java - 在 JComponent 中存储形状

Question

我不确定如何使用一个形状类型的数组列表来存储多个不同的形状。这是主要内容。

public class A1 {
public static boolean rDraw = false;
public static boolean eDraw = false;
public static boolean lDraw = false;
public static void main(String[] args) {
    JFrame frame = new JFrame();
    JButton rect = new JButton("Rectangle");
    rect.addActionListener(new ActionListener (){
        public void actionPerformed(ActionEvent e){
            if(e.getSource()==rect){
                rDraw = true;
                eDraw = false;
                lDraw = false;
            }
        }
    });
    JButton ellipse = new JButton("Ellipse");
    ellipse.addActionListener(new ActionListener (){
        public void actionPerformed(ActionEvent e){
            if(e.getSource()==ellipse){
                rDraw = false;
                eDraw = true;
                lDraw = false;      
            }
        }
    });
    JButton edge = new JButton("Edge");
    edge.addActionListener(new ActionListener (){
        public void actionPerformed(ActionEvent e){
            if(e.getSource() == edge){
                rDraw = false;
                eDraw = false;
                lDraw = true;       
            }
        }
    });
    JButton label = new JButton("Label");
    JTextField labelField = new JTextField(20);
    JPanel panel = new JPanel();
    panel.add(rect);
    panel.add(ellipse);
    panel.add(edge);
    panel.add(label);
    panel.add(labelField);
    frame.add(panel,BorderLayout.NORTH);
    JComponent canvas = new Canvas();
    frame.add(canvas,BorderLayout.CENTER);
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.setSize(600, 600);
    frame.setTitle("Graph Draw");
    frame.setVisible(true);
    }
}

在我的 Canvas 中，我不确定如何使用drawShape？以及在paintComponent 中放入什么来存储形状。

public class Canvas extends JComponent {
private Point p,p2;
private Rectangle r;
private Ellipse2D ep;
private Line2D l;
ArrayList<Shape> shapes = new ArrayList<Shape>();

public Canvas(){
    class MyMouseListener implements MouseListener{
        @Override
        public void mouseClicked(MouseEvent arg0) {
            // TODO Auto-generated method stub

        }

        @Override
        public void mouseEntered(MouseEvent arg0) {
            // TODO Auto-generated method stub

        }

        @Override
        public void mouseExited(MouseEvent arg0) {
            // TODO Auto-generated method stub

        }
        @Override
        public void mousePressed(MouseEvent e) {
            if(A1.rDraw == true && A1.eDraw == false && A1.lDraw == false){
                p = e.getPoint();
                r = new Rectangle(p.x, p.y, p.x - p.x, p.y - p.y);  
            }
            else if (A1.rDraw == false && A1.eDraw == true && A1.lDraw == false){
                p = e.getPoint();
                ep = new Ellipse2D.Double(p.x, p.y, p.x - p.x, p.y - p.y);
            }
            else if (A1.rDraw == false && A1.eDraw == false && A1.lDraw == true){
                p = e.getPoint();
                l = new Line2D.Double(p.x, p.y, p.x - p.x, p.y - p.y);
            }
        }
        @Override
        public void mouseReleased(MouseEvent e) {
            if(A1.rDraw == true && A1.eDraw == false && A1.lDraw == false){
                if (r.width != 0 || r.height != 0)
                {
                    addRectangle(r);
                }

                r = null;
            }
            else if (A1.rDraw == false && A1.eDraw == true && A1.lDraw == false){
                if (ep.getWidth() != 0 || ep.getHeight() != 0){
                    addEllipse(ep);
                }
                ep = null;
            }
            else if (A1.rDraw == false && A1.eDraw == false && A1.lDraw == true){
                if (l.getP1() != null || l.getP2() != null){
                    addLine(l);
                }
                l = null;
            }
        }
    }
    class MyMouseMotionListener implements MouseMotionListener{
        @Override
        public void mouseDragged(MouseEvent e) {
            if(A1.rDraw == true && A1.eDraw == false && A1.lDraw == false){
                int x = Math.min(p.x, e.getX());
                int y = Math.min(p.y, e.getY());
                int width = Math.abs(p.x - e.getX());
                int height = Math.abs(p.y - e.getY());
                r.setBounds(x, y, width, height);
                repaint();
            }
            else if (A1.rDraw == false && A1.eDraw == true && A1.lDraw == false){
                int x = Math.min(p.x, e.getX());
                int y = Math.min(p.y, e.getY());
                int width = Math.abs(p.x - e.getX());
                int height = Math.abs(p.y - e.getY());
                ep.setFrame(x, y, width, height);
                repaint();
            }
            else if (A1.rDraw == false && A1.eDraw == false && A1.lDraw == true){
                p2 = e.getPoint();
                l.setLine(p, p2);
                repaint();
            }
        }
        @Override
        public void mouseMoved(MouseEvent arg0) {
            // TODO Auto-generated method stub

        }
    }
    MouseListener mListener = new MyMouseListener();
    addMouseListener(mListener);
    MouseMotionListener mmListener = new MyMouseMotionListener();
    addMouseMotionListener(mmListener);
}
public void paintComponent(Graphics g){
    super.paintComponent(g);
    Graphics2D g2d = (Graphics2D) g;
    for (Shape shape:shapes){

    }
    if(A1.rDraw == true && A1.eDraw == false && A1.lDraw == false){
        g2d.draw(r);
    }
    else if (A1.rDraw == false && A1.eDraw == true && A1.lDraw == false){
        g2d.draw(ep);
    }
    else if (A1.rDraw == false && A1.eDraw == false && A1.lDraw == true){
        g2d.draw(l);
    }
}
public void addRectangle(Rectangle rect){
    if(r != null){
        Rectangle cR = new Rectangle(rect);
        shapes.add(cR);
        repaint();
    }
}
public void addEllipse(Ellipse2D ellipse){
    if (ep != null){
        Ellipse2D cEp = new Ellipse2D.Double(ellipse.getX(),ellipse.getY(),ellipse.getWidth(),ellipse.getHeight());
        shapes.add(cEp);
        repaint();
    }
}
public void addLine(Line2D line){
    if(l != null){
        Line2D cL = new Line2D.Double(line.getP1(), line.getP2());
        shapes.add(cL);
        repaint();
    }
}
}

Answer 1

你的paintComponent方法似乎做了太多和太少的事情:太少了，因为它没有绘制形状，太多了，因为它试图用静态 boolean 字段做一些不应该做的事情。

"...and what to put in the paintComponent to store the shapes."

这不应该是paintComponent方法的一部分。此方法用于在组件上绘制项目，仅此而已。它不应该用于程序逻辑。用于存储形状的代码应该位于鼠标监听器类型代码中，而不是位于paintComponent 中。

我认为在paintComponent中你所需要的只是这样:

public void paintComponent(Graphics g) {
    super.paintComponent(g);
    Graphics2D g2d = (Graphics2D) g;
    for (Shape shape : shapes) {
        g2d.draw(shape); // !! added
    }
}

作为一些旁注:

• 您的 A1 类中有太多静态代码(包括静态字段)，其中大部分都应该是实例代码，并且 main 方法中的大部分代码应该被删除并放入构造函数中。 main 方法应该非常小。
• 您需要将 Canvas 类重命名为不同的名称，因为这会与核心 Java 类 java.awt.Canvas 产生潜在的名称冲突，并且可能会让其他人感到困惑，甚至编译器也应该这样做您将来可以将此类移至另一个包中。
• 您可以将 MouseListener 和 MouseMotionListener 代码合并到一个扩展 MouseAdapter 的类中。这将简化您的代码，并允许您避免发布空方法停止。
• 由于您的绘图选择是互斥的，因此我将使用 JRadioButtons 或 JToggleButtons 全部保存在单个 ButtonGroup 中，以便用户可以轻松查看当前处于 Activity 状态的选择，并且选择一个按钮会关闭对所有按钮的选择其他人。