鼠标移动时java绘制线条

我想在我的应用程序中添加一个function，允许用户通过在起始位置单击鼠标并在结束位置释放它来绘制直线。 当鼠标移动直到它最终被释放时，线应该移动; 类似于使用Microsoft Paint应用程序绘制线条的方式。

如何实现这一点，以便线条在移动时重新绘制，而不重新绘制可能已在该矩形区域中绘制的其他内容？

Answer 1

试试这个…当鼠标移动（拖动）时，在屏幕上画一条红线。

public static void main(String args[]) throws Exception { JFrame f = new JFrame("Draw a Red Line"); f.setSize(300, 300); f.setLocation(300, 300); f.setResizable(false); JPanel p = new JPanel() { Point pointStart = null; Point pointEnd = null; { addMouseListener(new MouseAdapter() { public void mousePressed(MouseEvent e) { pointStart = e.getPoint(); } public void mouseReleased(MouseEvent e) { pointStart = null; } }); addMouseMotionListener(new MouseMotionAdapter() { public void mouseMoved(MouseEvent e) { pointEnd = e.getPoint(); } public void mouseDragged(MouseEvent e) { pointEnd = e.getPoint(); repaint(); } }); } public void paint(Graphics g) { super.paint(g); if (pointStart != null) { g.setColor(Color.RED); g.drawLine(pointStart.x, pointStart.y, pointEnd.x, pointEnd.y); } } }; f.add(p); f.setVisible(true); } 

Answer 2

MouseListener接口是您的朋友。 您可以只实现mousePressed和mouseReleased函数。 MouseListener接口具有以下可以使用的方法：

 public void mouseEntered(MouseEvent mouse){ } public void mouseExited(MouseEvent mouse){ } public void mousePressed(MouseEvent mouse){ } public void mouseReleased(MouseEvent mouse){ } 

Answer 3

  JFrame frame = new JFrame("Lines"); frame.add(new JComponent() { private Shape line = null; { line = new Line2D.Double(100, 100, 200, 200); prevPoint = new Point(); newPoint = new Point(); MouseAdapter mouseAdapter = new MouseAdapter() { @Override public void mousePressed(MouseEvent e) { prevPoint = e.getPoint(); System.out.println("Prev Point=" + prevPoint.toString()); repaint(); } @Override public void mouseDragged(MouseEvent e) { int dx = 0; int dy = 0; dx = (int) (prevPoint.x - e.getPoint().getX()); dy = (int) (prevPoint.y - e.getPoint().getY()); Line2D shape = (Line2D) line; int x1 = (int) (shape.getX1() - dx); int y1 = (int) (shape.getY1() - dy); int x2 = (int) (shape.getX2() - dx); int y2 = (int) (shape.getY2() - dy); Point startPoint = new Point(x1, y1); Point endPoint = new Point(x2, y2); if (shape != null) { shape.setLine(startPoint, endPoint); prevPoint = e.getPoint(); repaint(); } } @Override public void mouseReleased(MouseEvent e) { repaint(); } }; addMouseListener(mouseAdapter); addMouseMotionListener(mouseAdapter); } @Override protected void paintComponent(Graphics g) { Graphics2D g2d = (Graphics2D) g; g2d.setPaint(Color.BLUE); g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON); if (line != null) { g2d.draw(line); } } }); frame.setSize(650, 400); frame.setLocationRelativeTo(null); frame.setVisible(true); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 

这将移动鼠标移动线。希望这有助于..