java - 在绘制矩形和徒手绘制之间切换

Question

我的 Java 绘画程序有一些问题。

我有一个 JComboBox，我可以在其中选择绘制矩形或徒手绘制。对象被添加到 ArrayList。我希望能够在绘制矩形和徒手绘制之间切换，然后返回绘制矩形，然后再徒手绘制……等等。

如果我按照现在的代码那样做，它首先会很好地绘制矩形，然后当我切换到自由手时它会很好地绘制线条，但是当我切换回矩形时它仍然会绘制线条(或者有时线条与看起来很奇怪的矩形)。我切换得越多，它就越奇怪。

谁能看出代码有什么问题，因为我看不到？

public abstract class Draw  {
    public int startX, startY, endX, endY, width, height, w, h;
    public String color = "Black";


    public Draw(int startX, int startY, int width, int height) {
        this.startX = startX;
        this.startY = startY;
        this.width = width;
        this.height = height;
    }

    public abstract void draw(Graphics2D g);       

    public int getX() {
        return startX;
    }

    public void setX(int startX) {
        this.startX = startX;
    }

    public int getY() {
        return startY;
    }

    public void setY(int startY) {
        this.startY = startY;
    }

    public int getWidth() {
        return width;
    }

    public void setWidth(int width) {
        this.width = width;
    }

    public int getHeight() {
        return height;
    }

    public void setHeight(int height) {
        this.height = height;
    }

    public void setColor(String color) {
        this.color = color;
    }
}



public class Rectangle extends Draw {

    public Rectangle(int x, int y, int width, int height) {
        super(x, y, width, height);
    }        

    @Override
    public void draw(Graphics2D g2) {
        g2.drawRect(getX(), getY(), getWidth(), getHeight());
    }  
}

public class FreeHand extends Draw {

     public FreeHand(int x, int y, int width, int height) {
        super(x, y, width, height);
    }

    @Override
    public void draw(Graphics2D g2) {            
        g2.drawLine(getX(), getY(), getWidth(), getHeight());
    }
}

public class PaintProgram extends JFrame implements ActionListener {

    public ArrayList<Draw> shapeList = new ArrayList<>();   
    int startX, startY, endX, endY, w, h;
    private JPanel topPanel;   
    private JPanel bottomPanel;
    private JPanel leftPanel;
    private JPanel rightPanel;
    private JComboBox comboBox;
    private final String[] boxOptions = new String[] {"Rectangle", "Freehand"};   
    Container cp = getContentPane();
    private int count = 0;


    public JavaApplication30(String title) {
        super(title);
        this.setLayout(new BorderLayout());
        this.setDefaultCloseOperation(DO_NOTHING_ON_CLOSE);
        this.setLocationRelativeTo(null);        
        this.setSize(840, 500);     
        this.initComponents();
        this.setVisible(true);            
    }


    private void initComponents() {

        cp.setBackground(Color.WHITE);

        comboBox = new JComboBox(boxOptions);
        topPanel = new JPanel();     
        bottomPanel = new JPanel(new GridLayout(1,2));  
        rightPanel = new JPanel(new FlowLayout(FlowLayout.RIGHT));
        leftPanel = new JPanel(new FlowLayout(FlowLayout.LEFT));

        comboBox.setSelectedIndex(0);          
        comboBox.addActionListener(this); 

        topPanel.setPreferredSize(new Dimension(0,40));        
        bottomPanel.setPreferredSize(new Dimension(0,30));                       
        bottomPanel.setBackground(Color.LIGHT_GRAY);        

        topPanel.add(comboBox);
        bottomPanel.add(leftPanel);        
        bottomPanel.add(rightPanel);

        this.add(topPanel, BorderLayout.PAGE_START);          
        this.add(bottomPanel, BorderLayout.PAGE_END);                  
    }


    @Override
    public void paint(Graphics g) {
        if(count == 0) {
            cp.repaint();
        }
        Graphics2D g2 = (Graphics2D) g;

        for (Draw d : shapeList) {
            d.draw(g2);
        }        

        g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);

        g2.setStroke(new BasicStroke(1));

        if (startX != 0 && startY != 0 && endX != 0 && endY != 0) {

            int width = Math.abs(startX - endX);
            int height = Math.abs(startY - endY);

            int minX = Math.min(startX, endX);
            int minY = Math.min(startY, endY);               

            Rectangle r = new Rectangle(minX, minY, width, height);

            g2.setPaint(Color.WHITE);
            g2.fillRect(r.getX(), r.getY(), r.getWidth(), r.getHeight()); 
            r.setColor(pickedColor);

            r.draw(g2);
        }
    }


    @Override
    public void actionPerformed(ActionEvent e) {

        count++;

        if (e.getSource().equals(comboBox)) {    

            JComboBox cb = (JComboBox)e.getSource();

            if (cb.getSelectedItem().equals("Rectangle")) {

                this.addMouseListener(new MouseAdapter() {    

                    @Override
                    public void mousePressed(MouseEvent e) {                   
                        startX = e.getX();     
                        startY = e.getY(); 

                        endX = startX;  
                        endY = startY;  
                        repaint(); 
                    }

                    @Override
                    public void mouseReleased(MouseEvent e) {
                        endX = e.getX();
                        endY = e.getY();

                        int width = Math.abs(startX - endX);
                        int height = Math.abs(startY - endY);

                        int minX = Math.min(startX, endX);
                        int minY = Math.min(startY, endY);               

                        Rectangle r =  new Rectangle(minX, minY, width, height);
                        shapeList.add(r);
                        r.setColor(pickedColor);

                        startX = 0;
                        startY = 0;
                        endX = 0;
                        endY = 0;
                        repaint();
                    }
                });    

                this.addMouseMotionListener(new MouseMotionAdapter() {
                    @Override
                    public void mouseDragged(MouseEvent e) {
                        endX = e.getX();
                        endY = e.getY();
                        repaint();
                    }
                });
            }            


            else if (cb.getSelectedItem().equals("Freehand")) {

                this.addMouseListener(new MouseAdapter() {                   
                    @Override
                    public void mousePressed(MouseEvent e) {                   
                        startX = e.getX();
                        startY = e.getY();                       
                        addCoordinate(startX, startY);
                    }
                });

                this.addMouseMotionListener(new MouseMotionAdapter() {
                    @Override
                    public void mouseDragged(MouseEvent e) {                
                        Graphics g = getGraphics();    
                        Graphics2D g2 = (Graphics2D) g;         

                        FreeHand fh =  new FreeHand(startX, startY, e.getX(), e.getY());
                        shapeList.add(fh);
                        fh.setColor(pickedColor);
                        fh.draw(g2);                    
                        startX = e.getX();
                        startY = e.getY();                         
                    }
                });    
            }
        }
    }                 

    public static void main(String args[]) {
        new PaintProgram("Paint");
    }
}

Answer 1

您添加了 MouseListener 但没有删除它们。每次您在组合框中选择某些内容时，都会添加一个新的监听器。因此，当您绘制某些内容时，每个监听器都会被应用，并且会发生奇怪的事情。

您应该在添加新的 MouseListener 之前删除之前的 MouseListener。您可能需要在实例变量中记住它。

或者，您可以在开始时添加所有监听器，但检查监听器中组合框的值。如果该值不对应于监听器的用途，则它不应该执行任何操作。

编辑:以下是删除所有听众的方法

    for (MouseListener listener : this.getMouseListeners()) {
        this.removeMouseListener(listener);
    }
    for (MouseMotionListener listener : this.getMouseMotionListeners()) {
        this.removeMouseMotionListener(listener);
    }

在 actionPerformed() 方法中添加新的监听器之前放入此代码