在java中绘制形状对象（可拖动，可resize并可以旋转）

我正在尝试绘制可用于创建图片的形状（三角形，矩形，正方形和圆形）。 用户应该能够在canvas上放置一个形状并将其拖动或者甚至将其放大以创建所需的图片。

我尝试覆盖paintComponent()来实现这一点但是要意识到Jpanels的形状仍然是一个正方形所以当你有一个圆圈时你仍然可以拖动它，即使你不一定要触摸它，因为它在一个正方形内并且还有难以绘制三角形

你会建议哪些图书馆？

Answer 1

Shape接口和派生类（如Path2D，Ellipse2D和Rectangle2D）将在这里为您提供帮助，因为从中派生的所有类都必须具有可以使用的contains(Point p)方法。

例如：

 import java.awt.*; import java.awt.event.*; import java.awt.geom.*; import javax.swing.*; @SuppressWarnings("serial") public class DragShape extends JPanel { private static final int PREF_W = 800; private static final int PREF_H = 700; private static final Color SHAPE_COLOR = new Color(255, 100, 100); private Path2D myShape = new Path2D.Double(); public DragShape() { myShape.append(new Ellipse2D.Double(150, 50, 200, 200), true); myShape.append(new Rectangle2D.Double(150, 150, 200, 400), true); myShape.append(new Ellipse2D.Double(350, 250, 150, 150), true); myShape.append(new Ellipse2D.Double(150, 450, 200, 200), true); MyMouseAdapter myMouseAdapter = new MyMouseAdapter(); addMouseListener(myMouseAdapter); addMouseMotionListener(myMouseAdapter); } @Override protected void paintComponent(Graphics g) { super.paintComponent(g); Graphics2D g2 = (Graphics2D) g; g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON); if (myShape != null) { g2.setColor(SHAPE_COLOR); g2.fill(myShape); } } @Override public Dimension getPreferredSize() { return new Dimension(PREF_W, PREF_H); } class MyMouseAdapter extends MouseAdapter { private boolean pressed = false; private Point point; @Override public void mousePressed(MouseEvent e) { if (e.getButton() != MouseEvent.BUTTON1) { return; } if (myShape != null && myShape.contains(e.getPoint())) { pressed = true; this.point = e.getPoint(); } } @Override public void mouseDragged(MouseEvent e) { if (pressed) { int deltaX = e.getX() - point.x; int deltaY = e.getY() - point.y; myShape.transform(AffineTransform.getTranslateInstance(deltaX, deltaY)); point = e.getPoint(); repaint(); } } @Override public void mouseReleased(MouseEvent e) { pressed = false; } } private static void createAndShowGui() { DragShape mainPanel = new DragShape(); JFrame frame = new JFrame("DragShape"); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); frame.getContentPane().add(mainPanel); frame.pack(); frame.setLocationByPlatform(true); frame.setVisible(true); } public static void main(String[] args) { SwingUtilities.invokeLater(new Runnable() { public void run() { createAndShowGui(); } }); } } 

我会让你弄清楚旋转和重新调整尺寸。