Swing 应用中动态绘制图形的刷新机制与优化

public void mouseDragged(MouseEvent e) {
    try {
        if (currPolygon.contains(x, y)) {
            // ... 移动多边形逻辑 ...
            repaint(); // 问题所在：此处的 repaint() 调用在 PentominoShape (JFrame) 实例上
        }
    }catch (NullPointerException ex){
        // 不推荐的空指针处理方式
    }
}

public void mouseDragged(MouseEvent e) {
    // 优先处理 currPolygon 为 null 的情况，避免 NullPointerException
    if (currPolygon == null) {
        return;
    }

    // 原始逻辑中 currPolygon.contains(x, y) 的判断可能不准确，
    // 因为 x, y 是上次鼠标按下的位置，而不是当前拖动点的起始位置。
    // 如果目的是判断拖动是否发生在当前选中的多边形内部，
    // 应该在 mousePressed 中确定 currPolygon，并在 mouseDragged 中直接移动 currPolygon。
    // 这里我们假设 currPolygon 已经被正确选中且就是要移动的对象。

    System.out.println("Dragged");
    int dx = e.getX() - x;
    int dy = e.getY() - y;
    currPolygon.translate(dx, dy);
    x = e.getX(); // 更新 x, y 为当前鼠标位置，为下一次拖动计算位移做准备
    y = e.getY();

    // 关键修复：在承载绘制内容的 JPanel 上调用 repaint()
    shapePane.repaint();
}

// DrawingPanel.java
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.util.ArrayList;
import java.util.List;

public class DrawingPanel extends JPanel implements MouseListener, MouseMotionListener {
    private List<Polygon> polygons = new ArrayList<>();
    private List<Color> colors = new ArrayList<>();
    private Polygon currPolygon;
    private int x, y;

    public DrawingPanel() {
        // 初始化多边形和颜色
        initShapes();
        // 添加鼠标监听器到自身
        addMouseListener(this);
        addMouseMotionListener(this);
    }

    private void initShapes() {
        // 省略大量多边形和颜色初始化代码，与原 PentominoShape 相同
        // ...
        Polygon fig1 = new Polygon(new int[]{10, 50, 50, 10}, new int[]{10, 10, 200, 200}, 4);
        polygons.add(fig1);
        colors.add(new Color(25, 165, 25));
        // 添加所有其他多边形和颜色
        // ...
    }

    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        Graphics2D g2 = (Graphics2D) g;
        for (int i = 0; i < polygons.size(); i++) {
            g2.setColor(colors.get(i));
            g2.fill(polygons.get(i));
        }
    }

    @Override
    public void mousePressed(MouseEvent e) {
        for (Polygon polygon : polygons) {
            if (polygon.contains(e.getPoint())) {
                currPolygon = polygon;
                x = e.getX();
                y = e.getY();
                break; // 找到即退出
            }
        }
    }

    @Override
    public void mouseDragged(MouseEvent e) {
        if (currPolygon != null) {
            int dx = e.getX() - x;
            int dy = e.getY() - y;
            currPolygon.translate(dx, dy);
            x = e.getX();
            y = e.getY();
            repaint(); // 在 DrawingPanel 自身上调用 repaint()
        }
    }

    @Override
    public void mouseReleased(MouseEvent e) {
        currPolygon = null;
    }

    // 实现其他 MouseListener/MouseMotionListener 接口方法
    @Override public void mouseClicked(MouseEvent e) {}
    @Override public void mouseEntered(MouseEvent e) {}
    @Override public void mouseExited(MouseEvent e) {}
    @Override public void mouseMoved(MouseEvent e) {}
}

// Pentomino.java
import javax.swing.*;
import java.awt.*;

public class Pentomino extends JFrame {
    public Pentomino() {
        initUI();
    }

    private void initUI() {
        setTitle("Пентамино");
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        setSize(1500, 900);
        setResizable(false);

        // 创建并添加 DrawingPanel
        DrawingPanel drawingPanel = new DrawingPanel();
        add(drawingPanel); // JFrame 的默认布局是 BorderLayout，会填充整个中央区域

        setLocationRelativeTo(null);
        setVisible(true);
    }

    public static void main(String[] args) {
        // 在 EDT 中运行 Swing 应用程序
        SwingUtilities.invokeLater(Pentomino::new);
    }
}

// CustomShape.java
import java.awt.*;

public class CustomShape {
    private Polygon polygon;
    private Color color;

    public CustomShape(Polygon polygon, Color color) {
        this.polygon = polygon;
        this.color = color;
    }

    public void draw(Graphics g) {
        Graphics2D g2 = (Graphics2D) g;
        g2.setColor(color);
        g2.fill(polygon);
    }

    public Polygon getPolygon() {
        return polygon;
    }

    public Color getColor() {
        return color;
    }

    public boolean contains(Point p) {
        return polygon.contains(p);
    }

    public void translate(int dx, int dy) {
        polygon.translate(dx, dy);
    }
}

// DrawingPanel.java (部分修改)
// ...
public class DrawingPanel extends JPanel implements MouseListener, MouseMotionListener {
    private List<CustomShape> shapes = new ArrayList<>(); // 存储 CustomShape 对象
    private CustomShape currShape; // 当前拖动的 CustomShape
    private int x, y;

    public DrawingPanel() {
        initShapes();
        addMouseListener(this);
        addMouseMotionListener(this);
    }

    private void initShapes() {
        // 示例：初始化 CustomShape
        Polygon fig1 = new Polygon(new int[]{10, 50, 50, 10}, new int[]{10, 10, 200, 200}, 4);
        shapes.add(new CustomShape(fig1, new Color(25, 165, 25)));
        // 添加所有其他 CustomShape 对象
        // ...
    }

    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        for (CustomShape shape : shapes) {
            shape.draw(g); // 调用 CustomShape 的 draw 方法
        }
    }

    @Override
    public void mousePressed(MouseEvent e) {
        for (CustomShape shape : shapes) {
            if (shape.contains(e.getPoint())) {
                currShape = shape;
                x = e.getX();
                y = e.getY();
                break;
            }
        }
    }

    @Override
    public void mouseDragged(MouseEvent e) {
        if (currShape != null) {
            int dx = e.getX() - x;
            int dy = e.getY() - y;
            currShape.translate(dx, dy); // 调用 CustomShape 的 translate 方法
            x = e.getX();
            y = e.getY();
            repaint();
        }
    }

    @Override
    public void mouseReleased(MouseEvent e) {
        currShape = null;
    }
    // ... 其他方法 ...
}