如何為g.setColor();設定顏色使用KeyListener繪制圓圈時？

我的代碼將根據用戶單擊的位置繪制圓圈，然后繪制連接這些圓圈的線。我希望將圓圈和線條的顏色默認設定為黑色，但用戶可以鍵入 r,b,g,l (red, blue,green,black) 來設定 NEXT 圓圈和線條的顏色被繪制。我必須在 KeyTyped 方法中放入什么？每當用戶輸入 r、b、g 或 l 時，我都會設定 if/else 陳述句。

import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Point;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.event.MouseMotionListener;
import java.util.ArrayList;
import java.util.List;
import javax.swing.JFrame;
import javax.swing.JPanel;

public class Circle extends JPanel implements MouseListener, KeyListener, MouseMotionListener {

    private List<Point> points;

    public static void main(String[] args) {

        EventQueue.invokeLater(() -> new Circle().buildAndDisplayGui());
    }

    public Circle() {
        points = new ArrayList<>();
        setPreferredSize(new Dimension(500, 500));
        setBackground(Color.white);
        addMouseListener(this);
    }

    private void buildAndDisplayGui() {
        JFrame frame = new JFrame();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.add(this);
        frame.pack();
        frame.setLocationByPlatform(true);
        frame.setVisible(true);
        frame.addKeyListener(this);
    }

    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        g.setColor(Color.black);
        int count = points.size();
        for (int i = 0; i < count; i  ) {
            Point pt0 = points.get(i);
            g.fillOval(pt0.x - 10, pt0.y - 11, 20, 20);
            if (i > 0) {
                Point pt1 = points.get(i - 1);
                g.drawLine(pt1.x, pt1.y, pt0.x, pt0.y);
            }
        }
    }

    @Override
    public void mouseClicked(MouseEvent e) {
        //Prints the coordinates of the clicks
        System.out.println("X: "   e.getX()   "  Y: "   e.getY());
        Point pt = new Point(e.getX(), e.getY());
        points.add(pt);
        repaint();
    }

    @Override
    public void mouseEntered(MouseEvent e) {
        // Do nothing.
    }

    @Override
    public void mouseExited(MouseEvent e) {
        // Do nothing.
    }

    @Override
    public void mousePressed(MouseEvent e) {
        // Do nothing.
    }

    @Override
    public void mouseReleased(MouseEvent e) {
        // Do nothing.
    }

    @Override
    public void mouseDragged(MouseEvent e) {

    }

    @Override
    public void mouseMoved(MouseEvent e) {

    }

    @Override
        public void keyTyped(KeyEvent e) {
    
     if (e.getKeyChar() == 'r') { 
         
        //Sets the color of the next circle and lines to red
    
        } else {
      
            if (e.getKeyChar() == 'b') { 
                
                //Sets the color of the next circle and lines to blue
      
                } else {
      
                    if (e.getKeyChar() == 'g') { 
                        
                        //Sets the color of the next circle and lines to green
      
                        } else {
      
                            if (e.getKeyChar() == 'l') { 
                                
                                //Sets the color of the next circle and lines to black
                            
                            } 
                        } 
                    } 
                } 
            }
     

    @Override
    public void keyPressed(KeyEvent e) {
        // TODO Auto-generated method stub

    }

    @Override
    public void keyReleased(KeyEvent e) {
        // TODO Auto-generated method stub

    }
}

電流輸出：

期望的輸出（如果用戶在兩次滑鼠點擊后按下“r”并且再點擊兩次滑鼠）：

uj5u.com熱心網友回復：

1. 將Color實體變數添加到class Circle. 在示例中，我將其稱為“currentColor”。我Color.black在建構式中將其設定為。

2. 將每個專案保存Color在points. 一種方法是擁有一個并行陣列。我不喜歡緊密耦合的陣列，所以我在示例中創建了一個輔助類。

class PointAndColor { 
     Point thePoint;
     Color theColor;
     PointAndColor () { 
         theColor = Color.black;
         thePoint = new Point (0,0);            
     }
        
     PointAndColor (Point point, Color color) { 
          theColor = color;
          thePoint = point;
     }
        
     Color getColor () { return theColor; }
     Point getPoint () { return thePoint; }
 }

我更改了點串列的通用型別：

  private List<PointAndColor> points;
  private Color currentColor;

用點保存顏色的示例：

@Override
public void mouseClicked(MouseEvent e) {
    //Prints the coordinates of the clicks
    System.out.println("X: "   e.getX()   "  Y: "   e.getY());
    Point pt = new Point(e.getX(), e.getY());
    points.add (new PointAndColor (pt, currentColor));
    repaint();
}

3. keyTyped在方法中設定當前顏色

   @Override
    public void keyTyped(KeyEvent e) {           
   
       switch (e.getKeyChar()) {
           case 'r':
               currentColor = Color.red;
               break;
   
           case 'g':
               currentColor = Color.green;
               break;
   
           case 'b':
               currentColor = Color.blue;
              break;
   
           case 'l':
               currentColor = Color.black;
               break;
   
           default:
               break;
    }
    System.out.println ("Color set to "   currentColor);
   

   }

4. Color使用檢索Point：

     
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        int count = points.size();
        for (int i = 0; i < count; i  ) {
            Point pt0 = points.get(i).getPoint();
            g.setColor (points.get(i).getColor());
            g.fillOval(pt0.x - 10, pt0.y - 11, 20, 20);
            if (i > 0) {
                Point pt1 = points.get(i - 1).getPoint();
                g.drawLine(pt1.x, pt1.y, pt0.x, pt0.y);
            }
        }
    }

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