如何在 JAVA 中在运行时设置描边颜色？

Question

我正在尝试创建一个界面，用户可以在其中更改线条的颜色以标记图像的背景或前景。到目前为止，我已经编码了：

private class ImageLine extends JComponent 
{

    java.awt.Point p1,p2;
    BufferedImage show;
    ArrayList <Shape> shapes = new ArrayList<Shape>();
    int flag = 0;
    Color color = Color.ORANGE;


    public ImageLine(BufferedImage img)
    {
        show = img;
        setPreferredSize(new Dimension(img.getWidth(), img.getHeight()));
        this.addMouseListener
        (
                new MouseAdapter()
                {
                    @Override
                    public void mousePressed(MouseEvent e)
                    {
                        p1 = e.getPoint();

                    }

                    @Override
                    public void mouseReleased(MouseEvent e)
                    {
                       p2 = e.getPoint();
                       Shape r = createLine(p1.x,p1.y,e.getX(),e.getY());

                       shapes.add(r);
                       repaint();


                    }

                    @Override
                    public void mouseDragged(MouseEvent e)
                    {

                        mouseReleased(e);
                        repaint();

                    }


                }


        );

        this.addKeyListener(

                new KeyAdapter()
                        {


                            @Override
                            public void keyPressed(KeyEvent e)
                            {

                                if(e.getKeyChar() == 'b')
                                {

                                    color = Color.GREEN;
                                    System.out.println("bck");

                                }
                                if(e.getKeyChar() == 'f')
                                {

                                    color = Color.RED;
                                    System.out.println("fgr");


                                }


                            }





                        }







        );

       this.setFocusable(true);


    }


    private Line2D.Float createLine(int x1, int y1, int x2, int y2) 
    {
          return new Line2D.Float(x1,y1 ,x2, y2);
    }

直到这部分一切正常，当我尝试重写 paintComponent() 方法时，我真正的问题来了，实际上我不知道如何设置颜色作为 keylistener 指示，在这种情况下，如果用户按下"b" 键线条的颜色必须变为绿色，另一方面，如果用户按下 "f" 键，线条的颜色必须变为红色，如果用户绘制不同的颜色lines ，这些线必须保持显示。我试过这段代码但没有成功：

public void paintComponent(Graphics g) {
      Graphics2D g2 = (Graphics2D) g;
      g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
      g2.setStroke(new BasicStroke(10));
      g2.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC_OVER, 0.50f));

      for (Shape s : shapes) {
        //g2.setPaint(Color.BLACK);
        g2.draw(s);
        g2.setPaint(color);
        //g2.fill(s);
      }

      if (p1 != null && p2 != null) {
        g2.setPaint(Color.CYAN);
        Shape r = createLine(p1.x, p1.y, p2.x, p2.y);
        g2.draw(r);
      }
    }

但是结果不是我想要的，我画了线条并改变了颜色，但是当这种情况发生时，我之前画的线条自动将它的颜色更改为选择的颜色，并且他们不保留它的"original color"。有什么建议吗？提前致谢。

Answer 1

查看 Custom Painting Approaches。

您可能希望使用 DrawOnImage 方法。它使用 ColoredRectangle class 来存储颜色和矩形的信息。然后在 paintComponent() 方法中循环遍历所有 ColoredRectangle classes 并绘制 Rectangle。

您需要添加逻辑来更改所选矩形的颜色。

Answer 2

有几种方法可以实现这一点，我有点喜欢将 Shape 和 Color 结合到一个对象中的想法，但这可能需要更多的工作当您添加更多形状时。

另一种解决方案可能是使用 Map 将线条简单地映射到一种颜色，例如

import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Point;
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.Line2D;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import javax.swing.AbstractAction;
import javax.swing.ActionMap;
import javax.swing.InputMap;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.KeyStroke;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class DrawLines {

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

    public DrawLines() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                    ex.printStackTrace();
                }

                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.add(new TestPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class TestPane extends JPanel {

        private Line2D currentLine;
        private Map<Shape, Color> mapColors;

        private Color currentColor;

        private List<Shape> shapes;

        public TestPane() {

            mapColors = new HashMap<>(25);
            shapes = new ArrayList<>(25);

            InputMap inputMap = getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW);
            ActionMap actionMap = getActionMap();

            inputMap.put(KeyStroke.getKeyStroke(KeyEvent.VK_F, 0), "foreground");
            inputMap.put(KeyStroke.getKeyStroke(KeyEvent.VK_B, 0), "background");

            actionMap.put("foreground", new AbstractAction() {
                @Override
                public void actionPerformed(ActionEvent e) {
                    currentColor = Color.GREEN;
                    if (currentLine != null) {
                        mapColors.put(currentLine, currentColor);
                        repaint();
                    }
                }
            });
            actionMap.put("background", new AbstractAction() {
                @Override
                public void actionPerformed(ActionEvent e) {
                    currentColor = Color.RED;
                    if (currentLine != null) {
                        mapColors.put(currentLine, currentColor);
                        repaint();
                    }
                }
            });

            MouseAdapter ma = new MouseAdapter() {

                private Point p1, p2;

                @Override
                public void mousePressed(MouseEvent e) {
                    p1 = e.getPoint();
                    currentLine = null;
                }

                @Override
                public void mouseReleased(MouseEvent e) {
                    p2 = e.getPoint();
                    if (currentLine == null) {
                        currentLine = createLine(p1.x, p1.y, e.getX(), e.getY());
                    } else {
                        currentLine.setLine(p1, p2);
                    }

                    mapColors.put(currentLine, currentColor);
                    shapes.add(currentLine);
                    repaint();                  
                }

                @Override
                public void mouseDragged(MouseEvent e) {
                    p2 = e.getPoint();
                    if (currentLine == null) {
                        currentLine = createLine(p1.x, p1.y, e.getX(), e.getY());
                    } else {
                        currentLine.setLine(p1, p2);
                    }

                    repaint();
                }

                private Line2D.Float createLine(int x1, int y1, int x2, int y2) {
                    return new Line2D.Float(x1, y1, x2, y2);
                }
            };

            addMouseListener(ma);
            addMouseMotionListener(ma);
        }

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(200, 200);
        }

        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            Graphics2D g2d = (Graphics2D) g.create();
            for (Shape shape : shapes) {
                Color color = mapColors.get(shape);
                if (color == null) {
                    color = Color.BLACK;
                }
                g2d.setColor(color);
                g2d.draw(shape);
            }

            if (currentLine != null) {
                Color color = mapColors.get(currentLine);
                if (color == null) {
                    color = currentColor;
                }
                g2d.setColor(color);
                g2d.draw(currentLine);
            }
            g2d.dispose();
        }

    }

}

另外，我避免使用KeyListener，而是使用快捷键API，这样比较省事

有关详细信息，请参阅 How to Use Key Bindings

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