绘制半透明矩形

Question

我在使用鼠标绘制矩形时遇到问题。我已经解决了我的问题并且得到了我想要的结果。但我有一个小问题。如果我想在单击鼠标按钮时开始绘制矩形，则按钮中的文本会发生变化。这是很小的差异，但我不想看到这个。这是代码：

    package draw;

import java.awt.*;
import java.awt.event.*;
import java.util.ArrayList;
import java.util.List;
import javax.swing.*;
import javax.swing.event.*;


public class Selection extends JPanel
    implements  ChangeListener {

    /**
     * 
     */
    private static final long serialVersionUID = 1L;
    private static final int WIDE = 640;
    private static final int HIGH = 640;  
    private List<Node> nodes = new ArrayList<Node>();
    private Point mousePt = new Point(WIDE / 2, HIGH / 2);
    private Rectangle mouseRect = new Rectangle();
    private boolean selecting = false;

    public static void main(String[] args) throws Exception {
        EventQueue.invokeLater(new Runnable() {

            public void run() {
                JFrame f = new JFrame("GraphPanel");
                f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                Selection gp = new Selection(); 
                gp.add(new JButton("Button"));
                f.add(new JScrollPane(gp), BorderLayout.CENTER);                
                f.pack();
                f.setVisible(true);
            }
        });
    }

    Selection() {

        this.setPreferredSize(new Dimension(WIDE, HIGH));      
        this.addMouseListener(new MouseHandler());
        this.addMouseMotionListener(new MouseMotionHandler());
    }

    @Override
    public void paintComponent(Graphics g) {
        g.setColor(new Color(0x00f0f0f0));
        g.fillRect(0, 0, getWidth(), getHeight());

        for (Node n : nodes) {
            n.draw(g);
        }
        if (selecting) {
            g.setColor(Color.BLACK
                    );
            ((Graphics2D) g).setComposite(AlphaComposite.getInstance(rule, alpha));
            g.fillRect(mouseRect.x, mouseRect.y,
                    mouseRect.width, mouseRect.height);

            g.drawRect(mouseRect.x, mouseRect.y,
                mouseRect.width, mouseRect.height);
        }
    }
    int rule = AlphaComposite.SRC_OVER;
    float alpha = 0.9F;


    private class MouseHandler extends MouseAdapter {

        @Override
        public void mouseReleased(MouseEvent e) {
            selecting = false;
            mouseRect.setBounds(0, 0, 0, 0);
            if (e.isPopupTrigger()) {

            }
            e.getComponent().repaint();
        }

        @Override
        public void mousePressed(MouseEvent e) {
            mousePt = e.getPoint();

                Node.selectNone(nodes);
                selecting = true;          
            e.getComponent().repaint();
        }      
    }

    private class MouseMotionHandler extends MouseMotionAdapter {

        Point delta = new Point();

        @Override
        public void mouseDragged(MouseEvent e) {
            if (selecting) {
                mouseRect.setBounds(
                    Math.min(mousePt.x, e.getX()),
                    Math.min(mousePt.y, e.getY()),
                    Math.abs(mousePt.x - e.getX()),
                    Math.abs(mousePt.y - e.getY()));

            } else {
                delta.setLocation(
                    e.getX() - mousePt.x,
                    e.getY() - mousePt.y);

                mousePt = e.getPoint();
            }
            e.getComponent().repaint();
        }
    }



    /** A Node represents a node in a graph. */
    private static class Node {

        private Color color;

        private boolean selected = false;
        private Rectangle b = new Rectangle();

        /** Draw this node. */
        public void draw(Graphics g) {
            g.setColor(this.color);

            if (selected) {
                g.setColor(Color.darkGray);
                g.drawRect(b.x, b.y, b.width, b.height);
            }
        }




       /** Mark this node as slected. */
         public void setSelected(boolean selected) {
            this.selected = selected;
        }

        /** Select no nodes. */
        public static void selectNone(List<Node> list) {
            for (Node n : list) {
                n.setSelected(false);
            }
        }
  }



    @Override
    public void stateChanged(ChangeEvent arg0) {
        // TODO Auto-generated method stub

    }

}

我认为这可能是我实现按钮的地方的问题。我使用的是eclipse SDK。 你能帮助我吗？

Answer 1

将你的 main 更改为这个。原因是您将 alpha 设置为 <整个面板为 1，因此按钮的颜色变得更浅。只需将按钮移出面板即可完成设置。

public static void main(String[] args) throws Exception {
    EventQueue.invokeLater(new Runnable() {

        public void run() {
            JFrame f = new JFrame("GraphPanel");
            f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            JPanel panel = new JPanel(new BorderLayout());
            JButton button = new JButton("Button");
            panel.add(button, BorderLayout.PAGE_START);
            Selection gp = new Selection(); 
            panel.add(gp, BorderLayout.CENTER);
            f.add(new JScrollPane(panel), BorderLayout.CENTER);                
            f.pack();
            f.setVisible(true);
        }
    });
}