用随机颜色填充对象

Question

我有一个有按钮的代码.按下按钮时,圆圈会随机出现在颜色随机的位置.只能有10个圆圈.

现在我添加了随机颜色功能,问题是在绘制每个圆之后,它的颜色开始变得无用.

我该怎么做才能让颜色不变？

class Panel extends JPanel  {

    private JButton button;
    private Ellipse2D.Double[] circles;
    Integer count;


    public Panel()  {
            setup();
    }

    private void setup()  {
            count=new Integer(0);
            circles=new Ellipse2D.Double[10];
            button=new JButton(count.toString());
            button.addActionListener(new ActionListener() {
               @Override
               public void actionPerformed(ActionEvent e) {
                            Random r=new Random();
                            //position circles with diameter 100 in a way 
                            //that it would fit in a window's size
                            int highX=getWidth()-100;
                            int highY=getHeight()-100;
                            circles[count]=new 
                                     Ellipse2D.Double(r.nextInt(highX), 
                                          r.nextInt(highY), 100, 100);
                            count++;

                            button.setText(count.toString());
                    }
                });

          add(button);
        }


    public void paintComponent(Graphics g)  {
            super.paintComponent(g);
            paintStuff(g);
            repaint(); 
        }

    private void paintStuff(Graphics g)  {
            Graphics2D g2=(Graphics2D) g;
            g2.setPaint(Color.RED);

            if (count!=0)  {
                for (int i=0; i<count; i++)  {
                        g2.draw(circles[i]);
                        Random r=new Random();
                        int red=r.nextInt(256);
                        int green=r.nextInt(256);
                        int blue=r.nextInt(256);
                        g2.setPaint(new Color(red, green, blue));
                        g2.fill(circles[i]);
                }
            }
    }
}

public class Frame extends JFrame  {
     private Panel panel;
     public Frame()  {
        panel=new Panel();
        add(panel);
     }

     public static void main(String[] args)  {
          Frame frame=new Frame();
     }
}

Answer 1

永远不要在绘画方法中调用重绘,因为这会导致"穷人"动画发生.而是在JButton的ActionListener中调用它.此外,不要在绘制方法中随机化,而是在ActionListener中执行此操作.绘画方法不在您的控制之下,您不希望使用它来更改对象的状态,而只是显示它.

其他建议:

• 您的代码仍需要设置JFrame的setDefaultCloseOperation
• 并且仍然需要将JFrame设置为可见
• 你从不建议在代码中调整大小.我自己,我建议覆盖public Dimension getPreferredSize()你的JPanel并pack()在添加JPanel之后但在显示它之前调用JFrame.
• 我将重命名您的类,以便名称不会与核心Java类冲突,并导致您的教师,我们或您未来的自我混淆.
• 不要在for循环中继续重新创建一个新的Random对象.相反,为什么不简单地给类一个Random字段,创建一次,但重复使用该对象.
• 您需要将颜色与形状/ Ellipse2D相关联.对于一对一的通信,请考虑使用诸如a之类的Map HashMap<Shape, Color>.

例如:

import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.Shape;
import java.awt.event.ActionEvent;
import java.awt.event.KeyEvent;
import java.awt.geom.Ellipse2D;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Random;

import javax.swing.*;

@SuppressWarnings("serial")
public class Panel2 extends JPanel {
    // preferred size constants
    private static final int PREF_W = 600;
    private static final int PREF_H = PREF_W;

    // map to hold circles and colors
    private Map<Shape, Color> shapeColorMap = new LinkedHashMap<>();

    public Panel2() {
        add(new JButton(new RandomColorAction()));
    }

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

    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        Graphics2D g2 = (Graphics2D) g;
        // create *smooth* drawings
        g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
        paintStuff(g2);
    }

    private void paintStuff(Graphics2D g2) {
        // iterate through our map extracting all circles and colors
        // and drawing them
        for (Entry<Shape, Color> entry : shapeColorMap.entrySet()) {
            Shape shape = entry.getKey();
            Color color = entry.getValue();
            g2.setColor(color);
            g2.fill(shape);
        }
    }

    // listener for our button
    private class RandomColorAction extends AbstractAction {
        private static final int CIRC_WIDTH = 100;
        private Random random = new Random();
        private int count = 0;

        public RandomColorAction() {
            super("Random Circle: 0");
            putValue(MNEMONIC_KEY, KeyEvent.VK_R);
        }

        @Override
        public void actionPerformed(ActionEvent e) {
            // create our random ellipses
            int x = random.nextInt(getWidth() - CIRC_WIDTH);
            int y = random.nextInt(getHeight() - CIRC_WIDTH);
            Shape shape = new Ellipse2D.Double(x, y, CIRC_WIDTH, CIRC_WIDTH);

            // create our random color using HSB for brighter colors
            float hue = random.nextFloat();
            float saturation = (float) (0.8 + random.nextFloat() * 0.2);
            float brightness = (float) (0.8 + random.nextFloat() * 0.2);
            Color color = Color.getHSBColor(hue, saturation, brightness);
            shapeColorMap.put(shape, color);

            // increment count, place items into map, repaint
            count++;
            putValue(NAME, "Random Circle: " + count);
            repaint();
        }
    }

    private static void createAndShowGui() {
        Panel2 mainPanel = new Panel2();

        JFrame frame = new JFrame("Panel2");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.getContentPane().add(mainPanel);
        frame.pack();
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }

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

在评论中,Camickr敏锐地指出:

绘制方法应绘制组件的当前状态.通过使用HashMap,您可以引入随机性的可能性.无法保证通过地图的迭代顺序.因此,当新条目添加到地图时,每个Shape的绘制顺序可能会发生变化.通常不是问题,但如果两个随机形状重叠,那么结果很好的是翻转,其形状被涂在彼此之上.

当然,他是绝对正确的,因为没有保证HashMap的顺序.幸运的是,变量本身被声明为Map类型,因此为了保持顺序,所有人需要做的是将实际的对象类型从HashMap更改为LinkedHashMap,这是一个根据其API的类:

此实现使其客户端免受HashMap(和Hashtable)提供的未指定的,通常混乱的排序,而不会导致与TreeMap相关的成本增加.

所以对于TLDR,改变这个:

private Map<Shape, Color> shapeColorMap = new HashMap<>();

对此:

private Map<Shape, Color> shapeColorMap = new LinkedHashMap<>();

编辑修复颜色计算.

只是为了它的乐趣,它引入了Path2D和AffineTransform与MouseListener/MouseMotionListener以允许拖动圆圈:

import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Point;
import java.awt.RenderingHints;
import java.awt.Shape;
import java.awt.event.ActionEvent;
import java.awt.event.KeyEvent;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.geom.AffineTransform;
import java.awt.geom.Ellipse2D;
import java.awt.geom.Path2D;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Random;
import java.util.Set;

import javax.swing.*;

@SuppressWarnings("serial")
public class Panel2 extends JPanel {
    // preferred size constants
    private static final int PREF_W = 600;
    private static final int PREF_H = PREF_W;

    // map to hold circles and colors
    private Map<Shape, Color> shapeColorMap = new LinkedHashMap<>();

    public Panel2() {
        add(new JButton(new RandomColorAction()));
        MyMouse myMouse = new MyMouse();
        addMouseListener(myMouse);
        addMouseMotionListener(myMouse);
    }

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

    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        Graphics2D g2 = (Graphics2D) g;
        // create *smooth* drawings
        g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
        paintStuff(g2);
    }

    private void paintStuff(Graphics2D g2) {
        // iterate through our map extracting all circles and colors
        // and drawing them
        for (Entry<Shape, Color> entry : shapeColorMap.entrySet()) {
            Shape shape = entry.getKey();
            Color color = entry.getValue();
            g2.setColor(color);
            g2.fill(shape);
        }
    }

    private class MyMouse extends MouseAdapter {
        private Entry<Shape, Color> selected = null;
        private Path2D path;
        private Point p = null;

        @Override
        public void mousePressed(MouseEvent e) {
            Set<Entry<Shape, Color>> entrySet = shapeColorMap.entrySet();
            // get Shape pressed
            for (Entry<Shape, Color> entry : entrySet) {
                if (entry.getKey().contains(e.getPoint())) {
                    selected = entry;
                }
            }

            if (selected != null) {
                path = new Path2D.Double(selected.getKey());
                // move it to the top
                entrySet.remove(selected);
                shapeColorMap.put(path, selected.getValue());

                p = e.getPoint();
                repaint();
            }
        }

        @Override
        public void mouseReleased(MouseEvent e) {
            if (selected != null) {
                moveSelected(e);
            }
            selected = null;
        }

        @Override
        public void mouseDragged(MouseEvent e) {
            if (selected != null) {
                moveSelected(e);
            }
        }

        private void moveSelected(MouseEvent e) {
            int x = e.getX() - p.x;
            int y = e.getY() - p.y;
            p = e.getPoint();

            AffineTransform at = AffineTransform.getTranslateInstance(x, y);
            path.transform(at);
            repaint();
        }
    }

    // listener for our button
    private class RandomColorAction extends AbstractAction {
        private static final int CIRC_WIDTH = 100;
        private Random random = new Random();
        private int count = 0;

        public RandomColorAction() {
            super("Random Circle: 0");
            putValue(MNEMONIC_KEY, KeyEvent.VK_R);
        }

        @Override
        public void actionPerformed(ActionEvent e) {
            // create our random ellipses
            int x = random.nextInt(getWidth() - CIRC_WIDTH);
            int y = random.nextInt(getHeight() - CIRC_WIDTH);
            Shape shape = new Ellipse2D.Double(x, y, CIRC_WIDTH, CIRC_WIDTH);

            // create our random color using HSB for brighter colors
            float hue = random.nextFloat();
            float saturation = (float) (0.8 + random.nextFloat() * 0.2);
            float brightness = (float) (0.8 + random.nextFloat() * 0.2);
            Color color = Color.getHSBColor(hue, saturation, brightness);
            shapeColorMap.put(shape, color);

            // increment count, place items into map, repaint
            count++;
            putValue(NAME, "Random Circle: " + count);
            repaint();
        }
    }

    private static void createAndShowGui() {
        Panel2 mainPanel = new Panel2();

        JFrame frame = new JFrame("Panel2");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.getContentPane().add(mainPanel);
        frame.pack();
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }

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