简单模拟word中对插入直线的操作。可以画直线，然后可以选择直线进行移动、拉伸、删除。并能显示直线的距离。
操作：点击按钮开始画线。鼠标左键点击一条直线进行移动，选择端点进行拉伸。
鼠标右键点击直线，删除它。
附上源代码
import java.awt.BasicStroke; import java.awt.BorderLayout; import java.awt.Color; import java.awt.Cursor; import java.awt.Graphics; import java.awt.Graphics2D; import java.awt.Paint; import java.awt.Point; import java.awt.Stroke; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import java.awt.event.MouseEvent; import java.awt.geom.GeneralPath; import java.awt.geom.Path2D; import java.awt.geom.Point2D; import java.util.ArrayList; import java.util.List; import javax.swing.AbstractAction; import javax.swing.JButton; import javax.swing.JFrame; import javax.swing.JMenuItem; import javax.swing.JOptionPane; import javax.swing.JPanel; import javax.swing.JPopupMenu; import javax.swing.SwingUtilities; import javax.swing.event.MouseInputListener; class MyLine { int a, b, c, d;// shape后直线的两个端点 boolean isSelected; boolean isSelectP0; // 选择线段的一个端点 boolean isSelectP1;// 选择线段的另一个端点 public static float lineWidth = 0.5f; // 线宽 static float len = 1.0f; //线宽的改变主要靠该参数 GeneralPath shape; double distance; int x0, y0, x1, y1; public void constructShape() { int m = Math.round(len / 2); a = x0 + m; b = y0 + m; c = x1 + m; d = y1 + m; double[] px = new double[4]; double[] py = new double[4]; distance = Math.hypot(c - a, d - b); if (c == a) { px[0] = a + len; py[0] = b; px[1] = c + len; py[1] = d; px[2] = c - len; py[2] = d; px[3] = a - len; py[3] = b; } else if (d == b) { px[0] = a; py[0] = b - len; px[1] = c; py[1] = d - len; px[2] = c; py[2] = d + len; px[3] = a; py[3] = b + len; } else { double sin = (c - a) / distance; double cos = (d - b) / distance; px[0] = a + len * cos; py[0] = b - len * sin; px[1] = c + len * cos; py[1] = d - len * sin; px[2] = c - len * cos; py[2] = d + len * sin; px[3] = a - len * cos; py[3] = b + len * sin; } shape = new GeneralPath(Path2D.WIND_NON_ZERO); shape.moveTo(px[0], py[0]); shape.lineTo(px[1], py[1]); shape.lineTo(px[2], py[2]); shape.lineTo(px[3], py[3]); shape.closePath(); } public boolean contains(int x, int y) { return Path2D.contains(shape.getPathIterator(null), new Point2D.Float(x, y)); } } public class TestLine extends JPanel { class MyMouseListener implements MouseInputListener { Point oldPoint; boolean isDragge; private void constructXY0(MyLine ln, int x, int y) { if (x > getWidth()) ln.x0 = getWidth(); else if (x < 0) ln.x0 = 0; else ln.x0 = x; if (y > getHeight()) ln.y0 = getHeight(); else if (y < 0) ln.y0 = 0; else ln.y0 = y; } private void constructXY1(MyLine ln, int x, int y) { if (x > getWidth()) ln.x1 = getWidth(); else if (x < 0) ln.x1 = 0; else ln.x1 = x; if (y > getHeight()) ln.y1 = getHeight(); else if (y < 0) ln.y1 = 0; else ln.y1 = y; } @Override public void mouseClicked(MouseEvent e) { } @Override public void mouseEntered(MouseEvent e) { } @Override public void mouseExited(MouseEvent e) { } @Override public void mouseMoved(MouseEvent e) { setCursor(Cursor.getPredefinedCursor(Cursor.DEFAULT_CURSOR)); if (pressIndex != 3) pressIndex = 0; // 先清空 for (MyLine line : lines) { line.isSelectP0 = false; line.isSelectP1 = false; line.isSelected = false; } if (pressIndex == 3) { setCursor(Cursor.getPredefinedCursor(Cursor.CROSSHAIR_CURSOR)); return; } // 判断是否选中直线，若是则将光标改变 for (MyLine line : lines) { if (line.contains(e.getX(), e.getY())) { line.isSelected = true; pressIndex = 1; setCursor(Cursor.getPredefinedCursor(Cursor.MOVE_CURSOR)); break; } } // 如果选中了某条直线，再判断该直线的端点是否被选中 if (selectedLine != null) { MyLine line = selectedLine; Point p1 = new Point(line.a, line.b); // 左端点 Point p2 = new Point(line.c, line.d); // 右端点 Point p = new Point(e.getX(), e.getY()); if (isRange(p1, p)) { line.isSelectP0 = true; pressIndex = 2; setCursor(Cursor.getPredefinedCursor(Cursor.CROSSHAIR_CURSOR)); } if (isRange(p2, p)) { line.isSelectP1 = true; pressIndex = 2; setCursor(Cursor.getPredefinedCursor(Cursor.CROSSHAIR_CURSOR)); } } } @Override public void mousePressed(MouseEvent e) { switch (pressIndex) { case 0: selectedLine = null; for (MyLine line : lines) { line.isSelectP0 = false; line.isSelectP1 = false; line.isSelected = false; } break; case 1: for (MyLine line : lines) { if (line.isSelected) { selectedLine = line; break; } } tmpSelectedLine = new MyLine(); tmpSelectedLine.x0 = selectedLine.x0; tmpSelectedLine.x1 = selectedLine.x1; tmpSelectedLine.y0 = selectedLine.y0; tmpSelectedLine.y1 = selectedLine.y1; tmpSelectedLine.constructShape(); oldPoint = new Point(e.getX(), e.getY()); break; case 2: break; case 3: inLine = new MyLine(); inLine.x0 = e.getX(); inLine.y0 = e.getY(); break; default: break; } } @Override public void mouseDragged(MouseEvent e) { switch (pressIndex) { case 0: break; case 1: Point point = new Point(e.getX(), e.getY()); int lenx = point.x - oldPoint.x; int leny = point.y - oldPoint.y; tmpSelectedLine.x0 = selectedLine.x0 + lenx; tmpSelectedLine.x1 = selectedLine.x1 + lenx; tmpSelectedLine.y0 = selectedLine.y0 + leny; tmpSelectedLine.y1 = selectedLine.y1 + leny; tmpSelectedLine.constructShape(); isDragge = true; break; case 2: MyLine line = selectedLine;// lines.get(selectPointInWhichLine); if (line.isSelectP0) { constructXY0(line, e.getX(), e.getY()); } if (line.isSelectP1) { constructXY1(line, e.getX(), e.getY()); } line.constructShape(); break; case 3: constructXY1(inLine, e.getX(), e.getY()); inLine.constructShape(); break; default: break; } repaint(); } @Override public void mouseReleased(MouseEvent e) { switch (pressIndex) { case 0: break; case 1: Point point = new Point(e.getX(), e.getY()); int lenx = point.x - oldPoint.x; int leny = point.y - oldPoint.y; selectedLine.x0 += lenx; selectedLine.x1 += lenx; selectedLine.y0 += leny; selectedLine.y1 += leny; selectedLine.constructShape(); tmpSelectedLine = null; if (!isDragge && e.isPopupTrigger()) { popup.show(e.getComponent(), e.getX(), e.getY()); } isDragge = false; break; case 2: MyLine line = selectedLine; if (line.isSelectP0) { constructXY0(line, e.getX(), e.getY()); } if (line.isSelectP1) { constructXY1(line, e.getX(), e.getY()); } line.constructShape(); break; case 3: constructXY1(inLine, e.getX(), e.getY()); inLine.constructShape(); lines.add(inLine); selectedLine = inLine; selectedLine.isSelected = true; inLine = null; pressIndex = 0; break; default: break; } // 统一在鼠标释放的时候重绘 repaint(); } } class PopupAction extends AbstractAction { private static final long serialVersionUID = 1L; public PopupAction(String name) { super(name); } @Override public void actionPerformed(ActionEvent e) { if (lines.remove(selectedLine)) { selectedLine = null; pressIndex = 0; // selectWhichLine = -1; // selectPointInWhichLine = -1; JOptionPane.showMessageDialog(null, "remove success", "Teemo", JOptionPane.INFORMATION_MESSAGE); } repaint(); } } private static final long serialVersionUID = 1L; public static void main(String[] args) { SwingUtilities.invokeLater(new Runnable() { @Override public void run() { final JFrame frame = new JFrame(); frame.setSize(400, 400); frame.setVisible(true); frame.setLocationRelativeTo(null); JButton jb = new JButton("add line"); final TestLine tl = new TestLine(); jb.addActionListener(new ActionListener() { @Override public void actionPerformed(ActionEvent e) { // tl.isDrawingLine = true; tl.pressIndex = 3; } }); frame.getContentPane().add(jb, BorderLayout.NORTH); frame.getContentPane().add(tl, BorderLayout.CENTER); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); } }); } private List<MyLine> lines = new ArrayList<MyLine>(); private MyLine inLine; private float range = 4f; JPopupMenu popup; private MyLine selectedLine; // 选中的line MyLine tmpSelectedLine; // 移动时临时的线 int pressIndex = 0; public TestLine() { MyMouseListener ml = new MyMouseListener(); addMouseListener(ml); addMouseMotionListener(ml); // addMouseListener(pl); constructPopup(); } private void constructPopup() { popup = new JPopupMenu(); JMenuItem menuItem = new JMenuItem(); menuItem.setAction(new PopupAction("remove line")); popup.add(menuItem); } private boolean isRange(Point a, Point b) { if (Math.hypot(a.x - b.x, a.y - b.y) < range) return true; return false; } // 画图的按钮的背景和标签 protected void paintComponent(Graphics g2) { super.paintComponents(g2); g2.setColor(new Color(255, 255, 255)); g2.fillRect(0, 0, getWidth(), getHeight()); Graphics2D g = (Graphics2D) g2; Paint oldPaint = g.getPaint(); Stroke s = g.getStroke(); int i = 0; for (MyLine line : lines) { g.setStroke(new BasicStroke(MyLine.lineWidth)); g.setPaint(Color.BLACK); GeneralPath shape = line.shape; g.drawString(i++ + "", line.x0, line.y0); int midx = Math.round((line.x0 + line.x1) / 2.0f); int midy = Math.round((line.y0 + line.y1) / 2.0f); g.drawString(String.format("%.2f", line.distance), midx, midy); g.fill(shape); } // 如果被选择，那么直线的两端应该会有两个黑点 if (selectedLine != null) { MyLine line = selectedLine; g.setPaint(Color.BLACK); int l = 6; g.drawOval(line.a - l / 2, line.b - l / 2, l, l); g.drawOval(line.c - l / 2, line.d - l / 2, l, l); g.setPaint(Color.GREEN); g.fillOval(line.a - l / 2, line.b - l / 2, l, l); g.fillOval(line.c - l / 2, line.d - l / 2, l, l); } if (tmpSelectedLine != null) { g.setStroke(new BasicStroke(MyLine.lineWidth)); g.setPaint(Color.BLACK); GeneralPath shape = tmpSelectedLine.shape; g.fill(shape); } // 画正在产生的直线 if (inLine != null) { g.setStroke(new BasicStroke(MyLine.lineWidth)); g.setPaint(Color.BLACK); GeneralPath shape = inLine.shape; if (shape != null) g.fill(shape); } g.setPaint(oldPaint); g.setStroke(s); g2.dispose(); } }