java - 在 Java 中单击按钮在 JPanel 中绘制一条线

Question

我想在 JPanel 中画一条线。这是我的 GUI，我想在 JPanel 中添加一条白色的线。

我找到了很多例子，但问题是如何使用它。

在许多示例中，它们总是绘制从 JPanel 扩展而来的 JFrame。

我想将面板添加到框架中并添加一些按钮以在多个方向上绘制线条并使用中心的 X 按钮来清理 JPanel。

这是接口(interface)的代码:

import java.awt.BorderLayout;
import java.awt.EventQueue;

import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.border.EmptyBorder;
import java.awt.Color;
import javax.swing.JScrollPane;
import javax.swing.JLabel;
import javax.swing.ImageIcon;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;


public class circuit extends JFrame {

 private JPanel contentPane;

 /**
  * Launch the application.
  */
 public static void main(String[] args) {
  EventQueue.invokeLater(new Runnable() {
   public void run() {
    try {
     circuit frame = new circuit();
     frame.setVisible(true);
    } catch (Exception e) {
     e.printStackTrace();
    }
   }
  });
 }

 /**
  * Create the frame.
  */
 public circuit() {
  setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
  setBounds(100, 100, 559, 332);
  contentPane = new JPanel();
  contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
  setContentPane(contentPane);
  contentPane.setLayout(null);

  JScrollPane scrollPane = new JScrollPane();
  scrollPane.setBounds(10, 21, 359, 255);
  contentPane.add(scrollPane);

  JPanel panel = new JPanel();
  scrollPane.setViewportView(panel);
  panel.setBackground(Color.WHITE);

  JLabel label = new JLabel("New label");
  label.addMouseListener(new MouseAdapter() {
   @Override
   public void mouseClicked(MouseEvent arg0) {


    /////////////


   }
  });
  label.setIcon(new ImageIcon("C:\\Users\\achermen\\Desktop\\up.png"));
  label.setBounds(447, 66, 46, 48);
  contentPane.add(label);

  JLabel label_1 = new JLabel("New label");
  label_1.setIcon(new ImageIcon("C:\\Users\\achermen\\Desktop\\down.png"));
  label_1.setBounds(447, 159, 46, 48);
  contentPane.add(label_1);

  JLabel label_2 = new JLabel("New label");
  label_2.setIcon(new ImageIcon("C:\\Users\\achermen\\Desktop\\right.png"));
  label_2.setBounds(495, 112, 46, 48);
  contentPane.add(label_2);

  JLabel label_3 = new JLabel("New label");
  label_3.setIcon(new ImageIcon("C:\\Users\\achermen\\Desktop\\left.png"));
  label_3.setBounds(398, 112, 46, 48);
  contentPane.add(label_3);

  JLabel label_4 = new JLabel("New label");
  label_4.setIcon(new ImageIcon("C:\\Users\\achermen\\Desktop\\1303860240_list-remove.png"));
  label_4.setBounds(447, 112, 46, 48);
  contentPane.add(label_4);
 }
}

这是画线的代码

public void paint(Graphics graphics)
{
    graphics.drawLine(10, 20, 300, 310);
}

那么如何使用这些线......

提前致谢。

最好的问候，

阿里

Answer 1

使用以下方法绘制线条可能更容易:

1. 点击标记第一个端点
2. 拖动以显示正在进行的行
3. 释放以标记第二个端点

此相关example可能会提供一些额外的指导。

附录

1. 下面的例子实现了上面的大纲。
2. 我更新了示例以展示如何使用按钮面板来影响绘图。
3. 另见此相关 example使用带有键绑定(bind)的 Action 接口(interface)。
4. 我已更新此示例以使用 Key Bindings .

LinePanel.java

import java.awt.BasicStroke;
import java.awt.BorderLayout;
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.RenderingHints;
import java.awt.event.ActionEvent;
import java.awt.event.KeyEvent;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import javax.swing.AbstractAction;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.KeyStroke;

/**
 * @see https://stackoverflow.com/questions/6991648
 * @see https://stackoverflow.com/questions/6887296
 * @see https://stackoverflow.com/questions/5797965
 */
public class LinePanel extends JPanel {

    private MouseHandler mouseHandler = new MouseHandler();
    private Point p1 = new Point(100, 100);
    private Point p2 = new Point(540, 380);
    private boolean drawing;

    public LinePanel() {
        this.setPreferredSize(new Dimension(640, 480));
        this.addMouseListener(mouseHandler);
        this.addMouseMotionListener(mouseHandler);
    }

    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        Graphics2D g2d = (Graphics2D) g;
        g2d.setColor(Color.blue);
        g2d.setRenderingHint(
            RenderingHints.KEY_ANTIALIASING,
            RenderingHints.VALUE_ANTIALIAS_ON);
        g2d.setStroke(new BasicStroke(8,
            BasicStroke.CAP_ROUND, BasicStroke.JOIN_BEVEL));
        g.drawLine(p1.x, p1.y, p2.x, p2.y);
    }

    private class MouseHandler extends MouseAdapter {

        @Override
        public void mousePressed(MouseEvent e) {
            drawing = true;
            p1 = e.getPoint();
            p2 = p1;
            repaint();
        }

        @Override
        public void mouseReleased(MouseEvent e) {
            drawing = false;
            p2 = e.getPoint();
            repaint();
        }

        @Override
        public void mouseDragged(MouseEvent e) {
            if (drawing) {
                p2 = e.getPoint();
                repaint();
            }
        }
    }

    private class ControlPanel extends JPanel {

        private static final int DELTA = 10;

        public ControlPanel() {
            this.add(new MoveButton("\u2190", KeyEvent.VK_LEFT, -DELTA, 0));
            this.add(new MoveButton("\u2191", KeyEvent.VK_UP, 0, -DELTA));
            this.add(new MoveButton("\u2192", KeyEvent.VK_RIGHT, DELTA, 0));
            this.add(new MoveButton("\u2193", KeyEvent.VK_DOWN, 0, DELTA));
        }

        private class MoveButton extends JButton {

            KeyStroke k;
            int dx, dy;

            public MoveButton(String name, int code,
                    final int dx, final int dy) {
                super(name);
                this.k = KeyStroke.getKeyStroke(code, 0);
                this.dx = dx;
                this.dy = dy;
                this.setAction(new AbstractAction(this.getText()) {

                    @Override
                    public void actionPerformed(ActionEvent e) {
                        LinePanel.this.p1.translate(dx, dy);
                        LinePanel.this.p2.translate(dx, dy);
                        LinePanel.this.repaint();
                    }
                });
                ControlPanel.this.getInputMap(WHEN_IN_FOCUSED_WINDOW)
                    .put(k, k.toString());
                ControlPanel.this.getActionMap()
                    .put(k.toString(), new AbstractAction() {

                    @Override
                    public void actionPerformed(ActionEvent e) {
                        MoveButton.this.doClick();
                    }
                });
            }
        }
    }

    private void display() {
        JFrame f = new JFrame("LinePanel");
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.add(this);
        f.add(new ControlPanel(), BorderLayout.SOUTH);
        f.pack();
        f.setLocationRelativeTo(null);
        f.setVisible(true);
    }

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

            @Override
            public void run() {
                new LinePanel().display();
            }
        });
    }
}