在java中绘制形状对象（可拖动，可调整大小并且可以旋转）

Question

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）。用户应该能够在画布上放置一个形状并拖动它，甚至可以放大它以创建所需的图片。

我尝试覆盖 JPanel 的 paintComponent() 来实现这一点，但意识到 Jpanels 形状仍然是正方形，所以当你有一个圆圈时，即使你不一定要触摸它，你仍然可以拖动它，因为它在里面一个正方形，也很难画出三角形

你会推荐什么库？

Answer 1

Shape 接口和派生类，例如 Path2D、Ellipse2D 和 Rectangle2D，将在这里为您提供帮助，因为从它派生的所有类都必须具有您可以使用的 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调整大小。