通过按JButton在随机JPanel上绘制圆圈

Question

我有一个带JPanels的网格，按下顶部的按钮我想要一个随机生成器在3个随机面板上绘制圆圈。 从理论上讲，我认为我必须用圆圈覆盖每个JPanel的PaintComponent，将标志置于false状态，当我按下按钮时，动作监听器将3个随机JPanels的标志置为true。

但我真的不知道该怎么做。有可能这样做吗？如果是的话，你能告诉我如果没有，你能告诉我还有什么我必须做的吗？非常感谢。到目前为止，这是我的代码：

package feld;

import javax.swing.*;
import java.awt.*;

public class Spielplan {

public static void main(String[] args) {



JFrame f1 = new JFrame();
f1.setLayout(new BorderLayout());
f1.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f1.setPreferredSize(new Dimension(800, 800));

JButton tokens = new JButton("Spielsteine setzen");
f1.add(tokens, BorderLayout.NORTH);

JPanel p1 = new JPanel();
p1.setLayout(new GridLayout(3,3));
f1.add(p1, BorderLayout.CENTER);

JPanel g1 = new JPanel();
g1.setBorder(BorderFactory.createLineBorder(Color.BLACK));
g1.setPreferredSize(new Dimension(100, 100));
g1.setVisible(true);
p1.add(g1);


JPanel g2 = new JPanel();
g2.setBorder(BorderFactory.createLineBorder(Color.BLACK));
g2.setPreferredSize(new Dimension(100, 100));
g2.setVisible(true);
p1.add(g2);

JPanel g3 = new JPanel();
g3.setBorder(BorderFactory.createLineBorder(Color.BLACK));
g3.setPreferredSize(new Dimension(100, 100));
g3.setVisible(true);
p1.add(g3);

JPanel g4 = new JPanel();
g4.setBorder(BorderFactory.createLineBorder(Color.BLACK));
g4.setPreferredSize(new Dimension(100, 100));
g4.setVisible(true);
p1.add(g4);

JPanel g5 = new JPanel();
g5.setBorder(BorderFactory.createLineBorder(Color.BLACK));
g5.setPreferredSize(new Dimension(100, 100));
g5.setVisible(true);
p1.add(g5);

JPanel g6 = new JPanel();
g6.setBorder(BorderFactory.createLineBorder(Color.BLACK));
g6.setPreferredSize(new Dimension(100, 100));
g6.setVisible(true);
p1.add(g6);

JPanel g7 = new JPanel();
g7.setBorder(BorderFactory.createLineBorder(Color.BLACK));
g7.setPreferredSize(new Dimension(100, 100));
g7.setVisible(true);
p1.add(g7);

JPanel g8 = new JPanel();
g8.setBorder(BorderFactory.createLineBorder(Color.BLACK));
g8.setPreferredSize(new Dimension(100, 100));
g8.setVisible(true);
p1.add(g8);

JPanel g9 = new JPanel();
g9.setBorder(BorderFactory.createLineBorder(Color.BLACK));
g9.setPreferredSize(new Dimension(100, 100));
g9.setVisible(true);
p1.add(g9);

f1.pack();
f1.setVisible(true);    




}
}

Answer 1

我能想到的最简单的方法是使用布尔值创建JPanel的子类，以确定是否应该绘制圆。我把它命名为CirclePanel：

public class CirclePanel extends JPanel{

    public static final Color circleColor = Color.BLACK;

    private boolean drawCircle;

    public CirclePanel() {
        drawCircle=false;
        setBorder(BorderFactory.createLineBorder(Color.BLACK));
        setBackground(Color.WHITE);
    }

    public void setDrawCircle(boolean drawCircle) {
        this.drawCircle = drawCircle;
    }

    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);

        if(drawCircle) {

            Graphics2D g2d = (Graphics2D) g;
            Color tmp = g2d.getColor();
            g2d.setColor(circleColor);

            g2d.fillOval(0, 0, getWidth(), getHeight());

            g2d.setColor(tmp);
        }
    }
}

然后我为框架创建了JFrame的子类，但您也可以在main方法中创建它。我将圆形面板放在一个数组中，以避免重复代码并将它们放在网格中。单击该按钮时，将创建List个索引，并随机删除三个索引。然后使用该列表设置面板的布尔变量。见下文：

public class CircleGrid extends JFrame implements ActionListener{

    private CirclePanel[] panels;
    private JButton button;


    public CircleGrid() {
        super("Circle test");

        setLayout(new BorderLayout());

        panels = new CirclePanel[9];
        JPanel center = new JPanel();
        center.setLayout(new GridLayout(3, 3));

        for (int i = 0; i < panels.length; i++) {
            panels[i] = new CirclePanel();
            center.add(panels[i]);
        }

        button = new JButton("Color in");
        button.addActionListener(this);

        this.add(button, BorderLayout.NORTH);
        this.add(center, BorderLayout.CENTER);

        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setSize(new Dimension(800, 800));
        setVisible(true);
    }

    @Override
    public void actionPerformed(ActionEvent e) {
        if(e.getSource().equals(button)) {
            // select three random circle indices -
            // https://stackoverflow.com/a/42353488/7015661
            ArrayList<Integer> indices = new ArrayList<Integer>();
            int numRandom = 3; // three indices

            for (int i = 0; i < panels.length; i++) {
                indices.add(i);
            }

            Random r = new Random();

            for (int i = 0; i < numRandom; i++) {
                int rndPos1 = r.nextInt(indices.size());
                indices.remove(rndPos1); // remove three indices from the list
            }

            // change panel boolean
            for (int i = 0; i < panels.length; i++) {
                CirclePanel pi = panels[i];

                if(indices.contains(i)) {
                    // no circle
                    pi.setDrawCircle(false);
                }else {
                    //draw circle
                    pi.setDrawCircle(true);
                }
            }

            repaint(); // redraw panels
        }
    }

    public static void main(String[] args) {
        new CircleGrid();
    }
}

我最终得到以下结论：

Answer 2

你要做的事情基本上是你在你的jPanel上画出白色整个面板然后画出你的圆圈应用下面的代码希望有帮助。

int name=(int) Math.random() * 100;
int name1=(int) Math.random() * 100;

然后，您将使用图形方法和相应的代码在JPanels上绘制圆圈。下面是在随机位置绘制圆圈的代码：

g.draw/fillOval (name,name1,100,100);