时器的ActionListener中调用它。

还请注意，每次以默认方式向JFrame的contentPane添加组件时，都会掩盖之前添加的组件。如果您按照我上面的建议，这并不是一个问题，因为您只需要将单个JPanel添加到其中。

例如：

import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.ArrayList;
import java.util.List;
import javax.swing.*;

@SuppressWarnings("serial")
public class ExampleGraphics2 extends JPanel {
    private static final int PREF_W = 650;
    private static final int PREF_H = 500;
    private static final int TIMER_DELAY = 20;
    private List<Surface> surfaces = new ArrayList<>();

    public ExampleGraphics2() {
        new Timer(TIMER_DELAY, new TimerListener()).start();
    }

    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        Graphics2D g2 = (Graphics2D) g;
        g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
        for (Surface surface : surfaces) {
            surface.draw(g);
        }
    }

    @Override
    public Dimension getPreferredSize() {
        if (isPreferredSizeSet()) {
            return super.getPreferredSize();
        }
        return new Dimension(PREF_W, PREF_H);
    }

    private class TimerListener implements ActionListener {
        private int index = 0;

        @Override
        public void actionPerformed(ActionEvent e) {
            index++;
            index %= 20;
            if (index == 0) {
                surfaces.add(new Surface(10, 10));
            }

            for (Surface surface : surfaces) {
                surface.runner();
            }
            repaint();
        }
    }

    private static void createAndShowGui() {
        JFrame frame = new JFrame("Example Graphics 2");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.getContentPane().add(new ExampleGraphics2());
        frame.pack();
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(() -> createAndShowGui());
    }
}

​

package foo1;

import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;

public class Surface {
    private int locX = 0;
    private int locY = 0;

    public Surface(int locX, int locY) {
        this.locX = locX;
        this.locY = locY;
    }

    public void runner() {
        locX = locX + 1;
    }

    public void draw(Graphics g) {
        Graphics2D g2d = (Graphics2D) g;
        g2d.setColor(Color.RED);
        g2d.fillOval(locX, locY, 10, 10);
    }
}