Question

我创建了一个使用MousePressed Listiner绘制4个形状的程序。该程序应绘制随机颜色的形状。我的程序正确地绘制形状，但没有用随机颜色绘制它们。你能告诉我如何编程吗。

由于

import java.awt.BorderLayout;
import java.awt.EventQueue;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JSeparator;
import javax.swing.JToolBar;
import javax.swing.border.EmptyBorder;

public class Pole extends JFrame {

    public static int i;
    public static void main(String[] args) {


    JFrame frame= new JFrame("Shape Stamper!");

   JPanel container;
     JButton circle = new JButton("Circle");
     JButton square = new JButton("Square");
      JButton rectangle = new JButton("Rectangle");
      JButton oval = new JButton("Oval");


        container = new JPanel(new GridLayout(1, 4));
        container.add(circle);
        container.add(square);
        container.add(rectangle);
        container.add(oval);


     circle.addActionListener(new ActionListener() {

            @Override
            public void actionPerformed(ActionEvent e) {
                i = 1;
            }
        });

     square.addActionListener(new ActionListener() {

            @Override
            public void actionPerformed(ActionEvent e) {
                i = 2;
            }
        });

     rectangle.addActionListener(new ActionListener() {

            @Override
            public void actionPerformed(ActionEvent e) {
                i = 3;
            }
        });

     oval.addActionListener(new ActionListener() {

            @Override
            public void actionPerformed(ActionEvent e) { 
                i = 4;
            }
        });


     MyComponent shape = new MyComponent();
      frame.setSize(500, 500);

      frame.add(shape, BorderLayout.CENTER);
        frame.add(container, BorderLayout.SOUTH);

        frame.setVisible(true);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

}
}




import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.geom.Ellipse2D;
import java.awt.geom.Point2D;
import java.awt.geom.Rectangle2D;
import java.util.ArrayList;
import java.util.Random;

import javax.swing.JComponent;

/**
 *
 * @author Taras
 */
public class MyComponent extends JComponent {
    int i;
    Color randColor;
    public MyComponent() 
    {
        this.i = i;
        addMouseListener(new MouseHandler());
    }

    private ArrayList<Rectangle2D> arrOfRect=new ArrayList<>();
    private ArrayList<Ellipse2D> arrOfEllipse=new ArrayList<>();
   // private ArrayList<Color> randColor = new ArrayList<>();
    public void paintComponent(Graphics g)
    {

        Graphics2D g2=(Graphics2D) g;

        g.setColor(new Color(randRed(), randGreen(), randBlue()));

        for(Rectangle2D r: arrOfRect){

            //g2.setColor(Color.GREEN);

            g2.draw(r);

        }
        for(Ellipse2D e: arrOfEllipse){

            g2.draw(e);}
      repaint();


    }
    public void add(Point2D p)
    {
        double x=p.getX();
        double y=p.getY();
        if (Pole.i == 1){
                Ellipse2D ellipse = new Ellipse2D.Double(x, y, 100,100);
                //randColor = new Color(randRed(), randGreen(), randBlue());

                arrOfEllipse.add(ellipse);
            }
        if (Pole.i == 2){
        Rectangle2D rectangls=new Rectangle2D.Double(x, y, 100, 100);
        arrOfRect.add(rectangls);

        }
        if (Pole.i == 3){
        Rectangle2D rectangls=new Rectangle2D.Double(x, y, 150, 100);
        arrOfRect.add(rectangls);

        }
        if (Pole.i == 4){
                Ellipse2D ellipse = new Ellipse2D.Double(x, y, 100,50);
                arrOfEllipse.add(ellipse);
            }
    }
    private class MouseHandler extends MouseAdapter {
        public void mousePressed(MouseEvent event)
        {
            add(event.getPoint());
            //Color rColor = new Color(randRed(), randGreen(), randBlue());
            //randColor.add(rColor);
            randColor = new Color(randRed(), randGreen(), randBlue());

        }

    }

    private int randRed() {
        int red;
        Random randomNumber = new Random();
        red = randomNumber.nextInt(255);
        return red;
    }

    private int randGreen() {
        int green;
        Random randomNumber = new Random();
        green = randomNumber.nextInt(255);
        return green;
    }

    private int randBlue() {
        int blue;
        Random randomNumber = new Random();
        blue = randomNumber.nextInt(255);
        return blue;
    }
}

Answer 1

您接下来的问题是，您只需为此处的所有组件设置Color一次：

g.setColor(new Color(randRed(), randGreen(), randBlue()));

但是如果你想改变每个形状的颜色，你每次都需要调用setColor()。

您可以使用Random的一个实例更改下一个paintComponent()方法，您的形状会有不同的颜色：

Random rand = new Random();
public void paintComponent(Graphics g) {
    super.paintComponent(g);
    Graphics2D g2 = (Graphics2D) g;

    for (Rectangle2D r : arrOfRect) {
        g.setColor(new Color(rand.nextFloat(), rand.nextFloat(), rand.nextFloat()));
        g2.draw(r);

    }
    for (Ellipse2D e : arrOfEllipse) {
        g.setColor(new Color(rand.nextFloat(), rand.nextFloat(), rand.nextFloat()));
        g2.draw(e);
    }

}

在repaint()方法中调用paintComponent()也是错误的，删除该行并在添加新形状后重新绘制面板，例如：

private class MouseHandler extends MouseAdapter {
    public void mousePressed(MouseEvent event) {
        add(event.getPoint());
        repaint();
    }
}

Answer 2

如果目标是使用随机颜色绘制每个形状，则必须为绘制的每个形状更新graphics颜色。即：

for (Rectangle2D r : arrOfRect) {
    g.setColor(getRandomColor());
    g2.draw(r);
}

无需在每次通话中分配新的Random，您可以将其设为私人会员。例如：

private Random randomNumber = new Random();

private Color getRandomColor() {
    return new Color(randomNumber.nextFloat(),
            randomNumber.nextFloat(), randomNumber.nextFloat());
}

如果你想为add()方法中的每个形状分配一个随机颜色并保留它，那么你必须保持一个颜色图或一些服务于目标的其他结构。

其他次要但重要的注意事项：

不要忘记在super.paintComponent()的实施中致电paintComponent。
请勿在{{1}}中致电repaint()，因为它最终会触发paintComponent()。所以你要创造不必要的重绘。
在paintComponent内调用repaint()以使用新创建的形状重新绘制组件。

有关详细信息和示例，请参阅Performing Custom Painting。

用随机颜色绘制形状

2 个答案: